Patent Publication Number: US-2017354425-A1

Title: Surgical measurement instrument

Description:
TECHNICAL FIELD 
     The present invention relates to surgical measurement instruments used when performing treatment on a bone of a patient. 
     BACKGROUND ART 
     For example, in spine correction surgery to correct spine distortion, an operation to connect nut members that are screwed into a plurality of vertebrae to one correction rod is performed (e.g. see Non-Patent Document 1). Due to the plurality of nut members entering a state of being connected to the correction rod, the nut members push the respective vertebrae toward the rod. As a result, the spine having the plurality of vertebrae is corrected so as to be straightened when seen from the back side of the patient. 
     In the above-described spine correction surgery, the correction rod connected to the plurality of nut members needs to be arranged parallel to the up-down direction of the patient (the direction in which the backbone extends). For this purpose, for example, it is conceivable to prepare a measurement rod to measure the direction in which the correction rod is arranged, in addition to the correction rod, and measure the direction of the correction rod using this measurement rod. 
     CITATION LIST 
     Patent Document 
     Patent Application Document 1: JP 5-505749A 
     Non-Patent Document 1: http://www.implamed.com.tr/medicrea_pass.php 
     DISCLOSURE OF THE INVENTION 
     Problem to be Solved by the Invention 
     However, if the measurement operation is performed using the measurement rod, a surgeon needs to keep holding the measurement rod, which is an elongated and heavy item, and this is troublesome. 
     There are also similar problems in other surgeries to perform treatment on a bone of a patient, particularly in artificial joint replacement surgery, in which the mutual positional relationship between a plurality of bones needs to be adjusted. 
     In view of the foregoing situation, an object of the present invention is to enable a measurement operation to be more readily performed using a surgical measurement instrument used in surgery. 
     Means for Solving the Problem 
     (1) A surgical measurement instrument according to the present invention to achieve the above-stated object is a surgical measurement instrument used in surgery to perform treatment on a bone of a patient, including: a laser application portion capable of applying a laser beam for measuring a positional relationship concerning the bone. 
     With this configuration, the laser application portion is configured to apply a laser beam to measure the positional relationship concerning a bone of the patient. This configuration does not require a surgeon to hold a heavy item such as a measurement rod in order to measure the positional relationship concerning a bone of the patient. Accordingly, the burden on the surgeon when measuring the positional relationship concerning a bone of the patient can be reduced. In addition, a laser beam can be formed in a thinner line than the measurement rod. Accordingly, the laser beam can be more readily and accurately applied to a predetermined portion of the patient. As a result, with the surgical measurement instrument according to the present invention, used in surgery, a measurement operation can be more readily performed using this surgical measurement instrument. 
     (2) Preferably, the laser application portion is configured to apply the laser beam to measure relative positions between a plurality of bones of the patient. 
     With this configuration, for example, in surgery to correct relative positions between a plurality of bones of the patient, the relative positions between the plurality of bones can be more readily measured. For example, in corrective surgery to treat scoliosis, i.e. an unnaturally curved vertebral column of the patient, the surgical measurement instrument can be used to measure the alignment direction of the spine. 
     (3) Preferably, the laser application portion is configured to apply the laser beam to measure a positional relationship between the bone of the patient and an instrument to be used in implant placement surgery to install a predetermined implant on the bone of the patient. 
     With this configuration, in implant placement surgery, the surgeon can more readily measure the positional relationship between the instrument and the bone of the patient. 
     (4) More preferably, the instrument is a jig for installing the implant in a body of the patient. 
     With this configuration, for example, in the case of temporarily placing, on the bone of the patient, the jig to be used in implant placement surgery, the surgeon can more readily measure the relative positions between this bone of the patient and the jig. 
     (5) More preferably, the implant placement surgery includes artificial leg joint implant placement surgery for installing the implant on a leg joint including a distal part of a tibia serving as the bone of the patient, the jig includes a tibia distal part cutting guide to be used when cutting the distal part to install the implant on the distal part, and the laser application portion is configured to apply the laser beam toward a knee joint center of the patient, in a state of being supported by the tibia distal part cutting guide. 
     With this configuration, in artificial leg joint implant placement surgery, the surgeon can more readily measure the position of the implant to be installed in the distal part of the tibia of the patient and the position of the knee joint center. In addition, the laser application portion is installed on the tibia distal part cutting guide portion. With this configuration, the laser application portion is held in a stable orientation by the distal part of the tibia. Accordingly, the surgeon can more accurately measure positions using the laser beam in a state where the laser beam position is less likely to shift, unlike in the case of a configuration in which, when the surgeon uses a measurement rod instead of the laser application portion and holds this measurement rod, the position of this measurement rod is likely to shift. 
     (6) Preferably, the surgery includes spine correction surgery for correcting a spine of the patient, the surgical measurement instrument further comprises a fixed jig that is to be fixed to a pelvis of the patient, and the laser application portion is configured to apply the laser beam to measure a plurality of vertebrae of the spine, in a state of being supported by the fixed jig. 
     With this configuration, in spine correction surgery, the alignment direction of the spine, for example, can be more readily measured by surgeon. In addition, the laser application portion is installed on the fixed jig. Thus, the laser application portion is held in a stable orientation by the fixed jig. Accordingly, the surgeon can more accurately measure positions using the laser beam in a state where the laser beam position is less likely to shift, unlike in the case of a configuration in which, when the surgeon uses a measurement rod instead of the laser application portion and holds this measurement rod, the position of this measurement rod is likely to shift. 
     (7) Preferably, the implant placement surgery includes artificial knee joint implant placement surgery for installing the implant on a knee joint including a distal part of a femur serving as the bone of the patient, the jig includes a guide member holder portion for holding a guide member that guides a bone-cutting position when cutting a bone in a proximal part of a tibia of the patient, the guide member holder portion includes a proximal side portion to be connected to the proximal part of the tibia, a distal side portion to be connected to the distal part of the tibia, and a rod for connecting the proximal side portion and the distal side portion to each other, and the laser application portion is configured to apply the laser beam to measure parallelism between the rod and the tibia, in a state of being supported by the guide member holder portion. 
     With this configuration, in artificial knee joint implant placement surgery, the surgeon can more readily measure the parallelism between the rod of the guide member holder portion and the tibia. In addition, the laser application portion is installed on the guide member holder portion. Thus, the laser application portion is held in a stable orientation by the guide member holder portion. Accordingly, the surgeon can more accurately measure positions using the laser beam in a state where the laser beam position is less likely to shift, unlike in the case of a configuration in which, when the surgeon uses a measurement rod instead of the laser application portion and holds this measurement rod, the position of this measurement rod is likely to shift. 
     (8) More preferably, the laser application portion is configured to apply the laser beam to measure the bone-cutting position in the proximal part of the tibia. 
     With this configuration, in artificial knee joint implant placement surgery, the surgeon can more readily and accurately measure the bone-cutting position in the proximal part of the tibia. 
     (9) Preferably, the implant placement surgery includes artificial knee joint implant placement surgery for installing the implant on a knee joint including a distal part of a femur serving as the bone of the patient, the jig includes a drill for forming a reamer hole in the distal part of the femur, and the laser application portion is configured to apply the laser beam to measure a coaxiality between the drill and the femur, in a state of being supported by the drill. 
     With this configuration, in artificial knee joint implant placement surgery, the surgeon can more readily measure the coaxiality between the distal part of the femur and the drill. In addition, the laser application portion is installed on the drill. Thus, the laser application portion is held in a stable orientation by the drill. As a result, the surgeon can more accurately measure the positions using the laser beam in a state where the laser beam position is less likely to shift. 
     (10) Preferably, the implant placement surgery includes artificial knee joint implant placement surgery for installing the implant on a knee joint including a distal part of a femur serving as the bone of the patient, the jig includes a valgus alignment guide to be attached to the femur to guide insertion of a predetermined medullary cavity rod into a medullary cavity portion of the femur, the valgus alignment guide being for adjusting a position of the medullary cavity rod in a valgus angle direction of the femur, and the laser application portion is configured to apply the laser beam to measure a positional relationship between the valgus alignment guide and the femur, in a state of being supported by the valgus alignment guide. 
     With this configuration, in artificial knee joint implant placement surgery, the surgeon can more readily measure the positional relationship between the distal part of the femur and the valgus alignment guide. In addition, the laser application portion is installed in the valgus alignment guide. Thus, the laser application portion is held in a stable orientation by the valgus alignment guide. Accordingly, the surgeon can more accurately measure positions using the laser beam in a state where the laser beam position is less likely to shift, unlike in the case of a configuration in which, when the surgeon uses a measurement rod instead of the laser application portion and holds this measurement rod, the position of this measurement rod is likely to shift. 
     (11) More preferably, the laser application portion is configured to apply the laser beam to indicate a bone head center of the femur, in a state of being supported by the valgus alignment guide. 
     With this configuration, the surgeon can more readily measure the positional relationship between the bone head center of the femur and the valgus alignment guide. In addition, the laser application portion is held in a stable orientation by the valgus alignment guide. Accordingly, the surgeon can more accurately measure positions using the laser beam in a state where the laser beam position is less likely to shift, unlike in the case of a configuration in which, when the surgeon uses a measurement rod instead of the laser application portion and holds this measurement rod, the position of this measurement rod is likely to shift. 
     (12) Preferably, the implant placement surgery includes artificial knee joint implant placement surgery for installing the implant on a knee joint including a distal part of a femur serving as the bone of the patient, the jig includes a spacer that is to be arranged between a cut-bone face formed in the distal part of the femur and a cut-bone face formed in a proximal part of a tibia of the patient, and the laser application portion is configured to apply the laser beam to indicate a bone head center of the femur and a leg joint center of the patient, in a state of being supported by the spacer. 
     With this configuration, when checking, for example, that the knee joint center, the bone head center of the femur, and the leg joint center are arranged in a straight line (alignment), the surgeon can more readily measure the alignment using the laser beam as a mark. In addition, the laser application portion is held in a stable orientation by the spacer. Accordingly, the surgeon can more accurately measure positions using the laser beam in a state where the laser beam position is less likely to shift, unlike in the case of a configuration in which, when the surgeon uses a measurement rod instead of the laser application portion and holds this measurement rod, the position of this measurement rod is likely to shift. 
