Abstract:
The present disclosure generally relates to fixation plates for use in correcting Hallux Valgus deformities under the Lapidus approach. The plate includes holes defined therethrough in such a way to facilitate multiplanar stability across the metatarsocuneiform joint. The plate is further sized and shaped to approximate the natural anatomic contour of the bone segments surrounding the metatarsocuneiform joint. Related methods for using the Lapidus approach to correct Hallux Valgus deformities are also described.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure generally relates to medical devices for use in correcting foot deformities, and methods for surgically installing such devices and correcting such deformities. 
       BACKGROUND 
       [0002]    Bunions have long been one of the more common types of painful foot deformities. The technical name for this type of deformity is Hallux Abducto Valgus (HAV), which is generally described as a medial deviation of the first metatarsal accompanied by a lateral deviation and/or valgus rotation of the hallux (or “big toe”). The result effect is a subluxation of the big toe joint (or first metatarsophalangeal joint (MTPJ)) creating a boney prominence (or eminence) on the inside of the foot, near the base of the big toe.  FIG. 1A  illustrates the normal anatomical configuration of a left human foot, which includes the first metatarsal  10  that extends between the medial cuneiform  12  and the hallux  13 . The first metatarsal  10  articulates with the medial cuneiform  12  at the first metatarsocuneiform joint  14  at its most proximal aspect; and is further connected to the hallux  13  at the metatarsophalangeal joint  15  at its most distal aspect. Located adjacent (lateral) to the first metatarsal  10  is the second metatarsal  16 , which articulates with the intermediate cuneiform  17  at the second metatarsocuneiform joint  18 . The joint between the medial cuneiform  12  and intermediate cuneiform  17  is the intermetatarsocuneiform joint  18 . The sesamoids  19  are located beneath (plantar to) the first metatarsal head at the first MTPJ, and articulates with the head of the first metatarsal. 
         [0003]      FIG. 1B  illustrates the resulting anatomical configuration of a human foot experiencing HAV. In particular, the first metatarsal  10  extends from the medial cuneiform  12  and deviates medially while the hallux  13  deviates laterally. As a result, the sesamoids  19  may rotate with the first metatarsal  10 . This condition may lead to painful motion of the big toe joint and/or difficulty fitting footwear. Other conditions associated with HAV may include: hammer toe formation of the adjacent toes, forefoot pain on the ball of the foot (aka metatarsalgia), stress fractures of the adjacent metatarsals, flat feet (pes planus), and arthritis of the first MTPJ or midfoot. 
         [0004]    Bunions may occur from a variety of causes, such as genetic factors, gender influences, biomechanical and structural causes, trauma (injury), and certain shoes. Some physicians believe genetics play a large role in the development of bunions. Dudley Morton suggested that bunions may be a result of evolutionary influence, and described a certain foot type that is associated with bunions—the so called Morton&#39;s foot (a condition where the first metatarsal is shorter than the other metatarsals. See Morton D J. The Human Foot: Its evolution, Physiology and functional Disorders. Columbia University Press, Morningside Heights, N.Y., 1935. Some people develop bunions when associated with a condition called hypermobility, where the midfoot (i.e., metatarsocuneiform joint or “MCJ,” illustrated in  FIG. 1A  as the joint defined at the meeting of the metatarsal  10  and the cuneiform  12 ) exhibits excessive motion. Less commonly, malshaped bones (hallux and/or first metatarsal) may give the appearance of and/or cause bunions. Many physicians attribute the progressive development of bunions to high heel and pointy toe shoes more commonly worn by women. It is well known that women are more likely to develop bunions than men. 
         [0005]    Surgeons use weightbearing radiographs to determine the severity of HAV in an attempt to quantity the deformity, and aid in surgical decision making. The most commonly utilized radiographic measurement is the intermetatarsal angle (IMA), which measures the angle between a longitudinal bisection of the first and second metatarsal shafts. The IMA essentially measures the extent with which the first metatarsal has deviated (medially) from the second metatarsal. The normal value for the IMA is less than 8 degrees. Another useful radiographic measurement is the hallux abductus angle (HAA), which measures the amount of lateral deviation of the big toe (hallux). The HAA essentially measures the extent with which the hallux has deviated (laterally) from its native position (nearly rectus with the more proximal metatarsal). The normal value for the HAA is less than 12 degrees. A patient with a mild HAV deformity may have an IMA of 10-12 degrees and an HAA of 21-30 degrees. A patient with a moderate HAV deformity may have an IMA of 12-16 degrees and an HAA of 31-40 degrees. A patient with a severe HAV deformity may have an IMA of greater than 16 degrees and an HAA of greater than 40 degrees. 
