Patent Publication Number: US-2023139676-A1

Title: Unibody orthopedic surgical instrument

Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to a unibody orthopedic surgical instrument. More specifically, the unibody orthopedic surgical instrument includes a body-integrated actuator operable to actuate a hinge that selectively opens a latching interface of a size and shape for select engagement with an orthopedic implant. 
     During knee arthroplasty, the proximal end of a patient tibia is resurfaced before affixing a knee replacement tibial baseplate to the bone and seating a tibial insert on the tibial baseplate. Resurfacing the proximal end of the tibia requires resecting the damaged portion of bone and cartilage to create a substantially flat surface for the tibial baseplate. Prior to affixing the tibial baseplate, a surgeon aligns a tibial trial generally following the peripheral edge of the resurfaced tibia to determine the size of the requisite tibial baseplate. This may require aligning incrementally sized tibial trials until the correct size is ascertained. Furthermore, the size of tibial insert is determined by a similar process using insert trials. The tibial insert is located between the tibial baseplate and a femoral component affixed to the distal end of a patient femur. The circumference of the tibial insert must match the tibial baseplate, and the height of the tibial insert must fit within the gap between the femoral component and tibial baseplate. As such, determining the correct sized tibial insert may require aligning incrementally sized insert trials. 
     Typically, the tibial trials, insert trials, and/or tibial sizers include integrated handles. Therefore, each incrementally sized trial or sizer with an integrated handle is unnecessarily large because the trials or sizers each have their own handle, as opposed to being adapted for use with a universal handle. Furthermore, knee arthroplasty generally utilizes surgical trays containing the trials, implant components, sizers, and surgical instruments. To accommodate large trials or sizers with integrated handles, the surgical trays are unnecessarily large, which is burdensome and undesirable for already crowded operating rooms. Furthermore, the surgical trays have mass constraints and, therefore, unnecessarily large trials or sizers can require multiple trays. This further crowds the operating room and creates an inconvenient procedural environment. Additionally, the cost of sterilizing the trials, implant components, sizers, and multiple surgical instruments can be undesirable. Therefore, the current practice for determining the size of the required tibial baseplate and insert is time-consuming, inconvenient, and costly. 
     Furthermore, the tibial baseplate includes a stem that extends into the patient tibia and anchors the baseplate to the bone. The tibial baseplate stem may need to be tightened or loosened to adjust the length of the stem depending on the size of the patient tibia and type of knee replacement being inserted. Alternatively, stems of varying lengths may be coupled or removed from the tibial baseplate. In either scenario, a stem wrench is used to tighten, loosen, couple, or remove the stem. Typically, this requires a separate stem wrench. Conventional practices, therefore, require that even more individual surgical devices be delivered and used in the operating room during surgery. 
     Current attempts to reduce the number of individual devices used for knee arthroplasty have been largely unsuccessful in satisfying the need and, in some cases, create additional problems. In one example prior art device, U.S. Pat. No. 5,733,290, the contents of which are herein incorporated by reference in its entirety, discloses a quick-release alignment handle system that includes a quick release mechanism with an attachable releasable lock for attaching the handle to a tibial tray trial component of a surgical instrument system for implanting artificial knees. While this device includes a handle that may couple to multiple tibial trials, it does not couple to insert trials or any other surgical instrument. Furthermore, existing devices include complicated mechanisms containing springs, sliding components, and/or multi-piece assemblies. As such, existing devices are more susceptible to wear and have more potential failure points relative to a unibody device. Another drawback of these complicated mechanisms is that they are more difficult to manufacture and assemble, thereby increasing costs. Additionally, any surgical instrument used during the procedure must be thoroughly cleaned and resterilized before use in subsequent procedures. This is more difficult with existing devices because the springs, sliding components, and/or multi-piece assemblies are prone to collect debris in areas difficult to clean. This consequently increases hospital reprocessing time and also adds to costs. Additional, current devices fail to incorporate a stem wrench and, therefore, conventional surgical instruments still require that multiple sterilized instruments be delivered to the operating room for any given surgery. 
