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Thumb Extensor Mechanism
- The thumb extensor tendons are retained in a central position at the MCP joint level by radial and ulnar attachments to the sagittal bands
- At this level, the extensor pollicis brevis (EPB) lies radial to the extensor pollicis longus (EPL) and attaches to the dorsal base of the proximal phalanx
- The adductor pollicis muscle and EPL join the extensor hood to form the terminal tendon
- The terminal tendon crosses the dorsal surface of the IP joint to attach to the dorsal base of the distal phalanx
- The thumb extensor mechanism will bring the IP joint into neutral extension via the abductor pollicis brevis when the EPL is absent
CLINICAL PEARL: With an extensor pollicus longus rupture the patient is unable to lift his or her thumb off the table. This motion is termed retropulsion