         [0006]    Various techniques have been developed to surgically correct HAV. The most basic technique simply involves resecting any enlarged bone at the medial aspect of the first metatarsal head, but this approach is typically used in conjunction with other more advanced techniques. A common technique involves an osteotomy (bone cut) procedure in which the first metatarsal is broken into two pieces and the distal portion of the bone is translated closer (medially) to the adjacent second metatarsal. The osteotomy may be performed at several locations on the first metatarsal, depending on the severity of the deformity. Less severe HAV deformities are typically corrected with an osteotomy near the head ( 10   a  in  FIG. 1 ) of the first metatarsal, whereas moderate and larger deformities are corrected with an osteotomy near the base ( 10   b  in  FIG. 1 ) of the first metatarsal. Whichever osteotomy technique is utilized, only the distal portion of the first metatarsal is relocated into a more lateral position while the proximal segment position remains unchanged. It should be understood that any osteotomy procedure reorients the first metatarsal by changing its shape from that of a straight bone to a more curved bone. 
         [0007]    Alternative techniques have been developed that do not require breaking of the bone, or changing the natural shape of the first metatarsal. One such technique calls for fusion of the MCJ, wherein the entire first metatarsal is relocated into a corrected position. This approach was originally developed by Dr. Paul Lapidus, and hence this particular technique is often referred to as the Lapidus approach (or Lapidus Bunionectomy or Lapidus Arthrodesis or Modified Lapidus Bunionectomy/Arthrodesis). In some situations the procedure may involve an isolated fusion of the 1 st  MCJ, and in other situations surgeons may also incorporate a fusion of the intermediate cueniform area and or 2 nd  metatarsal base. In general, the idea behind the Lapidus approach is to permanently fuse the base of the first metatarsal to the medial cuneiform bone in a corrected new position. This permanent fixation is carried out by first reducing the IMA and then fusing the MCJ. Implementation of this approach often involves the use of a number of screws across the joint or a plate that can accommodate screws to attach the plate to the metatarsal and medial cuneiform. In some cases, a fusion of the 1 st  MCJ that incorporates lengthening of the entire segment by adding bone graft (i.e., a block of bone) into the fusion site is better termed a distraction Lapidus. 
       BRIEF SUMMARY 
       [0008]    The present disclosure generally relates to an improved fixation or “Lapidus” plate for use in treating HAV deformities or other conditions that may call for a fusion of this joint and possibly concomitant fusion incorporating the 2 nd  metatarsal base and/or intermediate cuneiform. The term “Lapidus” as used herein is only meant to be descriptive in terms of a suggested use for the plate and does not confer any structural limitations on the plate described herein. In one exemplary embodiment, the Lapidus plate is used for joint arthrodesis at the first MCJ. The Lapidus plate according to the present disclosure provides mechanical stability of the first metatarsal while also accommodating and assisting reorientation of the first metatarsal to correct the HAV deformity. In one embodiment, the plate is generally elongated and comprises a thin and rigid stabilizing member of biocompatible material. The orientation of the fixation plate offers multiplanar stability including the plantar aspects of the joint to resist tensile forces transmitted across the fusion site. The screw configuration of the plate can be maintained for several different sizes of the plate while still maintaining desired multiplanar stability. Also, the positioning of the screw holes are designed to avoid invasion of the fusion site by the screws that ultimately pass therethrough. Indeed, the screw angles are designed for the post-Lapidus position. 
