Patent Abstract:
A detachable cutting tool capture for a cutting block provides a guide surface to convert an open surface block into a slotted block for plying a surgical cutting tool along the surfaces of the guide during a surgical procedure such as a bone resection with a blade. A magnetized catch provides a convenient device for securing the capture and the block together. A triangular cam on the detachable capture in conjunction with a “v” groove in a magnetized lever of the catch permits a pin of the catch to be selectively retracted from or extended into an aperture of the block when the lever is rotated so that when the pin extends, it serves to secure the combined apparatus for cutting. Mating surfaces of the block and capture provide additional structure for supporting the capture with the block to secure them from relative movement.

Full Description:
FIELD OF THE INVENTION 
   The present invention relates to surgical devices. More particularly, the invention involves a cutting block or guide with a detachable cutting instrument capture for precision cutting during a surgical procedure. 
   BACKGROUND OF THE INVENTION 
   Precision cutting instruments that promote accuracy are necessities in surgical procedures. For example, consider total knee arthroplasty. Total knee arthroplasty involves the replacement of portions of the patella, femur and tibia with artificial components. During the procedure, a proximal portion of the tibia and a distal portion of the femur are cut away (resected) and replaced with artificial components. The posterior surface of the patella may also be resected and resurfaced. As used herein, when referring to bones or other body parts, the term “proximal” means closest to the heart and the term “distal” means more distant from the heart. When referring to tools and instruments, the term “proximal” means closest to the practitioner and the term “distal” means distant from the practitioner. 
   There are several types of knee prostheses known in the art. One type is sometimes referred to as a “resurfacing type”. In these prostheses, the articular surface of the distal femur and proximal tibia are “resurfaced” with respective metal and plastic condylar-type articular bearing components. During primary knee replacement, these knee prostheses require minimal and precise bone resection to accommodate the components within the boundaries of the available joint space. 
   Often, due to normal wear over time, the prosthetic knee must be replaced via a procedure known as revision surgery. One method for accomplishing revision arthroplasty involves the use of several cutting blocks which may be aligned with reference to the IM canal. 
   During revision surgery, after the primary prosthetic is removed, the medullary canal is reamed and an intramedulary rod or the reamer itself is tapped in place with a mallet. A distal resection guide is attached to the reamer or the intramedulary rod and distal resection is completed via slots in the guide. The distal resection guide is removed from the rod or reamer and another cutting block is attached for the typical anterior-posterior resection and the anterior and posterior and chamfer resections. 
   The rotational alignment of the femoral component is critical to ensure correct patellar tracking. Since the posterior condyles are no longer present, this cutting block must be carefully aligned relative to the femoral epicondyles where the collateral ligaments are attached. 
   After anterior/posterior and chamfer resections are completed, if the posterior cruciate ligament is being sacrificed, the cutting block is removed and a fourth cutting block is attached to the reamer or rod in order to accomplish an intercondylar box resection. Of course, the box resection guide can be incorporated into the same guide used to make the A/P and chamfer cuts. 
   Following preparation of the femur, similar procedures are performed on the proximal tibia. For example, a reamer or intramedulary rod is installed with a mallet. Preferably, a resection block is pinned to the anterior tibia and a proximal portion of the tibia is resected. 
   It will be appreciated that given the use of multiple cutting blocks in the described procedure the design of each device should not also add to the complexity of the operation. Generally, such cutting blocks used in surgical procedures may be characterized as open or slotted. In an open block, one surface serves as an open face guide to rest or ply a cutting instrument. In contrast, a slotted block provides an envelope, or “slot” having multiple surfaces within which the block captures the cutting tool or blade to help maintain the blade tracking straight or in desired configuration or arrangement during cutting through the envelope or slot. 
