Anatomic Landmarks for Basal Joint Injections

OBJECTIVE Basal joint arthritis is a common cause of pain and disability, particularly in elderly women. Corticosteroid injection with splinting provides a reliable long-term relief for patients with mild arthritis. Proper location of the basal joint with anatomic landmarks can facilitate diagnosis and treatment of basal joint arthritis while avoiding inadvertent injury to local structures. The purpose of this study is to identify bony anatomic landmarks for basal joint injections and aid clinicians in avoiding inadvertent injury to surrounding structures on the radial side of the wrist. METHODS Twenty fresh cadaveric wrists were dissected with the aid of loupe magnification. The distal edge of the radial styloid and the palpable dorsal aspect of the thumb metacarpophalangeal joint were used as bony anatomic landmarks for the identification of the basal joint along a longitudinal vector. Measurements of the distance from our anatomic landmarks to the basal joint space were recorded. The locations of the radial artery and the superficial branch of the radial nerve were noted in relation to the borders of the anatomic snuffbox at the basal joint level. RESULTS The basal joint of the thumb is located 2.44 ± 0.34 cm distal to the distal edge of the radial styloid, and 4.47 ± 0.29 cm proximal to the metacarpophalangeal joint. At the level of the basal joint, the radial artery is found 0.76 ± 0.12 cm dorsal to the extensor pollicis brevis tendon. The first branch of the superficial branch of the radial nerve is volar to the abductor pollicis longus tendon in 84% of the specimens and courses over the abductor pollicis longus tendon in 16%. CONCLUSION The basal joint of the thumb is approximately 2.4 cm distal to the radial styloid and 4.5 cm proximal to the metacarpophalangeal joint. Placement of a needle in the basal joint space immediately dorsal to extensor pollicis brevis tendon while applying longitudinal traction on the thumb is more likely to avoid damage to the radial artery and the superficial branch of the radial nerve.