Patent Publication Number: US-2023157680-A1

Title: Anatomical Joint Distractor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the filing date of U.S. Provisional Application No. 63/281,142, filed Nov. 19, 2021, the disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Total knee arthroplasty (“TKA”) or total knee replacement is a common orthopedic procedure in which damaged or diseased articular cartilage and/or bone of the knee is replaced with prosthetic components. Prior to implanting such prosthetic components, a surgeon generally resects a portion of the patient&#39;s native bone to receive an associated prosthesis. For example, a surgeon might make one or more planar cuts at a distal end of a femur and proximal end of a tibia so that corresponding surfaces of femoral and tibial prosthetic components can be respectively attached thereto. 
     Prior to making such resections, the joint laxity of the native knee is often assessed to help determine the depth and orientation of the resections to be made. One common technique of assessing joint laxity in the native knee prior to bone resection is to pry the joint apart to ascertain the degree to which the joint opens and the amount of force needed to do so. This is, of course, a subjective tactile assessment based on surgeon experience. 
     Two commonly used devices to pry the knee joint apart are an osteotome, and a spoon tensioner. Osteotomes, such as the one shown in  FIG.  1 A , are like a carpenter&#39;s wood chisel in that they are specifically designed to cut hard tissue, such as bone or cartilage by impaction. All knee replacement procedures have osteotomes readily available as part of the standard instrumentation that is brought into the operating theater. It is almost certain that the repurposed use of an osteotome to distract the joint arose through surgeon improvisation by having a narrow and thin instrument within easy reach. The spoon tensioner, such as the one shown in  FIG.  1 B , is colloquially named for its similarity to the eating utensil and is an attempt to create a device for the express purpose of distracting the knee joint. 
     Although commonly used for the purpose of assessing joint laxity, such instruments fall well short of being effective at fulfilling the desired functionality. At least one reason such instruments are inadequate has to do with their shape. Native femoral condyles and tibial condyles are respectively convex and concave in the sagittal and coronal planes. Placing any device within the joint space that is flat in at least one of the two said planes creates an ill-fitting and unstable construct. As shown, the osteotome is flat in both the sagittal and coronal planes, notwithstanding that it is dangerously sharp. The spoon tensioner, while being slightly curved in the coronal plane, is nonetheless flat in the sagittal plane. Additionally, both devices have smooth contacting surfaces as well as constant proximal/distal thicknesses. When placed in the joint space, any flexion/extension movement of the leg tends to eject, or “spit” out the instrument, which results in extra work and time for the surgeon. This is exacerbated by the fact that these instruments are used prior to any bone resection, meaning that they are inserted into a joint space partially covered in cartilage and synovium fluid, resulting in a very low friction, slippery environment. Therefore, further improvements are desirable. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect of the present disclosure, a knee joint distractor includes a handle that has a length that extends along a longitudinal axis of the knee joint distractor and a distraction head connected to the handle and extending therefrom. The distraction head has a femoral contact side and a tibial contact side. The femoral contact side has a first femoral contact portion. The tibial contact side gas first and second tibial contact portions. The first tibial contact portion defines an inferior apex of the tibial contact side. The second tibial contact portion has a plurality of teeth offset from the inferior apex in a direction toward the handle. 
     Additionally, the teeth may each extend in a direction transverse to the longitudinal axis of the knee joint distractor. The length of each tooth may be interrupted by a recessed channel. Each tooth may include a first and second edge disposed at opposing sides of the recessed channel. Also, each tooth may include a third and fourth edge disposed at respective opposed ends thereof. 
     Continuing with this aspect, the tibial contact side may be curved in a sagittal plane such that it defines an arc length having a first radius of curvature. The first tibial contact portion may have a curved surface that is congruent with the arc length in the sagittal plane. The curved surface of the first tibial contact portion may be curved in a coronal plane orthogonal to the sagittal plane. Each tooth may have a sagittal plane profile that extends no further than the arc length. The sagittal profile of each tooth may be congruent with the arc length. 
     Furthermore, the first femoral contact portion may be concavely curved in sagittal and coronal planes. The femoral contact side includes a second femoral contact portion that is convexly curved in the coronal plane. The distractor of claim  12 , wherein the second femoral contact portion is concavely curved in the sagittal plane. The distractor of claim  1 , wherein the distractor head has first and second ends and is tapered such that a thickness measured between the femoral and tibial contact sides increases from the first end to the second end, the second end being connected to the handle. 
