Abstract
BackgroundBariatric surgery candidates have a high prevalence of foot pain, depression and elevated plantar pressures. There is, however, limited research into how these factors interact pre- and post-surgery. The aims of this study were therefore to investigate the mechanical and non-mechanical factors associated with foot pain severity before, and the change after, surgery.MethodsBariatric surgery candidates underwent baseline and six-month follow-up measures. Foot pain was measured with the Manchester-Oxford Foot Questionnaire. Mechanical measures included body mass index (BMI), dynamic plantar pressures, radiographic foot posture, and hindfoot range of motion. Depressive symptoms, the non-mechanical measure, were assessed by questionnaire. Multivariable linear regression was used to determine which variables were associated with foot pain at baseline and at follow-up. Multilevel repeated models assessed the associations between foot pain and plantar pressure, adjusting for the interaction between group and follow-up time.ResultsForty-five participants (84% female), with mean (SD) age of 45.7 (9.4) years were recruited. Twenty-nine participants had bariatric surgery and 16 participants remained on the waiting list (controls). Following bariatric surgery, foot pain reduced significantly by - 35.7 points (95% CI -42.2 to - 28.8), while depressive symptoms and whole foot peak pressures had a significant mean change of - 5.9 points (95% CI -10.3 to - 1.5) and - 36 kPa (95% CI -50 to - 22), respectively. In multivariable analysis, depressive symptoms were associated with foot pain at baseline β = 0.7 (95% CI 0.2 to 1.2) after controlling for age, gender, BMI, foot posture and plantar pressure. Depressive symptoms were also associated with foot pain at follow-up in those undergoing bariatric surgery, β = 1.2 (95% CI 0.8 to 1.7). Foot posture and hindfoot range of motion did not change following surgery and a change in plantar pressures was not associated with a change in foot pain.ConclusionsFoot pain severity in bariatric surgery candidates was associated with depressive symptoms at baseline. Reduced foot pain following bariatric surgery was associated with an improvement in depressive symptoms, without a significant change in foot posture or foot function. Foot pain severity in bariatric candidates may be mediated by non-mechanical or non-local factors before and following surgery.
Highlights
Bariatric surgery candidates have a high prevalence of foot pain, depression and elevated plantar pressures
Two additional participants from the treatment group were unavailable for follow-up plantar pressure data collection and four participants from the control group were unavailable for follow-up plantar pressure and foot posture data collection
The change in foot pain severity between baseline and follow-up was not associated with peak pressure when adjusted for other covariates. Both group (β = − 11.2, 95% confidence interval (CI) -23.8 to 1.4, p = 0.081) and follow-up time (β = − 7.7, 95% CI -18.5 to 3.2, p = 0.168) variables were associated with a reduction in foot pain, but only the group*time (6-months) interaction was statistically significant (β = − 21.1, 95% CI -40.8 to − 13.5, p < 0.001) (Table 5). This is the first study to comprehensively examine the effect of weight loss following bariatric surgery on foot pain, and to explore the mechanical and non-mechanical factors associated with foot pain severity
Summary
Bariatric surgery candidates have a high prevalence of foot pain, depression and elevated plantar pressures. The aims of this study were to investigate the mechanical and non-mechanical factors associated with foot pain severity before, and the change after, surgery. Obesity is a risk factor for the development of foot pain [2], and an elevated body mass index (BMI) is strongly associated with both chronic plantar heel pain and non-specific foot pain [3]. Studies have found that people with obesity display increases in plantar pressures that are not uniform, with the areas of highest pressure being the midfoot and forefoot, when compared to non-obese people [5,6,7]. Given that obesity is strongly associated with plantar heel pain [8, 9], increased plantar pressure elsewhere is discordant if pain was strongly related to excessive pressure. Chronic foot pain in people with obesity may be more than mechanical overload, involving a complex interplay between mechanical, metabolic and psychological factors
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