Clinical Outcomes of Extracorporeal Shock Wave Therapy for Achilles Tendinopathy: an Analysis of Injury Location, Age, and Body Mass Index

CATEGORY: Sports; Other INTRODUCTION/PURPOSE: Extracorporeal Shock Wave Therapy (ESWT) is one of the major advances in orthopedics over the last 20 years as a method for orthopedic surgeons to conservatively treat tendon pathologies such as Achilles tendinopathy (AT). Unfortunately, previous studies involve only a small number of cases, relatively short duration of symptoms, and simple measures of pain. The purpose of this study is to evaluate the impact of age, body mass index (BMI), and location of AT (Insertional (IAT) or Non-Insertional (nIAT)) on clinical outcomes and return to sport (RTS) time after ESWT. METHODS: This is a retrospective cohort study that included existing clinical data from 40 patients from a single academic institution. Patients greater than 18 years of age who underwent ESWT for Achilles tendinopathy in the office setting between 8/1/2019 to 8/30/2021 were included. Clinical outcomes of patients were evaluated through the self-reported Visual Analogue Scale (VAS) and Victorian Institute of Sport Assessment-Achilles (VISA-A) scores for assessing pain and functional outcomes of Achilles Tendinopathy. Descriptive statistics were used to provide an overview of the patient characteristics, including sex, age, laterality of injury, BMI, duration of symptoms, RTS time, and follow-up. For these data, mean and standard deviation were calculated, and paired samples T-tests and Welch's T-tests were performed on clinical outcome scores. RESULTS: This study included 48 patients (62 heels), with an average age of 50.8+-14.2 years, BMI of 27.3+-5.3, follow-up of 6.41+- 6.9 months, and RTP time of 5.39+-5.3 weeks. Patients with a BMI <25.0 had significantly higher post-operative VISA-A scores (p=0.007) compared to those with a BMI >25.0, and post-operative VAS scores displayed this trend without significance (p=0.07). Patients <=50 years old had significantly higher post-operative VISA-A scores (p=0.02) compared to those >50 years old, and post-operative VAS scores displayed this trend without significance (p=0.1). Pre- and post-operative VISA-A scores, and post- operative VAS scores, were not significantly different between IAT and nIAT cohorts, except for pre-operative VAS scores where nIAT was higher (p=0.03). Additionally, we found significant improvements in pre-operative to post-operative scores for VAS scores for IAT and nIAT cohorts (p<0.0001), as well for VISA-A for the IAT cohort (p=0.008), but no significant improvement in VISA for the nIAT cohort (p=0.119). CONCLUSION: Increased BMI and age are determinant factors that significantly adversely affect functional scores (VISA-A) in patients with AT treated with ESWT, but no significant differences were found for these risk factors in terms of pain improvement (VAS). Additionally, we found that the nIAT cohort had significantly higher pre-operative pain than IAT, and no significant improvement in VISA-A scores (though there was a trend of functional improvement). This aligns with the fact that the mid- substance of the Achilles tendon is a watershed area with relatively low vascularity compared to the insertional portion, where lower perfusion weakens the healing benefits of ESWT.