title: Bone strength is related to muscle volume in ambulant individuals with bilateral spastic cerebral palsy.
abstract: OBJECTIVE
  The aim of this study is to investigate how bone strength in the distal femur and proximal tibia are related to local muscle volume in ambulant individuals with bilateral spastic cerebral palsy (CP).
  
  
  METHODS
  Twenty-seven participants with CP (mean age: 14.6±2.9years; Gross Motor Function Classification System (GMFCS) levels I-III) and twenty-two typically developing (TD) peers (mean age: 16.7±3.3years) took part in this study. Periosteal and medullary diameter in the distal femur and cortical bone cross-sectional area (CSA) and thickness (CT) in the distal femur and proximal tibia were measured along with nine lower limb muscle volumes using MRI. Additionally, the polar section modulus (Zp) and buckling ratio (BR) were calculated to estimate bone bending strength and compressional bone stability respectively in the distal femur. The relationships of all measured parameters with muscle volume, height, age, body mass, gender, and subject group were investigated using a generalized linear model (GZLM).
  
  
  RESULTS
  In the distal femur, Zp was significantly positively related to thigh muscle volume (p=0.007), and height (p=0.026) but not significantly related to subject group (p=0.076) or body mass (p=0.098). BR was not significantly different between groups and was not related to any of the variables tested. Cortical bone CSA was significantly lower in the CP group at both the distal femur (p=0.002) and proximal tibia (p=0.009). It was also positively associated with thigh muscle volume (p<0.001) at the distal femur, and with subject height (p=0.005) at the proximal tibia.
  
  
  CONCLUSIONS
  Bending and compressional strength of the femur, estimated from Zp and cortical bone CSA respectively, is associated with reduced thigh muscle volume. Increasing muscle volume by strength training may have a positive effect on bone mechanics in individuals with CP.
authors.affiliation: Division of Imaging Sciences Biomedical Engineering, King's College London, The Rayne Institute, 4th Floor, Lambeth Wing, St Thomas' Hospital, London SE1 7EH, United Kingdom; One Small Step Gait Laboratory, Guy's and St Thomas' NHS Foundation Trust, Guy's Hospital, London SE1 9RT, United Kingdom. Electronic address: jonathan.noble@gstt.nhs.uk.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Noble
authors.affiliation: One Small Step Gait Laboratory, Guy's and St Thomas' NHS Foundation Trust, Guy's Hospital, London SE1 9RT, United Kingdom.
authors.forename: Nicola
authors.initials: N
authors.lastname: Fry
authors.affiliation: Division of Imaging Sciences Biomedical Engineering, King's College London, The Rayne Institute, 4th Floor, Lambeth Wing, St Thomas' Hospital, London SE1 7EH, United Kingdom; One Small Step Gait Laboratory, Guy's and St Thomas' NHS Foundation Trust, Guy's Hospital, London SE1 9RT, United Kingdom.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Lewis
authors.affiliation: Department of Medical Physics, Guy's and St Thomas' NHS Foundation Trust, The Rayne Institute, 4th Floor, Lambeth Wing, St Thomas' Hospital, London SE1 7EH, United Kingdom.
authors.forename: Geoffrey D
authors.initials: GD
authors.lastname: Charles-Edwards
authors.affiliation: Department of Medical Physics, Guy's and St Thomas' NHS Foundation Trust, The Rayne Institute, 4th Floor, Lambeth Wing, St Thomas' Hospital, London SE1 7EH, United Kingdom.
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Keevil
authors.affiliation: One Small Step Gait Laboratory, Guy's and St Thomas' NHS Foundation Trust, Guy's Hospital, London SE1 9RT, United Kingdom.
authors.forename: Martin
authors.initials: M
authors.lastname: Gough
authors.affiliation: One Small Step Gait Laboratory, Guy's and St Thomas' NHS Foundation Trust, Guy's Hospital, London SE1 9RT, United Kingdom.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Shortland
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena; D001842:Bone and Bones / Q000503:physiopathology*; D002547:Cerebral Palsy / Q000503:physiopathology*; D055119:Elastic Modulus; D005260:Female; D005269:Femur / Q000503:physiopathology; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology* / Q000503:physiopathology*; D009929:Organ Size; D013977:Tibia / Q000503:physiopathology; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Body; Bone structure; Cerebral palsy; Growth; Muscle; Skeletal