     (13) Preferably, the implant placement surgery includes artificial knee joint implant placement surgery for installing the implant on a knee joint including a distal part of a femur serving as the bone of the patient, the jig includes a sizer member for positioning a pin that is to be driven into a cut-bone face formed in the distal part of the femur, and the laser application portion is configured to apply the laser beam to measure a positional relationship between the cut-bone face and the sizer member, in a state of being supported by the sizer member. 
     With this configuration, the surgeon can more readily measure the positional relationship between the cut-bone face and the sizer member. In addition, the laser application portion is held in a stable orientation by the sizer member. As a result, the surgeon can more accurately measure the positions using the laser beam in a state where the laser beam position is less likely to shift. 
     (14) Preferably, the implant placement surgery includes artificial knee joint implant placement surgery for installing the implant on a knee joint including a distal part of a femur serving as the bone of the patient, the jig includes a guide member that is to be installed in a cut-bone face formed in the distal part of the femur, the guide member being for guiding a cutter for forming an additional cut-bone face in the distal part, and the laser application portion is configured to apply the laser beam to measure a positional relationship between the guide member and the distal part, in a state of being supported by the guide member. 
     With this configuration, the surgeon can more readily measure the positional relationship between the cut-bone face and the guide member. In addition, the laser application portion is held in a stable orientation by the guide member. As a result, the surgeon can more accurately measure the positions using the laser beam in a state where the laser beam position is less likely to shift. 
     (15) Preferably, the laser application portion is configured to radially apply the laser beam to the patient. 
     With this configuration, the laser beam is applied to more portions. Thus, the surgeon can more readily visually check the positional relationship between each portion to which the laser beam is applied and a reference portion. 
     Effects of the Invention 
     With the surgical measurement instrument according to the present invention, used in surgery, a measurement operation can be more readily performed using this surgical measurement instrument. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view showing a surgical measurement instrument  1  according to a first embodiment of the present invention, a portion of the skeleton of a patient, and the like. 
         FIG. 2  is a front elevational view showing the surgical measurement instrument  1 , a portion of the skeleton of a patient, and the like. 
         FIG. 3  is a flowchart showing the main points of an exemplary flow of artificial leg joint implant placement surgery. 
         FIG. 4  is a rear view showing a measurement instrument  23  according to a second embodiment of the present invention and a portion of the skeleton of a patient. 
         FIG. 5  is a rear view showing a state where the spine has been corrected. 
         FIG. 6  is a flowchart showing the main points of an exemplary flow of spine correction surgery. 
         FIG. 7  is a diagram illustrating a third embodiment of the present invention, and is a side view with a partial cross section showing a state where an artificial knee joint implant has been installed in a patient. 
         FIG. 8  is a perspective view showing a state where a surgical device  40  has been attached to a tibia. 
         FIG. 9  is a perspective view showing a surgical device  55  and the like. 
         FIG. 10  is a perspective view showing the main points to illustrate a procedure for forming a reamer hole in a distal part of a femur. 
         FIG. 11  is a perspective view showing the main points to illustrate a procedure for inserting a medullary cavity rod in a distal part of a femur. 
         FIG. 12  is a front elevational view showing a surgical device  78  and the like. 
         FIG. 13  is a front elevational view illustrating a procedure for checking a gap between a main face of a cut-bone face of a femur and a cut-bone face of a tibia. 
         FIG. 14  shows a modification of a measurement instrument  81  to be attached to a spacer. 
         FIG. 15  is a perspective view showing the main points to illustrate a procedure for fixing a sizer member to a distal part of a femur. 
         FIG. 16  is a side view showing the main points to illustrate a procedure for installing a guide member  122  in a distal part of a femur. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, modes for implementing the present invention will be described with reference to the drawings. The present invention can be widely applied as a surgical measurement instrument. 
     First Embodiment 
       FIG. 1  is a side view showing a surgical measurement instrument  1  according to the first embodiment of the present invention, a portion of the skeleton of a patient  100 , and the like.  FIG. 2  is a front elevational view showing the surgical measurement instrument  1 , a portion of the skeleton of the patient  100 , and the like. 
     This embodiment will describe, with reference to  FIGS. 1 and 2 , the main points regarding artificial leg joint implant placement surgery, which is implant placement surgery, i.e. surgery to perform treatment on a bone of the patient  100 . The artificial leg joint implant placement surgery is surgery to replace a leg joint  103 , which includes a distal part  101   b  of a tibia  101  of the patient  100 , with an artificial leg joint implant  2 . Note that, although  FIGS. 1 and 2  show the skeleton of the patient  100 , artificial leg joint implant placement surgery is performed with an incision made only in the periphery of the leg joint  103  of the patient  100 . 
     Note that, in the following description, “front” and “rear” refer to the front and rear of the patient in a standing state. “Above/upper” and “below/lower” refer to the above/upper and below/lower of the patient in a standing state. “Left” and “right” refer to the left and right of the patient. The surgical measurement instrument  1  will be described based on a reference state where the surgical measurement instrument  1  is installed in the patient  100 . 
     The artificial leg joint implant  2  has a tibia component  3 , which is to be fixed to the distal part  10   b  of the tibia  101  of the patient  100 , and a talus component  4 , which is to be fixed to a talus  104  and can be displaced relative to the tibia component  3 . 
     The tibia component  3  is formed in a block shape. The tibia component  3  has, when seen from the front, a fixing portion  3   a , which is formed in a trapezoid shape, and a slide face  3   b , which faces the talus component  4  side. An outer face of the fixing portion  3   a  is fixed to a cut-bone face  101   c , which is formed in the distal part  101   b  of the tibia  101 . The talus component  4  is formed in a block shape. The talus component  4  is fixed to the talus  104 . The talus component  4  has a slide face  4   a . The slide faces  4   a  and  3   b  are formed to be curved. The slide face  4   a  is in slidable contact with the slide face  3   b , and cooperates with the slide face  3   b  to form a joint. With this configuration, as a result of the slide faces  3   b  and  4   a  sliding against each other, the talus  104  is displaced relative to the tibia  101 . 
     The aforementioned tibia component  3  is fixed to the cut-bone face  101   c  of the tibia  101 , as mentioned above. This cut-bone face  101   c  is formed by a surgeon using a surgical device  5 . 
     The surgical device  5  has a cutter  6  to cut a portion of the distal part  101   b  of the tibia  101 , a tibia distal part cutting guide  7 , and the surgical measurement instrument  1 . 
     The tibia distal part cutting guide  7  is an example of an “instrument” according to the present invention, and is also an example of a “jig”. The tibia distal part cutting guide  7  is used when cutting the distal part  101   b  in order to install the tibia component  3  on the distal part  101   b  of the tibia  101 . The tibia distal part cutting guide  7  is a Y-shaped member that is formed using a plate-shaped member. The tibia distal part cutting guide  7  is formed in a substantially V-shape when seen from the side. 
     The tibia distal part cutting guide  7  has a guide body  8  and an extension portion  9 . 
     The guide body  8  is a portion that is to be placed along the distal part  101   b  of the tibia  101 , and is formed in a substantially U-shape. A guide face  10  is formed in the guide body  8 . The guide face  10  is formed in a shape that matches the shape of the outer face of the fixing portion  3   a  of the tibia component  3 . The guide face  10  is a portion that is to be placed along the distal part  101   b  when the surgeon forms the fixing portion  3   a  in the distal part  101   b  of the tibia  101  using the cutter  6 . The surgeon forms the fixing portion  3   a  in the distal part  101   b  by moving the cutter  6  along this guide face  10 . 
     Fixing pin holes  11  and  12  are formed in the guide body  8 . These fixing pin holes  11  and  12  are arranged substantially at the center of the guide body  8 , and are arranged in the longitudinal direction of the tibia distal part cutting guide  7 . Corresponding fixing pins  13  and  14  are inserted into the respective fixing pins  11  and  12 . These fixing pins  13  and  14  are fixed to the distal part  101   b  of the tibia  101 . Thus, the tibia distal part cutting guide  7  is fixed to the tibia  101 . The extension portion  9  extends from the guide body  8 . 
     The extension portion  9  is a portion that extends away from the tibia  101  as it extends away from the guide body  8 . The surgical measurement instrument (hereinafter also referred to simply as a measurement instrument)  1  is installed on this extension portion  9 . 
     The measurement instrument  1  has a laser application portion  15  and a connecting portion  18 . 
     The laser application portion  15  is configured to apply a laser beam to measure a positional relationship concerning the skeleton of the patient  100 . In this embodiment, the laser application portion  15  is configured to apply a laser beam L 1  in order to measure the positional relationship between a knee joint center  105  of the patient  100  and the tibia distal part cutting guide  7  that is used in artificial leg joint implant placement surgery to install the tibia component  3  on the tibia  101 . 
     The laser application portion  15  has a configuration in which, for example, a battery and a laser beam source (not shown) are housed in a casing  16 , which is made of a synthetic resin. The laser beam L 1  is applied from an application face  17 , which is formed in a side face of the casing  16  of the laser application portion  15 . The laser application portion  15  is installed on the extension portion  9  so that the laser beam L 1  extends in a direction that coincides with the longitudinal direction of the extension portion  9 . The laser application portion  15  is supported by the extension portion  9  via the connecting portion  18 , and the application face  17  of the laser application portion  15  faces the knee joint center  105  side of the patient  100 . 
     The connecting portion  18  is provided in order to connect the laser application portion  15  to the tibia distal part cutting guide  7 . The connecting portion  18  is a plate-shaped attachment member, for example. The extension portion  18  is fixed to, for example, a leading end of the extension portion  9 , and is also fixed to the casing  16  of the laser application portion  15 . The laser application portion  15  is arranged so as to apply the laser beam L 1  toward the knee joint center  105  of the patient  100 , in a state of being supported by the tibia distal part cutting guide  7  via the connecting portion  18 . 
     Specifically, as a result of the surgeon adjusting the position of the tibia distal part cutting guide  7  relative to the tibia  101 , the laser beam L 1  is set to pass through the knee joint center  105  when seen in plan view. Note that “seen from the front” refers to a visual point of the surgeon in a state of facing the front of the patient  100 . “Seen from the side” refers to a visual point of the surgeon in a state of facing the right side or left side of the patient  100 . The laser application portion  15  is configured to radially emit the laser beam L 1  when seen from the side. Thus, the laser beam L 1  is applied to a plurality of portions on the skin surface of the leg of the patient  100 . 
