Frozen shoulder after simple arthroscopic shoulder procedures: What is the risk?

Frozen shoulder is a recognised complication following simple arthroscopic shoulder procedures, but its exact incidence has not been reported. Our aim was to analyse a single-surgeon series of patients undergoing arthroscopic subacromial decompression (ASD; group 1) or ASD in combination with arthroscopic acromioclavicular joint (ACJ) excision (group 2), to establish the incidence of frozen shoulder post-operatively. Our secondary aim was to identify associated risk factors and to compare this cohort with a group of patients with primary frozen shoulder. We undertook a retrospective analysis of 200 consecutive procedures performed between August 2011 and November 2013. Group 1 included 96 procedures and group 2 104 procedures. Frozen shoulder was diagnosed post-operatively using the British Elbow and Shoulder Society criteria. A comparative group from the same institution involved 136 patients undergoing arthroscopic capsular release for primary idiopathic frozen shoulder. The incidence of frozen shoulder was 5.21% in group 1 and 5.71% in group 2. Age between 46 and 60 years (p = 0.002) and a previous idiopathic contralateral frozen shoulder (p < 0.001) were statistically significant risk factors for the development of secondary frozen shoulder. Comparison of baseline characteristics against the comparator groups showed no statistically significant differences for age, gender, diabetes and previous contralateral frozen shoulder. These results suggest that the risk of frozen shoulder following simple arthroscopic procedures is just over 5%, with no increased risk if the ACJ is also excised. Patients aged between 46 and 60 years and a previous history of frozen shoulder increase the relative risk of secondary frozen shoulder by 7.8 (95% confidence interval (CI) 2.1 to 28.3)and 18.5 (95% CI 7.4 to 46.3) respectively.