How does a varus deformity of the humeral head affect elevation forces and shoulder function? A biomechanical study with human shoulder specimens.

Objectives: A biomechanical study was performed to test the hypothesis that a varus deformity of the humeral head decreases supraspinatus (SSP) efficiency and increases deltoid elevation forces in human specimens.

Methods: Twenty-four fresh-frozen human shoulder specimens were prepared by preserving the rotator cuff and deltoid. A defined, medial closed-wedge osteotomy was performed and lateral locked plate applied to simulate a varus deformity of 45° in Group I (n = 8) and 20° in Group II (n = 8).