A Systematic Review of Extracorporeal Shock Wave Therapy (ESWT) for Insertional and Non- Insertional Achilles Tendinopathy

Abstract

Category: Sports; Other Introduction/Purpose: Depending upon the site of injury, Achilles tendinopathy (AT) can be either Insertional (IAT) or Non- Insertional (nIAT). AT has long been managed by conservative measures such as eccentric exercises, but now extracorporeal shock wave therapy (ESWT) has emerged as a non-invasive treatment to stimulate self-repair. However, the native biology at the insertion of the Achilles tendon and mid-substance are intrinsically different, with the mid-substance (2 to 6 cm above the insertion) being significantly less perfused. Thus, we performed a systematic review of the literature on shockwave therapy to determine if there was a difference in efficacy for patients who have undergone ESWT for IAT and nIAT. Methods: In January 2022, the MEDLINE and EMBASE databases were systematically reviewed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We included randomized controlled trials, prospective and retrospective studies, published in English, with pre- and post-operative scores for at least either Visual Analogue Scale (VAS) or Victorian Institute of Sport Assessment - Achilles (VISA-A). We excluded basic science studies, systematic reviews and meta- analyses, retrospective studies, case reports, studies without pre-operative scores, studies that don't differentiate IAT and nIAT. The LoE and QoE of the included studies were evaluated using the Journal of Bone and Joint Surgery Criteria and the Modified Coleman Methodology Score, respectively. We calculated weighted mean values for age, body mass index (BMI), the number of ESWT sessions and their frequency, duration of symptoms prior to ESWT, follow-up time, as well as for each outcome score. Results: 16 studies were included in this review, six with Level I evidence, four with Level II, five with Level III, and one with Level IV. There were 505 cases of AT: 325 patients with IAT and 180 with nIAT. For the IAT cohort, the weighted mean (WM) duration of symptoms prior to treatment was 18.1 months, and WM follow-up was 8.1 months. For the nIAT cohort, the WM duration of symptoms prior to treatment was 15.0 months, and WM follow-up was 11.6 months. In terms of outcome scores, for VAS, the WM pre-operative scores were 6.89 for IAT and 7.76 for nIAT and the WM post-operative scores were 2.76 for IAT and 2.49 for nIAT. For VISA-A, the WM pre-operative scores were 49.3 for IAT and 42.8 for nIAT, and the WM post-operative scores were 75.4 for IAT and 75.7 for nIAT. Conclusion: As the mid-substance portion of the Achilles tendon has diminished blood supply compared to the insertional portion, we expected outcomes after ESWT to be inferior for the nIAT cohort. Interestingly, the VAS pain scores and VISA-A functional scores displayed similar positive results for both cohorts. We see that the virtually equivalent functional and pain outcomes mean that ESWT is stimulating cellular components of the tendon to promote healing regardless of injury location.