Subacromial impingement: influence of coracoacromial arch geometry on shoulder function

OBJECTIVE: To find correlations between radiological coracoacromial arch geometry and shoulder function in patients with subacromial impingement syndrome. PATIENTS AND METHODS: During a prospective study of the efficacy of arthroscopic subacromial decompression, we evaluated the function of the treated and contralateral shoulders using Constant's functional score and confronted the results to several radiographic parameters reflecting coracoacromial arch geometry. RESULTS: Constant's score values were low (42 +/- 15) because of pain and a low level of activity. Males had significantly higher scores than females. Constant's score was unaffected (P > 0.05) by patient age, the side, the level of activity, or the duration of symptoms, but was significantly influenced by the orientation of the acromion with respect to the scapular spine and to the vertical scapular axis. The preoperative Constant's score was significantly higher in patients with a more horizontal acromion (P = 0.01). A very tight correlation was found between the preoperative Constant's score and the angle between the acromion and scapular spine (P = 0.0003). CONCLUSION: Based on our results, we defined an open and a closed coracoacromial arch geometry. Coracoacromial arch geometry is correlated with shoulder function syndrome and can assist in the interpretation of rotator cuff impingement.