Summary

High critical shoulder angle (CSA) measured by either X-ray or MRI shows strong interrater reliability and is a significant predictive factor for biceps-pulley-lesions.

Abstract

Biceps-pulley-lesions (BPL) are a common source of shoulder pain but it remains a high rate of hidden lesions that were underestimated during arthroscopy. Goal of the study was to evaluate CSA as a predictive factor for BPL. We hypothesized that measurement of CSA using MRI is equal to its measurement using x-rays and that a high CSA is related to a BPL.

In 305 consecutive patients (w 156, m 149) that were treated for shoulder pathologies CSA was preoperatively observed using standardized x-rays in true-a.p.-view as well as MRI. Three blinded independent observers specialized in shoulder surgery observed the radiological results and estimated the CSA. Interrater-reliability using interclass correlation coefficient with confidence interval CI 95% and F-Test with true value were used for statistical analysis.

Interrater-reliability in x-rays shows an excellent consistently agreement between observers results (ICC = 0,97 [95% CI 0,96; 0,98], p<.001) as well as an excellent absolute agreement (ICC = 0,96 [95% CI 0,95; 0,98], p< .001). MRI results were similar with an excellent consistent as well as absolute agreement (ICC = 0,92 [95% CI 0,88; 0,94], p<.001 versus ICC = 0,91 [95% CI 0,88; 0,94], p< .001). Intraoperatively, in 45,6% of patients with a CSA less than 35° a BPL was observed whereas in 58% of patients with a CSA of more than 35° a BPL was found observing a significant difference (X2 (1.00) = 4.65, p= 0.031, Cramers V=0.12).

Findings suggest that a high grade of CSA is more likely to result in a biceps pulley-lesion whereas CSA rated less than 35° results in a less likelihood observing a BPL. Measurement of CSA with x-ray as well as MRI shows a high and safe interrater-reliability and could be observed with both methods as a risk factor for the development of BPL.