Lesser metatarsophalangeal joint (MPJ) pathology is one of the most common conditions affecting the forefoot. Most commonly located at the second MPJ, progressive subluxation and dislocation of the phalangeal base on the metatarsal head primarily results from the disruption of the plantar plate, which often begins as predislocation syndrome.1 Painful dislocation of the toe in the dorsal plane, and less commonly in the medial or lateral planes, causes pain with ambulation and shoegear. Anatomic studies have demonstrated the importance of the plantar plate in stabilization of the MPJ in the sagittal plane.2,3 The physician diagnoses a plantar plate rupture primarily by clinical examination. By employing a vertical stress test (Lachman), one can evaluate the integrity of the MPJ plantar plate structure in order to determine the dorsal-plantar stability.4 When the clinician applies a dorsal-plantar force of the proximal phalanx on a stabilized metatarsal head, patients with a positive vertical stress exam will exhibit pain and subluxation or dislocation at the MPJ. A positive vertical stress exam indicates damage to the plantar plate. Digital deformities, such as a hammertoe or clawtoe contracture, may also be present in conjunction with a plantar plate tear. It is important to examine the patient in both a seated and standing position. The digital deformity may often change position during weightbearing or assume a position of maximum pain. Additionally, concomitant hallux valgus may be present with an overlapping second toe, also creating instability in the transverse plane. Standard weightbearing radiographs are useful to determine the metatarsal parabola and the amount of subluxation that may be present in the lesser MPJs. Advanced imaging, such as a magnetic resonance imaging (MRI) or ultrasound, may be advantageous to the diagnosis of a plantar plate tear. Klein and colleagues recently identified 100 percent specificity and a 73.9 percent sensitivity when correlating intraoperative findings to preoperative MRI evaluations for a plantar plate tear.5 In another study by Klein and colleagues, a longitudinal ultrasound image had a positive predictive value and sensitivity of 91.1 percent while transverse plane ultrasound only had an accuracy of 38 percent in correctly identifying a plantar plate tear.6 Conservative treatment of MPJ instability with a plantar plate tear focuses on palliating the dorsally dislocated toe and plantar pain. One can accomplish this with various modalities, such as crossover taping, strapping, splints or customized orthotics with an offloading metatarsal pad. When conservative treatment fails, surgery is often warranted for pain relief and deformity correction. Tendon transfers, metatarsal osteotomies, hammertoe correction and plantar plate repairs are all reportedly successful. Researchers have discussed combining a dorsal approach to plantar plate repair with a shortening metatarsal osteotomy but this can be technically challenging and often complicated with the inability to fully visualize and repair a plantar plate tear.7,8
A Step-By-Step Guide To Surgical Technique
To provide increased visualization of the plantar plate and allow a direct primary plantar plate repair, we present our plantar-based approach to lesser MPJ instability repair. One should ensure supine positioning of the patient on the operating room table and the use of a well-padded thigh tourniquet. We most frequently utilize a regional popliteal block and general anesthesia. First, make a dorsal incision over the MPJ to address the soft tissue dorsiflexion contracture. Carry dissection down to the level of the MPJ where you can perform a transverse capsulotomy and release of the collateral ligaments. If a concomitant shortening metatarsal osteotomy or hammertoe correction is also indicated, perform that procedure at this time. Following the release of the MPJ from the dorsal incision, place a wire by hand from dorsal to plantar through the MPJ and plantar skin to identify the proper location for the plantar incision. Proceed to make a curvilinear plantar incision around the wire for the direct visualization of the plantar plate. One can then remove the wire and perform further layered dissection. Using a self-retaining soft tissue retractor is helpful to protect the digital neurovascular bundle and spread the subcutaneous tissue present in this location. After identifying the flexor digitorum longus and brevis tendon sheaths, incise the sheaths parallel to the tendons and retract them medially or laterally. At this point, the plantar plate is readily identifiable. The plantar plate is a thick fibrocartilaginous structure having attachments at both the proximal phalanx and metatarsal head. Most commonly, one will see a transverse partial plantar plate tear at the level of the insertion into the base of the proximal phalanx. A proposed anatomic grading system can be helpful in classifying the extent of the plantar plate tear.9 If a partial tear or attenuation is visible in the plantar plate, the surgeon must complete the tear in order to perform an adequate end-to-end repair. To allow for repair of the plantar plate, pin the toe and metatarsal in slight plantarflexion with a 0.062 inch wire. This plantarflexed position will allow the resection of a 2 to 3 mm wedge of redundant plantar plate in order to complete a primary repair. Repair of the plantar plate occurs with a #0 or #2 absorbable suture in a pants-over-vest manner. If we encounter a complete tear, we will perform the repair with a small suture anchor to provide additional stability with the fixation into bone. Then close the incision in layers with absorbable and non-absorbable sutures with proper skin eversion. Place the extremity in a posterior compression splint and emphasize a non-weightbearing gait for the patient in the first postoperative week. After one week, physicians can allow patients to wear an immobilizing boot with heel-touch weightbearing for an additional three weeks. At four weeks, one typically removes the wire in the office and permits weightbearing in a tennis shoe.