     There exists, therefore, a significant need in the art for a unibody orthopedic surgical instrument that includes a body-integrated actuator operable to actuate a hinge that opens a latching interface of a size and shape for select pull-tight engagement with an orthopedic instrument, the unibody surgical instrument further including a body-integrated alignment rod aperture and a tibial stem wrench, thereby combining multiple operating room surgical instrument tools into one. The present invention fulfills these needs and provides further related advantages. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment, a unibody orthopedic surgical instrument may include a handle, a latching interface outwardly extending from the handle, a hinge operably coupled with the latching interface, and a spring-biased lever arm coupled to the hinge in a configuration to actuate the latching interface. The handle may further include an alignment rod and a tibial stem wrench, thereby combining multiple surgical instruments into one. 
     Alternatively, in other embodiments, the unibody orthopedic instrument may include an elongated handle, a latching interface outwardly extending relative to the elongated handle and selectively couplable to an orthopedic component, and a hand accessible spring-biased lever arm operable with a hinge coupled to the elongated handle about a pivot. The hinge normally positions the latching interface in a first latched position for locking engagement with the orthopedic component and is otherwise operable by the spring-biased lever arm about the pivot to reposition the latching interface from the normally latched position to an unlatched position for disengagement from the orthopedic component. 
     In one embodiment, the spring-biased lever arm may turn about and extend away from the hinge in an offset position relative thereto. Alternatively, the spring-biased lever arm may orthogonally extend out and away from the hinge; or the spring-biased lever arm may extend out relative to the hinge at an angle relative to the hinge or the elongated handle. In some embodiments, the elongated handle may further include an aperture having a size and shape for select sliding engagement with an alignment rod and/or the elongated handle may further include a body-integrated tibial stem wrench. More specifically, the aperture may include an alignment rod lock movable between a free moving position permitting movement of the unibody orthopedic instrument relative to the alignment rod and a restricted position in friction fit engagement with the alignment rod to inhibit movement of the unibody orthopedic instrument relative to the alignment rod. 
     The unibody orthopedic instrument may further include a lock movable relative to an operable end of the spring-biased lever arm between an unlocked position allowing the movement of the operable end of the spring-biased lever arm and a locked position obstructing movement of the operable end of the spring-biased lever arm. Here, the lock may include a rod movable within a channel separating the operable end of the spring-biased lever arm and the elongated body between the unlocked position and the locked position. The elongated handle may further include a stop that projects into the channel to locate the lock underneath the spring-biased lever arm in the locked position. Additionally, the spring-biased lever arm may terminate in a C-shaped enclosure generally encompassing an end stop outwardly projecting from the elongated handle. Here, the spring-biased lever arm may be deflectable relative to the elongated handle by a distance formed between opposing sides of the C-shaped channel. 
     Additionally, the latching interface may include a pair of pretensioned prongs positioned relatively closer to one another when in the latched position than when in the unlatched position. One of the pair of pretensioned prongs may include a chamfered prong having a chamfered leading edge and the other of the pair of pretensions prongs may include a hooked prong having a notch formed thereunder. Accordingly, the latching interface may be of a size and shape for select slide-in reception within a pair of receptors integrated into the orthopedic component for locking engagement therewith. Once connected thereto, the unibody orthopedic instrument may manipulate the orthopedic component, such as during surgery. 
     In an alternative embodiment, the unibody orthopedic instrument may include a handle, a latching interface outwardly extending relative to the handle and selectively couplable to an orthopedic component, and a spring-biased lever arm integrated with a hinge coupled to the handle about a pivot normally positioning the latching interface in a first latched position for locking engagement with the orthopedic component. Here, the hinge may be operable by the spring-biased lever arm about the pivot to reposition the latching interface from the normally latched position to an unlatched position for disengagement from the orthopedic component. Moreover, a lock may be movable relative to the spring-biased lever arm between an unlocked position allowing movement of the spring-biased lever arm and a locked position obstructing movement of the spring-biased lever arm. The spring-biased lever arm may alternatively orthogonally extend out and away from the hinge or turn about and extend over the hinge in spaced-apart relation thereof. 
