Effect of Body Mass Index on Pedobarographic and Patient Reported Outcome Measures in Symptomatic Adolescent Flexible Flat Foot Deformity

Category: Midfoot/Forefoot; Hindfoot Introduction/Purpose: The purpose of this study was to use pedobarography and patient reported outcome measures (PROs) to determine if obese adolescents with flexible flatfoot deformity (FFD) have more severe alterations in dynamic plantar pressures than patients with FFD who fall within normal BMI percentiles (wnBMI), and if such alterations affect pain and activity. Methods: A retrospective review of patients aged 10 to 18 years with non-syndromic symptomatic FFD enrolled in a prospective IRB approved registry, was performed. Overweight (BMI≥ 85%) patients were compared to wnBMI patients with regard to dynamic plantar pressure measures and PRO scores. Pedobarograph foot data were subdivided into regions: medial/lateral - hindfoot, midfoot and forefoot. Plantar pressure variables were normalized to account for differences in foot size, body weight and walking speed. Contact area was normalized by the total foot (CA%), maximum force by body weight (MF%) and contact time by total time of the roll over process (CT%). Two foot-specific PROs were assessed including the Foot and Ankle Outcome Score (FAOS) and the Oxford Ankle Foot Measure for Children (OxAFQ-C). Results: Of the 48 adolescents studied, 27(56%) were overweight and 21(44%) were wnBMI. After normalization of the data, overweight patients had significantly greater medial midfoot MF%, while CT% was increased across the medial and lateral midfoot and hindfoot regions (Table 1). Significant correlations were made between BMI percentile and MF% in the medial midfoot (r = 0.39, p = 0.006), CT% in the medial (r=0.52, p< 0.001 and CT% lateral (r=0.55, p< 0.001) midfoot. There were no significant differences between the overweight and wnBMI cohorts for CA% or any PRO pain or activity sub-scores. No significant correlations were made between pedobarograph parameters and PRO sub-scores. Conclusion: Although obese adolescents with FFD exhibit greater forces and greater time spent during the rollover process in the medial midfoot than patients with wnBMI, they do not report worse pain or disability. While it seems intuitive that increased body weight would be associated with higher levels of pain in adolescents with FFD, this does not seem to be the case. Though significant increases in plantar force and contact time were found in the obese adolescents, this did not result in greater discomfort or functional limitation. It, therefore, cannot be concluded that BMI alone is a differentiating factor in FFD symptomatology.