Higher coracoacromial ligament thickness, critical shoulder angle and acromion index are associated with rotator cuff tears in patients who undergo arthroscopic rotator cuff repair

PURPOSE To evaluate the effect of several shoulder anatomical parameters in the development of rotator cuff tear (RCT). METHODS Between 2014 and 2018, all consecutive patients who underwent arthroscopic rotator cuff repair due to full-thickness rotator cuff tear with a minimum 2-year follow-up were identified. Inclusion criteria were (1) age>18 years, (2) patients with degenerative RCT, (3) full-thickness RCTs, (4) patients underwent arthroscopic RCR due to unresponsive conservative treatment, (5) minimum 2-year follow-up period. Exclusion criteria were traumatic RCT, history of previous shoulder surgery, shoulder deformity, neurologic or neuromuscular dysfunction, glenohumeral and/or acromioclavicular joint arthritis, cuff-tear arthropathy, history of fracture around shoulder and inadequate or low-quality magnetic resonance images (MRI). Acromion index (AI), Critical shoulder angle (CSA), Coracoacromial ligament (CAL) thickness, Subacromial space (SS) width, Acromiohumeral distance (AHD), CAL/SS ratio, Lateral acromial angle (LAA) and glenoid version angle (GVA) parameters were measured on MRI. Intra- and interobserver reliability were measured. Regression analysis was used to evaluate the association between anatomical parameters and RCT development. Receiver operating curves (ROC) were created for independent risk factors. The correlation between measurement parameters were evaluated. RESULTS There were 1029 patients met the inclusion criteria. After exclusions, 437 patients were included. Age- and sex matched 437 patients without any shoulder pathologies were selected as control group. There was almost perfect intra- (ICC>0.85) and interobserver (ICC> 0.81) reliability regarding all measurement parameters. There was significant difference between RCT group and control group regarding AI (0.67±0.07 vs. 0.61±0.08, p<0.001), CSA (33.58±3.93 vs. 31.50±4.01, p<0.001), CAL thickness (1.81±0.64 vs. 1.53±0.50, p<0.001), CAL/SS ratio (0.29±0.14 vs. 0.23±0.10, p<0.001) and GVA (-16.69±6.69 vs. -15.37±5.95, p=0.002) parameters. AI (OR: 1.998, P<0.001), CAL thickness (OR: 2.801, p<0.000) and CSA (OR: 3.055, p<0.001) were found to be independently associated with the increased risk of RCT development. Area under curve (AUC) of the AI, CSA, and CAL thickness were 71.4%, 71.3%, and 70.2%, respectively. Cut-off values for AI, CSA, and CAL thickness were 0.62, 36.4° and 1.47 mm, respectively. There was significantly positive strong correlation between AI and CSA (p<0.001, r=0.814). CONCLUSION Higher AI, CSA and CAL thickness independently associated with full-thickness RCT development. In clinical practice, these parameters may be useful in the prediction of rotator cuff rupture.