Progressive Collapsing Foot Deformity

Excerpt

Progressive collapsing foot deformity, previously known as adult-acquired flatfoot or posterior tibial tendon dysfunction, is a complex pathology defined by the collapse of the medial longitudinal arch of the foot with continued progressive deformity of the foot and ankle (see Image. Progressive Collapsing Foot Deformity). Progressive collapsing foot deformity is a debilitating condition that affects up to 5 million people in the United States.

The anatomy of the foot and ankle are complex, with multiple structures involved in the stability and function needed to walk and bear weight. The posterior tibial tendon is a structure principally engaged in the development of progressive collapsing foot deformity. In addition to plantar flexion, the posterior tibial tendon is the primary inverter of the foot. This tendon inserts principally on the navicular tuberosity but has lesser insertions on other tarsal and metatarsal structures. The spring and deltoid ligaments are crucial to the stability of the foot and ankle. The spring ligament, the most frequently involved in progressive collapsing foot deformity, supports the ankle by connections from the sustentaculum tali of the calcaneus to the navicular. The spring ligament supports the head of the talus. The deltoid ligament is usually affected later in the progression of the adult-acquired flatfoot. The superficial deltoid ligament has a wide insertion on the navicular to the posterior tibiotalar capsule. This ligament is the primary support against tibiotalar valgus angulation. The deep deltoid ligament prevents axial rotation of the talus, where the ligament inserts from the origin on the intercollicular groove and posterior colliculus. The deltoid ligament is critical in supporting the articulating surfaces of the ankle and the spring ligament.

Acquired flatfoot grading utilizes the Johnson and Strom classification system, which has classification grades of I to III.[7] Myerson added a fourth grade in 1997. The classification system aids clinicians in identifying the severity and can also guide treatment plans. Characteristically, stage I disease presents with posterior tibial tendon tenosynovitis with no arch collapse. Patients with stage II progressive collapsing foot deformity will have foot collapse and will be unable to perform a single-leg heel rise. This stage is further subcategorized into stages IIa and IIb. Stage IIa is foot collapse with valgus deformity of the hindfoot but no midfoot abduction, while in stage IIb, midfoot abduction is present. Patients with stage III progressive collapsing foot deformity will have fixed deformity with hindfoot valgus and forefoot abduction. Patients with stage IV deformity will have ankle valgus secondary to deltoid ligament attenuation.

The classification systems enable clinicians to identify the severity of the condition and can also guide treatment plans. However, over the past few years, a better understanding of the biomechanics of the medial longitudinal arch and the progression of flatfoot led to a new classification system. The newly accepted terminology of progressive collapsing foot deformity acknowledges the involvement of soft tissue structures and joint alignment of the midfoot, rearfoot, and ankle.