   In theory, open face blocks induce a greater margin of error than slotted blocks since it is more dependent on surgeon skill to maintain the cutting tool aligned with the guiding surface (e.g., keeping the blade flat against the block). Moreover, a substantially open cutting block may be easier to clean or sterilize when compared to a slotted block. Nevertheless, whether an open face or slotted cutting block is used during surgery is a matter of surgeon preference. To accommodate physician preference it may be appropriate for a medical institution or hospital to have both types of blocks available for the many different procedures for which blocks are designed. However, a drawback of having both slotted and open-face blocks is that it doubles the inventory required to meet the institution&#39;s needs. This means more sterilization procedures, more storage issues and ultimately higher costs. 
   SUMMARY OF THE INVENTION 
   This apparatus conveniently joins an open-face cutting block and a capture, thus giving the user the option to use either open face guide or a slotted guide during a surgical procedure. In one embodiment, the apparatus includes a cutting block which has a guiding surface to guide a surgical cutting instrument. The apparatus further includes a detachable capture which also includes a guiding surface to guide a surgical cutting instrument. The capture is configured for removable coupling with the cutting block. Preferably, the capture includes a biased catch having a biasing force such as a magnetized catch for magnetically securing the cutting block and capture together or a catch with a spring configured for securing them with an elastic force. In one embodiment, the capture includes a projection for gradually changing the catch from a secured to an unsecured position. The assembled apparatus may be used as a slotted guide during a surgical procedure such as a bone resection. 
   In one embodiment of the invention, an apparatus for guiding an oscillating saw blade for resecting bone includes an open face means for supporting a saw blade during a resection procedure of a bone. The open face means may be temporarily fixed to a bone for the procedure. A detachable capture means converts the open face means to a slotted guide. The apparatus also includes a securing means for removably fixing the capture and the open face means into a coupled position. This preferably includes a rib and a slotted tab corresponding with the rib such that when the rib is inserted in the slotted tab in the coupled position, movement of the detachable capture means is prevented with respect to the open face means in any direction along a first axis. The securing means further includes a plate and mating surfaces corresponding with the plate such that when the plate is inserted between the mating surfaces in the coupled position, movement of the detachable capture means is impeded with respect to the open face means in any direction along a second axis being perpendicular to the first axis. Finally, the securing means includes a pin aperture and a traversing pin corresponding with the pin aperture so that when the pin is inserted in the pin aperture in the coupled position, movement of the detachable capture means is impeded with respect to the open face means. 
   In still another embodiment, an apparatus for guiding a cutting tool during a surgical procedure includes a cutting block having a surface for guiding a cutting tool. The cutting block is configured to be fixable to bone for making a cut in the bone. The detachable capture has another surface to guide the cutting tool. The detachable capture is configured for coupling with the cutting block in a coupled position in which the surfaces combine to form an envelope for the cutting tool. The apparatus also includes a cam with a configuration to selectively secure and unsecure the cutting block and the detachable capture in the coupled position. A catch corresponds with the cam for securing the detachable capture and the block in the coupled position. In this regard, the catch includes a reciprocal portion corresponding to a projection of the cam such that when the reciprocal portion and projection coincide, the catch secures the cutting block and the detachable capture in the coupled position. Moreover, the catch includes a non-reciprocal portion corresponding to the projection of the cam such that when the non-reciprocal portion and projection coincide, the detachable capture and the cutting block are not secured. In a preferred embodiment, the reciprocal portion of the catch has a triangular shape. 
   In yet another embodiment, the cutting guide apparatus for a surgical procedure has a cutting block with a first open face surface for guiding a surgical instrument. A detachable capture includes a second open face surface for guiding an instrument for a surgical procedure. The detachable capture is configured to couple with the cutting block to form a slotted guide from the first open face surface of the cutting block and the second open face surface of the detachable capture. 
   Additional aspects of the invention will be apparent from an understanding of the details contained in the detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For the purposes of illustrating the invention, there are shown in the drawings, a form that is presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. 