     In some embodiments, the latching interface may include a pair of pretensioned prongs positioned relatively closer to one another when in the latched position than when in the unlatched position. Additionally, the pair of pretensioned prongs may be of a size and shape for select slide-in reception within a pair of receptors integrated into the orthopedic component for locking engagement therewith. Here, one of the pair of pretensioned prongs may include a chamfered prong having a chamfered leading edge and the other of the pair of pretensioned prongs may include a hooked prong having a notch formed thereunder. The chamfered leading edge may facilitate self-actuation of the latching interface when coupling the unibody orthopedic instrument with the receiving interface of the orthopedic component. 
     Furthermore, in alternative embodiments, the lock may be a rod movable within a channel separating an operable end of the spring-biased lever arm and the handle. Here, the rod may be in the locked position when underneath at least a portion of the operable end of the spring-biased lever arm adjacent a stop projecting into the channel. The spring-biased lever arm may terminate in a C-shaped enclosure generally encompassing at least a portion of the handle. This allows the spring-biased lever arm to float relative to the handle by a distance of the C-shaped enclosure. Moreover, the handle may further include an aperture having a size and shape for select sliding engagement with an alignment rod and the handle may include a body-integrated tibial stem wrench. Here, the aperture may include a locking mechanism that allows the handle to lock to the alignment rod at a desired position along the length thereof. In one embodiment, the locking mechanism may be a brake-style locking mechanism that engages the alignment rod by friction fit engagement. Moreover, the body-integrated tibial stem wrench may include one or more indents (e.g., six) that correspond with one or more ribs (e.g., six) on the tibial stem to enhance engagement therewith. The handle may be ergonomically shaped, and the unibody orthopedic surgical instrument may be made out of a metal such as stainless steel, titanium, aluminum or the like. 
     The latching interface may couple to a tibial trial, insert trial, tibial cutting guide, or any other suitable knee arthroplasty component via the corresponding reception interface. The latching interface may include a pair of prongs, with a first prong being a chamfered prong relatively longer than a second prong being a hooked prong. The reception interface may include a pair of reception channels respectively configured for select-slide in engagement of the first prong and the second prong. The reception channels may transition to a relatively wider back channel forming a pair of shoulders therebetween. Here, a chamfered leading edge of the first prong may facilitate slide-in mating with a first recess and one of the shoulders formed within the back channel; and a latch and notch combination of the second prong may facilitate slide-in mating with a second recess and another shoulder formed within the back channel. Here, the latch and the notch may improve coupling of the prongs to the tibial trial, insert trial, tibial cutting guide, or any other suitable knee arthroplasty component. 
     In another aspect of the embodiments disclosed herein, a process for engaging an orthopedic component with a unibody orthopedic instrument as disclosed herein may include steps for moving a hinge operable by a spring-biased lever arm about a pivot from a normal latched position to an unlatched position, actuating a latching interface at least partially coupled with the hinge in response to movement of the hinge about the pivot, inserting the latching interface into a reception interface coupled with the orthopedic component, and returning the hinge to the normal latched position thereby locking the unibody orthopedic instrument to the orthopedic component. 
     In some embodiments, the actuating step may include separating a pair of pretensioned prongs. Here, a chamfered edge of one of the pair of pretensioned prongs may slide into engagement with at least one reception channel of the reception interface of the orthopedic component. The returning step may accordingly include the step of engaging at least one of the pair of pretensioned prongs having a hook and recess with a shoulder within a back channel of the reception interface. Alternatively, the spring-biased lever arm may be locked in the normal latched position by sliding a lock positioned within a channel formed between the spring-biased lever arm and a body of the unibody orthopedic instrument to a stop upwardly projecting within the channel and generally positioned underneath an operable end of the spring-biased lever arm. Moreover, the process disclosed herein may further include inserting an alignment rod into an aperture integrated within the unibody orthopedic instrument and retaining the alignment rod relative to the unibody orthopedic instrument; and turning a tibial stem via a body-integrated tibial stem wrench formed from a portion of the unibody orthopedic instrument. 
