Repetitive low-energy shock wave application without local anesthesia is more efficient than repetitive low-energy shock wave application with local anesthesia in the treatment of chronic plantar fasciitis

Abstract

Background: It remains unclear whether application of local anesthesia (LA) interferes with clinical efficacy of extracorporeal shock wave therapy (ESWT) for chronic plantar fasciitis.

Aims: To evaluate the effect of local anesthesia on the clinical outcome after repetitive low-energy ESWT for chronic plantar fasciitis.

Methods: Eighty-six patients with chronic plantar fasciitis were randomly assigned to receive either low-energy ESWT without LA, given weekly for three weeks (Group I, n = 45; 3 × 2000 pulses, total energy flux density per shock 0.09 mJ/mm²) or identical ESWT with LA (Group II, n = 41). Primary outcome measure was: Reduction of pain from baseline to month 3 post-treatment in a pain numeric rating scale [0–10 points] during first steps in the morning, evaluated by an independent blinded observer. Calculations were based on intention-to-treat.

Results: No difference was found between the groups at baseline. At 3 months, the average pain score was 2.2 ± 2.0 points for patients of Group I, and 4.1 ± 1.5 points for patients of Group II. The mean between-group difference was 1.9 points (95% CI: [1.1–2.7 points]; P < .001). Significantly more patients of Group I achieved ⩾50% reduction of pain compared to Group II (67% vs 29%, P < .001).

Conclusion: ESWT as applied should be done without LA in patients suffering from chronic heel pain. LA applied prior treatment reduced the efficiency of low-energy ESWT.

Introduction

Plantar heel pain, commonly referred to as insertional plantar fasciitis, is a common condition among athletes as well as the general population. The characteristic complaints are knife-like pain at the calcaneal insertion of the medial part of the plantar fascia, typically worse on first arising in the morning, and often lasting months to years. Many treatment regimens exist but effectiveness is variable [8], [52], [55], [63]. Multiple publications focused on the evaluation of a clinically relevant effect of shock wave application on plantar heel pain, either of high-energy extracorporeal shock wave treatment (ESWT), applied in a single session with local or regional anesthesia [3], [6], [9], [28], [35], [36], [38], [59] or of low-energy ESWT, applied repetitively without local anesthesia [1], [4], [7], [11], [20], [21], [22], [23], [27], [44], [45], [46], [48], [51].

A shock wave is defined as an acoustic wave at the front of which pressure rises from the ambient value to its maximum within a few nanoseconds. Typical characteristics are a high peak-pressure amplitude with a rise time of nanosecond duration, a short lifecycle of microsecond duration, and a frequency spectrum ranging from the audible to the far ultrasonic level. A recently published multicenter trial [16] failed to show effectiveness of repetitive low-energy ESWT compared to placebo ESWT in patients with a recalcitrant plantar fasciitis. In this trial a local anesthesia was used to secure blinding of the patients. However, other authors pointed at flaws in the study design such as use of simultaneous local anesthesia [4], [12], [34], [47]. In an Austrian pilot study [4], 6 weeks after repetitive low-energy ESWT without local anesthesia 60% of cases achieved ⩾50% reduction of pain compared to 29% when identical ESWT was applied under local anesthesia.

This preliminary report provided new important aspects in the use of local anesthesia which needed to be confirmed in a prospective randomized controlled trial.