[Rare cause of acute carpal tunnel syndrome: acute metacarpal osteomyelitis].

Acute carpal tunnel syndrome resulting from acute metacarpal osteomyelitis is an exceptional etiopathogenic entity. A 6-year-old boy developed an acute carpal tunnel syndrome on the left four days after trauma. The carpal tunnel was opened in an emergency setting and exploration revealed a pale median nerve with infiltration of neighboring tissue. After release, pus issued from the depth of the tunnel. A posterior approach disclosed the collection and a total loss of the 4th metacarpal periosteum, leading to the diagnosis of acute osteomyelitis. Edema and pain regressed rapidly with antibiotic therapy. A pathologic fracture of the 4th metacarpal discovered three months later was treated conservatively. At 10 months, the child has a very good functional result despite persistence of a short 4th metacarpal after healing. There was no motor or sensitive neurological deficit and thumb opposition was complete. We have been unable to find any other report of acute metacarpal osteomyelitis leading to acute carpal tunnel syndrome. Emergency treatment is crucial. Opening the annular ligament is the only way to achieve complete nerve recovery.