Point-Counterpoint: Is Plantar Plate Repair More Effective Than Flexor Tendon Transfer?

Yes. After discussing the importance of the plantar plate in facilitating MTPJ stability, this author points out key shortcomings of the flexor tendon transfer and emphasizes the more direct focus of plantar plate repair. By Leon Reber, DPM When it comes to pain below the metatarsal head, clinicians have described this with various names such as predislocation syndrome, monoarticular nontraumatic synovitis, capsulitis or simply metatarsalgia. Although the terminology varies, the one thing they have in common is pressure. Excessive pressure below the metatarsal head is the reason the patient has pain. Given the etiology, lesser metatarsal overload is actually a more descriptive and appropriate term. The second metatarsophalangeal joint (MTPJ) is most commonly involved. In the earlier stages of lesser metatarsal overload, the condition is sometimes misdiagnosed as a second innerspace neuroma. Pain associated with attenuation or rupture of the plantar plate represents the symptoms of a dysfunctional foot. Accordingly, one should focus on eliminating the biomechanical source of lesser metatarsal overload. Causes of lesser metatarsal overload include an insufficient first ray with or without hallux valgus, long second metatarsal and equinus.1-4 As with many disease processes, the etiology may be multifactorial and one should generally regard primary repair of the plantar plate as an adjunctive procedure. Recognition of each of the potential contributing factors that cause overload will allow the surgeon to effectively address not just the symptoms but the etiology as well. Instability of the MTPJ results from weakening of the periarticular structures, namely the plantar plate. Once the joint is unstable, the flexor tendons deviate the toe medially.5 Primary repair of the plantar plate has been gaining popularity because it addresses the actual focus of pathology. The plantar plate as a static stabilizer of the MTPJ is well known.6,7 However, the role of the plantar plate, when it comes to dynamic stability of the MTPJ, is underappreciated. The strongest attachment of the plantar plate is into the base of the proximal phalanx, which helps create a socket for the metatarsal head. The plantar plate is the only significant distal attachment of the plantar fascia. In fact, one can think of the plantar plate as a thickening of the plantar fascia below the metatarsal head. Given this relationship, the plantar plate is an integral part of the windlass mechanism that helps dynamically stabilize the MTPJ. How The Plantar Plate Stabilizes The MTPJ The windlass mechanism describes the effects dorsiflexion of the toes have on the foot. Dorsiflexion of the toes tightens the plantar fascia, which causes the arch to rise. In contrast, the reverse windlass describes the effects the foot has on the toes. Loading the foot through weightbearing tightens the plantar fascia and causes the toes to plantarflex. Hicks and Sarrafian recognized the plantar fascia as a plantarflexor of the toes through the reverse windlass mechanism. Sarrafian notes that upon weightbearing, “the toes are plantarflexed by the tensioning of the plantar aponeurosis.”8,9 As early as 1977, Scheck recognized the role of the plantar plate and plantar fascia as dynamic contributors to the MTPJs.10 Scheck further believed that elongation of the plantar structures creates a dynamic imbalance, resulting in hammertoe deformities. Hammel, et. al., consider the toes to have passive and active plantarflexors.11 They describe the plantar fascia as a passive plantarflexor and the flexor tendons as an active plantarflexor of the toes. They not only found the plantar fascia to be a significant flexor of the toes but found that the plantar fascia allows the flexor tendons to act more effectively. They demonstrated that when the flexor tendons pull without the stabilization of the plantar fascia, the toes had a tendency to curl. This study implies that without a stabilized MTPJ, the flexor tendons are a deforming force. The role of the plantar fascia as a plantarflexor and stabilizer of the toes is highlighted in case presentations in which plantar fascia ruptures and surgical excision have led to the development of hammertoes.12 The plantar plate essentially serves as a link that connects the plantar fascia to the proximal phalanx. Any tear or attenuation of the plantar plate disrupts this link and is likely to cause a dampening of the reverse windlass mechanism, and reduce the plantarflexion force on the toes during weightbearing. One can observe this mechanism clinically with the Kelikian push-up test. The clinician loads his or her