Six Key Surgical Tips To Remember
1) One should perform a small dorsal incision for release of the MPJ contracture and a metatarsal osteotomy (if necessary) first.
2) Complete a partial tear in a transverse fashion and resect 2 to 3 mm of redundant plantar plate once you have pinned the toe and MPJ with a wire.
3) Utilize a pants-over-vest primary repair with a non-absorbable suture and a UR-6 needle to allow for easier suture passing.
4) If one encounters a complete tear from the proximal phalanx, consider a small suture anchor in the proximal phalanx for added fixation.
5) Maintain the use of a wire in a plantarflexed position for at least four weeks postoperatively during healing.
6) Careful anatomic dissection and retraction, as well as eversion of skin edges during closure, will help prevent a painful plantar scar.
We have found this direct plantar approach repair of plantar plate tears to be our preferred technique. Increased visualization of the anatomic structures and a direct primary repair of the plantar plate allow a dramatic correction of the deformity. Careful dissection and closure have minimized painful plantar scars. Additionally, this repair has also eliminated a floating toe or the recurrence of the deformity postoperatively. Dr. Peterson is a Fellow at the Orthopedic Foot and Ankle Center in Westerville, Ohio. Dr. Hyer is a Fellow of the American College of Foot and Ankle Surgeons, and serves on its Board of Directors. He is the Fellowship Director and an attending physician at the Orthopedic Foot and Ankle Center in Westerville, Ohio. References 1. Yu GV, Judge MS, Hudson JR, Seidelmann FE. Predislocation syndrome. Progressive subluxation/dislocation of the lesser metatarsophalangeal joint. J Am Podiatr Med Assoc. 2002; 92(4):182-199. 2. Coughlin MJ. Subluxation and dislocation of the second metatarsophalangeal joint. Orthop Clin North Am. 1989; 20(4):535-551. 3. Deland JT, Lee KT, Sobel M, Dicarlo EF. Anatomy of the plantar plate and its attachments in the lesser metatarsal phalangeal joint. Foot Ankle Int. 1995; 16(8):480-486. 4. Thompson FM, Hamilton WG. Problems of the second metatarsophalangeal joint. Orthopedics. 1987; 10(1):83-89. 5. Klein EE, Weil L Jr, Weil LS Sr, Knight J. Magnetic resonance imaging versus musculoskeletal ultrasound for identification and localization of plantar plate tears. Foot Ankle Spec. 2012; 5(6):359-365. 6. Klein EE, Weil L Jr, Weil LS Sr, Knight J. Musculoskeletal ultrasound for preoperative imaging of the plantar plate: a prospective analysis. Foot Ankle Spec. 2013; 6(3):196-200. 7. Gregg J, Silberstein M, Clark C, Schneider T. Plantar plate repair and Weil osteotomy for metatarsophalangeal joint instability. Foot Ankle Surg. 2007; 13(3):116-121. 8. Weil L Jr, Sung W, Weil LS Sr, Malinoski K. Anatomic plantar plate repair using the Weil metatarsal osteotomy approach. Foot Ankle Spec. 2011; 4(3):145-150. 9. Coughlin MJ, Schutt SA, Hirose CB, et al. Metatarsophalangeal joint pathology in crossover second toe deformity: a cadaveric study. Foot Ankle Int. 2012; 33(2):133-40. For further reading, see “Emerging Concepts In Treating Second Crossover Toe Deformity” in the October 2009 issue of Podiatry Today.