     Next, an overview of a surgical procedure for artificial leg joint implant placement surgery will be described.  FIG. 3  is a flowchart showing the main points of an exemplary flow of artificial leg joint implant placement surgery. Note that, when a description is given with reference to a flowchart, diagrams other than the flowchart will also be referred to as appropriate. 
     Referring to  FIG. 3 , in artificial leg joint implant placement surgery, first, pre-surgery planning is carried out (step S 1 ). In the pre-surgery planning, first, the lower half of the body of the patient  100  that includes an affected area of the patient  100  and the surrounding portion of the affected area is subjected to X-ray imaging or CT imaging. The surgeon then determines the size of the artificial leg joint implant  2  based on images obtained through X-ray imaging or CT imaging. 
     Next, the surgeon begins surgery. Specifically, the surgeon visually checks the position of the knee joint center  105  (step S 2 ). Next, the surgeon makes an incision in an area near the leg joint  103  of the patient  100  from the front side of the patient  100 , and exposes the distal part  101   b  of the tibia  101  (step S 3 ). Next, the surgeon fixes the tibia distal part cutting guide  7 , to which the laser application portion  15  has been fixed, to the distal part  101   b  of the tibia  101  using one fixing pin (fixing pin  13  or fixing pin  14 ) (step S 4 ). At this time, the surgeon appropriately sets the distance between the distal part  101   b  of the tibia  101  and the guide face  10  in accordance with the size of the tibia component  3  that is to be installed in the distal part  101   b  of the tibia  101 . 
     Next, the surgeon performs a measurement operation and an operation to adjust the position of the tibia distal part cutting guide  7 , using the laser beam L applied from the laser application portion  15  (step S 5 ). More specifically, the surgeon, in a state of looking at the patient  100  from the front, adjusts the orientation of the laser application portion  15  (tibia distal part cutting guide  7 ) so that the laser beam L overlaps the knee joint center  105 . Next, the surgeon fixes the tibia distal part cutting guide  7  to the distal part  101   b  of the tibia  101  using the other fixing pin (fixing pin  13  or fixing pin  14 ) (step S 6 ). Thus, the tibia distal part cutting guide  7  is fixed to the tibia  101 . 
     Next, the surgeon moves the cutter  6  along the guide face  10  of the tibia distal part cutting guide  7 , thereby cutting the distal part  101   b  of the tibia  101  into a shape that simulates the shape of the guide face  10  (step S 7 ). Thus, the fixing portion  3   a  is formed on the distal part  101   b  of the tibia  101 . Thereafter, the surgeon removes the tibia distal part cutting guide  7  from the tibia  101 . The tibia component  3  is fixed to the fixing portion  3   a  of the tibia  101  (step S 8 ). Thereafter, the surgeon performs the remaining treatment, such as an operation to attach the talus component  4  to the talus  104  and stitch the incision area near the leg joint  103  (step S 9 ). 
     As described above, with the surgical measurement instrument  1 , the laser application portion  15  is configured to apply the laser beam L 1  to measure the positional relationship concerning the tibia  101  of the patient  100 . With this configuration, the surgeon does not need to hold a heavy item, such as a measurement rod, in order to measure the positional relationship concerning the tibia  101  of the patient. Accordingly, the burden on the surgeon when measuring the positional relationship concerning the tibia  101  of the patient  100  can be reduced. In addition, the laser beam L 1  can be formed as a thinner line than a measurement rod. Accordingly, the laser beam L 1  can be more readily and accurately applied to the knee joint center  105  of the patient  100 . As a result, a measurement operation can be more readily performed using the measurement instrument  1 . 
     The measurement instrument  1  is configured to apply the laser beam L 1  in order to measure the positional relationship between the tibia  101  of the patient  100  and the tibia distal part cutting guide  7  that is used in the artificial leg joint implant placement surgery. With this configuration, in artificial leg joint implant placement surgery, the surgeon can more readily measure the positional relationship between the tibia distal part cutting guide  7  and the talus  104  of the patient. 
     Regarding the measurement instrument  1 , the tibia distal part cutting guide  7  is a jig for installing the artificial leg joint implant  2  in the body of the patient  100 . With this configuration, in the case of temporarily installing the tibia distal part cutting guide  7  that is used in artificial leg joint implant placement surgery on the tibia  101  of the patient  100 , the surgeon can more readily measure the relative positions between the tibia  101  of the patient  100  and the tibia distal part cutting guide  7 . 
     Regarding the measurement instrument  1 , the laser application portion  15  is configured to apply the laser beam L 1  to the knee joint center  105  of the patient  100 , in a state of being supported by the tibia distal part cutting guide  7  via the connecting portion  18 . With this configuration, in artificial leg joint implant placement surgery, the surgeon can more readily measure the position of the tibia component  3  to be installed in the distal part  101   b  of the tibia  101  of the patient and the position of the knee joint center  105 . In addition, the laser application portion  15  is installed on the tibia distal part cutting guide  7 . With this configuration, the laser application portion  15  is held in a stable orientation by the distal part  101   b  of the tibia  101 . Accordingly, the surgeon can more accurately measure the positions using the laser beam L 1  in a state where the position of the laser beam L 1  is less likely to shift, unlike in the case of a configuration in which, when the surgeon uses a measurement rod instead of the laser application portion  15  and holds the measurement rod, the position of the measurement rod is likely to shift. 
     Regarding the measurement instrument  1 , the laser application portion  15  is configured to radially apply the laser beam L 1  to the patient  100 . With this configuration, the laser beam L 1  is applied to more portions. Thus, the surgeon can more readily visually check the positional relationship between each portion to which the laser beam L 1  is applied and a reference position (the tibia distal part cutting guide  7 ). 
     Second Embodiment 
       FIG. 4  is a rear view showing a measurement instrument  23  according to the second embodiment of the present invention and a portion of the skeleton of the patient  100 . This embodiment will describe the main points regarding spine correction surgery to perform treatment on vertebrae  111  of the patient  100 , with reference to  FIG. 4 . Spine correction surgery is correction surgery to bring the shape of the spine  110  of the patient  100 , the spine  110  curving due to scoliosis or the like, close to the original shape of the spine  110 . 
     Note that  FIG. 4  only partially shows a portion of the skeleton and the like of the patient  100 . However, spine correction surgery is performed with an incision made only in a portion around the spine  110  of the patient  100 . A surgical device  20  is used in spine correction surgery. 
     The surgical device  20  has a plurality of fixing screws  21 , a correction rod  22 , and a measurement instrument  23 . 
     The fixing screws  21  are each provided as a portion that is fixed to any one of the vertebrae  111  of the spine  110  and is connected to the other fixing screws  21  via the correction rod  22 . The number of fixing screws  21  that are to be used in spine correction surgery is appropriately set in accordance with the symptoms of the patient  100 , for example. 
     The fixing screws  21  each has an male screw portion  21   a , and a rod holder portion  21   b , which is attached to the male screw portion  21   a.    
     The male screw portion  21   a  is fixed to a corresponding vertebra  111  by being screwed into the vertebra  111  from the back side of the patient  100 . The rod holder portion  21   b  is attached to the male screw portion  21   a  via a ball joint (not shown), and can pivot around the male screw portion  21   a . A through hole, through which the correction rod  22  passes, is formed in the rod holder portion  21   b . The correction rod  22 , which passes through this through hole, is arranged so as to extend in an up-down direction X 1  of the patient  100 . The correction rod  22  connects the plurality of fixing screws  21  to one another by passing through the through holes of the plurality of fixing screws  21 . 
     In spine correction surgery, the fixing screws  21 , to which the correction rod  22  is attached, are screwed into the corresponding vertebrae  111 , and the vertebrae  111  are thus brought toward the correction rod  22 . Thus, the shape of the spine  110  is corrected to have a shape extending in the up-down direction X 1 . Then, the orientation of the spine  110 , which has been corrected using the fixing screws  21  and the correction rod  22 , is measured using the measurement instrument  23 . As a result, whether or not the orientation of the corrected spine  110  is a desired orientation is checked. 
     Note that, although not shown in the diagram, one more correction rod  22  is connected to the spine  110  using a plurality of fixing screws  21 . The two correction rods  22  are connected so as to be parallel to each other, using a connecting member (not shown). 
     The measurement instrument  23  has a fixed jig  24 , the laser application portion  15 , a connecting portion  26 , and marker members  25 . 
     The fixed jig  24  is provided as a jig that is to be temporarily fixed to the pelvis  112  of the patient  100 . The fixed jig  24  is formed in a rectangular frame shape, for example. The fixed jig  24  may be provided in a plurality of sizes according to the physique of the patient  100 , or one type of the fixed jig  24  may be configured so that the size of the fixed jig  24  can be changed in accordance with the shape of the pelvis  112  of the patient  100 . 
     The fixed jig  24  is fixed to the patient  100  by sandwiching the pelvis  112  of the patient  100  from both sides in a left-right direction Y 1 , for example. A front portion  24   a  of the fixed jig  24  is arranged on the front face side of the patient  100 , and extends in the left-right direction Y 1 . A rail  24   b  is formed in this front portion  24   a . The rail  24   b  extends straight in the left-right direction Y 1 . The laser application portion  15  is supported by the rail  24   b  in the front portion  24   a  via the connecting portion  26 . 
     In this embodiment, the laser application portion  15  is configured to apply a laser beam L 2  to measure the relative positional relationship between the vertebrae  111  of the patient  100 . 
     The laser application portion  15  is installed to the fixed jig  24  so that the laser beam L 2  extends in a direction that coincides with the up-down direction X 1  of the patient  100  (the direction in which the head and the end of the leg are connected; the direction in which the spine  110  originally extends). The application face  17  of the laser application portion  15  faces toward the head of the patient  100 . 
