Clinical and radiographic results of acute acromioclavicular type III dislocation: low incidence of scapular dyskinesis and sick scapula syndrome at long term follow-up.

Introduction The ideal treatment for acute type III acromioclavicular (AC) dislocations is controversial. In fact, the literature reports little evidence on which treatment (surgical versus conservative) results in better clinical outcome. Recently, evidences for long term better outcome of surgical treatment have been published in literature, and development of scapular dyskinesis and SICK scapular syndrome following conservative treatment was described. Materials and methods We evaluated 34 patients surgically treated for acute type III AC dislocations with different techniques. Functional outcome, radiographic evaluation of clavicular reduction and scapular kinematics were all evaluated. Results Excellent Constant shoulder score (mean 95.7 points, SD ± 5.3) and Simple Shoulder Test (mean 11.2 points, SD ± 0.8) results were observed. In 4 patients recurrence of separation was observed. Scapular dyskinesis was observed in only 4 (11.7 %) patients, of which only 1 (2.9 % of the sample) was affected by SICK scapula syndrome. Scapular dyskinesis was classified as type I in 3 cases (75 %) and type III in 1 case (25 %). Discussion Excellent Constant shoulder score (mean 95.7 points, SD ± 5.3) and Simple Shoulder Test (mean 11.2 points, SD ± 0.8) results were observed. In 4 patients recurrence of separation was detected. The incidence of scapular dyskinesis and SICK scapula syndrome in the present study was significantly lower with respect to conservative treatment. On the other hand, the distribution of dyskinesis types was comparable, suggesting a possible common cause. However, pathogenesis of scapular dyskinesis following type III AC dislocation is still not clear: periscapular muscle dynamic stabilisation seems to be the means by which the scapula correctly accomplishes its functions, while the results hereby presented do not allow surely establishing a correlation between clavicle reduction and scapular dysfunctional syndromes. Conclusions Excellent clinical results for surgical treatment of type III acute AC joint dislocations at long term follow up are confirmed. Surgical treatment is also associated with a lower incidence of scapular dyskinesis and SICK scapula syndrome if compared to conservative treatment.