Peroneal spastic flatfoot, also known as spastic pes planus, is a rare condition characterized by a rigid, flattened foot accompanied by involuntary muscle spasms in the peroneal muscles, which run along the outer side of the lower leg and foot. This condition often results from an underlying neurological or musculoskeletal disorder, such as cerebral palsy, tarsal coalition, or trauma, which disrupts normal foot mechanics. The spasms cause the foot to invert and the arch to collapse, leading to a stiff, painful flatfoot that resists normal movement. Unlike flexible flatfoot, which is often asymptomatic and adaptable, the rigidity and spasticity in peroneal spastic flatfoot make weight-bearing activities challenging and can significantly impact mobility.
The etiology of peroneal spastic flatfoot is often linked to tarsal coalition, a congenital condition where two or more tarsal bones in the foot are abnormally fused, restricting motion and triggering compensatory muscle spasms. Other causes may include inflammatory conditions like rheumatoid arthritis, traumatic injuries, or neuromuscular disorders that affect muscle tone and coordination. The peroneal muscles, particularly the peroneus brevis and longus, contract excessively, pulling the foot into an inverted and pronated position. This abnormal posture, combined with a collapsed arch, leads to pain, difficulty walking, and potential secondary complications like ankle instability or stress fractures if untreated.
Diagnosis of peroneal spastic flatfoot typically involves a thorough clinical evaluation and imaging studies. A physical exam may reveal a rigid foot with limited range of motion, muscle spasms, and tenderness along the peroneal tendons. X-rays, CT scans, or MRI imaging can confirm structural abnormalities like tarsal coalition or joint degeneration. Electromyography (EMG) may be used to assess muscle activity and rule out neurological causes. Early diagnosis is critical to prevent progression and guide treatment, which aims to relieve pain, reduce spasticity, and restore as much foot function as possible.
Treatment approaches for peroneal spastic flatfoot depend on the underlying cause and severity. Conservative management includes physical therapy to improve muscle flexibility, orthotic devices to support the arch, and anti-inflammatory medications to reduce pain. In cases of tarsal coalition, casting or bracing may help manage symptoms. For severe or refractory cases, surgical intervention, such as tarsal coalition resection, tendon lengthening, or arthrodesis (joint fusion), may be necessary to correct the deformity and stabilize the foot. Ongoing management often involves a multidisciplinary team, including orthopedic specialists, neurologists, and physical therapists, to optimize outcomes and improve the patient’s quality of life.