     Other features and advantages of the present invention will become apparent from the following more detailed description, when taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate the invention. In such drawings: 
         FIG.  1    is a is a perspective view of an exemplary embodiment of a unibody orthopedic surgical instrument as disclosed herein; 
         FIG.  2    is an enlarged perspective view taken about the circle  2  in  FIG.  1   , further illustrating that one of a pair of prongs includes a chamfered edge and that the other of the pair of prongs includes a combination latch and notch; 
         FIG.  3    is an enlarged perspective view similar to  FIG.  2   , further illustrating alignment of the pair of prongs with a respective pair of reception channels formed within a modular tibial sizer; 
         FIG.  4    is a perspective view similar to  FIG.  3   , further illustrating locking insertion of the pair of prongs within the reception channels of the modular tibial sizer; 
         FIG.  5    is a perspective view of the modular tibial sizer, further illustrating the reception channels and a receptive back channel; 
         FIG.  6    is a top plan view illustrating the unibody orthopedic surgical instrument with the pair of prongs coupled with the reception channels of the module tibial sizer; 
         FIG.  7    is an enlarged top plan view taken about the circle  6  in  FIG.  1   , further illustrating a lock selectively positionable to prevent actuation of a spring-biased lever arm; 
         FIG.  8    is a perspective view illustrating the unibody orthopedic surgical instrument engaged with an alignment rod and having the pair of prongs coupled with a tibial trial; 
         FIG.  9    is a perspective view similar to  FIG.  8   , further illustrating the unibody orthopedic surgical instrument engaged with the alignment rod and having the pair of prongs coupled with an insert trial; 
         FIG.  10    is a perspective view similar to  FIGS.  8  and  9   , additionally illustrating the unibody orthopedic surgical instrument engaged with the alignment rod and having the pair of prongs coupled with a tibial cutting guide; 
         FIG.  11    is a perspective view the unibody orthopedic surgical instrument with a body-integrated stem wrench engaged with a tibial baseplate stem; and 
         FIG.  12    is a perspective view of an alternative embodiment of the unibody orthopedic surgical instrument illustrating an orthogonal lever arm selectively operable with a hinge to actuate the pair of prongs. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in the exemplary drawings for purposes of illustration, the present invention for a unibody orthopedic surgical instrument is illustrated in  FIGS.  1 ,  6 , and  8 - 12    with respect to reference numeral  20 . As illustrated, the unibody orthopedic surgical instrument  20  includes an integrated handle  22  at one end and a latching interface  24  having a pair of prongs  26 ,  28  generally outwardly extending therefrom at an opposite end thereof, wherein each of the pair of prongs  26 ,  28  are separated by a gap  30 . The pair of prongs  26 ,  28  may include a chamfered prong  26  and a hooked prong  28  designed for select engagement with a medical device, as discussed in more detail below. In alternative embodiments, the latching interface  24  may include three or more prongs; or just a single prong as long as there is sufficient latching between components. Moreover, the unibody orthopedic surgical instrument  20  may further include a hinge  32  also formed from a portion of the integrated handle  22 , the hinge  32  being operably coupled with the hooked prong  28 . Although, of course, the hinge  32  could also be operably coupled with the chamfered prong  26  in the alternative. A spring-biased lever  34  arm selectively actuates the hinge  32  to increase the width of the gap  30 , thereby spreading apart the chamfered prong  26  and hooked prong  28 . The spring-biased lever arm  34  may generally hold the chamfered prong  26  and hooked prong  28  in a pretensioned closed position wherein the prongs  26 ,  28  are relatively closer together as compared to an open position when a surgeon depresses the spring-biased lever arm  34  toward the hinge  32 , thereby actuating the hinge  32  to spread apart the prongs  26 ,  28  as disclosed herein. 
