Biomechanical Evaluation of Shear Force Vectors Leading to Injury of the Biceps Reflection Pulley A Biplane Fluoroscopy Study on Cadaveric Shoulders

BackgroundThe clinical importance of the biceps reflection pulley (BRP), which stabilizes the long head of the biceps tendon (LHB) as it exits the joint, has been shown. However, there is controversy on the pathomechanism of injury to the BRP. The angular orientation of the LHB relative to its origin and distal course changes with joint positions and may place the BRP at risk for injury.PurposeTo measure the course of the LHB in common arm positions and to determine the shear and normal (stabilizing) force vectors as well as the excursion of the LHB.Study DesignDescriptive laboratory study.MethodsThe LHBs of 8 fresh-frozen cadaveric shoulders were marked with arthroscopically injected microbeads and mounted in a custom-built shoulder rig. Data for neutral arm position, forward flexion, and abduction were collected in internal, neutral, and external rotation using biplane fluoroscopy. Bone and LHB position were reconstructed in 3 dimensions.ResultsThe shear component of the resulting vector was significant...