hand onto the patient’s foot and generates tension in the plantar fascia, which brings the toe down. If the toe does not come down, something is likely wrong with the plantar plate. Repairing a compromised plantar plate restores the reverse windlass mechanism and improves plantarflexion of the toes. When Flexor Tendon Transfers Fail Flexor tendon transfers are considered the mainstay of treatment for an unstable MTPJ and basically function as a dynamic tether with no static stabilization. However, complications of stiffness, continued pain or a non-purchasing toe may persist.13 These complications occur relatively often. A recent study showed residual dorsiflexion in 34 percent of patients who underwent flexor tendon transfers and 27 percent had continued pain.13 The flexor tendons and plantar plate/plantar fascia work in concert to stabilize the toe.11 Flexor tendon transfers have mixed results in the literature because they are often incapable of acting as the sole stabilizer of the toe. Plantar plate repair restores the natural balance. This procedure allows the flexors and plantar plate to assume their respective roles and stabilize the toe. There is a general reluctance to make plantar incisions despite numerous papers describing plantar incisions for the treatment of interdigital neuromas without plantar scars. This reluctance has shifted attention away from the focus of pathology. In addition, medial displacement of the flexor tendon apparatus has been confirmed intraoperatively at our institution when performing plantar plate repairs. This finding may help explain some of the failures we have seen with flexor tendon transfers. With the flexor tendon apparatus appropriately aligned, the metatarsal head acts as a drum upon which the flexor tendon transfer may help to plantarflex the MTPJ. However, in a foot with medial displacement of the flexor tendons, the metatarsal head no longer acts as a drum. In this setting, a flexor tendon transfer may provide less than optimal plantarflexory strength to the MTPJ, resulting in a non-purchasing toe. Furthermore, with advanced stages of plantar plate insufficiency, a flexor tendon transfer alone may provide incomplete resolution of pain because the metatarsal head may continue to herniate through the defect in the plantar plate during push-off.14 Although evidence-based medicine supporting primary repair of the plantar plate is lacking, we have seen this procedure performed many times with equal or better results than flexor tendon transfers. It makes sense that if pathology in the plantar plate leads to instability and deformity, then one should at least consider addressing the focus of pathology. It should be noted that pathology affecting the second toe can range from pre-dislocation syndrome to a chronic medially deviated crossover toe. Primary repair of the plantar plate has met the most success when surgeons perform the procedure in the earlier stages of the deformity. As the deformity progresses to that of a chronic situation, performing a plantar plate repair alone is often inadequate. In these cases, including a flexor tendon transfer along with a plantar plate repair is often necessary. In Conclusion The plantar plate and flexor tendons work in concert to stabilize the toe. Utilizing a flexor tendon transfer with known insufficiency of the plantar plate may be inadequate to stabilize the joint fully, resulting in a floating toe and/or pain during push-off. A compromised plantar plate leads to instability and deformity of the second toe. Restoring anatomy by addressing the actual focus of pathology increases the likelihood of success. Plantar plate repair restores the natural balance and stability to the toe. When non-operative measures have failed, one should regard plantar plate repair as an adjunctive procedure to those procedures that address the etiology and effectively reduce pressure below the metatarsal head. Dr. Reber is a third-year resident at the Northwest Podiatric Surgical Residency Program in Seattle. He is beginning private practice at the Foot and Ankle Institute in St. George, Utah. No. When it comes to more common, chronic cases of plantar plate tears, this author says the flexor tendon transfer provides more stability and long-term correction. By Babak Baravarian, DPM The treatment of plantar plate tears and associated hammering of the digit has evolved dramatically in the past decade. What was not truly understood or treated 10 years ago is well researched and rarely misdiagnosed or mistreated at this time. There are two forms of treatment for a plantar plate tear. The dilemma for surgeons is choosing between a primary repair of the torn plantar plate or a secondary flexor tendon