     The connecting portion  26  is provided in order to connect the laser application portion  15  to the fixed jig  24 . For example, the connecting portion  26  is a plate-shaped attachment member, and is fixed to the casing  16  of the laser application portion  15 . A groove portion into which the rail  24   b  fits is formed in the connecting portion  26 . The connecting portion  26  can slide relative to the rail  24   b  in the longitudinal direction of the rail  24   b  (left-right direction Y 1 ). 
     The laser application portion  15  is arranged so as to apply the laser beam L 2  that extends in the up-down direction X 1  of the patient  100 , in a state of being supported by the fixed jig  24  via the connecting portion  26 . That is to say, the laser application portion  15  applies the laser beam L 2  in order to measure the positional relationship between the plurality of vertebrae  111  of the spine  110 . The position of the laser beam L 2  is set in the left-right direction Y 1  so as to coincide with the position of at least one marker member  25 . 
     The marker member  25  is attached to a vertebra  111  to which a fixing screw  21  has been attached, or a vertebra  111  to which no fixing screw  21  has been attached. The marker member  25  is provided as a member serving as a mark during measurement using the laser beam L 2  from the laser application portion  15 . For example, the marker member  25  is a round shaft member, and is fixed to one of the vertebrae  111  by being driven into the back side of this vertebra  111 . The portion at which the marker member  25  is to be installed is set during pre-surgery planning. For example, marker members  25  are installed on a vertebra  111  on one end side of the spine  110 , a vertebra  111  located substantially at the center, and a vertebra  111  on the other end side in the up-down direction X 1 . 
     Then, for example, if all marker members  25  are aligned with the laser beam L 2  when the back of the patient  100  is seen from the back side as shown in  FIG. 5 , it indicates that the spine  110  extends substantially straight in a desired direction (up-down direction X 1 ). In this case, it is determined that spine correction surgery has been correctly performed. 
     On the other hand, if at least some of the marker members  25  are not aligned with the laser beam L 2  when the back of the patient  100  is seen from the back side as shown in  FIG. 4 , it indicates that the spine  110  does not extend straight in the desired direction (up-down direction X 1 ). In this case, the surgeon readjusts the position of the vertebrae  111  so that all marker members  25  are aligned with the laser beam L 2  when the patient  100  is seen from the back side. Note that the laser application portion  15  is configured to radially emit the laser beam L 2  when seen from the side. Thus, the laser beam L 2  is applied to a plurality of portions on the skin surface of the back of the patient  100 . 
     Next, an overview of a procedure for spine correction surgery will be described.  FIG. 6  is a flowchart showing the main points of an exemplary flow of spine correction surgery. 
     Referring to  FIG. 6 , in spine correction surgery, first, pre-surgery planning is carried out (step S 21 ). In the pre-surgery planning, first, the upper half of the body of the patient  100  that includes an affected area of the patient  100  and the surrounding area of the affected area is subjected to X-ray imaging or CT imaging. The surgeon then determines the number and installation positions of the fixing screws  21  to be used in spine correction surgery, and the number and installation positions of the marker members  25 , based on images obtained through X-ray imaging or CT imaging. 
     Next, the surgeon begins surgery. Specifically, the surgeon installs the fixing screws  21  and marker members  25  on predetermined vertebrae  111  that have been determined during the pre-surgery planning (step S 22 ). At this time, the fixing screws  21  are installed so that the amount of screwing the fixing screws  21  into the corresponding vertebrae  111  is smaller than that at the time when the surgery is complete. Note that the marker members  25  may be installed on the fixing screws  21 . 
     Next, the correction rod  22  is arranged so as to pass through the through holes in the rod holder portions  21   b  of the fixing screws  21 . Thus, the correction rod  22  is attached to the fixing screws  21  (step S 23 ). As a result, the fixing screws  21  are connected to one another via the correction rod  22 . 
     Next, the surgeon attaches the fixed jig  24  to the pelvis  112  of the patient  100  (step S 24 ). Next, the surgeon corrects distortion of the spine  110  (step S 25 ). Specifically, the surgeon displaces the vertebrae  111 , to which the fixing screws  21  are fixed, toward the correction rod  22  by appropriately increasing the amount of screwing the fixing screws  21  into the corresponding vertebrae  111 . 
     Thereafter, the surgeon performs a measurement operation and an operation to adjust the position of the spine  110  using the laser beam L 2  applied from the laser application portion  15  installed on the fixed jig  24  (step S 26 ). More specifically, the surgeon checks whether or not the laser beam L 2  applied in a direction parallel to the up-down direction X 1  is aligned with all of the plurality of marker members  25  arranged in the up-down direction X 1  when the patient  100  is seen from the back side. If the laser beam L 2  is aligned with all of the plurality of marker members  25  arranged in the up-down direction X 1  when the patient  100  is seen from the back side, the surgeon determines that the spine  110  has been correctly corrected as per the pre-surgery planning. 
     On the other hand, if the laser beam L 2  is not aligned with at least one of the plurality of marker members  25  arranged in the up-down direction X 1  when the patient  100  is seen from the back side, the surgeon determines that the spine  110  has not been correctly corrected in accordance with the pre-surgery planning. In this case, the surgeon appropriately resets the amount by which the respective fixing screws  21  are screwed in. The surgeon thus adjusts the position of the vertebrae  111  relative to the position of the correction rod  22 . Thereafter, the surgeon performs the remaining treatment, such as stitching up the incision portion of the patient  100  (step S 27 ). 
     As described above, in the measurement instrument  23 , the laser application portion  15  is configured to apply the laser beam L 2  to measure the positional relationship between the vertebrae  111  of the patient  100 . With this configuration, the surgeon does not need to hold a heavy item, such as a measurement rod, in order to measure the positional relationship concerning the vertebrae  111  of the patient  100 . Accordingly, the burden on the surgeon when measuring the positional relationship concerning the vertebrae  111  of the patient  100  can be reduced. In addition, the laser beam L 2  can be formed in a thinner line than a measurement rod. Accordingly, the laser beam L 2  can be more readily and accurately applied to the vertebrae  111  of the patient  100  and the marker members  25 . As a result, the surgeon can more readily perform a measurement operation using the measurement instrument  23 . 
     In the measurement instrument  23 , the laser application portion  15  is configured to apply the laser beam L 2  in order to measure the relative positions between the plurality of vertebrae  111  of the patient  100 . With this configuration, the relative positions between the plurality of vertebrae  111  can be more readily measured in spine correction surgery to correct the relative positions between the plurality of vertebrae  111  of the patient  100 . That is to say, during correction surgery to treat scoliosis, i.e. an unnaturally curved spine  110  of the patient  100 , for example, the measurement instrument  23  can be used in order to measure the alignment direction of the plurality of the vertebrae  111 . 
     Regarding the measurement instrument  23 , the laser application portion  15  is configured to apply the laser beam L 2  in order to measure the plurality of vertebrae  111  of the spine  110 , in a state of being supported by the fixed jig  24  via the connecting portion  26 . With this configuration, in spine correction surgery, the surgeon can more readily measure the alignment direction of the spine  110 , for example. The laser application portion  15  is installed on the fixed jig  24 . Thus, the laser application portion  15  is held in a stable orientation by the fixed jig  24 . Accordingly, the surgeon can more accurately measure positions using the laser beam L 2  in a state where the position of the laser beam L 2  is less likely to shift, unlike in the case of a configuration in which, when the surgeon uses a measurement rod instead of the laser application portion  15  and holds the measurement rod, the measurement rod position is likely to shift. 
     Third Embodiment 
       FIG. 7  is a diagram illustrating the third embodiment of the present invention, and is a side view with a partial cross section showing a state where an artificial knee joint implant  31  has been installed in the patient  100 . The third embodiment of the present invention will describe the main points of artificial knee joint implant placement surgery, which is implant placement surgery to perform treatment on a bone of a patient, with reference to  FIG. 7 . Note that, in this embodiment, uneven shapes of the surfaces of the tibia  101  and femur  102  are schematically shown with mesh lines. 
     Artificial knee joint implant placement surgery is surgery to install the artificial knee joint implant  31  in a knee joint  106 , which includes the distal part  102   b  of the femur  102  and the proximal part  101   a  of the tibia  101  of the patient  100 . Note that, although  FIG. 7  shows the skeleton of the patient  100 , artificial knee joint implant placement surgery is performed with an incision made only in the periphery of the knee joint  106  of the patient  100 . 
     The artificial knee joint implant  31  has a femur component  32 , which is to be fixed to the distal part  102   b  of the femur  102  of the patient  100 , and a tibia component  33 , which is to be fixed to the proximal part  10   a  of the tibia  101 . 
     A portion of the femur component  32  that is to be received by the tibia component  33  is formed in a protruding curved shape. A portion of the tibia component  33  that is to be received by the femur component  32  is formed in a recessed shape. The femur component  32  and the tibia component  33  relatively slide against each other with bending motion of the knee of the patient  100 . Thus, the bending motion of the tibia  101  relative to the femur  102  is guided through the cooperation of the femur component  32  and the tibia component  33 . 
     A fixed face  34  is formed on an inner face of the femur component  32  that faces the distal part  102   b  side of the femur  102 . The fixed face  34  is provided in order to fix the femur component  32  to a cut-bone face  102   c  of the femur  102 . 
     The cut-bone face  102   c  is a face that is artificially formed by the surgeon in artificial knee joint implant placement surgery. The cut-bone face  102   c  is formed as a result of the surgeon making an incision in a portion of the distal part  102   b  of the femur  102  using an instrument such as a cutter. 
     The cut-bone face  102   c  has a main face  102   d , which is arranged substantially horizontally when the patient  100  assumes an upright posture on a horizontal surface, a pair of inclined faces  102   e  and  102   f , which extend from the front end and rear end, respectively, of the main face  102   d , and a pair of opposing faces  102   g  and  102   h , which are arranged on the front end side and back end side, respectively, of the femur  102  and extend from the pair of inclined faces  102   e  and  102   f  toward the proximal part of the femur  102 . 
     A procedure for forming the main face  102   d , the pair of inclined faces  102   e  and  102   f , and the pair of opposing faces  102   g  and  102   h  will be described later in detail. 