     In another aspect of the present disclosure, a knee joint distractor includes a handle that has a length that extends along a longitudinal axis of the knee joint distractor and a distraction head that is connected to the handle and extends therefrom. The distraction head has a femoral contact side and a tibial contact side. The femoral contact side has a first femoral contact portion. The tibial side has first and second tibial contact portions and an arc length defined by at least the first tibial contact portion that has a first radius of curvature. The second tibial contact portion has a plurality of teeth bounded by the arc length such that the teeth do not extend radially beyond the arc length. 
     Additionally, each tooth of the plurality of teeth may have a radial profile congruent with the arc length. The radial profile of each tooth may be convexly curved in a sagittal plane and a coronal plane. The teeth may each extend in a direction transverse to the longitudinal axis of the knee joint distractor. The length of each tooth may be interrupted by a recessed channel. Each tooth may include a first and second edge disposed at opposing sides of the recessed channel. Each tooth may include a third and fourth edge disposed at respective opposed ends thereof. 
     Continuing with this aspect, the tibial contact side may be curved in a sagittal plane such that it defines an arc length having a first radius of curvature. The first tibial contact portion may have a curved surface that is congruent with the arc length in the sagittal plane. The curved surface of the first tibial contact portion may be curved in a coronal plane orthogonal to the sagittal plane. Each tooth may have a sagittal plane profile that extends no further than the arc length. 
     Furthermore, the first femoral contact portion may be concavely curved in sagittal and coronal planes. The femoral contact side may include a second femoral contact portion that is convexly curved in the coronal plane. The second femoral contact portion may be concavely curved in the sagittal plane. The distractor head may have first and second ends and may be tapered such that a thickness measured between the femoral and tibial contact sides increases from the first end to the second end. The second end may be connected to the handle. 
     In an even further aspect of the present disclosure, a knee joint distractor includes a handle that has a length extending along a longitudinal axis of the knee joint distractor and a distraction head connected to the handle. The distraction head has a femoral contact side that has first and second femoral contact portions and a tibial contact side that has a first tibial contact portion. The first femoral contact portion is concavely curved in a coronal plane, and the second femoral contact portion is convexly curved in the coronal plane. 
     In a still further aspect of the present disclosure a knee joint distractor includes a handle that has a length extending along a longitudinal axis of the knee joint distractor and a distraction head connected to the handle. The distraction head has a femoral contact side and a tibial contact side. The femoral contact side has a first femoral contact portion concavely curved in a sagittal plane and a coronal plane. The tibial contact side has first and second tibial contact portions convexly curved in the sagittal and coronal planes. The second contact portion has a plurality of teeth. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings in which: 
         FIG.  1 A  is a perspective view of a prior art osteotome. 
         FIG.  1 B  is a perspective view of a prior art spoon tensioner. 
         FIG.  2 A  is a perspective view of a joint distractor according to an embodiment of the present disclosure. 
         FIG.  2 B  is a partial bottom perspective view of the joint distractor of  FIG.  2 A . 
         FIG.  2 C  is a side view of the joint distractor of  FIG.  2 A . 
         FIG.  2 D  is a cross-sectional view of the joint distractor of  FIG.  2 CA  taken along line D-D thereof. 
         FIGS.  3 A- 3 C  depict application of the joint distractor of  FIG.  2 A  to a knee joint. 
         FIG.  4 A  is a side view of a joint distractor according to another embodiment of the present disclosure. 
         FIG.  4 B  is a cross-sectional view of the joint distractor of  FIG.  4 A  taken along line B-B thereof. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein unless stated otherwise, the term “proximal” means closer to the heart, and the term “distal” means further from the heart. The term “anterior” means toward the front part of the body or the face, the term “posterior” means toward the back of the body. The term “medial” means closer to or toward the midline of the body, and the term “lateral” means further from or away from the midline of the body. The term “inferior” means closer to or toward the feet, and the term “superior” means closer to or toward the crown of the head. 
       FIGS.  2 A- 2 D  depict a joint distractor  10  according to an embodiment of the present disclosure. Joint distractor  10  generally includes a handle or shank  20  and a distraction head  30 . 
