Factors Affecting Dropped Biceps Deformity After Tenotomy of the Long Head of the Biceps Tendon

Purpose: The anatomic and biomechanical factors that influence distal migration of the long head of the biceps tendon (LHBT) after biceps tenotomy procedures are currently not known. This study evaluates the morphology of the proximal LHBT and the force required to cause the biceps to drop distally after tenotomy. Methods: Fourteen human fresh-frozen cadaveric shoulders (mean age, 63.6 years) were inspected and placed into diseased and healthy LHBT groups. Diseased tendons showed degenerative changes of fraying, splitting, or hypertrophy, whereas healthy tendons were opaque and intact. The humerus was fixed and the LHBT was detached from the glenoid. The biceps tendon inferior to the bicipital groove was secured to the head of a materials testing device. Force data were recorded to pull the LHBT through the bicipital groove. The tendons were then frozen and cut into 5-mm sections. Digital pictures were taken perpendicular to the sections, and imaging software was used to measure the cross-sectional areas and tendon morphology. Results: Of the LHBTs, 7 were diseased and 7 were healthy. The force required to simulate a dropped biceps deformity was significantly greater in the diseased tendons than in the healthy tendons (mean, 33.03 ± 10.46 N v 21.61 ± 9.1 N; P < .05). The maximum tendon cross-sectional area was also larger in the diseased tendons than in the healthy tendons (mean, 91.29 ± 39.33 mm2 v 63.93 ± 19.77 mm2 ; P = .1). Diseased tendons had broader cross-sectional dimensions (flattening) than healthy tendons (mean, 16.39 ± 1.50 mm v 10.97 ± 1.48 mm; P < .05). Conclusions: This study shows that diseased tendons with greater flattening have increased force required to travel through the bicipital groove. Clinical Relevance: These data help explain the clinical observation that cosmetic deformity may not result after biceps tenotomy in tendons with disease causing hypertrophy and flattening.