MTP Dislocations - Foot & Ankle

Introduction
A condition characterized by multiplanar instability of MTP joint often seen with "crossover toe" dorsomedial subluxation Pathoanatomic stages plantar plate disrupted can be caused by traumatic rupture chronic inflammation (more common) lateral collateral ligament fails leads to medial deviation of the second toe plantar plate, with its flexor tendon attachments, displace medially medial displacement of the proximal phalanx relative to the metatarsal medial structures become contracted lumbrical and interosseous tendons, medial collateral ligament (MCL), and medial capsule become tight and contracted creating adduction force plantar plate subsequently fails hyperextension forces on the proximal phalanx result in dorsal instability Associated conditions MTP synovitis, deformity often accelerated by cortisone injection done for either misdiagnosed Morton's neuroma or into the MPJ for synovitis.
Anatomy
Plantar plate anatomy broad, thick ligamentous structure that spans the plantar aspect of the MTP joint origin on the metatarsal head via a thin synovial attachment, just proximal to the metatarsal articular surface insertion plantar base of the proximal phalanx function resists tensile loads in the sagittal plane (particularly in dorsiflexion of the joint) cushion the joint and support weightbearing forces
Presentation
Symptoms pain walking on “marble in the ball of their foot” early instability (prior to deformity) may be confused with Morton's neuroma, deformity often follows cortisone injection for presumed neuroma Physical exam callus under the metatarsal head dorsomedial deviation of the toe in relation to the metatarsal hammertoe (flexion at the PIPJ, extension at the MPJ) dorsal instability found on "drawer test " grip toe (proximal phalanx) with one hand and the metatarsal head with the other and move toe dorsally
Imaging
Radiographs recommended views weightbearing AP, oblique, and lateral findings AP shows dislocation of the proximal phalanx (medial more often than lateral) weightbearing lateral shows hyperextension and dorsal dislocation of the proximal phalanx MRI indications rule out other pathology elucidate pathology of surrounding structures used in early stages of MTP synovitis to evaluate plantar plate but not necessarily useful in dislocation
Treatment
Nonoperative taping, shoe modification, metatarsal pads, Budin splint, and NSAIDS indications first line of treatment will not correct deformity Operative distal oblique shortening MT osteotomy (Weil procedure) indications significant pain and loss of function fixed deformity plantar plate repair performed with metatarsal osteotomy sutures passed through distal plantar plate and then through drill holes in proximal phalanx flexor to extensor tendon transfer FDL split and brought over top of proximal phalanx to stabilize joint EDB transfer under intermetatarsal ligament
Surgical Techniques
Distal oblique shortening MT osteotomy (Weil procedure) soft tissue balancing dorsal and medial capsular release with lateral capsular reefing can be used in combination with Weil osteotomy EDB tendon transfer after rerouting tendon through transverse intermetatarsal ligament results in a dynamic stabilizer of incompetent lateral structures flexor digitorum longus (FDL)–to–extensor digitorum longus (EDL) tendon transfer (Girdlestone-Taylor procedure) resection arthroplasty of the metatarsal head (DuVries) plantar plate repair as above osteotomy intra-articular osteotomy that achieves longitudinal decompression through shortening and allows joint reduction. metatarsal (MT) is exposed and the direction of shortening in the original Weil procedure runs mostly parallel to the plantar aspect of the foot. fixation osteotomy is fixed by means of a screw running perpendicular to the osteotomy line.
Complications
Floating toe deformity inability to flex MTP joint causing 2nd digit dorsiflexion deformity (ie. floating toe) most common complication Toe vascular compromise if correcting a chronic dislocation, the soft tissue (including vasculature) can contract stretching of the vasculature can compromise flow procedure may need to be reversed to save digit