A Closer Look At Tendon Transfers For Crossover Hammertoe
Given the tricky nature of second digit metatarsophalangeal joint instability/crossover hammertoe, surgeons need an effective remedy. Accordingly, these authors advocate for the use of tendon balancing procedures as viable alternatives that surgeons can combine with a modified Lapidus and endoscopic gastrocnemius recession when adjunctive procedures are warranted.
Coughlin first introduced the term “second crossover toe” in 1987 to characterize a multi-plane deformity at the metatarsophalangeal joint (MPJ).1 Second MPJ instability is all too often a point of consternation for the foot and ankle surgeon.
Crossover toe deformity commonly results from instability of the second MPJ in conjunction with further weakness resulting from hallux abductovalgus deformity and often gastrocnemius equinus. Instability occurs in the sagittal plane but in terms of the crossover toe, this is also combined with a subluxation and/or dislocation in a dorsal and medial direction.2 Once the second MPJ is overloaded in a chronic state, plantar plate rupture and collateral ligament damage can also occur. Further weakened by hallux abductovalgus deformity, instability of the second MPJ can ultimately lead to crossover toe deformity.
Proper treatment of this condition has long been a topic of debate. Regardless, it is paramount to address the underlying biomechanical factors. One should also be cognizant that this is not a result of bony pathology and surgeons can achieve suitable correction through soft tissue balancing procedures.
Understanding The Possible Etiological Factors Of Crossover Hammertoe
Common surgical procedures for the correction of the second MPJ abnormalities include single tenodesis techniques, such as flexor-to-extensor tendon transfer, a variety of metatarsal osteotomies, digital arthroplasty or arthrodesis, second MPJ arthrodesis, direct plantar plate repair, and even amputation.3-9
When it comes to second MPJ instability, the literature notes several etiologic factors including seronegative and seropositive rheumatoid arthritis as well as hypermobility (e.g. Ehlers-Danlos syndrome).1 Lesser MPJ instability can be associated with hallux valgus, hallux rigidus, interdigital neuromas and hammertoe deformities.10 Regardless of pathology, authors have described the plantar plate as the most significant factor in stabilizing the MPJ.7
In the early stages of the deformity, the diagnosis can be challenging with a second intermetatarsal space neuroma and synovial cyst being included in the forefront of the differential diagnoses.2,5 Despite the name “crossover hammertoe,” the misalignment does not always progress to crossing over or under the adjacent digit until later stages, and can also affect other lesser digits besides the second digit.10 However, the second MPJ is the most common chronically dislocated joint in the foot so we will focus on that.7
There are several etiological theories as to the underlying etiology of the subluxed/dislocated second MPJ.7 Acute trauma or, more commonly, chronic microtrauma to the MPJ can cause disruption and deterioration of the plantar plate, joint capsule and collateral ligaments, leading to instability.11 Yu and colleagues originally coined early stage MPJ instability as predislocation syndrome.12 Crossover toes represent an end-stage deformity with the abnormality being previously noted in the plantar plate as well as in the collateral ligaments of the lesser MPJ complex.8