     Handle  20  includes a first portion or grip portion  22  and a second portion or intermediate portion  26 . Thus, first portion  22  is generally gripped by a surgeon and can have a variety of ergonomic shapes to comfortably fit in a hand. In the embodiment shown, first portion  22  is elongate with a generally rectangular cross-section. In other embodiments, first portion  22  may have finger grooves and the like that are configured to conform to the surgeon&#39;s hand. First and second portions  22 ,  26  are delineated from each other by a hand stop  24 , which in the embodiment depicted is in the form of dual projections extending sideways from joint distractor  10 . 
     Second portion  26  is intermediate first portion  22  and distraction head  30 . Second portion  26  has a reduced superior to inferior (S-I) or top to bottom thickness as compared to first portion  22 . This reduction in thickness is created by a cutout or recess  27  that forms a clearance space for an anterior tibia as the joint distractor  10  is used in a knee joint space, as described further below. It is noted that, although first and second portions  22 ,  26  are shown as having the same orientation along a longitudinal axis of distractor  10 , second portion  26  may be canted relative to first portion  22  depending on the circumstances and/or surgeon preference. For example, second portion  26  may be canted inferiorly or superiorly such that first and second portions  22 ,  26  form an oblique angle therebetween to provide the surgeon with a different feel or leverage. 
     Distraction head  30  extends from handle  20  and generally has a femoral bone contact side  31  and a tibial bone contact side  32 . Femoral and tibial bone contact sides  31 ,  32  are configured to conform to corresponding lateral and/or medial condyles of a femur  50  and a tibia  60 , as shown in  FIG.  3 A , and to provide anti-skid characteristics that allow joint distractor  10  to distract the joint space between these bones without slippage or being ejected out of such joint space. 
     As shown in  FIG.  2 C and  3 A , femoral and tibial contact sides  31 ,  32  are each curved in a first plane or sagittal plane such that each side  31 ,  32  defines an arc length that has a radius of curvature. Femoral bone contact side  31  has a first arc length AL 1  that has a first radius of curvature R 1 , and tibial bone contact side  32  has a second arc length AL 2  that has a second radius of curvature R 2 , as shown in  FIG.  3 A . The centers of curvature C 1 , C 2  for each side  31 ,  32  are offset from each other in the sagittal plane in both an anteroposterior direction and a superior-inferior direction. More specifically, the center of curvature C 2  of AL 2  is positioned anteriorly and inferiorly to the center of curvature C 1  of AL 1 . In the embodiment depicted, R 1  is greater than R 2 . For example, R 1  may be 1.50 in. and R 2  may be 1.32 in. Although R 1  is greater than R 2 , the offset position of C 1  and C 2  causes AL 1  and AL 2  to be divergent such that the thickness of distraction head  30  increases in a posterior to anterior direction to form a posterior to anterior expanding taper. In other words, a thickness of distraction head  10 , which is defined between femoral and tibial bone contact sides  31 ,  32 , increases from a first end of distraction head  10  to a second end of distraction head  10 . The second end of distraction head  10  is connected to handle  20 . This taper helps facilitate insertion of distraction head  30  into a joint space, as best shown in  FIG.  3 A . 
     Femoral contact side  31  includes a first femoral contact portion  34  and a second femoral contact portion  36 . AL 1  spans the respective lengths of first and second femoral contact portions  34 ,  36  and is generally congruent with at least first or second femoral contact portions  34 ,  36 , but preferably congruent with both. In this regard, AL 1  is defined at least by first femoral contact portion  34 , but preferably also second femoral contact portion  36 . First femoral contact portion  34  is in the form of a concavely curved surface which is curved in the sagittal plane such that it is congruent with AL 1 . Thus, the sagittal curvature of first femoral contact portion  34  has a radius of curvature equal to R 1  of AL 1 . First femoral contact portion  34  is also concavely curved in a coronal plane, as shown in  FIG.  2 D . 
