Count Age (y) Height (cm) Weight (kg) BMI (kg/m 2 ) (DOI) (mo) Tetra/Para Male/Female N=15 35±15 174± ± ±5.4 54±71 9 / 6 12 / 3 Range 20 – – – – – 240 ____ Table 1. Characteristics of the Subjects Underestimation of Bone Loss of the PA Spine by Dual Energy X-ray Absorptiometry in Persons with Spinal Cord Injury Christopher M. Cirnigliaro MS 1,2 ; A. Marley Jensen, MS 1,2 ; Gail F. Forrest PhD 2,4 ; Steven C. Kirshblum MD 2,4 ; Ann M. Spungen EdD 1,3 and William A. Bauman MD 1,3 1 James J. Peters VA Medical Center, Bronx, NY; 2 Kessler Institute for Rehabilitation and Kessler Foundation Research Center, West Orange, NJ; 3 Mount Sinai School of Medicine, NY, NY; and 4 University Medical School of New Jersey, Newark, NJ Underestimation of Bone Loss of the PA Spine by Dual Energy X-ray Absorptiometry in Persons with Spinal Cord Injury Christopher M. Cirnigliaro MS 1,2 ; A. Marley Jensen, MS 1,2 ; Gail F. Forrest PhD 2,4 ; Steven C. Kirshblum MD 2,4 ; Ann M. Spungen EdD 1,3 and William A. Bauman MD 1,3 1 James J. Peters VA Medical Center, Bronx, NY; 2 Kessler Institute for Rehabilitation and Kessler Foundation Research Center, West Orange, NJ; 3 Mount Sinai School of Medicine, NY, NY; and 4 University Medical School of New Jersey, Newark, NJ Objective: Dual energy x-ray absorptiometry (DXA) measurements of the posterior-anterior (PA) lumbar (L) spine capture the posterior elements of the vertebrae that are high in cortical bone. These areas are prone to extraneous calcification due to degenerative joint disease. The inclusion of these areas can falsely elevate standardized scores and underestimate bone loss of the L-vertebrae. The objective of this study was to evaluate if PA L-spine measurements underestimate bone loss compared with those of the lateral (LAT) L- spine in persons with spinal cord injury (SCI). Methods: Bone mineral density (BMD), T-scores, Z-scores of the PA & LAT L-spine (L1, L2, & L2-L3), total hip (TH), and femoral neck (FN) were obtained by DXA (GE Lunar Prodigy Advance) on 9 male and 6 female subjects with SCI (n=15) using the standard analysis software (Table 1). Results: The characteristics of the subjects are presented (Table 1). In contrast to the PA L-spine, T and Z- scores of the LAT L-spine and TH and FN demonstrated that subjects had relatively low BMDs (Table 2). With the exception of the Z-score for L2, there was a significant difference between the T and Z-scores of the LAT and PA L-spine. Comparison of the LAT L-spine with the TH and FN revealed no significant difference, except for L2 (Figure 2). In subjects, duration of injury (DOI) was significantly inversely related to BMD for the LAT spine L3, L2-L3, TH and FN but not for any measurement of the PA L- spine (Table 3). Conclusions: Compared with the LAT spine, the PA spine underestimated bone loss in persons with SCI. Thus, LAT spine measurements may be a more sensitive measurement to identify patients with SCI who have low vertebral bone mass. With increasing DOI and associated progressive decreases in BMD, the risk of L-spine compression fracture would be expected to increase. Acknowledgement: VA Rehabilitation R&D Service; Center for Disease Control (CDC); Christopher and Dana Reeve Foundation (CDRF); and New Jersey Commission on Spinal Cord Injury Research. Figure 1. DXA L-spine images : (A) Lateral Spine and (B) Posterior-Anterior Spine Figure 1. DXA L-spine images : (A) Lateral Spine and (B) Posterior-Anterior Spine Table 3. Correlations of Duration of Injury with PA L-spine, LAT L-Spine, Total Hip, and Femoral Neck for the BMD, T- and Z-Scores Count (n)= 15BMDT-ScoreZ-Score RPRPRP PA- Spine L2-0.40ns-0.33ns-0.15ns PA-Spine L3-0.16ns-0.08ns0.13ns PA-Spine L2-L3-0.29ns-0.21ns0.00ns LAT-Spine L2-0.42ns-0.14ns0.07ns LAT-Spine L ns LAT-Spine L2-L3-0.57< ns-0.21ns Total Hip < ns Femoral Neck < ns A B LAT PA T- Score Z- Score § ‡ P< P<0.05 P< P<0.01 P< § ‡ THFN L2L3L2 – L3 Figure 2. T-Scores and Z-scores by Region § T-score and Z-score: Total Hip vs. PA L2, L3, and L2-3 (P<0.01) ‡ T-score and Z-score: Femoral Neck vs. PA L2, L3, and L2-L3 (P<0.01) * Z-score: Total Hip vs. LAT L2 (P<0.01) * Table 2. T- and Z-Score Results for the Total Group Count (n)= 15 BMD LAT-Spine Mean±SDMean±SDP Value T-Score L2L <0.01 L3L <0.002 L 2 -L <0.001 Z-Score L2L ns L3L <0.01 L 2 -L <0.005