UCLA

One of the three components of the dorsal extensor hood, the sagittal band is a sheet of connective tissue that provides lateral stability to the extensor digitorum tendon at the metacarpophalangeal joint. Rupture of one of the two portions of the sagittal band can lead to contralateral subluxation or dislocation of the extensor tendon. Closed sagittal band injury is commonly associated with high-energy impact or inflammatory conditions, such as rheumatoid arthritis. In cases of high-energy impact, a closed sagittal band injury may co-occur with a “boxer’s knuckle,” the metacarpophalangeal joint and the extensor mechanism injury that has been historically reported in boxers after blunt impact to the joint in forceful flexion. In this case report, we present a 64-year-old woman with no known history of rheumatoid arthritis and with a closed sagittal band injury received while using the fists to support changing her body position in bed. Ultrasonography and MRI are useful in the evaluation of a sagittal band injury. The use of dynamic ultrasound imaging can help visualize the extensor tendon subluxation with metacarpophalangeal joint flexion and confirm the diagnosis of sagittal band injury.