         [0009]    The Lapidus plate according to the present disclosure includes additional features that accommodate the desired reorientation of the first metatarsal during correction. For example, the Lapidus plate described herein includes a degree of twist along its longitudinal axis to follow the contour of the first metatarsal and medial cuneiform, thereby facilitating reorientation of the first metatarsal to its natural position. The Lapidus plate is further anatomically configured to include a recess, which accommodates the natural crests of the medial cuneiform and the first metatarsal. In this manner, the first metatarsal can be guided against the medial cuneiform and the plate such that the base of the first metatarsal fits within the recess. The recess thus facilitates a desired location and orientation of the first metatarsal that approximates its natural position. In this manner, the Lapidus plate according to the present disclosure accommodates the final position of the fusion of the MCJ. The fixation plate is anatomically configured to provide rigid support of the realigned MCJ fusion site while positioning screws to avoid invasion into the fusion site thus achieving desired stability. It is to be appreciated that the plate described herein can be adapted for use on both right and left feet with a right foot plate being a mirror-image of a left foot plate. 
         [0010]    A surgical method for preparing the MCJ for receipt of the Lapidus plate and subsequently implanting the plate is further described. In patients with HAV, surgical procedures may be concomitantly performed near the first metatarsal head. A capsular release of the first MTPJ and resection of the medial eminence, if present, is often performed in conjunction with release of the adductor tendon and lateral sesamoidal ligament. Next, all cartilage is removed from the first MCJ with either a reciprocal saw and/or manual resection. Removal of the cartilage is preferred to allow for bone on bone contact to allow for a fusion between the medial cuneiform and first metatarsal. The first metatarsal is then repositioned back to its native position (IMA as close to zero as possible). However, in order to compensate for the shortening that occurs with removal of the cartilage of the first MCJ, the first metatarsal must be translated inferiorly and/or angulated inferiorly (plantarflexed) to restore the weightbearing mechanics of the first metatarsal head at the ball of the foot. Lastly, the fusion site is stabilized with the fixation plate described herein. In some embodiments, the plate is placed on the dorsal medial surface of the segment to avoid contact with muscular attachments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Reference is now made to the following descriptions taken in conjunction with the accompanying drawings. 
           [0012]      FIG. 1A  illustrates a top view of a human foot; 
           [0013]      FIG. 1B  illustrates a top view of a human foot experiencing the condition of Hallux Valgus; 
           [0014]      FIG. 2  illustrates a top view of a fixation plate according to one embodiment of the present disclosure; 
           [0015]      FIG. 3A  illustrates a side view of the fixation plate of  FIG. 2 ; 
           [0016]      FIG. 3B  illustrates a side view of the fixation plate of  FIG. 2  positioned adjacent to the MCJ; 
           [0017]      FIG. 4  illustrates a schematic view depicting the gradual twist of the fixation plate of  FIG. 2 ; 
           [0018]      FIG. 5A  illustrates a perspective view of the fixation plate of  FIG. 2  positioned against the medial cuneiform and first metatarsal; 
           [0019]      FIG. 5B  illustrates another perspective view of the fixation plate of  FIG. 2  positioned against the medial cuneiform and first metatarsal; 
           [0020]      FIG. 6  illustrates a top view of the fixation plate of  FIG. 2  affixed to the medial cuneiform and first metatarsal; 
           [0021]      FIG. 7  is a bottom perspective view of the fixation plate of  FIG. 6  showing the orientation of the screws; and 
           [0022]      FIG. 8  is a perspective view of another embodiment of the fixation plate wherein the plate is a distraction plate. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Various aspects of a Lapidus plate and methods of using same according to the present disclosure are described. It is to be understood, however, that the following explanation is merely exemplary in describing the devices and methods of the present disclosure. Accordingly, several modifications, changes and substitutions are contemplated. 
