Clearly, many cases of severe crossover second toe deformity have an underlying flexible first metatarsal, which is often elevated and lax at the metatarso-cuneiform joint. With increased peak pressure values plantar to the long second metatarsal, there is trauma or fraying of the plantar plate apparatus. It is not clear why the lateral aspect of the second MPJ plantar joint tears more often than the medial aspect. However, this lateral tearing of the plantar plate allows multiple deforming factors to occur.
The first and most critical of these deforming forces is medial deviation of the plantar plate and flexor apparatus. This allows the second toe to begin a medial pattern of deviation at the MPJ. Over time, an increased medial pull of the flexor apparatus results in rupture or attenuation of the lateral collateral ligaments of the second MPJ complex, exacerbating the underlying problem.
A second deforming force is the dorsal pull of the long and short extensor tendons without opposition from the plantar plate resulting in a hammertoe deformity with dorsal contracture or dislocation of the toe at the MPJ. Finally, in Deland and Sung’s cadaver study of the crossover second toe deformity, there was an associated direct pressure from the medial base of the third toe proximal phalynx on the second metatarsal lateral aspect.1 No conclusion was made about this pressure but it may be possible that this direct pressure from the third toe may be partly responsible in the tearing of the lateral ligamentous structure about the second toe.
The ultimate result of a crossover second toe is a dorsal contracture of the second toe at the MPJ with possible dislocation, contracture of the proximal phalynx at the interphalangeal joint, possible hallux valgus deformity (in moderate to severe cases), possible plantar keratoma formation and difficulty with shoe gear.
Most patients complain of pain about the joint and may even have certain symptoms similar to a neuroma in the second interspace. During the early stages, there is often pain directly plantar to the second MPJ associated with a partial tear of the plantar plate. However, there is less pain with an increase in the deformity. I associate this with complete attenuation of the plantar plate and minimal functional stability on the plantar surface of the joint. The most common complaint associated with a crossover second toe is difficulty with shoe gear due to the abnormal position of the second toe and the associated bunion deformity.
Essential Examination Pointers
Examining the patient with crossover second toe syndrome is quite simple with progression of the deformity. The essential stages of testing are grade II and III. At this time, it is essential to treat the deformity before complete dislocation of the joint occurs.
Begin your examination with a complete vascular and neurological examination of the foot. You should consider a vascular examination of the second toe given the dorsal contracture of the toe. I will often pull the toe into a corrected position and note any color changes while holding the toe in this position for several minutes. Although it is rare to see a dramatic change, such a test may help to identify cases which may be difficult to fully correct in one sitting due to tight vascular structures about the second toe.