Abstract:
A device for taking length and depth measurements during surgery. The device comprises a first longitudinal member and a second longitudinal member telescopically positioned within the first longitudinal member. The second longitudinal member may have a front part connectable thereto. The front part may have an opening, a passageway, and a moveable piece in the passageway. The device may also have a sliding member for moving the moveable piece between a first position where a portion of the moveable piece is outside the front part to a second position where the entire moveable piece is within the front part. The first and second longitudinal member may be locked with respect to one another. The prevent invention also discloses methods of using the device to take length and depth measurements during surgery.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     The present application is a continuation of International Patent Application PCT/CH02/00071 filed Feb. 7, 2002, the entire content of which is expressly incorporated herein by reference thereto.  
       FIELD OF THE INVENTION  
       [0002]     The invention relates to a device for length and depth measurements in surgery and, in particular, a device for positioning through a borehole in a bone to measure the distance from one side of the bone to the other side of the bone.  
       BACKGROUND OF THE INVENTION  
       [0003]     Bone screws are commonly used in osteosynthetic repair of, for example, bone fractures. Frequently, bone screws are screwed into a bone perpendicular to its longitudinal axis. In so doing, the bone screws may penetrate into an opposite bone wall. However, the tip of the screw should not protrude excessively into the surrounding soft-tissue for this may result in irritation of or damage to the soft parts. An accurate determination of length of the borehole is therefore important for choosing the bone screw, which is to be inserted into a pre-drilled borehole.  
         [0004]     In previously known devices for measuring length or depth, a piston with a hook was introduced through a borehole and engaged an opposite bone wall on the soft-tissue side. Subsequently, a measuring sleeve was shifted on the piston in the direction of the bone surface until the front end of the measuring sleeve came into contact with this surface. However, in so doing, the danger exists that the hook may slip off the opposite bone wall and, consequently, the displacement of the measuring sleeve may pull the hook into the bone. This may result in incorrect length measurements and, consequently, may result in the selection of a bone screw of the incorrect length.  
         [0005]     The invention solves this problem and is designed to provide a length or depth measurement device, which enables a hook to extend beyond the opposite bone wall after the piston is moved into the borehole so that a positive connection to the bone can be achieved. Moreover, reading the length measurement does not have to occur in situ.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention comprises two telescopic parts disposed coaxially with a longitudinal axis. The first part may be constructed as a measuring piston and the second part may be constructed as a measuring sleeve. The measuring piston may be moved axially in a central borehole of the measuring sleeve and its front part may be inserted into a borehole in a bone. The measuring piston may have a tip at its front part, and may also comprise a movable arresting means, which may be disposed movably within the measuring piston, and a hook, which may be extended and retracted at the tip in a direction transverse to the longitudinal axis.  
         [0007]     In order to take measurements, the measuring piston may be inserted into a borehole in a bone while the measuring sleeve is in a retracted position and pushed therethrough until the tip protrudes beyond the opposing bone wall. Subsequently, the hook at the tip may be moved out of the front part. With the hook extended, the measuring piston may no longer be pulled out of the borehole and the device, as a whole, may no longer be withdrawn from the bone. Thereafter, the measuring sleeve may be moved on the measuring piston in the direction of the bone surface, until the front end of the measuring sleeve rests on the bone surface. At the same time, the bone may be clamped between the extended hook and the measuring sleeve. Finally, the hook may be retracted once again in a direction transverse to the longitudinal axis of the measuring piston, and the device may be pulled out of the borehole in the bone and removed from the field of the surgery.  
         [0008]     In a preferred embodiment of the inventive device, the measuring sleeve and the measuring piston may comprise locking means. The locking means may hold the measuring piston in a selected position relative to the measuring sleeve, so that the device may be removed from the bone and the length measurement may be read outside of the surgical field. This allows for easy reading of the length measurement outside of the surgical field. The operating surgeon may freely hold the device such that neither light reflection off the device nor the style/font of the measurement markings affect the surgeon&#39;s measurement readings.  