     Second femoral contact portion  36  extends from first femoral contact portion  34  toward handle  20  and is in the form of a saddle shape surface. In this regard, second femoral contact portion  36  is concavely curved in the sagittal plane, as shown in  FIG.  2 C , while being convexly curved in the coronal plane, as shown in  FIG.  2 D . In the coronal plane, second femoral contact portion  36  has a crest or ridge  38  located at about the midline of distraction head  30  which forms the highest point of second femoral contact portion  36 , whereas the lowest points of second femoral contact portion  36  are located at opposing sides of distraction head  30 . Ridge  38  follows the sagittal curvature of femoral contact side  31  and is therefore congruent with AL 1  just as first femoral contact portion  34 . However, as indicated above, in some embodiments only first femoral contact portion  34  may be congruent and therefore may only define AL 1 . In the embodiment depicted in which there is congruency between each of first and second femoral contact portions  34 ,  36 , there is a seamless transition from first femoral contact portion  34  to second femoral contact portion  36 . This transition can be seen in  FIG.  2 A  in which first and second femoral contact portions  34 ,  36  intersect at a triangular interface. The saddle shaped configuration of second femoral contact portion  36  provides clearance with an anterior prominence  56  of a trochlear groove  54  of femur  50 , as illustrated in  FIG.  3 C . 
     Tibial contact side  32  includes a first tibial contact portion  33  and a second tibial contact portion  35 . AL 2  spans the respective lengths of first and second tibial contact portions  33 ,  35  and is generally congruent with at least first or second femoral contact portions  33 ,  35 , but preferably congruent with both. In this regard, AL 2  is defined by first tibial contact portion  33 , but preferably also second femoral contact portion  35 . First tibial contact portion  33  is in the form of a convexly curved surface which is curved in the sagittal plane and is congruent with AL 2 . Thus, the sagittal curvature of first tibial contact portion  33  has a radius of curvature equal to R 2  of AL 2 . First tibial contact portion  33  is also convexly curved in the coronal plane, such that first tibial contact portion  33  has a dual convexity that defines the most inferior point of distraction head  10  relative to a longitudinal axis of handle  20 . This most inferior point is referred to as the inferior apex and is intersected by axis A-A in  FIG.  2 C . 
     Second tibial contact portion  35  extends from first tibial contact portion  33  toward handle  20  and is also convexly curved in the sagittal plane and coronal plane such that it also has a dual convexity. Second tibial contact portion  35  is generally positioned offset from the inferior apex in a direction toward handle  20  and is located on an upslope from first tibial contact portion  33 . This allows first tibial contact portion  33  to contact a sulcus of a tibial condyle which second tibial contact portion  35  can engage sloped wall of the tibial condyle rising from the sulcus, which helps provide anterior-posterior resistance to movement particularly since second tibial contact portion has anti-slip properties. 
     Second tibial contact portion  35  includes a plurality of teeth or serrations  39  arranged or arrayed along a length thereof. Teeth  39  each have a length that extends in a lateral-medial direction, as best shown in  FIG.  2 B . In the embodiment depicted, a recessed channel  37  interrupts the lateral-medial span of each tooth  39 . This interruption forms inner edges  39   a, b  at opposite sides of recessed channel  37 , as shown in  FIG.  2 D . Additionally, each tooth  39  has outer edges  39   c, d  formed at its terminal ends. This configuration enables each tooth  39  to engage a tibia with at least two points of contact regardless of the radius value of the coronal curvature of a tibial condyle within which distraction head  30  is positioned. For example,  FIG.  2 D  depicts representative curvatures C 1  and C 2  of two differently sized tibial condyles. As shown, each tooth  39  contacts the larger curvature C 1  at two nearer inner edges  39   a, b  while each tooth  39  contacts the smaller curvature C 2  at two points located nearer outer edges  39   c, d . Thus, regardless of the radius of curvature of the tibial condyle, contact should occur at a point between inner and outer edges  39   a, c  and inner and outer edges  39   b, d.    