       FIG. 1  is perspective view of an embodiment of a modular capture of the invention; 
       FIG. 2  is another perspective view of an embodiment of a modular capture of the invention; 
       FIG. 3  is a further perspective view of an embodiment of a modular capture of the invention; 
       FIG. 4  is an additional perspective view of an embodiment of a modular capture of the invention; 
       FIG. 5  is a section of an embodiment of a modular capture of the invention taken along line B--B of  FIG. 11  with the catch raised on its cam in an unsecured position; 
       FIG. 6  is a side elevation view of an embodiment of a modular capture with the catch raised on its cam in its unsecured position; 
       FIG. 7  is a top plan view of an embodiment of a modular capture with the catch lowered in a secured position; 
       FIG. 8  is a side elevation view of an embodiment of a modular capture with the catch lowered in a secured position; 
       FIG. 9  is a bottom plan view of an embodiment of a modular capture; 
       FIG. 10  is a front elevation view of an embodiment of a modular capture with the catch lowered in a secured position; 
       FIG. 11  is a front elevation view of an embodiment of a modular capture with the catch raised on the cam in its unsecured position; 
       FIG. 12  is a front elevation view of an embodiment of a modular capture coupled to a cutting block with the catch raised on the cam in an unsecured position; 
       FIG. 13  is a side elevation view of the modular capture coupled to a cutting block of  FIG. 12  in an unlocked position; 
       FIG. 14  is a section view of the modular capture coupled to a cutting block of  FIG. 12  taken along line C--C; 
       FIG. 15  is a front elevation of an embodiment of a cutting block to which a modular capture may be coupled; 
       FIG. 16  is a top elevation view showing an alternative embodiment of the capture having a spring-biased locking mechanism; 
       FIG. 17  is a front elevation illustration of the capture of  FIG. 16 ; and 
       FIG. 18  is a sectional view of the capture of  FIG. 16  taken along line D--D of  FIG. 17 . 
   

   DETAILED DESCRIPTION 
   The invention generally involves a detachable or modular capture apparatus that attaches to an open-face cutting block and provides a slot for guiding a cutting tool such as an oscillating saw blade to make a bone cut. The device preferably converts the open-face cutting block to a slotted block, thus giving a user the option to use either. 
   With particular reference to  FIGS. 1 through 11 , in a preferred embodiment of the detachable capture  2 , the device consists of a main housing  4  and a locking mechanism or catch  6 . The preferred embodiment of the catch  6  includes a locking lever  8 , locking pin  10 , and integrated magnet  12  that can bias the catch  6  in a locked or unlocked position. 
   To prevent the catch  6  from disassembling from the main housing  4 , the locking pin  10  of the catch  6  preferably consists of two coaxial cylindrical portions. The first cylindrical portion  16  has a larger diameter than the second cylindrical portion  18  to form a shoulder  20 . The main housing  4  also includes a corresponding counter-bored hole  22 . The counter-bored hole  22  and the locking pin  10  are closely dimensioned to allow translation of the pin  10  along the axis of the counter-bored hole  22 . The close dimensioning also permits rotation of the pin  10  in the counter-bored hole  22 . However, the pin shoulder  20  prohibits disassembly in one direction as a result of the corresponding diameters of the counter-bored hole  22 . 
   The lever  8  also impedes removal of the pin  10  from the main housing  4  of the detachable capture  2  when the lever  8 , which is larger than the counter-bored hole  22 , is fixed to the pin  10 . For convenience, the pin  10  is press fit with the lever  8 . In this regard, the lever  8  has an upper lever surface  24  and a lower lever surface  26 , which may be parallel to each other. A locking pin hole  28 , preferably perpendicular to the upper surface  24 , optionally extends from the upper surface to the lower surface  26 . The locking pin hole  28  is dimensioned to accept the second cylindrical portion  18  of locking pin  10  by press fitting. 
   As a result, depending on the length of the pin  10 , the locking lever  8  may be employed as a handle to extend or retract the locking pin  10  through the counter-bored hole  22  of the main housing  4 , but due to the impediments of the lever  8  and the pin shoulder  20 , the catch  6  remains movable or traversable but also a component of the main housing  4 . Thus, the length of the locking pin  10  is chosen such that when it is housed in the counter-bored hole  22  and placed perpendicularly through a lower surface of main housing  4 , it extends through the entire thickness of main housing  4  and into the lever  8 . 