     As illustrated in  FIG.  2   , the chamfered prong  26  may be relatively longer than the hooked prong  28  and may include a chamfered leading edge  36 . The hooked prong  28  may include a latch  38  generally outwardly projecting into the gap  30  and a trailing notch  40  formed underneath the latch  38  and into a portion of the hooked prong  28  as best illustrated in  FIG.  2   . As illustrated in  FIG.  3   , the latching interface  24  including the prongs  26 ,  28  may generally correspond to a reception interface  42  that may include a first and second reception channel  44 ,  46 . As illustrated in  FIGS.  3 - 5   , the reception interface  42  may be located on a modular tibial sizer  48 . The reception interface  42  may further include a partition  50  separating the first and second reception channels  44 ,  46 , whereby the gap  30  between the chamfered prong  26  and the hooked prong  28  must be of a sufficient distance to receive the partition  50  therein. In alternative embodiments wherein the latching interface  24  includes three or more prongs, the reception interface  42  may include three or more corresponding reception channels. 
     As illustrated in  FIG.  3   , the surgeon may insert the latching interface  24  into the reception interface  42  along arrows  52  so the chamfered prong  26  may engage the reception channel  44  via slide through reception and the hooked prong  28  may engage the reception channel  46  in the same manner. If the prongs  26 ,  28  are not in the open position, i.e., where the gap  30  is sufficiently wide enough to accept the partition  50  therein, the prongs  26 ,  28  may contact the partition  50 , thereby being prevented from entering the reception channels  44 ,  46 . In this embodiment, the surgeon may need to actuate the hinge  32  via the spring-biased lever arm  34  to open the gap  30  between the prongs  26 ,  28  by a sufficient distance to facilitate inserting the prongs  26 ,  28  into the reception channels  44 ,  46  along arrows  52 . 
     Alternatively, one or both of the prongs  26 ,  28  may contact a portion of the partition  50 , such as along the chamfered leading edge  36  of the chamfered prong  26 . Here, the partition  50  may slide along the chamfered leading edge  36  thereby separating the prongs  26 ,  28  during insertion without the need to actuate the hinge  32  with the spring-biased lever arm  34 . In this embodiment, the prongs  26 ,  28  may essentially self-actuate to a position to be received within each of the reception channels  44 ,  46  for locking engagement within the reception interface  42 . 
     As best illustrated in  FIG.  4   , the surgeon may release the spring-biased lever arm  34  after the prongs  26 ,  28  enter the reception channels  44 ,  46  for friction fit engagement therein. More specifically, the pretensioned interaction of the spring-biased lever arm  34  relative to the hinge  32  will attempt to return the prongs  26 ,  28  to the closed position, i.e., closing the gap  30  therebetween. But, since the width of the pretensioned gap  30  is relatively smaller than the partition  50 , a pair of interior walls  54 ,  56  of the respective chamfered prong  26  and the hooked prong  28  will contact the partition  50  within the reception channels  44 ,  46 . Because the partition  50  is wider than the pretensions gap  30  while the unibody orthopedic surgical instrument  20  is at rest, the prongs  26 ,  28  will exert a latching force along directional arrows  58 ,  60 , respectively. As such, and as best illustrated in  FIG.  6   , this couples the unibody orthopedic surgical instrument  20  to the modular tibial sizer  48  so the surgeon may manipulate and position the modular tibial sizer  48 , as needed. 
