Underestimation of bone loss of the spine with posterior-anterior dual-energy X-ray absorptiometry in patients with spinal cord injury.
BACKGROUND
Bone mineral density (BMD) of the lumbar spine (L-spine) has been reported to be normal by routine posterior-anterior (PA) bone density imaging in patients with chronic spinal cord injury (SCI).


OBJECTIVE
To determine BMD of the L-spine by PA and lateral (LAT) dual-energy radiographic absorptiometry (DXA) in patients with chronic SCI.


METHODS
Prospective study.


METHODS
Veterans Affairs Medical Center and a private rehabilitation facility.


METHODS
Measurements of the PA and LAT L-spine and hip were performed in 15 patients with SCI: 9 with tetraplegia and 6 with paraplegia. The DXA (GE Lunar Advance DXA) images were obtained using standard software. Results are reported as mean +/- SD.


RESULTS
The mean age was 35 +/- 15 years (range = 20-62 years), and the duration of injury was 57 +/- 74 months (range = 3-240 months). T- and Z-scores were lower for the LAT L-spine than those for PA L-spine (T-scores L2: -0.7 +/- 1.2 vs. 0.0 +/- 1.4, P < 0.01; L3: -0.9 +/- 1.6 vs. 0.3 +/- 1.3, P < 0.002; L2-L3: -0.8 +/- 1.3 vs. 0.2 1.3 vs. 0.2 +/- P < 0.001; Z-scores Z-0.3 +/- 1.1 vs. 0.2 +/- 1.2, P < 0.05; L3: -0.6 +/- 1.3 vs. 0.5 +/- 1.3, P < 0.01; L2-L3: -0.4 +/- 1.1 vs. 0.4 +/- 1.2, P < 0.005). The T- and Z-scores for the total hip (-1.1 +/- 1.0 and -1.0 +/- 1.0, respectively) and L2-L3 LAT L-spine demonstrated remarkable similarity, whereas the L2-L3 PA L-spine scores were not reduced. Bone mineral density of the LAT L-spine, but not the PA L-spine, was significantly reduced with increasing duration of injury.


CONCLUSIONS
Individuals with SCI may have bone loss of the L-spine that is evident on LAT DXA that may be misdiagnosed by PA DXA, underestimating the potential risk of fracture.
Bauman
William A
WA
Veterans Affairs Rehabilitation Research and Development Center of Excellence for the Medical Consequences of Spinal Cord Injury, James J. Peters Veterans Affairs Medical Center, Bronx, New York 10468, USA. william.bauman@va.gov
Kirshblum
Steven
S
Cirnigliaro
Christopher
C
Forrest
Gail F
GF
Spungen
Ann M
AM
D015502:Absorptiometry, Photon / Q000009:adverse effects* / Q000379:methods; D000328:Adult; D000704:Analysis of Variance; D015519:Bone Density / Q000502:physiology*; D001851:Bone Diseases, Metabolic / Q000000981:diagnostic imaging* / Q000209:etiology*; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009460:Neurologic Examination; D013119:Spinal Cord Injuries / Q000150:complications* / Q000000981:diagnostic imaging / Q000473:pathology; D013131:Spine / Q000000981:diagnostic imaging*; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D055815:Young Adult