Extensor pollicis brevis reconstruction using the extensor digitorum proprius tendon through the first dorsal compartment for a clasped thumb in an adolescent.

Clasped thumb is characterised by thumb adduction and flexion deformity at the metacarpophalangeal joint caused by abnormalities in the extensor tendons. While conservative treatments are effective in infants, surgical intervention is necessary for older who experience deformities or functional impairments. We report an adolescent patient with an untreated clasped thumb who underwent extensor pollicis brevis (EPB) reconstruction using the extensor indicis proprius (EIP) tendon through the first dorsal compartment. The patient suffered from a right thumb deformity and pain. EPB reconstruction was performed by passing the EIP tendon through the first dorsal compartment. After 1 year and 6 months of follow-up, the patient's right thumb function significantly improved, with an increased range of motion and strength of the thumb, and the preoperative pain was relieved. EPB reconstruction using EIP passing through the first dorsal compartment for clasped thumbs in adolescents can reconstruct the EPB function appropriately and is a possible treatment option.