Long-Term Outcome and Factors Affecting Prognosis of Extracorporeal Shockwave Therapy for Chronic Refractory Achilles Tendinopathy

OBJECTIVE: To investigate the factors affecting prognosis of extracorporeal shockwave therapy (ESWT) for chronic refractory Achilles tendinopathy (AT). METHODS: Thirty-six patients (48 consecutive feet) with chronic AT (>6 months) and who underwent ESWT for ‘poor’ or ‘fair’ grade in Roles-Maudsley Score (RMS) after unsuccessful conservative treatment were included in the present study. A maximum of 12 sessions of ESWT were conducted until treatment success: RMS reached ‘good’ or ‘excellent’. Termination of ESWT for no response, or ‘poor’ or ‘fair’ grade was regarded as treatment failure. Immediate outcome, long-term outcome (telephone interview after mean 26 months), and factors affecting treatment success were analyzed. RESULTS: Numeric Rating Scale was significantly decreased at immediate and long-term follow-up. Success rate was 71.1% and 90.3%, respectively. Univariate logistic regression identified that immediate treatment success was associated with retrocalcaneal enthesophyte on X-ray (odds ratio [OR], 0.06; 95% confidence interval [CI], 0.01–0.28), pretreatment abnormal ultrasonography echogenicity within Achilles tendon (OR, 18.89; 95% CI, 2.08–171.96), mean duration of ‘post-treatment soreness’ (OR, 0.55; 95% CI, 0.33–0.94), and duration of ‘post-treatment soreness after first ESWT’ (OR, 0.06; 95% CI, 0.01–0.34). The duration of ‘post-treatment soreness after first ESWT’ was found to be the only factor associated with long-term success (OR, 0.32; 95% CI, 0.10–0.99). CONCLUSION: ESWT appears to be effective in achieving long-term success in chronic refractory AT. Immediate success was associated with absence of retrocalcaneal enthesophyte on X-ray, presence of pretreatment abnormal ultrasonography echogenicity, shorter mean duration of ‘post-treatment soreness’, and shorter duration of ‘post-treatment soreness after first ESWT’. The shorter duration of ‘post-treatment soreness after first ESWT’ was identified as the only positive prognostic parameter in achieving long-term success.