抄録
One potential cause of thrower's "dead arm," the condition in which a patient cannot throw with his preinjury performance because of pain and subjective unease, is type2 superior labrum anterior and posterior (SLAP) lesion. Dynamic effect of the long head tendon of the biceps brachii muscle (LHB) is thought to be one of the major causes for this lesion. The purpose of the current study was to histoanatomically investigate the relation between LHB and superior labrum and to consider the pathomechanism of type2 SLAP lesion. 20 embalmed shoulder joints of 19 cadavers were used. After the shoulder girdle was cut off, posterior rotator cuff muscles were detached from the capsule. Posterior capsule was incised longitudinally and retracted and observation of the superior portion of the glenoid was followed. After recording of macroscopic findings, the superior-half of five glenoids was histologically studied with Hematoxylin-Eosin staining. The most part of LHB ran along a posterior rim of the glenoid. LHB had no connection with the anterosuperior labrum because the sheet like structure lay between them. This sheet like structure spread from the superior medial part of the internal wall of the glenohumeral joint to the anterosuperior labrum as well as to the rotator interval. The results suggested that most of the traction force of LHB is transmitted to the posterosuperior labrum regardless of the glenohumeral position. Internal impingement of the posterosuperior labrum and rotator cuff attachment always affects the posterosuperior labrum. While the LHB traction force (including Burkhart's peel-back phenomenon) and internal impingement were the most famous theories which show the pathomechanism of type2 SLAP lesion, they did not explain solitary anterosuperior lesion. Considering the continuity of the rotator interval and anterosuperior labrum, the repetitive traction from the rotator interval during throwing might cause solitary anterosuperior type2 SLAP lesion.
