The long head of the triceps: a detailed analysis of its capsular origin.

Whether the triceps brachii muscle provides any significant contribution to stability about the shoulder girdle is unknown. This study seeks to document the anatomy of the origin of the long head of the triceps tendon and to resolve discrepancies in the anatomic literature. Fifteen fresh frozen cadaveric shoulder girdle specimens were dissected, the long head of the triceps and the posterior capsule being exposed. The long head origin averaged 29.5 mm (range, 26-34 mm) in width and 5.7 mm (range, 4-7 mm) in thickness. The average cross-sectional area of origin of the tendon was 168 mm2, and the fibrous contribution from the glenohumeral capsule averaged 2.3% (range, 1.4% to 3.1%) of the tendon's area. A capsular contribution was found in each specimen. The documentation of this capsular contribution may warrant further biomechanical and electromyographic study.