   With regard to the magnetization of the catch  6 , for preference a magnet  12  is housed in a magnet aperture  30 . The magnet aperture  30  may be machined adjacent and parallel to locking pin hole  28  of locking lever  8 . The magnet aperture  30  is counter-bored, extending from upper surface  24  of locking lever  8  to a depth that is less than the overall thickness of locking lever  8  leaving a thin wall to allow the magnet to be in close proximity to the main housing  4 . A cylindrical cap  32  is pressed fitted into the counter-bore magnet aperture  30  to preferably hermetically seal the magnet. Thus, the locking lever  8  may be made of non-magnetic material, such as titanium, or type  304  stainless steel. 
   Beneficially, a recessed or inwardly projecting “v” Groove  34  is machined on lower surface  26  of locking lever  8 . This inward projection is reciprocally configured and dimensioned to couple with a matching cam  36  on a surface of main housing  4  of the detachable capture  2  giving them a profile with the same shape. In the preferred embodiment, the cam  36  includes an outwardly projecting triangular section  38 . The locking lever  8 , also includes a non-reciprocal portion not matching the cam  36 . The locking lever  8 , when positioned over the cam  36  so that the “v” groove  34  and triangular section  38  of the cam  36  match, will magnetically attach with the lower lever surface  26  of the locking lever  8  to upper main surface  40  of the main housing  4 , extending the pin  10  outward from an opposing surface of the main housing. In this position, the triangular section  38  is received in the “v” groove of the lever. This secured position of the catch  6  is best viewed in the illustrations in  FIGS. 7 ,  8  and  10 . When a non-reciprocal portion of the locking lever  8  is rotated to a position over the projection of the cam  36 , the lower lever surface  26  gradually departs from upper main surface  40  of the main housing  4 , rising on the cam  36 , and thereby retracts the locking pin  10  into the main housing  4  at the opposing surface of the main housing  4 . This unsecured position of the catch  6  is best illustrated in  FIGS. 1 through 6  and  11  through  14 . 
   The main housing  4  includes an upper main surface  40  and a lower main surface  42 , which, is adjacent and parallel to upper main surface  40 . The lower main surface  42  may serve as part of a slotted guide or guide envelope for a cutting tool when coupled to a cutting block mated for the detachable capture  2 . The upper main surface  40  is formed of a magnetic material such that it will be attracted by the magnet  12  of the magnetized catch  6 . 
   Extending from the central region of lower main surface  42  is a raised pad  44  of constant thickness forming a step with lower main surface  42 . The raised pad  44  is chosen to be a preferred slot thickness for the cutting envelope formed when the detachable capture is coupled to the cutting block because the raised pad  44  will serve to separate the opposing surfaces of the formed cutting envelope. Optionally, the raised pad  44  may include a beveled end  45  to facilitate coupling of the capture  2  with a cutting block as the cutting block is positioned onto the cutting block. 
   Adjacent to lower main surface  42  is a tab  46  with a rectangular configuration. Tab  46  contains an upper tab surface  48  and a lower tab surface  50  to form a thickness and is connected to the main housing by a bridged portion  52 . Upper tab surface  48  and lower tab surface  50  of tab  46  are parallel with lower main surface  42  of main housing  4 . Tab  46  is bisected by a tab slot  54 , which extends from upper tab surface  48  to lower tab surface  50  of tab  46 . 
   As will be described in more detail herein, together the surfaces of the tab  46 , the surface of the raised pad  44 , and the catch  6  in conjunction with mating or corresponding features of a cutting block  56 , serve as a means for securing the detachable capture  2  with a cutting block to form a cutting envelope. 
