The influence of critical shoulder angle on secondary rotator cuff insufficiency following shoulder arthroplasty.

TLDR: A good inter-observer reliability was found for the CSA method and there were no significant differences of CSA values between patients who had undergone shoulder replacement and experienced late cuff failure and those in whom the same procedure had been successful.

Abstract: Secondary cuff failure after shoulder replacement is disabling and often requires additional surgery Increased critical shoulder angle (CSA) has been found in patients with cuff tear compared to normal subjects The interobserver reliability of the CSA and the relationship between CSA and symptomatic secondary cuff failure after shoulder replacement were investigated Nineteen patients with symptomatic cuff failure after anatomic shoulder replacement (mean FU 45 months) were compared to a control group of 29 patients showing no signs of symptomatic cuff failure (mean FU 1057 months) The CSA was measured by two blinded surgeons at a mean follow-up of 45 and 1057 months, respectively Inter-observer reliability was calculated The mean CSA in the study group in neutral, internal and external rotations were 33°, 34° and 34°, respectively Corresponding values in the control group were 32°, 32° and 32° The interclass correlation coefficient for the whole population between the two examiners were 0956 (P < 001), 0964 (P < 001) and 0955 (P < 001), respectively There were no significant differences of CSA values between patients who had undergone shoulder replacement and experienced late cuff failure and those in whom the same procedure had been successful A good inter-observer reliability was found for the CSA method