transfer to the digit for stabilization of the dislocating toe. To date, the questions as to which procedure is preferred or which one has better results have not been answered. For years, our institute has performed both procedures with select reasoning behind each treatment. In general, we have found that a flexor tendon transfer offers a greater ease of treatment, allows for better correction and has fewer secondary complications when compared to a primary repair of the plantar plate. This is not to say that we do not perform primary plantar plate repairs. However, we only use the primary plantar plate repair in cases of acute tear when there is a good chance of repair with minimal scar formation at the site of rupture. Differentiating Between Acute And Chronic Cases Acute cases of plantar plate rupture are rare and often present with a history of trauma, especially sports-related trauma. Clinicians will often note pain in association with the traumatized joint. The main pain is from a dorsal drawer of the digit and there is direct pain plantar to the metatarsophalangeal joint (MPJ). While these patients will have minimal to no hammering of the digit, clinicians will note minimal medial or lateral shift of the digit. The more common presenting situation is a chronic overload of an MPJ with an associated tear of the plantar plate. In these cases, one will note a positive dorsal drawer and pain in the plantar MPJ. There is also a moderate to severe hammering of the digit, partial to complete dislocation of the MPJ and a mild to severe lateral or, more commonly, medial shift of the digit. The patient may also have a mild numbness or tingling of the medial or lateral interspace, which is often secondary to irritation of the digital nerve from swelling of the MPJ and abnormal pressure on the nerve. When it comes to detecting plantar plate tears, the diagnosis ranges from a simple examination finding to pursuing multiple diagnostic tests before arriving at the underlying problem. It is difficult at times to differentiate a mild plantar plate tear from capsulitis and/or neuritis of the digital nerve. Specific examination findings include pain and laxity with dorsal drawer, pain on pressure to the associated plantar metatarsal head, and a dorsal and medial or lateral shift of the associated toe. Commonly, the region of tear is either on the medial or, more commonly, on the corner of the plantar plate attachment to the base of the phalynx. Therefore, there is a medial or lateral shift of the toe associated with the dorsal contracture. Ultrasound testing has been a simple and often excellent source of information for plantar plate tears. There is often a thinning and scarring of the plantar plate in the region of tear. A dynamic dorsal drawer test can show laxity and dorsal migration of the associated toe under ultrasound testing. Finally, a local injection into the associated MPJ under ultrasound guidance can show leakage if there is a tear. However, keep in mind that not all injections will leak if there is scar tissue filling of the tear region. Magnetic resonance imaging (MRI) has also been noted as a good diagnostic tool in plantar plate tears. However, tears are difficult to locate and clinicians often use the test to rule out other problems such as avascular necrosis, capsulitis, neuroma formation or stress fracture. While radiographs are not as specific, they have shown some standard findings with plantar plate tears. There is a medial or lateral shift of the toe, and mild to moderate dorsal migration of the proximal phalynx at the MPJ. Radiographs are excellent when it comes to showing the length of the associated metatarsal and the metatarsal parabola. Clinicians may also see first metatarsal laxity and hallux valgus deformity. Pertinent Treatment Considerations In acute cases of plantar plate tears, we often emphasize a non-weightbearing cast and strapping of the toe into a plantarflexed position. After three weeks, we fit the patient for a walking cast or removable boot and continue strapping for an additional three months. At this point, the patient may proceed to wearing stiff shoes with continued strapping for three months. If you note poor stability one month after the patient has ceased using strapping, you may consider primary repair. However, it is important to alert the patient to the fact that a secondary flexor transfer may be necessary as primary repair may not be possible due to poor tissue or shredding of the torn plantar plate. Chronic cases are far simpler to treat. After ensuring an accurate diagnosis, one would proceed to a period of conservative care with strapping and a stiff walking boot. If there is still pain and laxity, or if there