   In this regard, the mating features of a preferred cutting block  56  that can be magnetically secured in a coupled position with the detachable capture  2  are illustrated in  FIGS. 12-15 . The cutting block  56 , which includes an open face guide  58  against which a cutting tool may ply, consists of a plate  60  having an upper plate surface  62  and a lower plate surface  64  which is adjacent and parallel with upper plate surface  62  and a central rib  66 , which is preferably perpendicular to upper plate surface  62 . As illustrated in the preferred embodiment, the upper plate surface  62  may serve as an open face guide  58 . The cutting block  56  also includes a pin aperture  68  sized and positioned to receive the locking pin  10  of the catch  6 . The surfaces of the plate  60 , the rib  66 , and pin aperture  68  serve as the mating features of the block for securing the capture and the block. 
   In an alternative embodiment of the capture, the catch  6  (with or without the magnet  12 ) may include a locking spring  13  to bias or further bias the pin  10 . In such an embodiment, the spring may be configured with the pin  10  or lever  8  to bias the catch  6  with an elastic force to remain in the locked position when the detachable capture  2  and cutting block  56  are coupled. An example of the embodiment with a spring is illustrated in  FIGS. 16 to 18 . As illustrated in  FIG. 18 , locking spring  13  is installed around the first cylindrical portion  18  of the locking pin  10 . Although other implementations are possible, in this example the locking spring  13  provides an elastic compression force between shoulder  20  of the locking pin  10  and the pin aperture of the main housing  4  to bias the locking pin  10  to extend from the main housing  4  into the pin aperture  68  of the cutting block  56 . Thus, when the lever  8  of the catch  6  is lifted from the upper main surface  40  of the main housing  4  or rotated to its unlocked position on the peak of the cam  36  as illustrated in  FIGS. 17 and 18  an elastic force is compressed into the spring providing a bias for its return to the locked position. As such, it will tend to return to the locked position unless the lever  8  is positioned on the peak of the cam  36 , out of the “v” grove  34  of the lever  6 . 
   In operation, the main housing  4  may be engaged with the cutting block  56  such that raised pad  44  and upper tab surface  48  of tab  46  straddle the plate. Thus, the raised pad  44  contacts the upper plate surface  62  and the upper tab surface  48  contacts the lower plate surface  64 . Similarly, tab  46  straddles the central rib  66  when the rib  66  resides in the tab slot  54 . Finally, the locking lever  8  may be rotated so that the “v” groove  34  of the lever is positioned over the triangular section  38  of the cam  36 . In this position, lever  8  may be lowered to magnetically attach to the upper main surface  40  of the main housing when the triangular section  38  enters the “v” groove  34 . Consequently, the locking pin  10  traverses to extend out of the main housing through the raised pad  44  to extend into and couple with the pin aperture  68 , thereby securing the cutting block  56  and the detachable capture in a coupled position. 
   When so assembled, movement of the main housing  4  with respect to the cutting block in the X-Y directions illustrated in  FIGS. 11  or  12  is limited only by the clearance that exists between mating surfaces. Thus, when the rib  66  is inserted in the tab slot  54 , the opposing surfaces of the tab slot  54  and rib  66  impede movement of the detachable capture  2  with respect to the cutting block  56  in any direction along the imaginary X axis illustrated by the X axis of  FIGS. 11  or  12 . Similarly, when the upper tab surface  48  of the tab  46  and the surface of the raised pad  44  straddle the plate, the opposing surfaces of the tab  46 , raised pad  44  and plate  60 , impede movement of the capture  2  with respect to the block  56  in any direction along the imaginary Y axis of  FIGS. 11  or  12 . The X and Y axes and the directions discussed above with respect to each are generally perpendicular to each other. 
   Finally, the insertion of the locking pin  10  into the pin aperture  68  prevents or impedes movement of the detachable capture  2  with respect to cutting block  56  in any direction along the imaginary Z axis illustrated in  FIG. 14 . Optionally, a surface of the bridge portion  52  and a side  53  of the plate (see in  FIG. 14 ) may mate so as to impede relative movement of the cutting block  56  and the detachable capture along a direction of the imaginary Z axis. With such contact between the side  53  of the plate  60  and the bridge portion  52 , a stop is provided to simplify alignment of the locking pin  10  with the pin aperture  68  for insertion. Generally, the Z axis and the directions of movement described above with respect to it are perpendicular to the X and Y axes of  FIG. 11  or  12 . 
