The role of negative intraarticular pressure and the long head of biceps tendon on passive stability of the glenohumeral joint

Background: The purpose of this study was to determine the effect of intraarticular pressure and the long head of biceps (LHB) tendon on passive translations of the glenohumeral (GH) joint. Tenotomy or tenodesis of the LHB are common procedures but the consequences on shoulder stability are unclear. Methods: A novel shoulder laxity testing rig permitting six degrees of freedom of motion was used to test passive translations in anterior, posterior, superior, and inferior directions in 10 cadaveric shoulders. Specimens were tested in neutral rotation with 0 degrees, 30 degrees, 60 degrees, or 90 degrees of GH abduction in the scapular plane. Translation loads up to 30N were applied, and displacements measured in an intact joint, vented joint and with the biceps tendon loaded (20N). Results: The GH joint was most lax at 30 degrees GH abduction. Venting of the joint increased translations in all positions and directions (mean +/- standard error of the mean), the greatest difference was 12.5 (3.9) mm in the anterior-posterior direction and 7.5 (3.9) mm in the SI direction. Loading the LHB tendon with 20N decreased translations in all directions. The largest difference was observed in the anterior direction, 13.9 (2.8) mm (P < .0005) and inferior direction, 12.0 (2.8) mm (P < .0005). Conclusion: Negative intraarticular pressure and the LHB contribute significantly to overall passive stability of the GH joint. Surgical division or transfer of the LHB tendon may impact on joint stability and function.