title: Compressive and shear hip joint contact forces are affected by pediatric obesity during walking.
abstract: Obese children exhibit altered gait mechanics compared to healthy-weight children and have an increased prevalence of hip pain and pathology. This study sought to determine the relationships between body mass and compressive and shear hip joint contact forces during walking. Kinematic and kinetic data were collected during treadmill walking at 1ms(-1) in 10 obese and 10 healthy-weight 8-12 year-olds. We estimated body composition, segment masses, lower-extremity alignment, and femoral neck angle via radiographic images, created personalized musculoskeletal models in OpenSim, and computed muscle forces and hip joint contact forces. Hip extension at mid-stance was 9° less, on average, in the obese children (p<0.001). Hip abduction, knee flexion, and body-weight normalized peak hip moments were similar between groups. Normalized to body-weight, peak contact forces were similar at the first peak and slightly lower at the second peak between the obese and healthy-weight participants. Total body mass explained a greater proportion of contact force variance compared to lean body mass in the compressive (r(2)=0.89) and vertical shear (perpendicular to the physis acting superior-to-inferior) (r(2)=0.84) directions; lean body mass explained a greater proportion in the posterior shear direction (r(2)=0.54). Stance-average contact forces in the compressive and vertical shear directions increased by 41N and 48N, respectively, for every kilogram of body mass. Age explained less than 27% of the hip loading variance. No effect of sex was found. The proportionality between hip loads and body-weight may be implicated in an obese child׳s increased risk of hip pain and pathology.
authors.affiliation: Functional and Applied Biomechanics Section, Rehabilitation Medicine Department, National Institutes of Health, Bethesda, MD, USA; School of Biomedical Engineering, Colorado State University, Fort Collins, CO, USA. Electronic address: Zachary.Lerner@nih.gov.
authors.forename: Zachary F
authors.initials: ZF
authors.lastname: Lerner
authors.affiliation: School of Biomedical Engineering, Colorado State University, Fort Collins, CO, USA; Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA.
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Browning
mesh_terms: D001696:Biomechanical Phenomena; D001835:Body Weight; D016022:Case-Control Studies; D002648:Child; D019245:Compressive Strength; D005080:Exercise Test; D005260:Female; D006621:Hip Joint / Q000503:physiopathology*; D006801:Humans; D007700:Kinetics; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D063766:Pediatric Obesity / Q000503:physiopathology*; D011312:Pressure; D033081:Shear Strength; D016138:Walking
keywords: Gait biomechanics; Joint loading; Musculoskeletal modeling; Obesity; OpenSim; Orthopedics; Personalized