Snapping Junctura Tendinum to the Small Finger Simulating Radial Sagittal Band Rupture

Abstract

Snapping of the extensor tendon over the metacarpophalangeal joint usually involves a longitudinal or oblique tear of the radial sagittal band1, with subsequent displacement of the extensor tendon in an ulnar direction2. Most reports have dealt with pathologic snapping secondary to inflammatory joint disease and posttraumatic subluxation of the extensor tendons, which usually occurs in either the long or ring finger. Because of its rarity, little attention has been given to snapping at the metacarpophalangeal level of the small finger2,3. We report two cases of snapping of junctura tendinum in the fourth intermetacarpal space over the radial side of the fifth metacarpal head, which could be misdiagnosed as extensor tendon subluxation due to sagittal band injury. Surgical treatments together with anatomic variations in this area are also discussed. The patients were informed that data concerning their cases would be submitted for publication, and they consented. Case 1. A twenty-year-old woman was referred because of a three-month history of painful snapping of the left small finger. She had started to play the drums three weeks before the symptoms had developed, and she noted constant and painful snapping with flexion of the metacarpophalangeal joint. On examination, the extensor tendon of the small finger dislocated radially at the level of the metacarpophalangeal joint with flexion of >30°. There was an obvious snapping sound at the time of dislocation (Fig. 1, A ). This finding was not related to wrist or elbow motion. A diagnosis of extensor tendon dislocation of the small finger was made, and surgical reconstruction of the sagittal band was planned. Fig. 1 Case 1. A: The extensor tendon of the small finger dislocated to the radial side of the metacarpophalangeal joint with flexion. B: Surgical exploration revealed a thick cord-like structure (arrows) crossing obliquely …