         [0009]     The advantages achieved by the present invention are apparent in that due to the present invention: 
        when the hook is extended, the measuring piston may be prevented from slipping off an opposite bone wall;     any unintentional movement of the measuring piston relative to the measuring sleeve may be prevented by a locking means, which may be disposed between the measuring piston and the measuring sleeve, and     the length measurement may not have to be read in situ and, thus, good readability may be achieved.        
 
         [0013]     In a further embodiment of the present invention, the arresting means may comprise a sliding element with an arresting mechanism, which may be moved coaxially with the longitudinal axis. At the front end of the sliding element, a rod having a wire may be mounted coaxially, with the wire forming an extended or retracted hook depending on the axial position of the sliding element. A curved or angled central borehole in the front part of the first part may result in the bending of the hook. The sliding element may be locked and unlocked by the arresting mechanism.  
         [0014]     In yet another embodiment of the present invention, the arresting means may comprise a screw, which may be rotated into or out of the first part parallel to the longitudinal axis. A rod with a wire may be mounted so that it is rotatable but not axially moveable about the longitudinal axis and coaxial with the longitudinal axis at the front end of the screw. Similar to the embodiment described above, the wire may form the extended or retracted hook depending on the axial position of the screw. In another embodiment, an arresting mechanism, similar to those used as part of a conventional commercial ballpoint pen, may be used along with a wire to form the hook at the tip of the first part.  
         [0015]     Further advantageous developments of the present invention are discussed in the further detail below.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The invention and further developments of the invention are explained in even greater detail in the following exemplary drawings. The present invention can be better understood by reference to the following drawings, wherein like references numerals represent like elements. The drawings are merely exemplary to illustrate certain features that may be used singularly or in combination with other features and the present invention should not be limited to the embodiments shown.  
         [0017]      FIG. 1  is a partial cross-sectional view of an embodiment of the device of the present invention;  
         [0018]      FIG. 2  is a cross-sectional view of an embodiment of the device of the present invention with a retracted hook;  
         [0019]      FIG. 3  is a cross-sectional view of the embodiment of the device of  FIG. 2  with the an extended hook;  
         [0020]      FIG. 4  is a cross-sectional view of an another embodiment of the device of the present invention;  
         [0021]      FIG. 5  is a partial cross-sectional view of another alternative embodiment of the device of the present invention;  
         [0022]      FIG. 6  is a partial cross-sectional view of yet another alternative embodiment of the device of the present invention; and  
         [0023]      FIG. 7  is a partial cross-sectional view of another embodiment of the device of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0024]     As shown in  FIG. 1 , the present invention comprises a first part  1  and a second part  2 , the first  1  part may be constructed as a measuring piston and the second part  2  may be constructed as a measuring sleeve. It should, however, be understood that those of ordinary skill in the art will recognize many modifications and substitutions which may be made to various elements of the present invention.  
         [0025]     The first part  1  may be moved parallel to the longitudinal axis  4  within a central borehole  20  in the second part  2 . Depending on the position of the first part  1  relative to the second part  2 , the tip  14  of the front part  3  of the first part  1  may protrude beyond the front end  22  of the second part  2 . The front part  3  may be introduced into a borehole  40  in a bone  41 , until the tip  14  protrudes beyond the bone portion  43  of the bone  41 . The arresting means  27  may be disposed within the first part  1  so that it may be displaced parallel to the longitudinal axis  4 . A hook  6  may be connected with the arresting means  27  and may be extended from or retracted into the front part  3  transversely to the longitudinal axis  4 , such that the front part  3  may no longer be pulled out of the borehole  40  in the bone  41 . Furthermore, a scale  11  may be mounted on the first part  1 , so that the length to be measured may be read on the scale  11  at the rear end  21  of the second part  2 .  
         [0026]      FIG. 2  illustrates the first part  1  with the front part  3  and a sleeve  28 , the sleeve  28  may be connected with the rear end  15  of the front part  3  and may extend up to the rear end  31  of the first part  1 . The front part  3  may have a passage (such as borehole  16 ) therethrough which may extend from the rear end  15  to the tip  14 . The borehole  16  may be angled or curved at the tip  14  by means of a curvature  18  or an offset angle such that the outlet of the borehole  16  at the tip  14  may extend in a direction transverse to the longitudinal axis  4 . From the curvature  18 , the borehole  16  may extend to the rear end  15  coaxially with the longitudinal axis  4 . A sliding element  7  may be inserted into a central borehole  30  of the sleeve  28  so that it may be moved parallel to the longitudinal axis  4 . The sliding element  7  may have a rear end  8 , which may protrude beyond the rear end  31  of the first part  1 , and a front end  9 , which may contact the rear end  15  of the front part  3 .  
