Deformities of the foot often occur in patients with congenital and acquired neurological disorders. These deformities frequently cause pain when walking and difficulty with footwear. A range of conservative treatments and operative procedures can help to correct the deformity and improve comfort. A variety of deformities exist.
Pes cavus is a complex deformity, but is basically defined by an abnormally high longitudinal arch of the foot. Conditions such as cerebral palsy, poliomyelitis, Friedreich’s ataxia and spina bifida are frequently associated with pes cavus. It is also commonly found in peripheral neuropathies such as Charcot-Marie-Tooth disease. The key factor causing pes cavus is muscle imbalance. Classically the intrinsic muscles within the foot are weak and contracted, whilst the extrinsic muscles higher up in the leg remain strong.
Clinical features of pes cavus include a high longitudinal arch, clawing of the toes, in-turning of the heel (hindfoot varus) and a tendency to walk on the lateral border of the foot. Patients often develop hard skin (calluses) underneath the ball of the foot, on clawed toes and along the lateral border of the foot. In cases of hindfoot varus, ankle sprains are common. In patients with peripheral neuropathy, sensation may also be diminished.
Useful tests include standing x-rays (to measure the severity of the deformity and help plan surgery), MRI (to outrule spinal pathology) and nerve conduction studies (in peripheral neuropathies).
Non-operative treatment concentrates on making supportive and comfortable footwear. Custom-made orthotic insoles can help reduce the occurrence of calluses. Boots and braces can help support an unstable ankle.
Indications for surgical treatment are progressive deformity, calluses beneath the metatarsal heads or ankle instability. There are three levels of surgical intervention that can be considered – soft tissue surgery, osteotomies (cutting and changing the shapes of the bones) and triple arthrodesis (fusing some of the joints).
When the foot is flexible, soft tissue surgery alone may be enough to rebalance the foot. Soft tissue procedures include plantar fascia release, peroneus longus to peroneus brevis tendon transfer, tibialis posterior tendon transfer and transfer of the toes extensors to the metatarsal heads (Jones procedure).
Osteotomies of the metatarsal bones involve removing a dorsal wedge in order to reduce the height of the longitudinal arch, whilst calcaneal osteotomies can correct hindfoot varus.
Triple arthrodesis is the final resort. It is used when other techniques will no longer be successful. It typically shortens the foot but should result in a better shaped foot that allows more normal walking.