Purpose: This study was aimed at evaluating whether scapular dyskinesis and, eventually, SICK (Scapular malposition, Inferior medial border prominence, Coracoid pain and malposition, and dysKinesis of scapular movement) scapula syndrome develop in patients with chronic type III acromioclavicular (AC) dislocation.
Methods: Scapulothoracic motion was studied in 34 patients with chronic AC dislocation by use of the protocol described by Kibler et al. and Burkhart et al. An anteroposterior radiograph of the scapulae with the arms abducted was also obtained. The SICK Scapula Rating Scale was applied to patients with SICK scapula syndrome. Shoulder function was assessed with the Constant score and Simple Shoulder Test (SST).
Results: Of the 34 patients, 24 (70.6%) had scapular dyskinesis with the arms at rest, and 14 of these (58.3%) had SICK scapula syndrome. The mean SICK Scapula Rating Scale score was 6.9 points (out of a possible 20 points). Clinical and radiographic evaluations with the arms abducted at 90 degrees confirmed scapular dyskinesis in 61.7% and 64.7% of patients, respectively (P > .05). The Constant score was 83 points for the pathologic side and 91 points for the contralateral side. The Constant score value was 75 and 88, respectively, in patients with dyskinesis and those without dyskinesis (P < .05); the mean value for the SST was 8 of 12 and 10 of 12, respectively.
Conclusions: Chronic type III AC dislocation causes scapular dyskinesis in 70.6% of patients. Of the latter, 58.3% have SICK scapula syndrome develop. Dyskinesis might be due to loss of the stable fulcrum of the shoulder girdle represented by the AC joint and due to the superior shoulder pain caused by the dislocation. The values for the Constant score and SST were lower in patients with dyskinesis.
Level of evidence: Level IV, prognostic case series.