title: The functional muscle-bone unit in patients with osteogenesis imperfecta type I.
abstract: BACKGROUND
  Osteogenesis imperfecta (OI) type I is a heritable bone fragility disorder that is caused by mutations affecting collagen type I. We recently showed that patients with OI type I frequently have muscle weakness. As muscle force and bone mass are usually closely related, we hypothesized that muscle weakness in OI type I could contribute to increase bone mass deficit in the lower extremities.
  
  
  OBJECTIVE
  To assess the muscle-bone relationship in the lower extremities of children and adolescents with OI type I.
  
  
  METHODS
  The study was carried out in the outpatients department of a pediatric orthopedic hospital. Patients and other participants Thirty children and adolescents with OI type I (20 females; mean age [SD]: 11.2 years [3.9]) were compared with 30 healthy age- and sex-matched controls (mean age [SD]: 11.1 years [4.5]).
  
  
  METHODS
  Tibia bone mineral content (BMC; mg/mm) was measured by peripheral quantitative computed tomography to estimate bone strength at the 4% and 14% sites. Lower extremity peak force (kN) was measured by mechanography using the multiple two-legged hopping test.
  
  
  RESULTS
  Compared with age- and sex-matched controls, patients with OI type I had 17% lower peak force (1.3 kN vs. 1.7 kN; p=0.002) as well as a 22% lower BMC (128 mg/mm vs. 165 mg/mm; p<0.001). Stepwise regression analysis showed that muscle force and tibia length were positively related to bone strength (r(2)=0.90, p<0.001) whereas there was no effect of the disease status (OI vs. control).
  
  
  CONCLUSIONS
  These results suggest that the muscle-bone relationship is similar between children and adolescents with OI type I and healthy age and sex-matched controls. It also suggests that muscle weakness may contribute to decreased bone strength in individuals with OI type I.
authors.affiliation: Shriners Hospital for Children, 1529 Cedar Avenue, Montréal, Québec H3G 1A6, Canada; Department of Pediatrics, McGill University, 1529 Cedar Avenue, Montréal, Québec H3G 1A6, Canada; Centre de Réadaptation Marie-Enfant, Research Center, Hôpital Sainte-Justine, 5200 Bélanger Street East, Montréal, Québec H1T 1C9, Canada. Electronic address: lnveilleux@shriners.mcgill.ca.
authors.forename: Louis-Nicolas
authors.initials: LN
authors.lastname: Veilleux
authors.affiliation: Shriners Hospital for Children, 1529 Cedar Avenue, Montréal, Québec H3G 1A6, Canada; Centre de Réadaptation Marie-Enfant, Research Center, Hôpital Sainte-Justine, 5200 Bélanger Street East, Montréal, Québec H1T 1C9, Canada; Département de Kinanthropologie, Université du Québec à Montréal, 141 Avenue du Président Kennedy Complexe des Sciences Pierre-Dansereau, Montréal, Québec H2X 1Y4, Canada.
authors.forename: Annie
authors.initials: A
authors.lastname: Pouliot-Laforte
authors.affiliation: Centre de Réadaptation Marie-Enfant, Research Center, Hôpital Sainte-Justine, 5200 Bélanger Street East, Montréal, Québec H1T 1C9, Canada; Département de Kinanthropologie, Université du Québec à Montréal, 141 Avenue du Président Kennedy Complexe des Sciences Pierre-Dansereau, Montréal, Québec H2X 1Y4, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Lemay
authors.affiliation: Shriners Hospital for Children, 1529 Cedar Avenue, Montréal, Québec H3G 1A6, Canada; Department of Pediatrics, McGill University, 1529 Cedar Avenue, Montréal, Québec H3G 1A6, Canada.
authors.forename: Moira S
authors.initials: MS
authors.lastname: Cheung
authors.affiliation: Shriners Hospital for Children, 1529 Cedar Avenue, Montréal, Québec H3G 1A6, Canada; Department of Pediatrics, McGill University, 1529 Cedar Avenue, Montréal, Québec H3G 1A6, Canada.
authors.forename: Francis H
authors.initials: FH
authors.lastname: Glorieux
authors.affiliation: Shriners Hospital for Children, 1529 Cedar Avenue, Montréal, Québec H3G 1A6, Canada; Department of Pediatrics, McGill University, 1529 Cedar Avenue, Montréal, Québec H3G 1A6, Canada; Centre de Réadaptation Marie-Enfant, Research Center, Hôpital Sainte-Justine, 5200 Bélanger Street East, Montréal, Québec H1T 1C9, Canada.
authors.forename: Frank
authors.initials: F
authors.lastname: Rauch
mesh_terms: D000293:Adolescent; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000503:physiopathology*; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010013:Osteogenesis Imperfecta / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Children; Mechanography; Mechanostat; Muscle–bone unit; Osteogenesis imperfecta; Peripheral quantitative computed tomography