Introduction
Recent scientific literature has suggested an association between scapular bony morphometry and the incidence of rotator cuff tears. Recently, the critical shoulder angle (CSA) was proposed as a potential risk factor for degenerative rotator cuff disease. Biomechanical studies support that a large CSA results in greater supraspinatus loading and potentially overload the rotator cuff during repetitive active shoulder abduction. Moreover, CSA has also been proposed as a factor that predisposes the patient to an increased likelihood of retear after surgical repair of a rotator cuff tear. Nonetheless, the influence of a larger CSA on the post-operative functional outcomes after arthroscopic rotator cuff repair is still not well stablished. Thus, the purpose of this study was to examine either a larger CSA is associated to the post-operative functional outcomes after arthroscopic rotator cuff repair. The hypothesis was that a larger CSA (>35º) would result in poorer postoperative outcomes.
Methods
A retrospective review of patients that underwent degenerative full-thickness rotator cuff tear arthroscopic repair was conducted. A total of 113 consecutive patients, with a minimum of one year of follow-up and operated between 2013 and 2017, were identified. Eighteen were excluded due to inappropriate pre-operative shoulder radiography and 12 were not available for follow-up. An independent reviewer measured the acromial index (AI), greater tuberosity angle (GTA), lateral acromion angle (LAA) and the CSA from the pre-operative radiographs. Number of retears, Quick Disability of the Arm, Shoulder and Hand (QuickDASH) and the American Shoulder and Elbow Surgeons (ASES) were collected prospectively at a mean follow-up of 37 ± 19 months. Patients were divided into two groups: CSA>35 (large CSA group) and CSA = 35 (control group). Statistical analysis was carried out with SPSS 25.0 software. The Mann-Whitney U test was used to compare the radiographic measures and fuctional scores between the two groups.
Results
A total of 65 patients (61.8 ± 6.6 years old, 82% female; 28.8 ± 3.9 kg/cm2, 40% left shoulder; 5% smokers and 20% had diabetes) were included in the large CSA group and 37 patients (61.6 ± 8.9 years old, 76% female; 28.1 ± 5.1 kg/cm2, 27% left shoulder; 11% smokers and 16% had diabetes) were included in the control group (2.70%). The large CSA groups had 4 (6.15%) retears compared with one on the control groups. Large CSA group had significantly higher CSA (39.8º ± 3.4º versus 32.5º ± 1.7º, p<0.001), lower LAA (73.1º ± 6.6º versus 80.9º ± 5.9º, p<0.001) and higher AI (0.82 ± 0.07 versus 0.75 ± 0.06, p<0.001). GTA showed no significantly differences between groups (65.1º ± 5.4º versus 58.3º ± 5.6º, p=0.07). QuickDASH and ASES functional scores did not show any significant difference between the large CSA and control groups (42.8 ± 21.3 versus 48.1 ± 18.6, p=0.113; 56.1 ± 25.5 versus 53.1 ± 24.0, p=0.587).
Conclusion
A large CSA (>35º) did not influence the post-operative functional outcomes in patients with rotator cuff arthroscopic repair. However a higher number of retears needing revision surgery was present in the large CSA group.