The neurohistology of the rotator cuff and capsule of shoulder / 中华骨科杂志

ABSTRACT

Objective The articular neurohistology is a new approach to explore stabilized and chronic pain mechanisms for joint research. Furthermore, the distribution of mechanoreceptors and their functional condition play an important role in the movement and stability of joint. The animal experimental study suggest that there is a various characteristics of the type and amount of mechanoreceptors in different joints. Pacini corpuscle, Ruffini corpuscle and Golgi tendon organs as joint mechanoreceptors are widely distributed on nearly all of human joint, and have impact on stabilization of joint. The present investigates the neurohistological features of Pacini corpuscle, Ruffini corpuscle and Golgi tendon organs in the rotator cuff and the capsule, and explores their behaviors for maintaining stability of the shoulder joint. Methods Six rotator cuffs and capsules of shoulder joint were obtained from cadavers died of the accident. The tendinous tissue of subscapularis, supraspinatus、infraspinatus, and teres minis were resected from the interface of tendon and muscle to great and lesser tuberosity of humerus, the capsule tissues of glenohumeral were harvested as well. Then, the tissues were cut into a small fragments fixed with the formalin buffer solution, and embed in paraffin. The section was made along the longitudinal axis of the tendon at 150 ?m interval with Leitz 1516 machine. The modified Bielschowsky staining and the S-100 immuohistochemical staining were adopted to observe the mechanoreceptors of Pacini corpuscle, Ruffini corpuscle and Golgi tendon organs. The distribution density and size of the sensitive nerve endings were analyzed with Leica imaging process system. Results The tendinous part of rotator cuff could be divided into three layers synovial, intermediate and articular layer. The morphology of the these three types of mechanoreceptors, Pacini corpuscle, Ruffini corpuscle and Golgi tendon organs, could be identified clearly in the every layer of the tendious tissues under microscopic examination. Pacini corpuscle was ellipse and had multi layer capsule with the thickness of 20-40 ?m; Ruffini corpuscle was columnar and 350-550 ?m in size; Most of Golgi tendon organs were found at the interface of tendon and muscle. Among of them, the Pacini corpuscle and Ruffini corpuscle were much more than the Golgi tendon organs in rotator cuff and capsule of shoulder. The results of immuohistochemical staining and the counting of nerve ending assisted by the computer showed the number of sensory nerve endings in the subscapularis, supraspinatus and anterior capsule of the shoulder were much more than in the infraspinatus, teres minis and posterior capsule. The diameter of nerve bundle in the subscapularis, supraspinatus and anterior capsule was thicker than in the other periarticular structures. In periarticular structures, the mean value of nerve fiber counting were 25 in infraspinatus, 25 in supraspinatus, 13 in subscapularis, 10 in teres minis, 22 in anterior capsule and 12 in posterior capsule. Conclusion Shoulder capsule and rotator cuff are rich in the three type of mechanoreceptors, Pacini corpuscle, Ruffini corpuscle and Golgi tendon organs. However, there are a different distribution density and size of them in rotator cuff and capsule of shoulder, but the three of mechanoreceptors are mainly concentrated in the subscapularis, supraspinatus and the anterior capsule. S-100 immuohistochemical staining is much more sensitive than the modified Bielschowsky silver staining in displaying the innervations of the rotator cuff and capsule. The characters of the sensory nerve ending distribution in shoulder imply that the innervations of the shoulder play an important role in keeping the stability and mobility of the shoulder.