Effect of Body Mass Index on Pedobarographic and Patient-Reported Outcome Measures in Adolescent Flexible Flat Feet.

Background: Although adolescent flexible flatfoot deformity (FFD) is common, little is known regarding the effect of weight on associated symptomatology. This study uses pedobarography and patient-reported outcome measures (PROs) to determine if overweight adolescents with FFD have more severe alterations in dynamic plantar pressures than normal body mass index percentiles (wnBMI) with FFD and if such alterations correlate with pain and activity.

Methods: A retrospective review of patients aged 10 to 18 years with nonsyndromic symptomatic FFD was performed. Overweight (BMI percentile ≥ 85%) patients were compared with wnBMI patients with regard to dynamic plantar pressure measures and PRO scores. Pedobarographic data were subdivided into regions: medial/lateral hindfoot and midfoot, and first, second, and third to fifth metatarsals. Plantar pressure variables were normalized to account for differences in foot size, body weight, and walking speed. Contact area (CA%), maximum force by body weight (MF%), and contact time as a percentage of the rollover process (CT%) were calculated. Two foot-specific PROs were assessed, including the Foot and Ankle Outcome Score and the Oxford Ankle Foot Measure for Children.

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%, whereas CT% was increased across the medial and lateral midfoot and hindfoot regions. Correlations showed positive trends: as BMI percentile increases, so will CA and MF in the medial midfoot, as well as CT in the medial and lateral midfoot and hindfoot. Significant differences were seen between groups, with the overweight group reporting lower sports and recreation subscores than the wnBMI group. No significant differences were seen in the pain and disability subscores.

Conclusions: Although overweight adolescents with FFD exhibit greater forces and more time spent during the rollover process in the medial midfoot than normal-weight patients, they did not report worse pain or disability associated with their flat foot deformity.

Level of evidence: Therapeutic level 3.