To purpose of this study: “Biomechanical Evaluation of Shear Force Vectors Leading to Injury of the Biceps Reflection Pulley”, was to measure the course of the long head biceps in common arm positions and to determine the shear and normal (stabilizing) force vectors as well as the excursion of the LHB. The 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.
The method used during this analysis was the long head biceps of eight fresh-frozen cadaveric shoulders marked with arthroscopically injected microbeads and mounted in a custom-built shoulder rig. The study did conclude that increased shear load at forward flexion with internal or neutral arm rotation and internal rotation at neutral arm position may cause injury to the BRP. Additionally, a sawing mechanism caused by the 12-mm linear excursion combined with a load of the LHB through the BRP during elevation may also lead to lesions. Download a copy of “Biomechanical Evaluation of Shear Force Vectors Leading to Injury of the Biceps Reflection Pulley” below.