         [0027]     A rod  10  may be connected at a rear end  13  to the sliding element  7  and may extend coaxially with the longitudinal axis  4  from the front end  9  of the sliding element  7  through the borehole  16  in the front part  3 . The rod  10  may also have a wire  17  at a front end  12 . The wire  17 , which may also be coaxial with the longitudinal axis  4 , may extend from the front part  12  of the rod  10  through the borehole  16  in the front part  3 . The wire  17  may be bent in a direction transverse to the longitudinal axis  4  by the curvature  18  of the tip  14 , thereby forming a hook.  
         [0028]     In  FIG. 2 , the sliding element  7  is shown in its rear position. In this rear position, the rod  10  and the wire  17  may be retracted into the borehole  16  towards the rear end  15  of the front part  3 , thus moving the hook  6  into the front part  3 . The sliding element  7  may be retracted with a return spring  5 , which may be positioned within a cavity  19  in the sliding element  7  and which may extend parallel to the longitudinal axis  4  from the front end  9  of the sliding element  7  to a position  23 . One end of the return spring  5  may be in contact with a portion of the cavity at the position  23  and the other may be in contact with the rear end  15  of the front part  3 . In addition to the sliding element  7 , the rod  10  and the wire  17 , the arresting means  27  may comprise an arresting mechanism  36 , which is in an inactive position when the hook  6  is retracted.  
         [0029]      FIG. 2  illustrates the present invention in a position prior to measuring a length or a depth. In this position, the second part  2  may be furthest to the rear—that is, the rear end  21  of the second part  2  may be proximate the rear end  31  of the first part  1 . A shoulder  37  in the central borehole  20  of the second part  2  may provide a stopping surface for this furthest rearward position. And, the sleeve  28  and the rear end  15  of the front part  3  may abut the shoulder  37 .  
         [0030]      FIG. 3  shows a position of the arresting means  27  in which the hook  6  is in its extended position. In order to achieve this position, the sliding element  7  may be moved forward in the sleeve  28  until the front end  9  of the sliding element  7  abuts the rear end  15  of the front part  3 . In this position, the arresting mechanism  36  may be in its active position (i.e., the hook  6  may be fixed in an extended position).  
         [0031]     The sliding element  7  may have a hole  39  coaxial with the longitudinal axis  4  and opened at the rear end  8  of the sliding element  7 . The arresting mechanism  36  may comprise a piston  38 , which may be axially displaceable and which may be positioned in a hole  39 . Bottom  46  may form a boundary of the hole  39  at a particular depth within sliding element  7 . The piston  38  may be moved manually by an operating means  29 —that is, moved towards the front end  9  of the sliding element  7 . The operating means  29  may protrude beyond the rear end  8  of the sliding element  7 . The path of travel of the operating means  29  parallel to the longitudinal axis  4  may be controlled by a pin  44 , which may be guided in an elongated slot  45  in the wall of the sliding element  7 .  
         [0032]     To move the piston  38 , the operating means  29  may be moved towards the tip  14  until the operating means  29  contact the rear end  47  of the piston  38  and subsequently moves the piston  38  towards the tip  14 . The path of travel of the piston  38  towards the tip  14  may be limited by the front end  48  of the piston  38  contacting the bottom  46  of the blind hole  39  ( FIG. 2 ). The piston  38  may be biased into a rear position by a first spring  49  which, at one end, may abut the piston  38  and, at another end, may abut the bottom  46  of the hole  39 . The operating means  29  may also be brought into a rear position by a second spring  50 . The second spring  50  may also be disposed in the hole  39  with one end of the spring contacting a shoulder  51  in the hole  39  and the other end of the spring contacting the operating means  29 .  
