Bone morphology of the femur and tibia captured by statistical shape modelling predicts rapid bone loss in acute spinal cord injury patients.
After spinal cord injury (SCI), bone loss in the paralysed limbs progresses at variable rates. Decreases in bone mineral density (BMD) in the first year range from 1% (slow) to 40% (rapid). In chronic SCI, fragility fractures commonly occur around the knee, with significant associated morbidity. Osteoporosis treatments await full evaluation in SCI, but should be initiated early and targeted towards patients exhibiting rapid bone loss. The potential to predict rapid bone loss from a single bone scan within weeks of a SCI was investigated using statistical shape modelling (SSM) of bone morphology, hypothesis: baseline bone shape predicts bone loss at 12-months post-injury at fracture-prone sites. In this retrospective cohort study 25 SCI patients (median age, 33 years) were scanned at the distal femur and proximal tibia using peripheral Quantitative Computed Tomography at <5 weeks (baseline), 4, 8 and 12 months post-injury. An SSM was made for each bone. Links between the baseline shape-modes and 12-month total and trabecular BMD loss were analysed using multiple linear regression. One mode from each SSM significantly predicted bone loss (age-adjusted P<0.05 R(2)=0.37-0.61) at baseline. An elongated intercondylar femoral notch (femur mode 4, +1 SD from the mean) was associated with 8.2% additional loss of femoral trabecular BMD at 12-months. A more concave posterior tibial fossa (tibia mode 3, +1 SD) was associated with 9.4% additional 12-month tibial trabecular BMD loss. Baseline bone shape determined from a single bone scan is a valid imaging biomarker for the prediction of 12-month bone loss in SCI patients.
Musculoskeletal Research Programme, University of Aberdeen, Aberdeen, UK.
Delaram
D
Varzi
Department of Biomedical Engineering, University of Strathclyde, Glasgow, UK; Scottish Centre for Innovation in Spinal Cord Injury, Queen Elizabeth National Spinal Injuries Unit, Southern General Hospital, Glasgow, UK.
Sylvie A F
SAF
Coupaud
Scottish Centre for Innovation in Spinal Cord Injury, Queen Elizabeth National Spinal Injuries Unit, Southern General Hospital, Glasgow, UK.
Mariel
M
Purcell
Scottish Centre for Innovation in Spinal Cord Injury, Queen Elizabeth National Spinal Injuries Unit, Southern General Hospital, Glasgow, UK.
David B
DB
Allan
Musculoskeletal Research Programme, University of Aberdeen, Aberdeen, UK.
Jennifer S
JS
Gregory
Musculoskeletal Research Programme, University of Aberdeen, Aberdeen, UK. Electronic address: r.j.barr@abdn.ac.uk.
Rebecca J
RJ
Barr
D000293:Adolescent; D000328:Adult; D000368:Aged; D015519:Bone Density; D003627:Data Interpretation, Statistical; D005260:Female; D005269:Femur / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000150:complications* / Q000000981:diagnostic imaging*; D010363:Pattern Recognition, Automated; D011857:Radiographic Image Interpretation, Computer-Assisted; D012044:Regression Analysis; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013119:Spinal Cord Injuries / Q000150:complications*; D013977:Tibia / Q000473:pathology*; D014057:Tomography, X-Ray Computed; D055815:Young Adult
Femur; Osteoporosis; Spinal cord injuries; Statistical shape model; Tibia; pQCT