title: Quantitative computed tomography in the evaluation of spinal osteoporosis following spinal cord injury.
abstract: Disuse osteoporosis occurs in the lower extremities of patients with spinal cord injury (SCI). However, spinal osteoporosis is not usually observed in these patients. We investigated lumbar spine bone mineral density (BMD) in SCI patients using single energy quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA). Our study population consisted of 64 patients with long-standing SCI. Spine BMD (g/cm3) was assessed by QCT at four vertebrae ranging from T11 to L4 with single mid-vertebral CT slices 1 cm thick parallel to the vertebral end-plates. Confounding variables affecting normal trabecular bone pattern, such as compression fractures, surgical hardware or fat replacement, were excluded. For a subset of 29 patients, DXA values of the spine and femoral neck were also measured, and QCT and DXA Z-scores were compared On the average, the 64 SCI patients had Z-scores 2.0 +/- 1.2 below those of age-matched controls. In the subset of 29 patients with both QCT and DXA measurements, the QCT and DXA Z-scores were 2.4 +/- 1.1 below and 1.3 +/- 2.3 above the mean, respectively (p < 0.0001). Our results indicate that QCT reveals osteoporosis of the spine after SCI, in contrast to DXA. We postulate that QCT is more valuable for evaluating spinal osteoporosis following SCI than DXA and thus recommend QCT for spinal BMD studies in SCI.
authors.affiliation: Department of Medicine, University of California San Diego and Veterans Affairs Medical Center, 3350 La Jolla Village Drive, Room 3172, Mail Code 9111C, San Diego, CA 92161, USA.
authors.forename: C C
authors.initials: CC
authors.lastname: Liu
authors.forename: D J
authors.initials: DJ
authors.lastname: Theodorou
authors.forename: S J
authors.initials: SJ
authors.lastname: Theodorou
authors.forename: M P
authors.initials: MP
authors.lastname: Andre
authors.forename: D J
authors.initials: DJ
authors.lastname: Sartoris
authors.forename: S M
authors.initials: SM
authors.lastname: Szollar
authors.forename: E M
authors.initials: EM
authors.lastname: Martin
authors.forename: L J
authors.initials: LJ
authors.lastname: Deftos
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D005272:Femur Neck / Q000503:physiopathology; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000000981:diagnostic imaging* / Q000209:etiology; D013119:Spinal Cord Injuries / Q000150:complications*; D013122:Spinal Diseases / Q000000981:diagnostic imaging* / Q000209:etiology; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*