Sagittal band rupture
The condition arises as a result of trauma or degenerative changes to the sagittal band, which can lead to instability of the extensor tendon at the level of the metacarpophalangeal (MCP) joint. The sagittal bands run on the radial and ulnar sides of the extensor tendon in the fingers and act to prevent subluxation of the extensor digitorum communis (EDC) tendon in the coronal plane at the MCP joint.
The proposed mechanism of injury is forced passive flexion of the finger while the wrist is in flexion and ulnar deviation. The injury can also occur following a fall onto the MCP joint. Spontaneous ruptures as well as congenital dislocations of the EDC tendon have been described.
In patients with rheumatoid arthritis, degenerative changes to the sagittal band can lead to ulnar subluxation of the EDC tendon without a history of trauma.
Classic history and presentation: The condition presents as subluxation of the extensor tendon of the finger at MCP joint. Patients may report a snapping sensation on the digit with extension, or inability to extend the digit out of flexion.
Risk factors: Risk factors include prior diagnosis of rheumatoid arthritis or participation in combative sports such as boxing or martial arts.
S66.399A – Other injury of extensor muscle, fascia and tendon of unspecified finger at wrist and hand level, initial encounter
428189005 – Traumatic rupture of extensor tendon of finger
Differential Diagnosis & Pitfalls