     The tibia component  33  is fixed to a cut-bone face  101   d , which is formed in the proximal part  101   a  of the tibia  101 . The cut-bone face  101   d  is a face that is artificially formed by the surgeon in artificial knee joint implant placement surgery. The cut-bone face  101   d  is formed as a result of the surgeon making an incision in a leading end face of the proximal part  101   a  using an instrument such as a cutter, for example. The cut-bone face  101   d  is formed so as to extend substantially horizontally when the patient  100  assumes an upright posture on a horizontal surface, for example. 
     Next, a description will be given of the main points of a procedure for forming the cut-bone face  101   d  of the tibia  101 , and the main points of the procedure for forming the cut-bone face  102   c  of the femur  102 . 
     First, the main points of the procedure for forming the cut-bone face  101   d  of the tibia  101  will be described.  FIG. 8  is a perspective view showing a state where a surgical device  40  has been attached to the tibia  101 . Referring to  FIG. 8 , the surgical device  40  is provided in order to guide displacement of the cutter when forming the cut-bone face  101   d  in the proximal part  101   a  of the tibia  101 . 
     The surgical device  40  has a measurement instrument  41 , a guide member holder portion  42 , and a guide member  43 . 
     The guide member holder portion  42  is a jig for installing the artificial knee joint implant  31  in the body of the patient  100 , and is an example of an “instrument to be used in implant placement surgery” according to the present invention. 
     The guide member holder portion  42  has a clamp  44 , a shaft  45 , a first rod  46 , an attachment  47 , a second rod  48 , a spike rod  49 , and a spike  50 . 
     The clamp  44  is an example of a “distal side portion to be connected to a distal part of a tibia” according to the present invention. The clamp  44  is a member that is to be fixed to the patient  100  as a result of clamping the leg of the patient  100  around the distal part  101   b  of the tibia  101  of the patient  100 , and is formed in a substantially C-shape. The shaft  45  extends from the clamp  44  in a front-rear direction Z 1 . The position of the shaft  45  in the left-right direction Y 1  is arranged so as to be aligned with the position of the axis of the tibia  101 . The first rod  46  is attached to the shaft  45 . 
     The first rod  46  is a member that extends in the up-down direction X 1 , and is configured to extend and contract. Note that the first rod  46 , the second rod  48 , and the spike rod  49  are examples of a “rod to connect a proximal side portion and a distal side portion to each other” according to the present invention. One end of the first rod  46  is connected to the shaft  45 , and is configured so that its position can be adjusted in the front-rear direction Z 1  relative to this shaft  45 . The other end of the first rod  46  supports the attachment  47 . 
     The attachment  47  supports the second rod  48  so that the second rod  48  can be displaced in the up-down direction X 1 , and supports the guide member  43 . A through hole that extends in the up-down direction X 1  is formed in the attachment  47 , and the second rod  48  passes through this through hole. The spike rod  49  is attached to the second rod  48 . The spike rod  49  is a shaft member that extends in the front-rear direction Z 1 , and is configured so that its position can be adjusted in the front-rear direction Z 1  relative to the second rod  48 . The spike rod  49  is arranged adjacent to the proximal part  101   a  of the tibia  101 . The spike  50  is fixed to one end of the spike rod  49 . 
     The spike  50  is an example of a “proximal side portion to be connected to a proximal part of a tibia” according to the present invention. The spike  50  is a protruding member and is provisionally fixed (temporarily fixed) to the tibia  101  as a result of being driven into an end face of the proximal part  101   a  of the tibia  101 . With this configuration, the clamp  44  is supported at the distal part  101   b  of the tibia  101  at one end of the guide member holder portion  42 . The spike  50  is supported at the proximal part  101   a  of the tibia  101  at the other end of the guide member holder portion  42 . The guide member holder portion  42  is thus installed on the patient  100 . As mentioned above, the guide member  43  is installed on the guide member holder portion  42 . 
     The guide member  43  is provided for guiding a bone-cutting position when the surgeon cuts the bone in the proximal part  101   a  of the tibia  101 . The guide member  43  is supported by the attachment  47 . The guide member  43  is a member that extends in an elongated manner in the left-right direction Y 1 . A slit hole  43   a , which extends in the left-right direction Y 1 , is formed in the guide member  43 . The slit hole  43   a  faces the proximal part  101   a  side of the tibia  101 . The surgeon inserts the cutter  6  into this slit hole  43   a , and thus performs bone-cutting treatment on the proximal part  101   a  of the tibia  101  using the cutter  6  in a state of being guided by the guide member  43 . The position, orientation, and the like of the guide member  43  are measured by the measurement instrument  41 . 
     The measurement instrument  41  has the laser application portion  15  and a connecting portion  51 . 
     In this embodiment, the laser application portion  15  is configured to apply a laser beam L 31  in order to measure the positional relationship between an axis L 101  of the tibia  101  and the guide member  43  (guide member holder portion  42 ) that is used in artificial knee joint implant placement surgery. 
     In this embodiment, the laser application portion  15  is installed on the guide member holder portion  42  so that the laser beam L 31  is parallel to the axis L 101  of the tibia  101  when seen from the side. The laser application portion  15  is supported, via the connecting portion  51 , by the spike rod  49  of the guide member holder portion  42 , and the application face  17  of the laser application portion  15  faces the distal part  101   b  side of the tibia  101  of the patient  100 . 
     The connecting portion  51  is provided in order to connect the laser application portion  15  to the spike rod  49  of the guide member holder portion  42 . The connecting portion  51  is a rod-shaped attachment member that extends straight, for example. One end of the connecting portion  51  is fixed to the spike rod  49 . The other end of the connecting portion  51  is arranged on a side of the proximal part  10   a  of the tibia  101  in the left-right direction Y 1 , and fixes the casing  16  of the laser application portion  15 . 
     The laser application portion  15  is configured to apply the laser beam L 31  to measure the parallelism between the first rod  46  and the axis L 101  of the tibia  101 , in a state of being supported by the guide member holder portion  42  via the connecting portion  51 . Note that the laser application portion  15  is configured to radially emit the laser beam L 31 . Thus, the laser beam L 31 , which extends in the up-down direction X 1  when seen from the side, is applied to a plurality of portions on the skin surface of the leg of the patient  100 . 
     In this case, the surgeon adjusts, for example, the position of the first rod  46  in the front-rear direction Z 1  relative to the shaft  45 . Thus, the inclination angles of the first rod  46  and the guide member  43  relative to the axis L 101  of the tibia  101  are adjusted, with the spike  50  acting as a fulcrum. As a result, the positions of the first rod  46 , the guide member  43 , and the like are adjusted so that the first rod  46  is parallel to the axis L 101  of the tibia  101 . 
     When the first rod  46  of the guide member holder portion  42  is parallel to the axis L 101  of the tibia  101 , i.e. when the orientation of the slit hole  43   a  in the guide member  43  is substantially perpendicular to the axis L 101  of the tibia  101 , the positioning of the guide member holder portion  42  (guide member  43 ) is complete. 
     Next, the surgeon uses a measurement instrument  56  in order to check the position of the slit hole  43   a  of the guide member  43 .  FIG. 9  is a perspective view showing a surgical device  55  and the like. Referring to  FIG. 9 , the surgical device  55  has the measurement instrument  56 , the guide member holder portion  42 , and the guide member  43 . 
     The measurement instrument  56  has the laser application portion  15  and a connecting portion  57 . 
     In the measurement instrument  56 , the laser application portion  15  is configured to apply a laser beam in order to measure the positional relationship between the axis L 101  of the tibia  101  and the guide member  43  (guide member holder portion  42 ) that is used in artificial knee joint implant placement surgery. 
     In this embodiment, the laser application portion  15  is installed on the guide member holder portion  42  so that the laser beam L 32  extends in a plane that is substantially perpendicular to the axis L 101  of the tibia  101 . The laser application portion  15  is supported by the spike rod  49  of the guide member holder portion  42  via the connecting portion  57 , and the application face  17  of the laser application portion  15  faces the proximal part  101   a  side of the tibia  101  of the patient  100 . 
     The connecting portion  57  is provided in order to connect the laser application portion  15  to the spike rod  49  of the guide member holder portion  42 . The connecting portion  57  is an L-shaped attachment member, for example. One end of the connecting portion  57  is fixed to the spike rod  49 . The other end of the connecting portion  57  is arranged on a side of the proximal part  101   a  of the tibia  101  in the left-right direction Y 1 , and fixes the casing  16  of the laser application portion  15 . 
     The laser application portion  15  is configured to apply the laser beam L 32  in order to measure the bone-cutting position in the proximal part  101   a  of the tibia  101 , in a state of being supported by the guide member holder portion  42  via the connecting portion  57 . Note that the laser application portion  15  is configured to radially emit the laser beam L 32  when the surgeon looks at the patient  100  along the up-down direction X 1 . With this configuration, the laser beam L 32 , which extends in the front-rear direction Z 1  when seen from the side, is applied to a plurality of portions on the skin surface of the leg of the patient  100 . 
     In this case, the surgeon adjusts the guide member  43  in the up-down direction X 1  relative to the first rod  46 , for example. Thus, the position of the guide member  43  in the up-down direction X 1  (a direction parallel to the axis L 101  of the tibia  101 ) is adjusted. As a result, the bone-cutting position in the proximal part  101   a  of the tibia  101  in the up-down direction X 1  is set. 
     The surgeon inserts the cutter  6  into the slit hole  43   a  of the guide member  43 , whose position has been determined, and forms the cut-bone face  101   d , which is substantially perpendicular to the axis L 101 , in the proximal part  101   a  of the tibia  101  of the patient  100 . 
     Next, the surgeon performs an operation to form the cut-bone face  102   c  in the distal part  102   b  of the femur  102 . A description will be given below of the main points of a procedure by which the surgeon forms the cut-bone face  102   c  of the femur  102 . 
       FIG. 10  is a perspective view showing the main points to illustrate a procedure for forming a reamer hole  113  in the distal part  102   b  of the femur  102 . Referring to  FIG. 10 , when forming the cut-bone face  102   c  in the femur  102 , the surgeon first forms the reamer hole  113  in the distal part  102   b  of the femur  102 . The reamer hole  113  is formed using a surgical device  60 . 
     The surgical device  60  has a measurement instrument  61  and a drill  62 . 