         [0024]    A Lapidus plate  20  for a human left foot according to the present disclosure is illustrated in  FIG. 2 . It is to be appreciated that a Lapidus plate according to the present disclosure for a human right foot would be substantially similar to and have a mirror image configuration of the plate  20  illustrated in  FIG. 2 . The plate  20  generally comprises a distal portion  22  for attachment to a metatarsal and a proximal portion  24  for attachment to a cuneiform. For purposes of illustration only, the distal and proximal portions  22 ,  24  are divided along a joint axis (J) generally corresponding to the fusion site (i.e., the interface between the cuneiform and metatarsal) as will be described. In one exemplary embodiment, the metatarsal is the first metatarsal  10  ( FIG. 1 ) and the cuneiform is the medial cuneiform ( FIG. 1 ). The plate  20  is sized and shaped to conform to the anatomical contours of the first MCJ and as such the distal portion  22  includes a relatively narrow and rounded end portion  26 . The distal portion gradually increases in width along a first side  28  of the plate towards the proximal portion  24 . The proximal portion  24  includes a slight gradual increase in width along the first side  28  of the plate  20  culminating in a rounded end portion  30  that is larger in width than the end portion  26  of the proximal portion  22 . The plate  20  further includes a substantially linear second side  32  opposite the first side  28 . 
         [0025]    The plate is configured and designed to avoid tendon and minimize soft tissue irritation, while also providing for optimal rigidity and stability. As such, in some embodiments, the end portion  26  of the distal portion  22  has an anatomically optimal width W 1  in the range of 10.5+/−3 mm, while the end portion  30  of the proximal portion  24  has an anatomically optimal width W 2  in the range of 16+/−4 mm. In some embodiments, the plate has a varying thickness of between 0.75 mm and 3.0 mm, thus minimizing tissue irritation. Moreover, the edges of the plate may be tapered. In one embodiment, the Lapidus plate according to the present disclosure is sized and shaped for placement in a “safe zone” of the area to be treated; that is, the place on the dorsal medial surface of the first metatarsal and medial cuneiform that is devoid of tendon attachments. It is to be appreciated that the Lapidus plate according to the present disclosure may have a configuration different than that described herein so long as the plate accommodates the contours of the particular anatomical region being treated. 
         [0026]    The distal and proximal portions  22 ,  24  of the plate  20  each include a plurality of screw holes formed therethrough to facilitate attachment of the plate to the respective metatarsal and cuneiform. In one embodiment, the distal portion  22  includes four screw holes formed through the plate  20  with two holes  40 ,  42  being positioned in proximity to the joint axis J and the remaining two holes  44 ,  46  being positioned distal of holes  40 ,  42 . In some embodiments, the holes  40 ,  42  and  46  are countersunk and threaded to accommodate screws having threaded heads as will be described. Hole  40  is positioned adjacent to the second side  32  and the joint axis J while hole  42  is positioned distal of hole  40  and closer to side  28  of the plate  20 . Hole  44  is positioned distally of holes  40 ,  42  and is generally elongated to accommodate movement of the plate  20  as will be described. The elongated nature of hole  44  defines a pair of substantially parallel sides  47 ,  49 , which are substantially parallel to second side  32  of the plate  20 . Hole  46  is positioned distal of hole  44  and also accommodates a screw (not shown) to assist with fixation of the plate  20  to the metatarsal. The location of hole  46  assists with distributing weight away from the fusion site. 
         [0027]    Similar to the distal portion  22  of the plate  20 , the proximal portion  24  includes a plurality of screw holes to accommodate fixation. In one embodiment, the proximal portion  24  of the plate  20  includes three holes  48 ,  50  and  52  formed therethrough. In some embodiments, the holes  48 ,  50  and  52  are countersunk and threaded to accommodate screws having threaded heads as will be described. Hole  48  generally corresponds to hole  40  of the metatarsal portion, and as such, is positioned adjacent to the second side  32  and the joint axis J. Hole  50  generally corresponds to hole  42  of the metatarsal portion, and as such, is positioned proximal of hole  48  and closer to side  28  of the plate  20 . Hole  52  is positioned proximal of holes  48 ,  50  and accommodates a screw (not shown) to assist with fixation of the plate  20  to the cuneiform bone. The location of hole  52  assists with distributing weight away from the fusion site. 
