Introduction
Symptomatic glenoid erosion is one of the most common causes of functional impairment after shoulder hemiarthroplasty. A decrease in the critical shoulder angle (CSA) has been associated with the development of shoulder arthritis. The inter-observer reliability of the CSA and the relationship between CSA and symptomatic glenoid erosion after shoulder hemiarthroplasty were investigated.
Materials and methods
Twenty-eight patients with symptomatic glenoid erosion after anatomic hemiarthroplasty were compared to a control group of 30 patients with no signs of symptomatic glenoid erosion. The CSA was measured by two blinded shoulder surgeons at a mean follow-up of 105.2 and 54.7 months, respectively. The inter-observer reliability was calculated.
Results
The mean CSA in the control group in neutral, internal, and external rotations was 34°, 33°, and 33°, respectively. The corresponding values in the study group were 33°, 33°, and 33° (<0.01). The interclass correlation coefficient between the two examiners was 0.917 (P < 0.01), 0.924 (P < 0.01), and 0.948 (P < 0.01), respectively. The Mann–Whitney test between the control group and the study group were, respectively, 0.907, 0.932, and 0.602.
Conclusion
There were no significant differences of CSA values between the two groups. Good inter-observer reliability was found for the CSA method.