title: Decreases in bone mineral density at cortical and trabecular sites in the tibia and femur during the first year of spinal cord injury.
abstract: BACKGROUND
  Disuse osteoporosis occurs in response to long-term immobilization. Spinal cord injury (SCI) leads to a form of disuse osteoporosis that only affects the paralyzed limbs. High rates of bone resorption after injury are evident from decreases in bone mineral content (BMC), which in the past have been attributed in the main to loss of trabecular bone in the epiphyses and cortical thinning in the shaft through endocortical resorption.
  
  
  METHODS
  Patients with motor-complete SCI recruited from the Queen Elizabeth National Spinal Injuries Unit (Glasgow, UK) were scanned within 5weeks of injury (baseline) using peripheral Quantitative Computed Tomography (pQCT). Unilateral scans of the tibia, femur and radius provided separate estimates of trabecular and cortical bone parameters in the epiphyses and diaphyses, respectively. Using repeat pQCT scans at 4, 8 and 12months post-injury, changes in BMC, bone mineral density (BMD) and cross-sectional area (CSA) of the bone were quantified.
  
  
  RESULTS
  Twenty-six subjects (5 female, 21 male) with SCI (12 paraplegic, 14 tetraplegic), ranging from 16 to 76years old, were enrolled onto the study. Repeated-measures analyses showed a significant effect of time since injury on key bone parameters at the epiphyses of the tibia and femur (BMC, total BMD, trabecular BMD) and their diaphyses (BMC, cortical BMD, cortical CSA). There was no significant effect of gender or age on key outcome measures, but there was a tendency for the female subjects to experience greater decreases in cortical BMD. The decreases in cortical BMD in the tibia and femur were found to be statistically significant in both men and women.
  
  
  CONCLUSIONS
  By carrying out repeat pQCT scans at four-monthly intervals, this study provides a uniquely detailed description of the cortical bone changes that occur alongside trabecular bone changes in the first year of complete SCI. Significant decreases in BMD were recorded in both the cortical and trabecular bone compartments of the tibia and femur throughout the first year of injury. This study provides evidence for the need for targeted early intervention to preserve bone mass within this patient group.
authors.affiliation: Department of Biomedical Engineering, School of Engineering, University of Glasgow, Glasgow G12 8QQ, United Kingdom; Scottish Centre for Innovation in Spinal Cord Injury, Queen Elizabeth National Spinal Injuries Unit, Southern General Hospital, Glasgow G51 4TF, United Kingdom. Electronic address: sylvie.coupaud@strath.ac.uk.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Coupaud
authors.affiliation: Scottish Centre for Innovation in Spinal Cord Injury, Queen Elizabeth National Spinal Injuries Unit, Southern General Hospital, Glasgow G51 4TF, United Kingdom.
authors.forename: Alan N
authors.initials: AN
authors.lastname: McLean
authors.affiliation: Scottish Centre for Innovation in Spinal Cord Injury, Queen Elizabeth National Spinal Injuries Unit, Southern General Hospital, Glasgow G51 4TF, United Kingdom.
authors.forename: Mariel
authors.initials: M
authors.lastname: Purcell
authors.affiliation: Scottish Centre for Innovation in Spinal Cord Injury, Queen Elizabeth National Spinal Injuries Unit, Southern General Hospital, Glasgow G51 4TF, United Kingdom.
authors.forename: Matthew H
authors.initials: MH
authors.lastname: Fraser
authors.affiliation: Scottish Centre for Innovation in Spinal Cord Injury, Queen Elizabeth National Spinal Injuries Unit, Southern General Hospital, Glasgow G51 4TF, United Kingdom.
authors.forename: David B
authors.initials: DB
authors.lastname: Allan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015519:Bone Density; D003710:Demography; D018483:Diaphyses / Q000000981:diagnostic imaging / Q000503:physiopathology; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010264:Paraplegia / Q000000981:diagnostic imaging / Q000503:physiopathology; D011884:Radius / Q000000981:diagnostic imaging / Q000503:physiopathology; D013119:Spinal Cord Injuries / Q000000981:diagnostic imaging / Q000503:physiopathology*; D013977:Tibia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Bone mineral density (BMD); Cortical; Osteoporosis; Peripheral Quantitative Computed Tomography (pQCT); Spinal cord injury (SCI); Trabecular