Factors associated with resorption of calcific deposits in the shoulder with extracorporeal shock wave therapy.

Background: Focused extracorporeal shock wave therapy (FSWT) is effective for treating calcific tendinitis of the shoulder. However, only a few reports exist on the factors related to calcium resorption after FSWT. Thus, this study aimed to investigate the factors associated with calcium resorption.

Methods: In 117 shoulders with chronic calcific rotator cuff tendinitis, FSWT was administered nine times once every 2 weeks (a total of 16 weeks). After nine sessions of FSWT, the shoulders were radiographed and categorized into complete resorption (CR) and incomplete resorption (ICR) groups. Evaluated parameters included age, duration of disease, Gärtner classification, size of calcium deposits, presence of blood flow around calcium deposits using the Doppler function of the ultrasound imaging system, Japanese Orthopaedic Association (JOA) score, University of California at Los Angeles score, disability of the arm, shoulder, and hand (UCLA) score, and tenderness.

Results: The CR group included 93 shoulders (79.4%) and the ICR group included 24 shoulders (20.6%). In the two-arm comparison, CR showed significantly longer disease duration (P=.012) and high tenderness (P=.0013). Blood flow around calcium deposits was observed in 79.5% of shoulders in the CR group (P<.0001) and 29.1% in the ICR group. Type 1 Gärtner classification (P=.0009) was observed in 28 shoulders (30.1%) in the CR group and 17 shoulders (70.8%) in the ICR group. The two groups had no significant differences in age, size of calcium deposits, JOA score, or UCLA score. Multiple logistic regression analysis was performed using the following items that showed significant differences: absence of blood flow (odds ratio [OR], 8.51, 95% confidence interval [CI]: 2.24-22.8), Gärtner classification (OR, 5.60, 95%CI: 1.73-13.3), and duration of disease (OR, 1.06, 95%CI: 0.97-1.26). Longer disease duration, Gärtner type 1, and absence of blood flow around calcium deposits resulted in difficulty in calcium resorption.

Conclusion: Patients with Gärtner type 1 with prolonged disease duration and absence of blood flow around calcium deposits may have difficulty in achieving complete resorption.