   In this magnetically and/or elastically biased secured or locked position, the lower lever surface  26  of the locking lever  8  is in full contact with the upper main surface  40  of main housing  4 . With such contact, the locking lever  8  remains biased to the locked position by the magnetic force of magnet  12  and/or the elastic force of the locking spring  13 . 
   The cutting block  56  and main housing  4  when assembled are dimensioned such that a guide slot  70  is formed for guiding a cutting tool, (e.g., a saw blade) by the upper plate surface  62  and the lower main surface  42 . This guide slot  70  is illustrated in  FIG. 12 . Cutting block  56  may optionally include multiple plates which may be converted by a single detachable capture  2  simply by re-attaching the capture  2  in a different position with respect to different plates to create different envelopes or slotted guides. In the preferred embodiment, the block also includes an integrated guide slot  72 . When the capture is not assembled with the block, the upper plate surface  62  may be utilized as an open face cutting guide. Of course, for a resection procedure on bone as previously described, the block would also include a fixing device  74  to temporarily fix the block to the bone for the surgical cutting procedure. 
   To remove the capture  2 , the locking lever  8  is turned 90 degrees. When it rotates about the axis of counter-bored hole  22  in main housing  4 , the camming action of the “v” groove and triangular cam results in the entire locking lever  8  being forced away from upper main surface  40 , thus retracting the locking pin  10  into the main housing  4  which disengages it from the pin aperture  68  on cutting block  56 . Conveniently, the magnet  12  of the lever  8  holds the lever  8  at the peak of the cam  36  in an unlocked or unsecured position by a magnetic force to impede the lever  8  from unintentionally returning to the locked position of the cam  36 . 
   With such a design for a detachable capture, cleaning is made easier. For example, by virtue of the readily removable nature of the capture, complete open access to the guide surfaces of the slotted guide is permitted. Thus, such a design is easier to clean than an integral capture, retractable or otherwise. Moreover, in a cutting block as illustrated in  FIGS. 12-15 , where the capture may be installed in multiple positions on multiple open face guides of the cutting block, a single capture may be reused, cutting down on the number of parts which need to be cleaned. 
   The locking features and method of attachment allows the capture to be rapidly and easily secured to the cutting block with minimal risk of disassociation during use. The magnet provides a positive locking implementation. In conjunction with the cam and mating surfaces, the locking feature provides an ergonomic, self-aligning locking mechanism. 
   Moreover, with the preferred design, the capture can be made very small since the locking mechanism itself is very small and is centralized with respect to the width of the capture. A smaller capture allows the cutting block to also be made smaller. This is a benefit since the current trend is to make minimally invasive incisions thus requiring smaller instruments. Adding to the smaller size theme is the use of a magnet to bias the locking lever in the locked position. This results in a very low profile locking lever, a benefit compared to the use of springs which require more room. 
   Although the invention herein has been described with reference to a particular preferred embodiment, it is to be understood that this embodiment is merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. For example, one skilled in the art will recognize that the mating surfaces associated with the rib  66  and tab slot  54  can be optional since the pin  10 , when residing in a pin aperture  68  that closely corresponds with the surfaces of the pin  10 , can limit relative movement between the capture  2  and the cutting block  56  along two perpendicular axes (e.g., axes Z and X) being generally perpendicular to a remaining axis (e.g., the Y axis). Relative movement with respect to this remaining axis would still be limited by the mating surfaces of the plate  60 , the raised pad  44  and the upper tab surface  48  of the tab  46 . Other modifications will also be apparent. 
   Throughout the description and claims of this specification, forms of the word “comprise” including all variations of the word, such as “comprising” and “comprises”, are not intended to exclude other additives, components, integers or steps etc.

Technology Classification (CPC): 0