         [0033]     The arresting means  36  may be moved into two positions—an active position ( FIG. 3 ), in which the sliding element  7  may be fixed in a forward position and the hook  6  may be fixed in an extended position, and an inactive position ( FIG. 3 ), in which the arresting mechanism  36  may not engage the sliding element  7  and the hook  6  may be fixed in a retracted position. The sliding element  7  may be held in a forward position by balls  55 , which may snap into a first groove  52  located in the periphery of the central borehole  30  of the sleeve  28  ( FIG. 3 ). The balls  55  may be moved transverse to the longitudinal axis  4  and may be supported in transverse boreholes  54 , which may pass completely through the sliding element  7 . In the active position of the arresting mechanism  36  ( FIG. 3 ), the balls  55  may be held by the piston  38 . In the inactive position of the arresting mechanism  36  (i.e., when the slide element  7  is in its rear position) the balls  55  may snap into a second groove  53 , which may be located on the periphery of the piston  38 . Accordingly, the sliding element  7  may be pushed towards its rear position by the force of the return spring  5  ( FIG. 2 ) or towards its front position relative to the sleeve  28 .  
         [0034]     The sliding element  7  may be held in its rear position by a pin  57 , which may be mounted transversely to the longitudinal axis  4  at the rear end  15  of the front part  3  and which may be received within a notch  56  of the rod  10 , so that movement of the sliding element  7  parallel to the longitudinal axis  4  and towards the rear end  31  of the sleeve  28  may be limited by the notch  56 .  
         [0035]     FIGS.  1  to  4  illustrate the present invention in use, for example, while taking the length measurement of a hole in a bone which will receive a bone screw to be screwed into a bone  41 . In order to measure length, the front part  3  of the first part  1  may be inserted into the borehole  40  in the bone  41  until the tip  14  protrudes beyond the opposite bone wall  43 . At this point, the rear end  21  of the second part  2  may be positioned adjacent the rear end  31  of the first part  1  (i.e., rear end  21  may be positioned furthest to the rear ( FIG. 2 )). Next, the hook  6  of the arresting means  27  may be extended using the operating means  29 , which may be disposed at the rear end  31  of the first part  1 , and may be fixed in an extended position. Subsequently, the second part  2  may be moved forward (i.e., in a direction towards the front part  3 ) until the front end  22  of the second part  2  is in contact with the surface of the bone  41  ( FIG. 3 ). At this point, the bone  41  may be clamped between the front end  22  of the second part  2  and the hook  6 . The second part  2  may be held in position relative to the first part  1  by a locking means  26  ( FIGS. 5 through 7 ). The hook  6  of the arresting means  37  may then be retracted by manipulating the operating means  29  and the device may be removed from the borehole  40  in the bone  41 . The length measured may be subsequently read from the scale  11  ( FIG. 1 ) in the operating room outside of the field of surgery.  
         [0036]     The embodiment illustrated in  FIG. 4  differs from the embodiments of  FIGS. 2 and 3  in that the arresting means  27  may comprise a screw  58  instead of the sliding element  7  of  FIGS. 2 and 3 . The rear end  61  of the screw  58  may protrude over the rear end  21  of the first part  1  and may be rotated manually. The screw  58  may be provided with an external thread extending along its front part to a front end  60 . The external thread  59  may be screwed into an internal thread  62  of the first part  1 . The internal thread  62  may be positioned in the central borehole  30  of the sleeve  28  and may extend up to the rear end  15  of the front part  3 . Accordingly, the screw  58  may be screwed into the first part  1  until the front end  60  of the screw  58  contacts the rear end  15  of the front part  3 . The hook  6  may be in a retracted position when the screw  58  is in a rear position. Otherwise, when the screw  58  is in a forward position (i.e., where the screw  58  is positioned so far into the first part  1  that the front end  60  of the screw  58  contacts the rear end  15  of the front part  3 ), the hook  6  may be fixed in an extended position. The hook  6  may be fixed in this position by the threaded connection between the first part  1  and the screw  58 .  
         [0037]     The rear end  13  of the rod  10  may have a spherical head  63 . The rear end  13  having spherical head  63  may be positioned in a hole  64 , which may be located in the screw  58 . The hole  64  may extend coaxially with the longitudinal axis  4  and may be open at the front end  60  of the screw  58 . The spherical head  63  may be fixed axially against the front end  60  of the screw  58 , for example, by an insert  65  in the hole  64 . Therefore, the rod  10  may be fixed axially but may be connected to the screw  58  so that the rod  10  may freely rotated about the longitudinal axis  4 .  