     As mentioned above, second tibial contact portion  35  is curved in both the sagittal and coronal planes. Thus, each tooth  39  has a profile or margin that is convexly curved in these planes. In the sagittal plane, teeth  39  are bounded by AL 2  to facilitate and not impede insertion of joint distractor  10  into a joint space. In other words, no portion of teeth  39  extend beyond an imaginary boundary extending from and defined by the curvature of first tibial contact portion  33 . For example, where first tibial contact portion  33  has a radius of 1.32 in., then the exterior margin of each tooth  39  is either equal to or less then 1.32 in. Where this exterior margin is equal, teeth  39  are then congruent with AL 2 . This contrasts with teeth  39  extended beyond the boundary defined by AL 2  in which introduction of distraction head  30  into a joint space would be more difficult since teeth  39  would dig into the tibia upon their insertion making it difficult to fully insert and seat distraction head  30 . However, in the embodiment depicted in which teeth  39  are bounded by AL 2 , after insertion of distraction head  30 , teeth  39  engage and dig into the anterior of a tibia condyle once handle  20  is rotated distally, as shown in  FIG.  2   . The synovium fluid and cartilage create a very slippery surface. The stabilizing ability of teeth  39  prevents joint distractor  10  from being squeezed or ejected out from the joint space particularly as the surgeon pushes down on handle  20  to lever open the joint space to assess soft tissue laxity. The posterior arrangement of second tibial contact portion  35  relative to first tibial contact portion  33  and its location on the upslope of tibial contact side  32  of distraction head  30  effectively places teeth  39  at the pivot point of joint distractor  10  so that teeth  35  remain engaged to tibia  60  while levering forces are applied to joint distractor  10  (see  FIG.  3 B ) that would ordinarily eject other instruments, such as the osteotome and spoon of  FIGS.  1 A and  1 B , respectively. 
     As discussed above, femoral and tibial bone contact sides  31 ,  32  are curved in coronal and sagittal planes. An anatomic sagittal plane generally extends in an anterior-posterior direction and superior-inferior direction relative to a human patient, while an anatomic coronal plane extends in a lateral-medial direction and superior-inferior direction. Reference herein to the sagittal and coronal planes is associated with the preferred application of joint distractor  10  to the human body. As illustrated in  FIGS.  3 A- 3 C , distraction head  30  is configured to be introduced into the joint space from an anterior to posterior direction. Thus, the use of the terms sagittal plane and coronal plane are in reference to the preferred application of joint distractor  10  to the human body. However, it should be understood that other embodiments of joint distractor  10  can be configured to be introduced into the joint space from a lateral or medial location, for example. In such embodiment, the joint distractor may appear similar to that of joint distractor  10  but with the curvatures of tibial and femoral contact portions oriented 90 degrees relative to their orientation in joint distractor  10 . Nonetheless, such embodiment would have dual curvatures to conform to the dual curvature of the anatomic condyles. 
     The coronal and sagittal curvatures of distractor head  30  can be determined based on a statistical analysis of a population of femoral and tibial bones in a bone database. One exemplary database is the Stryker Orthopaedics Modeling and Analytics (“SOMA”) database, which catalogues various bone morphology datasets relating to size, shape, density, cortical boundaries, location of bony landmarks, and the like, drawn from a collection of individual bones, such as a femur and a tibia. In this regard, the condylar curvatures of a select population of bones (e.g., population based on height, weight, sex, age, and/or the like) in the sagittal and coronal planes can be measured. Such measurements generally fit a normal distribution such that the first, second, and third standard deviations of these measurements for the particularly selected population can be determined. The curvatures of femoral and tibial contact sides of distraction head (e.g., R 1  and R 2 ) are then determined to encompass the first, second, or third standard deviation patients in the select population. First standard deviation curvatures may more closely conform to a condyle but exclude about 32% of the patients within the select population. To account for this, multiple joint distractors can be configured to cover the outlier patients to ensure distractor head optimally conforms to a particular patient within that population. 
       FIGS.  4 A and  4 B  depict another embodiment joint distractor  100 . For ease of review, like elements will be accorded like reference numerals to that of joint distractor  10 , but within the 100-series of numbers. In this regard, joint distractor  100  includes a handle  120  with a first portion  122  and a second portion  126  and a distraction head  130  with femoral and tibial contact sides  131 ,  132 . Additionally, femoral bone contact side  131  includes first and second femoral contact portions  134 ,  136 , and tibial contact side  132  includes first and second tibial contact portions  133 ,  135  that are similarly configured to those of joint distractor  10 . However, joint distractor  10  differs in that none of the teeth  139  of second tibial contact portion  135  has a recessed channel. Such configuration may result in single-point contact, rather than two-point contact, for tibial condyles of relatively large size, such as that of curvature C 1  in  FIGS.  2 B and  2 D . Thus, while this is an alternative embodiment, this embodiment is not preferred as it is generally more unstable than joint distractor  10  for larger tibial condyles. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are 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.