Abstract
Author(s): Lin, Jonathan; Chen, Johnathan | Abstract: The sagittal band is a sheet of connective tissue that provides lateral stability to the extensor digitorum tendon at the metacarpal joint. It is one of the three components of the dorsal extensor hood. Rupture of the one of the sagittal bands can lead to contralateral subluxation or dislocation of the extensor tendon. Closed sagittal band injury is commonly termed ‘boxer knuckle’ as it has been historically described in professional boxers who have sustained trauma to their closed fists. This injury is also associated with inflammatory conditions, such as rheumatoid arthritis. In this case report, we present a 64-year-old female with no known history of rheumatoid arthritis who sustained a closed sagittal band injury from shifting position in her bed. Ultrasonography and MRI are useful in the evaluation of a sagittal band injury. Using dynamic ultrasound imaging, the extensor tendon subluxation can be visualized with metacarpophalangeal (MCP) flexion, confirming the diagnosis of sagittal band injury.
Highlights
The extensor tendon courses over the MCP joint and inserts its middle and lateral tendon slips onto the bases of the middle and distal phalanxes, respectively
In its course through the phalanx, the extensor tendon (ET) is stabilized by the dorsal extensor hood, a fibrous tissue that is composed of the transverse, the oblique, and the sagittal bands
The sagittal band (SB) originates from the volar plate of the metacarpal neck and intermetacarpal ligament and courses
Summary
There was swelling of the metacarpophalangeal (MCP) joint and tenderness at the site of the radial portion of the sagittal band (SB). The examination revealed subluxation of the extensor tendon (ET) upon third MCP joint flexion.
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