The development of impingement syndrome: The role of muscle imbalance and scapular control in asymptomatic subjects with shoulder crepitus

• Main Authors: Ting-Yi Kuo, 郭定佾
• Other Authors: Wen-Ling Chen
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/32781491399227863145

碩士 === 國立成功大學 === 物理治療研究所 === 96 === Abstract Background: Subacromial impingement syndrome is the most common shoulder pathology, and the prevalence is 44~65%. Besides, internal impingement is commonly seen in athletes participating in overhead activities. Previous studies have reported that patients with impingement syndrome often demonstrated altered shoulder range of motion and muscle strength, decreased subacromial space, altered scapular muscle control and crepitus sign during shoulder movement. On the other hand, 30% of young people without shoulder pain were also reported to represent crepitus sign during shoulder movement. However, little has been done with respect to the scapular control strategies of asymptomatic people with shoulder crepitus. Purpose: The study aimed to identify the alterations in shoulder range of motion, muscle strength, static posture and scapular orientation, and scapular muscle control during arm elevation / lowering by comparing asymptomatic young subjects with shoulder crepitus and the controls. Methods: The first part of the study recruited 21 asymptomatic young subjects with unilateral shoulder crepitus for bilateral comparisons. The second part recruited 27 asymptomatic college students with shoulder crepitus in their dominant arms (13 badminton players and 14 non-badminton players), and 9 control students without shoulder crepitus for further group comparison. The measurements including shoulder range of motion, the tightness of posterior capsule, head and shoulder posture, static scapular orientation, scapular muscle activities, including deltoid, upper trapezius, serratus anterior and lower trapezius, during arm elevation and lowering movements, and the isometric strength of scapular muscles were performed for all participants. Several paired-sample t tests were conducted for bilateral comparison and one-way ANOVA were conducted for the comparison among badminton, non-badminton and control groups. Results: The crepitus shoulders were found to demonstrate significantly increased strength of shoulder internal rotators, significantly tighter pectoralis minor, significantly increased onset latency in ipsilateral upper trapezius, significantly greater muscle activities in lower trapezius, and significantly increased lower trapezius relative to serratus anterior ratio during arm lowering process (60°~0°) in comparison of non-crepitus shoulders except for those in badminton group. In addition, the crepitus shoulders in badminton group did not show similar scapular control strategies comparing with the crepitus shoulders in non-badminton player, yet demonstrated significantly decreased strength ratio of external to internal rotator, significantly tighter pectoralis minor, and significantly increased scapular internal rotation in static evaluation of scapular orientation. Conclusions: Although no pain was complained, similar scapular control strategy to those reported in impinged shoulders, namely increased muscle activities of lower trapezius during arm elevation, were found in asymptomatic young subjects with shoulder crepitus. It might be a kind of compensatory strategy to compromise the decrease of subacromial space. In addition, the badminton players demonstrated different characteristics, especially in significant imbalance of rotators strength and increased scapular internal rotation in static scapular orientation. Considering the alterations of scapular control in badminton players with crepitus, it might lead to atypical alteration of subacromial space comparing with the non-badminton players. It is possible that the crepitus found in our badminton group have provided evidence for excessive contact existing between the rotator cuff and the posterior-superior glenoid labrum, thus increasing the risk of internal impingement. In conclusion, shoulder crepitus might be a critical clinical symptom in young asymptomatic people as well as an early sign of shoulder impingement syndrome.