     In another embodiment, the chamfered leading edge  36  may contact the partition  50  before the hooked prong  28 . As briefly mentioned above, as the chamfered prong  26  slides into the reception channel  44 , the chamfered leading edge  36  may cause the prongs  26 ,  28  to deflect away from one another, thereby widening the gap  30  between the prongs  26 ,  28 . This may also facilitate slide through engagement of the prongs  26 ,  28  with the reception channels  44 ,  46  without the need to substantially actuate the hinge  32  via the spring-biased lever arm  34 . Furthermore, as best illustrated in  FIG.  4   , the width of the hooked prong  28  may be relatively smaller than the width of the reception channels  44 ,  46  and/or the chamfered prong  26 . As such, the surgeon may insert the hooked prong  28  at an angle and then pivot the unibody orthopedic surgical instrument  20  in the direction of arrow  62 . The chamfered leading edge  36  may then contact the partition  50  and deflect the prongs  26 ,  28  away from each other to allow the chamfered prong  26  to slide into the reception channel  44 . At the very least, the chamfered leading edge  36  deflecting the prongs  26 ,  28  away from each other may assist the surgeon in inserting the prongs  26 ,  28  while at the same time actuating the hinge  32  via the spring-biased lever arm  34 . 
     As best illustrated in  FIG.  5    with respect to the modular tibial sizer  48 , the reception channels  44 ,  46  may extend into a relatively wider back channel  64 . As such, the transition between the relatively narrower reception channels  44 ,  46  to the wider back channel  64  forms a set of shoulders  66  therebetween. Here, the prongs  26 ,  28  may extend through the reception channels  44 ,  46  and into the back channel  64  for engagement with the shoulders  66  to further secure the latching interface  24  to the reception interface  42 . As further illustrated in  FIG.  4   , the hooked prong  28  may extend into the reception channel  44  or  46 , and the shoulder  66  may extend into the notch  40 . As the notch  40  receives shoulder  66 , the latch  38  may extend over and exert a force on the shoulder  66  in the direction of arrow  68  for pull-tight engagement with the modular tibial sizer  48 . This may reduce backlash from the modular tibial sizer  48  when coupled to the unibody orthopedic surgical instrument  20  as the modular tibial sizer  48  is pulled towards the unibody orthopedic surgical instrument  20 . 
     Furthermore,  FIG.  6    illustrates the unibody orthopedic surgical instrument  20  coupled to a right-side modular tibial sizer  48  with the chamfered prong  26  engaged with the reception channel  44 , and the hooked prong  28  engaged with the reception channel  46 . Alternatively, the unibody orthopedic surgical instrument  20  may be flipped over for use with a left-side modular tibial sizer  48  with the chamfered prong  26  engaged with the reception channel  46  and the hooked prong  28  engaged with the reception channel  44 . As such, the unibody orthopedic surgical instrument  20  may be used with a knee arthroplasty for both the left and right knee of the patient. 
     As illustrated in  FIG.  7   , the unibody orthopedic surgical instrument  20  may further include a lock  70  having a lock rod  72  and, as best illustrated in  FIG.  1   , a pair of opposing end caps  74  (one illustrated in  FIG.  7    and two illustrated in  FIG.  1   ) outwardly extending from each end of the lock rod  72 . In this respect, the end caps  74  may be of a sufficient diameter or width to at least partially extend out over each side of the unibody orthopedic surgical instrument  20  to maintain the lock  70  in an engaged relationship with the integrated handle  22 . The surgeon may slide the lock  70  along an arrow  76  from an unlocked position illustrated in  FIG.  7    immediately below the spring-biased lever arm  34  to a locked position wherein the lock  70  is positioned immediately behind the spring-biased lever arm  34  as indicated in dotted line depiction  78  in  FIG.  7   . When in the locked position, the lock  70  may seat against an inwardly projecting curved member  80  that prevents the lock  70  from continuing too far past the locked position, and also biases the lock  70  into positive engagement with the spring-biased lever arm  34 . As such, when the lock  70  is in the locked position, the lock rod  72  prevents the spring-biased lever arm  34  from being depressed inwardly along directional arrow  82 , thereby effectively preventing actuation of the hinge  32  and the resultant widening of the gap  30  between the prongs  26 ,  28 . The lock  70  may be particularly useful when the unibody orthopedic surgical instrument  20  is used to align an insert trial. For example, the insert trial must be inserted into a gap between the tibial component and femoral component. This typically requires a significant amount of force. As such, the lock  70  may ensure that the force exerted on the insert trial does not cause disengagement of the prongs  26 ,  28  from the insert trial as a result of forcibly gripping the integrated handle  22 , including, e.g., the spring-biased lever arm  34 . Therefore, it follows that the lock  70  further ensures that the surgeon does not accidentally actuate the hinge  32 . 
