A stochastic structural reliability model explains rotator cuff repair retears

High rates of tendon retear following surgical repair of large rotator cuff tears have been reported. This study developed a probabilistic structural reliability model of retear with potential to guide quality improvement interventions. A probabilistic biomechanical model of survivorship from a recurrent tear, based on structural reliability and Markov processes, treated the capacity of the surgical repair to withstand tensile loading and the load applied by the supraspinatus muscle as independent lognormally distributed random variables. For a repair to remain intact at the end of the tth day, it had to remain intact on days 0, … , t − 1. After retear was predicted to occur, that repair remained torn in the model. The model predicted two-year survival of 75.7%, which is within the 95% confidence interval of the Kaplan–Meier for data reported by others. The model’s demonstrated prediction of retear can be used for improving repair survival: lowering the variance in both repair strength and in post-operative supraspinatus muscle loading is an effective method for lowering the retear rate. Variance reduction alone may be an effective way to improve surgical treatment of this disorder.