A Case Report of Unilateral Hypertrophy of Foot Intrinsics: Elastographic Properties of Hyperthrophied Muscles

Congenital hypertrophy of intrinsic foot muscles is a rare condition. We report an unusual case of a 24-year-old male with a painless swelling at the plantar and medial aspect of the right foot, which was present since birth. The significant size of deformity and discomfort in wearing shoes were major concerns. MRI revealed expansion of multiple intrinsic foot muscles, which are abductor hallucis, flexor digitorum brevis, and quadratus plantae. We used shear wave elastography (SWE) as an imaging technique besides MRI and ultrasonography, which has not been used or published previously. Muscle shear wave velocity values were measured in abductor hallucis, flexor hallucis brevis, flexor digitorum brevis, and quadratus plantaris muscles. The mean stiffness values of muscles on the affected side were significantly higher compared to the healthy side. The median SWE value was 6.67 kPa (range: 4.7-8.6 kPa) on the healthy side, while it ranged between 9.2 and 13.4 kPa on the affected side. Total excision of abductor hallucis and subtotal resection of flexor digitorum brevis and quadratus plantae muscles were performed, and motor and sensory functions were preserved by protecting the neurovascular bundle. Excess skin was also removed. Surgery and postoperative course were uneventful. The patient was allowed to bear weight as tolerated. There was no recurrence, and the patient was satisfied with the shape and size of his foot at the six-month follow-up. Congenital hypertrophy of foot muscle is uncommon especially when multiple intrinsic foot muscles are involved. The main aim is to relieve patients' concerns, correct deformities, and provide comfortable shoe wear.