is gross deformity after one month, one should consider surgical stabilization. The surgeon must consider several underlying factors, which include the metatarsal length, laxity of the first ray, hallux valgus deformity, neuritis of the interspace, medial or lateral shift of the toe, laxity of the MPJ and hammering of the digit. At our institute, we generally avoid performing a metatarsal osteotomy in these cases unless it is absolutely necessary. We will perform this procedure if there is a severe difference in the length of one metatarsal associated with plantar plate tear, iatrogenic shortening of the first metatarsal or a toe that cannot be relocated. In these cases, we commonly opt for a Weil type of procedure. We often will stabilize the first ray through a first metatarsal cuneiform fusion or perform an associated hallux valgus correction to remove the stress from the torn plantar plate region. Emphasizing Key Advantages Of The Flexor Tendon Transfer The flexor tendon transfer procedure that we prefer is a long flexor split to the dorsum of the foot. We have attempted transfer through the phalynx base with a drill hole and found tensioning and stabilization to be more difficult. Primary repairs in chronic tear cases have been difficult to perform as there is often poor ligament structure that limits the stability of the repair. There is also mild to moderate medial or lateral shift of the toe that is very difficult to correct with primary ligament repair. A special trick that we have used with great results is using the flexor tendon as a medial or lateral stabilizer of the MPJ. Surgeons can do this by taking the flap of flexor tendon that is on contralateral side to the deformity at the MPJ and tying it into the MPJ capsule under correct tension of the MPJ. This allows for moderate stabilization of deformity at the MPJ in a medial or lateral shift case. Researchers have shown that the flexor tendon transfer has stable and long-term corrective abilities in chronic cases of plantar plate tear. The tendon functions as a strong stabilizer of the MPJ and allows for a decrease in the dorsal drawer at the MPJ associated with plantar plate tear. As there is a need for hammertoe correction in most cases, flexor tendon transfer also allows for correction of the entire deformity through a single dorsal incision. There is also no need for a plantar incision and this negates the risk of a painful scar on the sole of the foot. Finally, there is very little chance of not achieving a stable transfer and repair. The quality of tendon for transfer does not limit the repair result as one might find with primary repair. There is also a decrease in the distal buckling of the distal phalynx that surgeons may see from time to time with fusion of the proximal phalynx. Through our modification and use of a portion of the flexor tendon to stabilize the medial or lateral collateral ligament, we have been able to correct medial or lateral contracture and deformity at the MPJ. Final Notes It is important to consider that we would always like to do a primary repair if possible. For example, secondary ankle ligament repair with a tendon transfer is rarely necessary as surgeons can perform primary repair in most cases with excellent outcomes. However, when it comes to the MPJ region, the techniques for primary repair have not been perfected. The tissue is very friable and easily falls apart during repair. The repaired tissue does not have good integrity and can fail under low amounts of tension. Correction of the medial or lateral shift of the toe at the MPJ is not very stable. There is an increased risk to incisions on the plantar sole of the foot and, finally, the hammering of the digit still needs correction through a dorsal incision. With time, primary plantar plate repairs may become the standard of care for plantar plate tears. However, at the present time, the flexor tendon transfer facilitates consistent, predictable and lasting results. Accordingly, this procedure is the preferred technique for chronically torn plantar plates at our institutes. n Dr. Baravarian is the Co-Director of the Foot and Ankle Institute of Santa Monica. He is an Associate Professor at UCLA Medical Center and is the Chief of Podiatric Surgery at Santa Monica/UCLA Medical Center. Dr. Baravarian may be reached at bbaravarian@mednet.ucla.edu. For related articles, see “Can Orthotics Address The Faulty Biomechanics Of Metatarsalgia?” in the June 2005 issue or “Metatarsalgia: Is The Plantar Plate Important?” in the January 2004 issue of Podiatry Today. Editor’s note: For related articles, visit the archives at www.podiatrytoday.com.
 

References:

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