Influence of local anesthesia and energy level on the clinical outcome of extracorporeal shock wave-treatment of chronic plantar fasciitis -: A prospective randomized clinical trial

Background: The efficacy of low energy extracorporeal shock wave treatment (ESWT) for chronic plantar fasciitis is discussed controversially. It is unclear whether the simultaneous application of local anesthesia (LA) interferes with clinical outcome. Methods: 60 patients with a chronic plantar fasciitis were enrolled in a triple-arm (20 patients per group), prospective randomized and observer-blinded pilot trial. The patients were randomly assigned to receive either active ESWT without LA (;3x1500 shocks, total energy flux density [EFD] per shock 0.09 mJ/mm(2) [GroupA]), ESWT with LA (3x1500 shocks, EFD 0.18 mJ/mm(2) per shock [GroupB]) or ESWT with LA (3x1500shocks, EFD 0.09mJ/mm(2) [GroupC]). Main outcome measures were: pain during first stepps in the morning (measured on a 0-10 point visual analogue scale) and number of patients with > 50% reduction of pain and no further therapy needed, measured at 6 weeks after the last ESWT. Results: Group A improved in the VAS from 6.4 (SD: 1.7) to 2.2 (SD: 2.6) points, group B from 6.7 (SD: 1.5) to 4.1 (SD: 2.4) points, group C from 6.2 (SD: 1.6) to 3.8 (SD: 2.5) points. A reduction of pain of at least 50% was achieved in 60% of group A, in 36% of group B and in 30% of group C. Group A without LA showed a significantly higher improvement in the VAS and subjective evaluation than groups B (p = 0.007) and C (p = 0.016). Conclusion: At 6 weeks success rates after low-energy ESWT with local anesthesia were significantly lower than after identical low-energy ESWT without local anesthesia. Higher energy levels could not balance the disadvantage of this effect. LA significantly influenced the clinical results after low energy ESWT in a negative way. Blinding patients by LA in ESWT studies must therefore be considered a systematic error in study design.