     The drill  62  is a jig for installing the artificial knee joint implant  31  in the body of the patient  100 , and is an example of an “instrument to be used in implant placement surgery” according to the present invention. The drill  62  is an electric drill for forming the reamer hole  113  in the distal part  102   b  of the femur  102 . 
     The drill  62  has a casing  63  and a drill body  64 . 
     The casing  63  is a portion to be held by the surgeon. The casing  63  has a grip portion to be gripped by the surgeon, and a housing portion to house an electric motor and a battery to drive this electric motor. The drill body  64  extends from the housing portion. 
     The drill body  64  is a shaft-shaped member having a blade portion, and rotates with the rotation of an output shaft of the electric motor arranged in the casing  16 . The distal part  102   b  of the femur  102  is shaved due to this rotation of the drill body  64 , and the reamer hole  113  is thus formed. 
     The orientation of the drill body  64  relative to the femur  102  is measured by the measurement instrument  61 . The measurement instrument  61  has the laser application portion  15  and a connecting portion  65 . 
     In the measurement instrument  61 , the laser application portion  15  is configured to apply a laser beam L 33  in order to measure the positional relationship between the femur  102  and the drill body  64  of the drill  62  that is used in artificial knee joint implant placement surgery. 
     In this embodiment, the laser application portion  15  is installed on the casing  63  of the drill  62  so that the laser beam L 33  is substantially aligned with an axis L 102  of the femur  102  when seen from the side. The laser application portion  15  is supported by the casing  63  of the drill  62  via the connecting portion  65 , and the application face  17  of the laser application portion  15  faces toward the distal part  102   b  of the femur  102  side. 
     The connecting portion  65  is provided in order to connect the laser application portion  15  to the casing  63  of the drill  62 . The connecting portion  65  is a portion that is to be connected to the drill  62  when the reamer hole  113  is formed in the distal part  102   b  of the femur  102 . The connecting portion  65  is an L-shaped attachment member, for example. 
     One end of the connecting portion  65  is fixed near a portion of the casing  63  at which the drill body  64  protrudes. The other end of the connecting portion  65  is arranged on a side of the distal part  102   b  of the femur  102  in the left-right direction Y 1 , and fixes the casing  16  of the laser application portion  15 . 
     The laser application portion  15  is configured to apply a laser beam L 33  in order to measure the coaxiality between the drill body  64  of the drill  62  and the axis L 102  of the femur  102 , in a state of being supported by the casing  63  of the drill  62  via the connecting portion  65 . The laser application portion  15  is configured to radially emit the laser beam L 33  when the patient  100  is seen from the side. Thus, the laser beam L 33 , which extends in the up-down direction X 1 , is applied to a plurality of portions on the skin surface on a side face of the leg of the patient  100 . 
     In this case, the surgeon adjusts the position of the drill  62  so that the axis of the drill body  64  substantially coincides with the axis L 102  of the femur  102 . The surgeon forms the reamer hole  113  in the distal part  102   b  of the femur  102  using the drill  62 , in a state where the axis of the drill body  64  substantially coincides with the axis L 102  of the femur  102 . 
       FIG. 11  is a perspective view showing the main points to illustrate a procedure for inserting a medullary cavity rod  72  into the distal part  102   b  of the femur  102 . Referring to  FIG. 11 , the surgeon forms the reamer hole  113  in the femur  102 , and thereafter inserts the medullary cavity rod  72  into the femur  102 . The medullary cavity rod  72  is a portion of a surgical device  70 . 
     The surgical device  70  has a measurement instrument  71 , the medullary cavity rod  72 , and a valgus alignment guide  73 . 
     The medullary cavity rod  72  is a rod-shaped member that extends straight and is to be inserted into a medullary cavity portion  114  of the femur  102  of the patient through the reamer hole  113  (not shown in  FIG. 11 ). The medullary cavity rod  72  is also called an IM (Intra Medullary rod), and is used to indicate the axis L 102  of the femur  102 . The medullary cavity rod  72  is inserted into the femur  102  so as to be coaxially aligned with the femur  102 , by the valgus alignment guide  3 . 
     The medullary cavity rod  72  and the valgus alignment guide  73  are jigs to install the artificial knee joint implant  31  in the body of the patient  100 , and are examples of the “instrument to be used in implant placement surgery” according to the present invention and are also examples of the “jig”. The valgus alignment guide  73  is attached to the femur  102  in order to guide the insertion of the medullary cavity rod  72  into the medullary cavity portion  114  of the femur  102 , and the position of the medullary cavity rod  72  can be adjusted in a valgus angle direction θ 1  of the femur  102 . 
     The valgus alignment guide  73  is installed in the distal part  102   b  of the femur  102 . The valgus angle direction θ 1  refers to a direction moving around an intersection point between an axis that passes through the femur  102  and is parallel to the up-down direction X 1  and the axis of the femur  102  when seen from the front. 
     The valgus alignment guide  73  has a body member  74  and a pivot member  75 . 
     The body member  74  is fixed to the distal part  102   b  of the femur  102  using a pin or the like (not shown). The body member  74  is formed in a substantially T-shape. The pivot member  75  is provided as a portion that pivotally supports the medullary cavity rod  72 . 
     The pivot member  75  is formed in an elongated cylindrical shape. A shaft portion  75   a  of the pivot member  75  is pivotably connected to the body member  74 . The medullary cavity rod  72  is inserted in the pivot member  75 . The pivot member  75  can pivot around the shaft portion  75   a  together with the medullary cavity rod  72 . 
     The orientation of the medullary cavity rod  72  relative to the femur  102  is measured by a measurement instrument  71 . The measurement instrument  71  has the laser application portion  15  and a connecting portion  76 . 
     In the measurement instrument  71 , the laser application portion  15  is configured to apply a laser beam L 34  in order to measure the positional relationship between the femur  102 , and the medullary cavity rod  72  and valgus alignment guide  73  that are used in artificial knee joint implant placement surgery. 
     In the measurement instrument  71 , the laser application portion  15  is installed on the body member  74  of the valgus alignment guide  73  so that the laser beam L 34  is substantially aligned with the axis L 102  of the femur  102  when seen from the side. The laser application portion  15  is supported by the body member  74  via the connecting portion  76 , and the application face  17  of the laser application portion  15  faces a bone head center  102   a  side of the femur  102  of the patient  100 . 
     The connecting portion  76  is an L-shaped attachment member, for example. One end of the connecting portion  76  is fixed to one end of the body member  74  in the left-right direction Y 1 . The other end of the connecting portion  76  is arranged on a side of the distal part  102   b  of the femur  102  in the left-right direction Y 1 , and fixes the casing  16  of the laser application portion  15 . 
     The laser application portion  15  is configured to apply a laser beam L 34  in order to measure the positional relationship between the axis L 102  of the femur  102 , and the medullary cavity rod  72  and valgus alignment guide  73 , in a state of being supported by the body member  74  of the valgus alignment guide  73  via the connecting portion  76 . Note that the laser application portion  15  is configured to radially emit the laser beam L 34  when seen from the front. Thus, the laser beam L 34 , which extends in the up-down direction X 1 , is applied to a plurality of portions on the skin surface on a side face of the leg of the patient  100 . 
     In this case, the surgeon adjusts the position of the medullary cavity rod  72  so that the laser beam L 34  and the medullary cavity rod  72  are aligned with the axis L 102  of the femur  102  when seen from the side. Note that, in the surgical device  70 , the medullary cavity rod  72  may be omitted. 
     Next, the surgeon uses a measurement instrument  77  in order to check the orientation of the medullary cavity rod  72  in the valgus angle direction θ 1 .  FIG. 12  is a front elevational view showing a surgical device  78  and the like. Referring to  FIG. 12 , the surgical device  78  has the measurement instrument  77 , the medullary cavity rod  72 , and the valgus alignment guide  73 . 
     The measurement instrument  77  has the laser application portion  15  and a connecting portion  79 . 
     In the measurement instrument  77 , the laser application portion  15  is configured to apply a laser beam L 35  in order to measure the positional relationship between a reference axis L 100 , which passes through the bone head center  102   a  of the femur  102  and the knee joint center  105  when seen from the front, and the medullary cavity rod  72  that is used in artificial knee joint implant placement surgery. 
     In this embodiment, the laser application portion  15  is installed on the body member  74  of the valgus alignment guide  73  so that the laser beam L 35  extends toward the bone head center  102   a  of the patient when seen from the front. The laser application portion  15  is supported by the body member  74  via the connecting portion  79 , and the application face  17  of the laser application portion  15  faces the bone head center  102   a  side of the patient  100 . 
     The connecting portion  79  is an L-shaped attachment member, for example. One end of the connecting portion  79  is fixed to the body member  74 . The other end of the connecting portion  79  opposes the distal part  102   b  of the femur  102  in the front-rear direction Z 1  (a direction perpendicular to the page of  FIG. 12 ). The casing  16  of the laser application portion  15  is fixed to the other end of the connecting portion  79 . 
     The laser application portion  15  is configured to apply the laser beam L 35  in order to indicate the bone head center  102   a  of the femur  102 , in a state of being supported by the body member  74  of the valgus alignment guide  73  via the connecting portion  79 . Note that the laser application portion  15  is configured to radially emit the laser beam when seen from the side. Thus, the laser beam L 35 , which extends in the front-rear direction Z 1 , is applied to a plurality of portions on the skin surface of the leg of the patient  100 . 
     In this case, for example, the surgeon measures the valgus angle, i.e. the angle formed between the laser beam L 35  and the medullary cavity rod  72  when the patient  100  is seen from the front. 
     Next, the surgeon fixes the guide member  73   a  to the distal part  102   b  of the femur  102 , with the guide member  73   a  attached to the valgus alignment guide  73 . Thereafter, the surgeon removes the valgus alignment guide  73  and the medullary cavity rod  72  from the femur  102 . The surgeon then cuts the bone at the distal part  102   b  using the cutter  6 , in a state where the cutter  6  has been passed through a slit hole  73   b  in the guide member  73   a  that is fixed to the distal part  102   b  of the femur  102 . Thus, the main face  102   d  of the cut-bone face  102   c  is formed in the distal part  102   b  of the femur  102 . 
