Dissociation between clinical and ultrasonographic response after radial shock wave therapy in refractory plantar fasciitis

Abstract

Background: Chronic plantar fasciitis refractory to conservative treatment is a frequent cause of persistent heel pain and functional limitation. Although radial extracorporeal shock wave therapy (rESWT) has shown potential benefit, the relationship between clinical improvement and structural ultrasonographic changes remains unclear. The aim of this study was to evaluate the clinical, functional, and ultrasonographic outcomes associated with rESWT in patients with refractory plantar fasciitis. Methods: We conducted a prospective observational single-center study including 287 patients with plantar fasciitis refractory to conservative treatment for at least 6 months and confirmed by ultrasonography (plantar fascia thickness >4 mm). All patients received four weekly sessions of rESWT. Pain intensity (visual analog scale [VAS]), foot function (Foot Function Index [FFI]), quality of life (EQ-5D), and plantar fascia thickness were assessed at baseline and 3 months after treatment. Results: Significant improvements were observed in pain (mean VAS change, −3.73 points), function (mean FFI-disability change, −32.37 points), and quality of life (improvement in at least one EQ-5D dimension in 81.5% of patients) (all p < 0.001). The mean reduction in plantar fascia thickness was 0.14 mm. Most responders (71.8%) showed clinical improvement despite the absence of a relevant structural change, defined as a reduction in plantar fascia thickness <0.5 mm. In multivariate analysis, physically demanding occupations were associated with a lower probability of response (odds ratio, 0.32; 95% confidence interval, 0.17–0.63). The prognostic model showed moderate discrimination (area under the curve, 0.71). Conclusions: In this observational cohort, rESWT was associated with improvements in pain, function, and quality of life in patients with refractory plantar fasciitis. Clinical improvement frequently occurred despite minimal changes in plantar fascia thickness, suggesting that ultrasonographic thickness may not adequately reflect symptomatic evolution. However, the absence of a control group prevents causal interpretation of these findings.