Surgical anatomy of the triceps brachii tendon: Anatomical study and clinical correlation

Background: The triceps tendon has been described as a single unit with contribution from each of the 3 heads of the muscle. An observation at the time of surgical repair of a triceps tendon injury led to an anatomical study to further define the anatomy of this tendon as it inserts on the olecranon. Hypothesis: The medial head of the triceps has a tendon that is distinct from, and deep to, the common tendon of the long and lateral heads. Study Design: Descriptive laboratory study and case report. Methods: Eight cadaveric elbows were dissected to examine the triceps tendon. None of the specimens had any evidence of prior injury or surgery to the elbow. All specimens were fresh-frozen and stored at -4°C until they were thawed for use. Skin and subcutaneous tissue were removed, and the tendon of each head of the triceps was explored from the muscle to its bony insertion. Results: In all 8 specimens, on gross inspection, the medial head had a separate insertion deep to the common insertion of the lateral and long heads. The muscle of the medial head extended further distally than did the long and lateral heads. The medial head was muscular to its deep insertion, with a small amount of tendon blended with the muscle distally. Histologic analysis demonstrated that the tendon of the medial head and that of the other 2 heads are confluent distally at their olecranon insertion. Conclusion: The medial head of the triceps has a tendon that is distinct from, and deep to, the common tendon of the long and lateral heads on gross inspection. Histologic studies show the insertion of these 2 tendons is confluent. Clinical Relevance: This anatomy has important implications for surgical repair of these tendon injuries. Rupture of the deep triceps insertion alone can occur and lead to weakness of elbow extension with the elbow flexed beyond 90°. Triceps strength should be tested with the elbow fully flexed when injury to the tendinous insertion is suspected.