     As illustrated in  FIGS.  1 ,  6 , and  8 - 12   , the unibody orthopedic surgical instrument  20  may include an alignment rod aperture  84  for slidable engagement with an alignment rod  86 . Furthermore, the unibody orthopedic surgical instrument  20  may serve as an indicator of rotation, thus improving alignment. The unibody orthopedic surgical instrument  20  may slide along the length of the alignment rod  86  wherein the surgeon may use a lock (not shown) to secure the unibody orthopedic surgical instrument  20  to a desired location along the length of the alignment rod  86 . The unibody orthopedic surgical instrument  20  may rotate around the alignment rod  86  about the alignment rod aperture  84 . Moreover, as further illustrated in  FIGS.  8 - 11   , the latching interface  24  may couple a plurality of knee replacement components and instruments such as the modular tibial sizer  48  ( FIG.  8   ), an insert trial  88  ( FIG.  9   ), and/or a tibial cutting guide  90  ( FIG.  10   ). As such, the insert trial  88  and the tibial cutting guide  90  may include the same or similar reception interface  42  as the modular tibial sizer  48  disclosed above. 
     As illustrated in  FIG.  11   , the unibody orthopedic surgical device  20  may include a tibial stem wrench  92  that may couple to a tibial stem  94  on a tibial baseplate  96 . The surgeon may rotate the tibial stem wrench  92  about the tibial stem  94  to extend or shorten the tibial stem  94 . In one embodiment, the tibial stem wrench  92  may include a series of indentations  98  that correspond to a set of ribs  100  on the tibial stem  94 . The indentations  98  may prevent the tibial stem wrench  92  from slipping or concentrically rotating around the tibial stem  94  instead of turning the tibial stem  94 . 
     More specifically with respect to the operation of the hinge  32 , the top plan view of  FIG.  6    best illustrates that the spring-biased lever arm  34  includes an actuation end  102  that terminates in a U- or C-shaped channel  104  that generally encompasses and floats within an end stop  106  generally projecting outwardly from a portion of the integrated handle  22  and into the C-shaped channel  104 . As such, the spring-biased lever arm  34  may only deflect by a distance of the open enclosure formed within the C-shaped channel  104  around the end stop  106 . In other words, the outwardly projecting end stop  106  prevents the spring-biased lever arm  34  from deflecting an undesirable distance by way of projecting into and contacting opposite sides of the C-shaped channel  104 , as needed. Such feature prevents over extension of the hinge  32  while at the same time maintaining the location of the spring-biased lever arm  34  in a generally lengthwise relationship with the integrated handle  22 . 
     Moreover, as also illustrated in  FIG.  6   , the spring-biased lever arm  34  is generally elongated and curves about itself into the hinge  32  carrying, at least in this embodiment, the hooked prong  28 . As shown, the hinge  32  extends back about the length of the spring-biased lever arm  34  in spaced apart relation relative thereto and couples with the alignment rod aperture  84 . The hinge  32  is also illustrated in  FIG.  6    being in spaced apart relation relative to the chamfered prong  26  positioned immediately below, which also couples with the alignment rod aperture  84 . As such, compression of the spring-biased lever arm  34  into the body of the integrated handle  22  exerts a force on the curvature where the spring-biased lever arm  34  transitions or curves back into the hinge  32 , thereby causing the hinge  32  to pull or retract away from the chamfered prong  26  about its connection to the alignment aperture  84 . The same or greater movement may be experienced where the hinge  32  couples to or otherwise pivots relative to the handle  22 , such as the part of the handle  22  forming the alignment rod aperture  84 . Such movement increases the width of the gap  30  between each of the chamfered prong  26  and the hooked prong  28 . This, in turn, provides the necessary clearance for inserting and/or removing each of the chamfered prong  26  and the hooked prong  28  into the respective reception channels  44 ,  46 , as discussed above. Releasing the spring-biased lever arm  34  returns the hinge  32  back to a substantial parallel relation with the chamfered prong  26  to facilitate engagement of the unibody orthopedic surgical instrument  20  with the modular tibial sizer  48 , as discussed herein. The unibody orthopedic surgical instrument  20  may be prefabricated such that the spring biased lever arm  34  and the hinge  32  are pretensioned relative to the chamfered prong  26  so that the gap  30  is somewhat smaller than the partition  50 , which facilitates engagement between the latching interface  24  and the reception interface  42  as discussed above. 
