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.