Adult Onset Flatfoot Associated With an Intramuscular Hemangioma of the Posterior Tibialis Muscle

Abstract

A 30-year-old man was referred for a painful mass in the left calf and planovalgus deformity of the left foot. The pain had been present for 15 years but recently had become severe. On examination there was a visible, exquisitely tender mass in the medial distal aspect of the lower leg. There was valgus deformity of the hindfoot, abduction of the forefoot, and complete loss of the longitudinal arch which was passively correctable to neutral. Magnetic resonance imaging showed a 3.035.5312.0-cm complex mass in the calf with a "bag of worms" appearance consistent with a vascular tumor. An incisional biopsy resulted in diagnosis of benign intermuscular hemangioma. A marginal resection of the mass was later performed. During operative resection, the tumor was found to involve the entire posterior tibialis muscle to the musculotendinous junction. The patient began full weight bearing 4 weeks postoperatively and was placed in an ankle-foot orthosis for correction of the planovalgus. At 19 months postoperative, he reported no pain and mild weakness of the left foot, and he had returned to full-time work. There was no recurrence of the tumor. Intermuscular hemangioma of the calf may cause acquired spasticity and equinus deformity of the foot. In addition, intramuscular hemangiomas have been reported to cause muscle weakness and tendon rupture. In this patient, the authors believe that the posterior tibialis muscle was weakened and elongated secondary to the replacement of the muscle tissue by the tumor, ultimately leading to the planovalgus deformity.