Response to “Letter Regarding: Effectiveness of Extracorporeal Shockwave Therapy in the Treatment of Chronic Insertional Achilles Tendinopathy”

Type of shockwave device

In our study, we used 4 courses of radial shockwave with 240 to 320 J/mm² energy flux density (EFD) for the treatment of chronic insertional Achilles tendinopathy per the protocol of Rompe ⁷ which showed an improvement in visual analog scale (VAS) score. In another study by Rompe ⁶ that classified shockwave into 3 groups based on EFD—low (<0.08 mJ/mm²), medium (<0.28 mJ/mm²), and high (<0.60 mJ/mm²)—the study showed that low and medium EFD had positive effects on pain relief and tendon healing whereas Chao et al ¹ revealed that a higher energy level had significant inhibitory effects on tenocyte proliferation and extracellular matrix metabolism. According to Furia et al, ³ the use of single-dose, high-energy, focus shockwave (604 J/mm²) might have inhibitory effects on tendon healing and using anesthesia to avoid discomfort to the patient during operation might cause confounding of the results. Insertional Achilles calcification was commonly found in chronic insertional Achilles tendinopathy (65%-80% in Kang et al, ⁴ 100% in our study). In the study by Rompe et al, ⁷ patients who presented with Haglund deformity were excluded, but the authors did not mention if patients with insertional Achilles calcification were excluded. In addition, Haglund deformity had no significant clinical correlation to insertional Achilles tendinopathy because it could be found in asymptomatic patients, ⁴ so it might not confound the effect of extracorporeal shockwave therapy (ESWT) on insertional Achilles tendinopathy.

Clinical focusing

We also use the clinical focusing technique by applying the shockwave probe at the point of maximum tenderness of the Achilles tendon insertion and circumferential area within 2 × 2 cm². It usually created pain during the procedure in the shockwave group as you comment, but the 2 patients in our study who experienced pain could not tolerate it and asked to withhold the procedure and resume when the pain had subsided. We had to use the lowest energy they could tolerate but not less than our shockwave protocol prescribes.

Standardized loading program

Because of low patient satisfaction (32%) of traditional eccentric exercise for insertional Achilles tendinopathy ² and no Level I evidence evaluated the effectiveness of modified eccentric exercise protocol in chronic insertional Achilles tendinopathy and we wanted to evaluate the real effectiveness of ESWT, so we did not include eccentric exercise into standard conservative treatments because that might confound the result.

Outcome measures

We used the Visual Analog Scale Foot and Ankle score (VAS-FA) because it had been validated in comparison to SF-36 in its Thai version, which patients in our study could complete it by themselves. Although VAS-FA had less specificity to Achilles tendinopathy than VISA-A, but it had 20 questions (3 categories: pain 4 questions, function 11 questions, and other complaints 5 questions) that covered most foot and ankle problems, including Achilles tendinopathy. Moreover, VISA-A has not been validated in the Thai version precluding proper outcome evaluation.

Rescue medications

We used nonsteroidal anti-inflammatory drugs as rescue drug because it was a standard medication for insertional Achilles tendinopathy. Theoretically, it may reduce efficacy in disrupting healing as you mentioned, but a few of our patients had used Naproxen for pain relief although not for a long period, and the healing had still occurred.