         [0028]    In one embodiment, the holes  40 ,  42  of the distal portion  22  and the holes  48 ,  50  of the proximal portion are designed to assist with screw fixation into the widest part of both bone segments while maintaining a safe distance from the fusion site such that the screws that ultimately pass through such holes do not penetrate the fusion site. In this regard, the holes  40 ,  42 ,  48  and  50  form a substantially trapezoidal shape, which facilitates the even distribution of load across the MCJ. It is to be appreciated that the arrangement of holes  40 ,  42 ,  48  and  50  may not form an exact trapezoid. For example, the line defined from the centerpoint of hole  40  to the centerpoint of hole  48  and the line defined from the centerpoint of hole  42  to the centerpoint of hole  50  may not be perfectly parallel. Rather, such lines may be only substantially parallel and thus the arrangement of holes  40 ,  42 ,  48  and  50  may form a substantially trapezoidal shape rather than a true trapezoidal shape. The substantially trapezoidal arrangement of the holes  40 ,  42 ,  48  and  50  define an angle θ measured between the nonparallel sides of the trapezoid (i.e., between the lines A 1  and A 2  shown for purposes of illustration in  FIG. 2 ). Also, the distance between the dorsal screw holes  40 ,  48  is measured by the distance D. In some embodiments, the angle θ is optimally 57+/−15 degrees and the distance between the dorsal screws  40 ,  48  is optimally 12+/−4 mm. 
         [0029]    Referring to  FIGS. 3A and 3B , the plate  20  according to the present disclosure further includes a recess  60  defined along a bone-contacting surface  62  of the plate. The recess  60  is generally defined at and adjacent to the joint axis J of the plate  20 . In this manner, the plate  20  is designed to accommodate the crests of the first metatarsal  10  and medial cuneiform  12  upon placement of the plate against the MCJ as illustrated in  FIG. 3B . In some embodiments, a channel  64  is formed laterally in the bone-contacting side of the plate  20  in a region generally corresponding to the recess  60  to facilitate additional flexibility at the fusion site along the joint axis J ( FIG. 2 ). This flexibility assists the surgeon with bending of the plate  20  to achieve the desired final position of the plate at the fusion site. 
         [0030]    In some HAV deformities, the first metatarsal experiences a lateral twist. As a result, the sesamoid bones are no longer in contact with the surface and are thus not able to carry most of the body load transferred through the forefoot during motion. This results in an extra load being placed on other adjacent metatarsals, thus increasing the possibility for metatarsalgia, or possibly stress fractures in those metatarsals. To correct this disorientation, in some embodiments, the plate  20  according to the present disclosure includes a degree of twist along its longitudinal axis (i.e., from end portion  30  to end portion  26  as shown in  FIG. 2 ). Referring to  FIG. 4 , the plate  20  has a gradual twist γ from proximal portion  24  to distal portion  22 . In some embodiments, the anatomically optimal twist is 12+/−6 degrees measured along the longitudinal axis of the plate  20  defined from end portion  30  to end portion  26 . 
         [0031]    In practice, the first MCJ is prepared for plate implantation by first performing a capsulotomy of the ligaments surrounding the first MCJ and then removing cartilage within this joint. Referring to  FIGS. 5A ,  5 B and  6 , the proximal portion  24  of the plate  20  is placed against the medial cuneiform  12  and attached thereto using screws  70  having threaded heads and threaded shafts. The threaded heads of the screws  70  thread into the corresponding countersunk threaded holes  48 ,  50  and  52  ( FIG. 2 ) such that the screws are fixed relative to the plate  20 . It is to be appreciated that in some embodiments, the screws may have non-threaded heads such that the screws are not locked into place relative to the plate  20 . Upon attachment of the plate  20  to the medial cuneiform  12 , the first metatarsal  10  is translated inferiorly in the direction I as illustrated in  FIG. 5B  to maintain a natural distribution of ground force over all the foot&#39;s sesamoid bones to avoid stress fracture or even breakage of the other four metatarsals. In some embodiments, the optimal amount of translation D I  is 3+/−3 mm to accommodate for the shortening that occurs when cartilage is removed from the joint. The first metatarsal  10  is also translated laterally and rotated in the direction R to return the metatarsal to its approximate natural anatomic orientation to reduce the intermetatarsal angle. The plate  20  according to the present disclosure is designed for placement against the medial cuneiform and first metatarsal in an area devoid of muscular and tendinous attachments. 