       FIG. 13  is a front elevational view illustrating a procedure for checking a gap G between the main face  102   d  of the cut-bone face  102   c  of the femur  102  and the cut-bone face  101   d  of the tibia  101 . Referring to  FIG. 13 , the surgeon forms the main face  102   d  of the cut-bone face  102   c  on the femur  102 , and thereafter measures the gap G between the cut-bone face  101   d  of the tibia  101  and the main face  102   d . This gap G is measured using the surgical device  80 . 
     The surgical device  80  has a measurement instrument  81  and a spacer  82 . 
     The spacer  82  is a jig for installing the artificial knee joint implant  31  in the body of the patient  100 , and is an example of an “instrument to be used in implant placement surgery” according to the present invention. The spacer  82  is a plate-shaped member having a predetermined thickness. 
     The surgeon selects a spacer  82  that fits the gap G, which has been determined through pre-surgery planning, from among a plurality of spacers  82 , which are prepared in advance and have different thicknesses. The spacer  82  is arranged between the main face  102   d  of the cut-bone face  102   c  of the femur  102  and the cut-bone face  10   d  of the tibia  101 . An extension portion  83 , which has a protruding shape extending from the spacer  82 , is provided in a peripheral portion of the spacer  82 . 
     When the surgeon measures the gap G using the spacer  82 , the bone head center  102   a  of the patient  100 , the knee joint center  105 , and a leg joint center  107  need to be aligned with one another in a straight line when seen from the front. This positional relationship is measured by the measurement instrument  81 . The measurement instrument  81  has two laser application portions  15  and a connecting portion  84 . 
     In the measurement instrument  81 , the laser application portions  15  are configured to apply laser beams L 36  in order to measure the positional relationship between the femur  102 , the tibia  101 , and the spacer  82  that is used in artificial knee joint implant placement surgery. In this embodiment, the surgeon checks the alignment (arrangement of the bone head center  102   a , the knee joint center  105 , and the leg joint center  107 ) and the gap G, using the laser beams L 36 . 
     In this embodiment, the application faces  17  of the two laser application portions  15  are arranged in opposite orientations, and apply the laser beams L 36  that extend in the up-down direction X 1  when seen from the front. In this embodiment, the laser application portions  15  are installed in the extension portion  83  of the spacer  82  so that the laser beams L 36  pass through the bone head center  102   a  of the femur  102  and the leg joint center  107  when seen from the front. The laser application portions  15  are supported by the extension portion  83  of the spacer  82  via the connecting portion  84 , which has a block shape. 
     The two laser application portions  15  are configured to apply the laser beams L 36  in order to indicate the bone head center  102   a  and the leg joint center  107 , in a state of being supported by the extension portion  83  of the spacer  82  via the connecting portion  84 . Note that the laser application portions  15  are configured to radially emit the laser beams L 36  when seen from the side. Thus, the laser beams L 36 , which extend along the up-down direction X 1  side, are applied to a plurality of portions on the skin surface on a front face of the leg of the patient  100 . 
     In this case, the surgeon adjusts the position of the spacer  82  so that the bone head center  102   a , the knee joint center  105 , and the leg joint center  107  are arranged substantially in a straight line when seen from the front. The surgeon checks the gap G in this state. 
     Note that an L-shaped connecting portion  85  may be used instead of the connecting portion  84 , as shown in  FIG. 14 . In this case, one end of the connecting portion  85  is fixed to the extension portion  83 . The other end of the connecting portion  85  is arranged on a side of the spacer  82  in the left-right direction Y 1 . The two laser application portions  15 ,  15  held at the other end of the connecting portion  85  are configured to apply the laser beams L 36  to indicate the bone head center  102   a  and the leg joint center  107 . Note that, in this case, the laser application portions  15  are configured to radially emit the laser beams L 36  when seen from the front. Thus, the laser beams L 36 , which extend in the up-down direction X 1 , are applied to a plurality of portions on the skin surface on a side face of the leg of the patient  100 . 
     After checking the gap G, the surgeon fixes a sizer member  92 , which is shown in  FIG. 15 , to the distal part  102   b  of the femur  102 . 
       FIG. 15  is a perspective view showing the main points to illustrate a procedure for fixing the sizer member  92  to the distal part  102   b  of the femur  102 . Referring to  FIG. 15 , the sizer member  92  is a portion of a surgical device  90 . 
     The surgical device  90  has a measurement instrument  91  and the sizer member  92 . 
     The sizer member  92  is a member that is to be installed in the distal part  102   b  of the femur  102  of the patient, via pin members  93 . The sizer member  92  is a jig for installing the artificial knee joint implant  31  in the body of the patient  100 , and is an example of the “instrument to be used in implant placement surgery” according to the present invention and is also an example of the “jig”. 
     The sizer member  92  is formed as a member that extends in the front-rear direction Z 1 , in a state of being fixed to the main face  102   d  of the cut-bone face  102   c  in the distal part  102   b  of the femur  102 . A pair of pin holes  94  are formed in the sizer member  92 . The pin holes  94  are formed as holes into which the pin members  93  are inserted. These pin members  93  are driven into the main face  102   d  of the cut-bone face  102   c  in the distal part  102   b , in a state of having been inserted in the pin holes  94 . That is to say, the sizer member  92  is used to position the pin members  93 . 
     The position of the sizer member  92  relative to the femur  102  is measured by the measurement instrument  91 . The measurement instrument  91  has the laser application portion  15  and a connecting portion  95 . 
     In the measurement instrument  91 , the laser application portion  15  is configured to apply a laser beam L 37  in order to measure the positional relationship between the femur  102  and the sizer member  92  that is used in artificial knee joint implant placement surgery. 
     In the measurement instrument  91 , for example, the laser application portion  15  is installed in the sizer member  92  so that the laser beam L 37 , which illuminates a projection plane (the main face  102   d ) in a cross shape, strikes the main face  102   d . The laser application portion  15  is supported by the sizer member  92  via the connecting portion  95 , which has a block shape, and the application face  17  of the laser application portion  15  faces the main face  102   d  of the femur  102  of the patient  100 . 
     The laser application portion  15  is configured to apply the laser beam L 37  having a cross shape in order to measure the positional relationship between the main face  102   d  of the cut-bone face  102   c  and the sizer member  92 , in a state of being supported by the sizer member  92  via the connecting portion  95 . 
     In this case, the surgeon adjusts the position of the sizer member  92  relative to the main face  102   d  of the cut-bone face  102   c , using the laser beam L 37  as a mark. After completing the positioning of the sizer member  92  relative to the main face  102   d , the surgeon inserts the pin members  93  into the pin holes  94  of the sizer member  92 , and fixes these pin members  93  to the femur  102 . Next, the surgeon removes the sizer member  92  from the pin members  93 . Thereafter, the surgeon attaches a guide member  122 , which is shown in  FIG. 16 , to the pin members  93  (the main face  102   d  of the cut-bone face  102   c  of the femur  102 ). 
       FIG. 16  is a side view showing the main points to illustrate a procedure for installing the guide member  122  in the distal part  102   b  of the femur  102 . Referring to  FIG. 16 , the guide member  122  is a member to guide the cutter  6  in order to further form, in the distal part  102   b  of the femur  102 , the faces in the cut-bone face  102   c  other than the main face  102   d , i.e. the pair of inclined faces  102   e  and  102   f  and the pair of opposing faces  102   g  and  102   h . The guide member  122  is a portion of a surgical device  120 . 
     The surgical device  120  has a measurement instrument  121  and the guide member  122 . 
     The guide member  122  is a jig for installing the artificial knee joint implant  31  in the body of the patient  100 , and is an example of the “instrument to be used in implant placement surgery” according to the present invention and is also an example of the “jig”. 
     The guide member  122  is a plate-shaped member. A pair of pin holes  123  (one of the pin holes  123  is not shown in  FIG. 16 ) are formed in the guide member  122 . Pin members  93  are inserted in the respective pin holes  123 , and the guide member  122  is thus supported at the distal part  102   b  of the femur  102  via the pin members  93 . A plurality of slit holes  122   a ,  122   b ,  122   c , and  122   d  are formed in the guide member  122 . 
     The slit holes  122   a ,  122   b ,  122   c , and  122   d  are formed so as to pass through the guide member  122 . The slit holes  122   a ,  122   b ,  122   c , and  122   d  are provided as portions that guide displacement of the cutter  6  when the pair of inclined faces  102   e  and  102   f  and the pair of opposing faces  102   g  and  102   h  of the cut-bone face  102   c  are formed, respectively. 
     The orientation of the guide member  122  relative to the femur  102  is measured by a measurement instrument  121 . The measurement instrument  121  has the laser application portion  15  and a connecting portion  124 . 
     In the measurement instrument  121 , the laser application portion  15  is configured to apply a laser beam L 38  in order to measure the positional relationship between the femur  102  and the guide member  122  that is used in artificial knee joint implant placement surgery. 
     In the measurement instrument  121 , for example, the laser application portion  15  is installed on the guide member  122  so that the laser beam L 38  is applied to a side face of the leg of the patient  100 . The laser application portion  15  is supported by the guide member  122  via the connecting portion  124 , and the application face  17  of this laser application portion  15  faces the side face of the leg of the patient  100 . The connecting portion  124  is an L-shaped member, for example, and holds the casing  16  of the laser application portion  15 . 
     The laser application portion  15  is configured to apply a laser beam L 38  in order to measure the positional relationship between the guide member  122  and the femur  102 , in a state of being supported by the guide member  122  via the connecting portion  124 . 
     In this case, the laser beam L 38  extends in the up-down direction X 1 . The laser application portion  15  is configured to radially emit the laser beams L 38  when seen from the front. Thus, the laser beam L 38 , which extends along the up-down direction X 1  side, is applied to a plurality of portions on the skin surface on the side face of the leg of the patient  100 . The surgeon adjusts the orientation of the guide member  122  relative to the main face  102   d  of the cut-bone face  102   c , using the laser beam L 38  as a mark. Next, the surgeon sequentially inserts the cutter  6  into the slit holes  122   a ,  122   b ,  122   c , and  122   d  of the guide member  43 . As a result, the pair of opposing faces  102   g  and  102   h  and the pair of inclined faces  102   e  and  102   f  are formed in the distal part  102   b  of the femur  102 . Thereafter, the surgeon removes the pin members  93  and the guide member  122  from the distal part  102   b  of the femur  102 . Thus, the operation to form the cut-bone face  102   c  in the distal part  102   b  of the femur  102  is completed. 
