Posterior Rotator Cuff Tears: Is Extracorporeal Shockwave Therapy a Risk Factor?

BACKGROUND: Negative effects of extracorporeal shock wave therapy (ESWT) on vulnerable tendon structures have been reported. Meanwhile, tears of the posterior rotator cuff tendon, which is thinner than the anterior, are not common, and the clinical features remain poorly understood. Therefore, we evaluated the relationship between ESWT and posterior rotator cuff tears (RCTs) by investigating the risk factors. METHODS: Of 294 patients who underwent rotator cuff repair between October 2020 and March 2021, a posterior RCT more than 1.5 cm from the biceps tendon or an isolated infraspinatus tear was identified in 24 (8.1%, group P). Sixty-two patients (21%) with an anterior RCT within 1.5 cm of the biceps tendon were analyzed as a control group (group A). Preoperative clinical characteristics were assessed to determine the risk factors of posterior RCTs. RESULTS: Calcific deposits were more frequently observed in group P (n = 7, 29.2%) than group A (n = 6, 9.7%, p = 0.024). Further, those in group P were more likely to undergo ESWT (n = 18, 75.0%) than those in group A (n = 15, 24.2%, p < 0.001). Of these, 7 patients experiencing calcific tendinitis from group P (29.2%) and 4 from group A (6.5%, p = 0.005) underwent ESWT for calcification removal. Furthermore, 11 patients experiencing tendinopathy from group P (45.8%), and 11 from group A (17.7%, p = 0.007) underwent ESWT for pain relief. The mean level of fatty infiltration of the supraspinatus was significantly higher in group A than group P (1.8 vs. 1.0, p < 0.001). CONCLUSIONS: Since a high prevalence rate of posterior RCTs was related to ESWT, it should be carefully considered when treating calcific tendinitis or pain in patients experiencing tendinopathy.