     Another alternative embodiment of the unibody orthopedic surgical instrument  20  is illustrated in  FIG.  12    with respect to an orthogonal lever arm  108  outwardly extending from a portion of the hinge  32 . The orthogonal lever arm  108  is able to selectively actuate the hinge  32  by applying an upward or downward force along directional arrow  110  to govern the width of the gap  30  between the chamfered prong  26  and the hooked prong  28 . In operation, e.g., the surgeon may hold the unibody orthopedic surgical instrument  20  by the handle  22  with one hand and use another hand to apply a force to the orthogonal lever arm  108  along the direction of arrow  110 . Applying the force along the directional arrow  110  in an upward or clockwise manner as illustrated in  FIG.  12    causes the hooked prong  28  to defect up and away from the chamfered prong  26 , thereby increasing the gap  30  in between. This facilitates disengagement of the latching interface  24  from the reception interface  42 , as discussed above in detail. 
     In alternative embodiments, the orthogonal lever arm  108  could also be pinched or pulled to apply the force along the directional arrow  110  to accomplish increasing or decreasing the gap  30  between the chamfered prong  26  and the hooked prong  28 . Additionally, applying the force in an opposite direction of the arrow  110  would naturally create the opposite effect, e.g., decreasing the gap  30  between the chamfered prong  26  and the hooked prong  28  as per the embodiment illustrated in  FIG.  12   . While  FIG.  12    illustrates the orthogonal lever arm  108  and the hinge  32  operably coupled to the hooked prong  28 , the orthogonal lever arm  108  and the hinge  32  could also be operably coupled with the chamfered prong  26  in the alternative. Although, regardless of the orientation, coupling, and/or the direction of the force applied thereto, the orthogonal lever arm  108  is able to effectuate actuations of the hinge  32  for purposes of moving the hooked prong  28  relative to the chamfered prong  26  to either increase or decrease the gap  30  in between, as may be desired. 
     Similar to that discussed above in detail with respect to  FIGS.  3 - 4   , once the prongs  26 ,  28  are inserted into the reception channels  44 ,  46 , release of the orthogonal lever arm  108  should cause the hinge  32  to return the prongs  26 ,  28  to the closed or locked position, thereby applying a latching force to the partition  50  to maintain the latching interface  24  in coupled arrangement with the reception interface  42 . 
     Alternatively, the unibody orthopedic surgical instrument  20  may include a commensurate orthogonal lever arm (not shown) extending away from the opposite side of the unibody orthopedic surgical instrument  20 , thereby allowing the unibody orthopedic surgical instrument  20  to be flipped over and used with a knee arthroplasty for both the left and right knee of the patient. While  FIG.  12    illustrates the orthogonal lever arm  108  generally extending perpendicular to the unibody orthopedic surgical instrument  20 , in alternative embodiments, the orthogonal lever arm  108  may extend away from the unibody orthopedic surgical instrument at any angle, or generally parallel to the unibody orthopedic surgical instrument. 
     Although several embodiments have been described in detail for purposes of illustration, various modifications may be made without departing from the scope and spirit of the invention. Accordingly, the invention is not to be limited, except as by the appended claims.