     As described above, in the measurement instruments  41 ,  56 ,  61 ,  71 ,  77 ,  81 ,  91 , and  121  according to the embodiments, the laser application portion  15  is configured to apply the laser beams L 31  to L 38  to measure the positional relationship concerning the tibia  101  or the femur  102  of the patient  100 . With this configuration, the surgeon does not need to hold a heavy item, such as a measurement rod, in order to measure the positional relationship concerning the tibia  101  or the femur  102  of the patient  100 . Accordingly, it is possible to reduce the burden on the surgeon when measuring the positional relationship concerning the tibia  101  or the femur  102 . In addition, the laser beams L 31  to L 38  can be formed in a thinner line than a measurement rod. Accordingly, the laser beams L 31  to L 38  can be more readily and accurately applied to the leg of the patient. As a result, the surgeon can more readily perform a measurement operation using the measurement instruments  41 ,  56 ,  61 ,  71 ,  77 ,  81 ,  91 , and  121 . 
     In the measurement instruments  41 ,  56 ,  61 ,  71 ,  77 ,  81 ,  91 , and  121 , the laser application portion  15  is configured to apply the laser beams L 31  to L 38  in order to measure the positional relationships between the guide member holder portion  42 , the drill  62 , the valgus alignment guide  73 , the spacer  82 , the sizer member  92 , and the guide member  122 , which serve as the instruments, and the corresponding tibia  101  or the femur  102 . With this configuration, in artificial knee joint implant placement surgery, the surgeon can more readily measure the positional relationships between the above respective instruments and the tibia  101  or the femur  102  of the patient. 
     The guide member holder portion  42 , the drill  62 , the valgus alignment guide  73 , the spacer  82 , the sizer member  92 , and the guide member  122  are jigs to install an artificial knee joint implant in the body of the patient. With this configuration, in the case of, for example, temporarily installing the guide member holder portion  42 , the valgus alignment guide  73 , the spacer  82 , the sizer member  92 , and the guide member  122  that are used in artificial knee joint implant placement surgery, on the tibia  101  or the femur  102  of the patient  100 , the surgeon can more readily measure the relative positions between the tibia  101  or the femur  102  of the patient  100  and the above jigs. 
     In the measurement instrument  41 , the laser application portion  15  is configured to apply the laser beam L 31  in order to measure the parallelism between the first rod  46  and the tibia  101 , in a state of being supported by the guide member holder portion  42  via the connecting portion  51 . With this configuration, in artificial knee joint implant placement surgery, the surgeon can more readily measure the parallelism between the first rod  46  of the guide member holder portion  42  and the tibia  101 . In addition, the laser application portion  15  is installed on the guide member holder portion  42 . Thus, the laser application portion  15  is held in a stable orientation by the guide member holder portion  42 . Accordingly, the surgeon can more accurately measure positions using the laser beam L 31  in a state where the position of the laser beam L 31  is less likely to shift, unlike in the case of a configuration in which, when the surgeon uses a measurement rod instead of the laser application portion  15  and holds the measurement rod, the measurement rod position is likely to shift. 
     In the measurement instrument  56 , The laser application portion  15  is configured to apply the laser beam L 32  in order to measure the bone-cutting position in the proximal part  101   a  of the tibia  101 . With this configuration, in artificial knee joint implant placement surgery, the surgeon can more readily and accurately measure the bone-cutting position in the proximal part  101   a  of the tibia  101 . 
     In the measurement instrument  61 , The laser application portion  15  is configured to apply a laser beam L 33  in order to measure the coaxiality between the drill  62  and the femur  102 , in a state of being supported by the drill  62  via the connecting portion  65 . With this configuration, in artificial knee joint implant placement surgery, the surgeon can more readily measure the coaxiality between the distal part  102   b  of the femur  102  and the drill  62 . In addition, the laser application portion  15  is installed in the drill  62 . Thus, the laser application portion  15  is held in a stable orientation by the drill  62 . As a result, the surgeon can more accurately measure positions using the laser beam L 33  in a state where the position of the laser beam L 33  is less likely to shift. 
     In the measurement instrument  71 , the laser application portion  15  is configured to apply the laser beam L 34  in order to measure the positional relationship between the valgus alignment guide  73  and the femur  102 , in a state of being supported by the valgus alignment guide  73  via the connecting portion  76 . With this configuration, in artificial knee joint implant placement surgery, the surgeon can more readily measure the positional relationship between the distal part  102   b  of the femur  102  and the valgus alignment guide  73 . In addition, the laser application portion  15  is installed on the valgus alignment guide  73 . Thus, the laser application portion  15  is held in a stable orientation by the valgus alignment guide  73 . Accordingly, the surgeon can more accurately measure positions using the laser beam L 34  in a state where the position of the laser beam L 34  is less likely to shift, unlike in the case of a configuration in which, when the surgeon uses a measurement rod instead of the laser application portion  15  and holds the measurement rod, the measurement rod position is likely to shift. 
     In the measurement instrument  77 , the laser application portion  15  is configured to apply the laser beam L 35  in order to indicate the bone head center  102   a  of the femur  102 , in a state of being supported by the valgus alignment guide  73  via the connecting portion  79 . With this configuration, the surgeon can more readily measure the positional relationship between the bone head center  102   a  of the femur  102  and the valgus alignment guide  73 . In addition, the laser application portion  15  is held in a stable orientation by the valgus alignment guide  73 . Accordingly, the surgeon can more accurately measure positions using the laser beam L 35  in a state where the position of the laser beam L 35  is less likely to shift, unlike in the case of a configuration in which, when the surgeon uses a measurement rod instead of the laser application portion  15  and holds the measurement rod, the measurement rod position is likely to shift. 
     In the measurement instrument  81 , the laser application portions  15  are configured to apply the laser beams L 36  in order to indicate the bone head center  102   a  of the femur  102  and the leg joint center  107 , in a state of being supported by the spacer  82  via the connecting portion  84 . With this configuration, when checking, for example, that the knee joint center  105 , the bone head center  102   a  of the femur  102 , and the leg joint center  107  are arranged in a straight line (alignment), the surgeon can more readily measure the alignment using the laser beams L 36  as marks. In addition, the laser application portions  15  are held in a stable orientation by the spacer  82 . Accordingly, the surgeon can more accurately measure positions using the laser beams L 36  in a state where the positions of the laser beams L 36  are less likely to shift, unlike in the case of a configuration in which, when the surgeon uses a measurement rod instead of the laser application portion  15  and holds the measurement rod, the measurement rod position is likely to shift. 
     In the measurement instrument  91 , the laser application portion  15  is configured to apply the laser beam L 37  in order to measure the positional relationship between the main face  102   d  of the cut-bone face  102   c  and the sizer member  92 , in a state of being supported by the sizer member  92  via the connecting portion  95 . With this configuration, the surgeon can more readily measure the positional relationship between the main face  102   d  of the cut-bone face  102   c  and the sizer member  92 . In addition, the laser application portion  15  is held in a stable orientation by the sizer member  92 . As a result, the surgeon can more accurately measure positions using the laser beam L 37  in a state where the position of the laser beam L 37  is less likely to shift. 
     In the measurement instrument  121 , the laser application portion  15  is configured to apply the laser beam L 38  in order to measure the positional relationship between the guide member  122  and the distal part  102   b , in a state of being supported by the guide member  122  via the connecting portion  124 . With this configuration, the surgeon can more readily measure the positional relationship between the cut-bone face  102   c  and the guide member  122 . In addition, the laser application portion  15  is held in a stable orientation by the guide member  122 . As a result, the surgeon can more accurately measure positions using the laser beam L 38  in a state where the position of the laser beam L 38  is less likely to shift. 
     Although the embodiments of the present invention have been described above, the present invention is not limited to those embodiments, and various modifications may be made within the scope of claims. For example, the following modifications may be implemented. 
     (1) The above embodiments have been described while taking, as examples, the modes in which the laser application portion  15  is used in artificial leg joint implant placement surgery, spine correction surgery, and artificial knee joint implant placement surgery. However, this need not be the case. The laser application portion  15  may be used in surgery other than the aforementioned types of surgery. 
     (2) The above embodiments have been described while taking, as examples, the modes in which the laser application portion  15  is connected to the instruments using connecting portions. However, this need not be the case. The laser application portion  15  may be directly attached to the instruments. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be widely applied as a surgical measurement instrument. 
     DESCRIPTIONS OF REFERENCE NUMERALS 
     
         
         
           
               1 ,  23 ,  41 ,  56 ,  61 ,  71 ,  77 ,  81 ,  91 ,  121  Surgical measurement instrument 
               2  Artificial leg joint implant 
               7  Tibia distal part cutting guide (instrument to be used in implant placement surgery/jig) 
               15  Laser application portion 
               18 ,  26 ,  51 ,  57 ,  65 ,  76 ,  79 ,  84 ,  95  Connecting portion 
               24  Fixed jig 
               31  Artificial knee joint implant 
               42  Guide member holder portion (instrument to be used in implant placement surgery/jig) 
               43  Guide member (instrument to be used in implant placement surgery/jig) 
               44  Clamp (distal side portion of guide member holder portion) 
               46  First rod (rod) 
               50  Spike (proximal side portion of guide member holder portion) 
               62  Drill (instrument to be used in implant placement surgery/jig) 
               72  Medullary cavity rod 
               73  Valgus alignment guide (instrument to be used in implant placement surgery/jig) 
               82  Spacer (instrument to be used in implant placement surgery/jig) 
               92  Sizer member (instrument to be used in implant placement surgery/jig) 
               101  Tibia (bone of patient) 
               101   a  Proximal part of tibia 
               101   b  Distal part of tibia 
               102  Femur (bone of patient) 
               102   a  Bone head center 
               102   b  Distal part of femur 
               103  Leg joint 
               105  Knee joint center 
               106  Knee joint 
               110  Spine 
               111  Vertebra (bone of patient) 
               112  Pelvis 
               113  Reamer hole 
             L 1 , L 2 , L 31  to L 38  Laser beam 
             θ 1  Valgus angle direction