Increased glenohumeral translation and biceps load after SLAP lesions with potential influence on glenohumeral chondral lesions: a biomechanical study on human cadavers

Purpose The aim of the study was to evaluate the stabilizing function of the long head of biceps tendon (LHB) and its tension, both without and with the presence of SLAP lesion to analyze a potentially occurring humeral chondral print of LHB with consecutive glenohumeral chondral lesions in SLAP lesions. Methods Testings were performed on 21 fresh frozen human cadaver shoulders with intact shoulder girdle by a 5 axis industrial robot with a force/moment sensor and 20 N joint compression, 50 N force in anterior, posterior, anterosuperior, and anteroinferior direction, and 0A degrees, 30A degrees, 60A degrees of abduction. LHB was connected over a force measuring sensor with 5 N and 25 N preload. A type IIC SLAP lesion was created arthroscopically. Results A significant increase in anterior and anteroinferior translation was evaluated, whereas the LHB tension increased significantly in at most anterior and anterosuperior direction. The highest increase in translation and LHB tension after SLAP lesion was measured in anterior translation in at most 60A degrees of abduction. The glenohumeral translation was significantly higher in SLAP lesions without LHB tenotomy than after isolated LHB tenotomy. Conclusions SLAP lesions lead to increased glenohumeral translation and concurrently LHB tension and load in at most anterior direction. The increased anterior glenohumeral instability and the increased LHB load pressing on the humeral head might cause glenohumeral chondral lesions with a typical chondral print-like lesion on the humeral head underneath the LHB.