         [0038]      FIGS. 5 through 7  of the present invention illustrate one embodiment of  FIGS. 1 through 4  with locking means  26  for selectively locking the relative axial position between the first part  1  and the second part  2 .  
         [0039]      FIG. 5  shows an embodiment of the present invention where the locking means  28  may comprise a flexible flap  68 , which may be flexible in a direction transverse to the longitudinal axis  4 , and teeth  69 , which may be mounted on the first part  1  parallel to the longitudinal axis  4 . A rigid end  71  of the flexible flap  66  may be fastened to the second part  2  proximate the rear end  21  of the second part  2 . The flexible flap  66  may be provided at its free end  70  with a protrusion  67 , which may extend towards the central borehole  20  of the second part  2 . The protrusion  67  may engage the teeth  69  so that the first part  1  may be fixed against axially movement with respect to the second part  2 . The teeth  69  may have, for example, notches at millimeter intervals so that the first part  1  may be fixed in millimeter intervals relative to the second part  2 . The protrusion  67  may be formed, for example, by a pin  68  whose tip engages the teeth  69 .  
         [0040]      FIG. 6  shows an embodiment of the present invention where the locking means  21  may comprise a fixing screw  72  having a screw axis  78  extending in a direction transverse to the longitudinal axis  4 . The shaft  73  of the fixing screw  72  may be passed through a borehole  79  in the second part  2  and screwed into an internal thread  77  of a bushing  75 . In this way, the front end  78  of the fixing screw  72  may extend into the central borehole  20  of the second part  2  and may be pressed against the first part  1 . The bushing  75  may be fastened to the second part  2 . The head  74  of the fixing screw  72  may extend out over the bushing  75  and may be rotated manually so that the first part  1  and the second part  2  may be locked together by tightening the fixing screw  72 . The internal thread  77  may also be provided in the borehole  79  of the second part  2  if the wall of the second part  2  between the outer surface and the central borehole  20  is sufficiently thick.  
         [0041]      FIG. 7  shows an embodiment of the present invention where the locking means  26  may comprise a flap  80  connected with the second part  2 , which may be elastically deformed and which may move in a direction transverse to the longitudinal axis  4 . A clamping sleeve  81 , which may be moved on the second part  2  parallel to the longitudinal axis  4 , may be used to press the flap  80  laterally against the first part  1  so that the first part  1  may be fixed relative to the second part  2 . In order to loosen or tighten the locking means  26 , the elastically deformable end  84  of the flap  80  may have a protrusion  82  adjacent the wall of the inner cone  83 . The inner cone  83  may taper towards the rear end  21  of the second part  2  and may be provided in the clamping sleeve  81 . If the clamping sleeve  81  is moved towards the front end  22  of the second part  2 , the inner cone  83  may press against the protrusion  82  and, thus, the flap  80  may be pressed laterally against the first part  1 . To loosen the locking means  26 , the clamping sleeve  81  may be moved axially towards the rear end  21  of the second part  2  until the inner cone  83  disengages the protrusion  82 . The axial movement of the clamping sleeve  81  towards the rear end  21  of the second part  2  may be limited by a first stop  85  at the rear end  21  of the second part  2  and axial movement towards the front end  22  of the second part  2  may be limited by a second stop  86 .  
         [0042]     After the front end of the second part  2  is brought into contact with the surface of the bone  41 , the second part  2  may be held in position relative to the first part  1  by the locking means  26 . Thus, after the hook  6  of the arresting means  27  is retracted, the device may be pulled out of the borehole  40  in the bone  41  without moving the axial position of the first part  1  relative to that of the second part  2 , which would otherwise be able to move.  
         [0043]     While the foregoing description and drawings represent the preferred embodiments of the present invention, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope of the present invention as defined in the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other specific forms, structures, arrangements, proportions, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. One skilled in the art will appreciate that the invention may be used with many modifications of structure, arrangement, proportions, materials, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and not limited to the foregoing description.