title: Cortical bone deficit and fat infiltration of bone marrow and skeletal muscle in ambulatory children with mild spastic cerebral palsy.
abstract: Nonambulatory children with severe cerebral palsy (CP) have underdeveloped bone architecture, low bone strength and a high degree of fat infiltration in the lower extremity musculature. The present study aims to determine if such a profile exists in ambulatory children with mild CP and if excess fat infiltration extends into the bone marrow.
  
  
  
  Ambulatory children with mild spastic CP and typically developing children (4 to 11years; 12/group) were compared. Magnetic resonance imaging was used to estimate cortical bone, bone marrow and total bone volume and width, bone strength [i.e., section modulus (Z) and polar moment of inertia (J)], and bone marrow fat concentration in the midtibia, and muscle volume, intermuscular, subfascial, and subcutaneous adipose tissue (AT) volume and intramuscular fat concentration in the midleg. Accelerometer-based activity monitors worn on the ankle were used to assess physical activity.
  
  
  
  There were no group differences in age, height, body mass, body mass percentile, BMI, BMI percentile or tibia length, but children with CP had lower height percentile (19th vs. 50th percentile) and total physical activity counts (44%) than controls (both p<0.05). Children with CP also had lower cortical bone volume (30%), cortical bone width in the posterior (16%) and medial (32%) portions of the shaft, total bone width in the medial-lateral direction (15%), Z in the medial-lateral direction (34%), J (39%) and muscle volume (39%), and higher bone marrow fat concentration (82.1±1.8% vs. 80.5±1.9%), subfascial AT volume (3.3 fold) and intramuscular fat concentration (25.0±8.0% vs. 16.1±3.3%) than controls (all p<0.05). When tibia length was statistically controlled, all group differences in bone architecture, bone strength, muscle volume and fat infiltration estimates, except posterior cortical bone width, were still present (all p<0.05). Furthermore, a higher intermuscular AT volume in children with CP compared to controls emerged (p<0.05).
  
  
  
  Ambulatory children with mild spastic CP exhibit an underdeveloped bone architecture and low bone strength in the midtibia and a greater infiltration of fat in the bone marrow and surrounding musculature compared to typically developing children. Whether the deficit in the musculoskeletal system of children with CP is associated with higher chronic disease risk and whether the deficit can be mitigated requires further investigation.
authors.affiliation: Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States.
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Whitney
authors.affiliation: Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States.
authors.forename: Harshvardhan
authors.initials: H
authors.lastname: Singh
authors.affiliation: Department of Orthopedics, Nemours AI duPont Hospital for Children, Wilmington, DE, United States.
authors.forename: Freeman
authors.initials: F
authors.lastname: Miller
authors.affiliation: Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, PA, United States.
authors.forename: Mary F
authors.initials: MF
authors.lastname: Barbe
authors.affiliation: Department of Radiology, Michigan State University, East Lansing, MI, United States.
authors.forename: Jill M
authors.initials: JM
authors.lastname: Slade
authors.affiliation: Biostatistics Core Facility, University of Delaware, Newark, DE, United States.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Pohlig
authors.affiliation: Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States. Electronic address: modlesky@udel.edu.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Modlesky
mesh_terms: D000273:Adipose Tissue / Q000473:pathology; D050154:Adiposity; D001696:Biomechanical Phenomena; D001853:Bone Marrow / Q000473:pathology*; D016022:Case-Control Studies; D002547:Cerebral Palsy / Q000473:pathology* / Q000503:physiopathology*; D002648:Child; D002675:Child, Preschool; D000071538:Cortical Bone / Q000473:pathology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology* / Q000503:physiopathology; D013977:Tibia / Q000473:pathology / Q000503:physiopathology; D016138:Walking
keywords: Bone strength; Bone structure; Cerebral palsy; Fat depots; Unloading