         [0032]    Upon proper positioning of the first metatarsal  10 , a screw (not shown) is placed through the elongated hole  44  and into the metatarsal with the elongation permitting movement of the bone. In some embodiments, the MCJ may be temporarily fixated in a corrected position using a k-wire. Also, the plate  20  may include k-wire holes such that k-wires can be used in conjunction with the plate to stabilize the first metatarsal for screw implantation. Upon stabilization, the first metatarsal  10  is then moved toward the medial cuneiform  12  whereupon the screw positioned through elongated hole  44  is tightened to compress the first MCJ. Once compression is achieved, the distal portion  22  of the plate  20  is further attached to the metatarsal using threaded screws  70  having threaded heads that are placed through screw holes  40 ,  42  and  46  ( FIG. 2 ) and into the bone. The threaded heads of the screws  70  thread into the corresponding countersunk threaded holes  40 ,  42  and  46  such that the screws are fixed relative to the plate  20 . It is to be appreciated that in some embodiments, the screws may have non-threaded heads such that the screws are not locked into place relative to the plate  20 . Once the plate is fixed to the medial cuneiform  12  and the first metatarsal  10 , the screw passing through elongated hole  44  may be removed. 
         [0033]    Referring to  FIG. 7 , the twist of the plate  20  along its longitudinal axis facilitates desired orientation of the screws into the metatarsal. More specifically, holes  40  and  42  are angled toward one another such that implantation of the screws  70  through these holes results in their axes crossing one another in a divergent manner. This, in turn, provides for optimal orientation of the screws  70  in the first metatarsal  10  to achieve desired stability. 
         [0034]    A variation of the Lapidus plate according to the present disclosure involves providing for distraction (or lengthening) at the fusion site. As illustrated in  FIG. 8 , this allows for bone graft  80  to be interposed between the 1 st  metatarsal base  10   b  and the medial cuneiform  12 , when the clinical situation arises. Providing for distraction at the fusion site maintains that the screw holes  40  and  42  purchase the 1 st  metatarsal base  10   b,  for which these holes are configured to provide maximal stability at the fusion site. The amount of distraction D′ most commonly required is between 1 mm-25 mm, with the distraction plate accommodating this length. It is to be appreciated, however, that other distraction lengths may be accommodated by the plate  20  of the present disclosure. In some embodiments, the plate  20  may add length by providing additional screw holes formed in distal portion  22  of the plate  20 . In some embodiments, fixation of the plate may occur via a screw passing through the fusion site into the intermediate cuneiform and/or second metatarsal. 
         [0035]    The Lapidus plate  20  described herein and associated method of implantation leads to fusion of the MCJ, which provides for mechanical stability of the first metatarsal and medial cuneiform and the reorientation to compensate for an HAV deformity. The orientation of the fixation achieved according to the principles of the present disclosure offers multiplanar stability including the plantar aspects of the MCJ to resist tensile forces across the fusion site. The screw configuration described herein can thus be maintained for several different sizes of distraction Lapidus arthrodesis. That is, the screw configuration provides multiplanar stability as distraction length is added to the plate  20 . 
         [0036]    While various embodiments of Lapidus plates and related methods of implanting such plates, have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the invention(s) should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. Moreover, the above advantages and features are provided in described embodiments, but shall not limit the application of the claims to processes and structures accomplishing any or all of the above advantages. 
         [0037]    Additionally, the section headings herein are provided for consistency with the suggestions under 37 CFR 1.77 or otherwise to provide organizational cues. These headings shall not limit or characterize the invention(s) set out in any claims that may issue from this disclosure. Specifically and by way of example, although the headings refer to a “Technical Field,” the claims should not be limited by the language chosen under this heading to describe the so-called technical field. Further, a description of a technology in the “Background” is not to be construed as an admission that technology is prior art to any invention(s) in this disclosure. Neither is the “Brief Summary” to be considered as a characterization of the invention(s) set forth in the claims found herein. Furthermore, any reference in this disclosure to “invention” in the singular should not be used to argue that there is only a single point of novelty claimed in this disclosure. Multiple inventions may be set forth according to the limitations of the multiple claims associated with this disclosure, and the claims accordingly define the invention(s), and their equivalents, that are protected thereby. In all instances, the scope of the claims shall be considered on their own merits in light of the specification, but should not be constrained by the headings set forth herein.