Changes in foot pain, structure and function following bariatric surgery

Bariatric 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.

Bariatric 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.

Forty-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.

Foot 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.