Can we predict which patients with plantar heel pain are more likely to benefit from insoles? A secondary exploratory analysis of a randomized controlled trial

N Rasenberg,S M Bierma‐Zeinstra,P J Bindels,L J M Dijkgraaf,M Van Middelkoop

doi:10.1186/s13047-022-00516-9

Abstract

BackgroundPlantar heel pain (PHP) is a common cause of foot complaints, for which treatment with custom-made insoles is frequently applied. So far few studies have investigated patient characteristics that predict response to these treatments. The aim of this secondary exploratory analysis was twofold; firstly, to identify patient characteristics that predict prognosis in patients with PHP treated with insoles, and secondly to identify characteristics that might interact with treatment with insoles.MethodsData from a randomized trial in which participants received either custom insoles (N = 70) or sham insoles (N = 69) were used. At baseline, information was collected on demographics, foot symptoms, foot and ankle range of motion, navicular drop, presence of neuropathic pain, physical activity and other illnesses in the last 12 months. The primary outcome of this study was the Foot Function Index score (FFI) at 26 weeks. Multivariable linear regression models were generated to identify patients characteristics that predict the outcome for each type of intervention (i.e. insoles and GP-led usual care).ResultsWe found two variables associated with a better function score at 26 weeks in patients treated with insoles, female sex (β − 9.59 95%CI -17.87; − 1.31) and a lower FFI score at baseline (β 0.56 95%CI 0.30; 0.82). Explorative analyses in patients treated with insoles showed no significant interaction effects between the type of insole (custom-made versus sham) and any of the potential predictive factors.ConclusionWhen communicating about the effect of insoles for PHP clinicians should take sex and the amount of pain and disability at first presentation into account. Women and people with better foot function scores at baseline (according to FFI) might respond better to treatment with insoles in terms of foot function.Trial registrationTrial registration: NTR5346.

Highlights

Plantar heel pain (PHP) is a common cause of foot complaints, for which treatment with custommade insoles is frequently applied
Some patients did report an improvement after receiving insoles, while others did not. In this trial no differences were found between custom-made insoles and sham insoles and blinding between these two groups was successful [15]. This means that the context for patients in these two groups was identical and that the data from these patients is suitable to assess the prognosis of PHP in patients treated with insoles as an overall group
Univariate analyses were performed using linear regression to test the association between each of the potential prognostic factors as described above and the outcomes ((i.e. Foot Function Index score (FFI) total score, recovery and first step pain respectively), in patients treated with insoles

Summary

Introduction

Plantar heel pain (PHP) is a common cause of foot complaints, for which treatment with custommade insoles is frequently applied. Few studies have investigated patient characteristics that predict response to these treatments. The long term prognosis of PHP is unknown, as the duration of complaints of PHP varies greatly among studies [1, 8, 9]. Treatment strategies vary greatly among GPs and multiple interventions are often applied in patients with PHP during the course of their complaints [3]. Rasenberg et al concluding: “Foot orthoses are not superior for improving pain and function compared with sham or other conservative treatment in patients with PHP.” [16] A recent best practice guideline based on systematic review of literature and clinical expert reasoning found: “good agreement to ‘step care’ using custom foot orthoses for general pain in the short term.” [17]

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Results

Conclusion