Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Bone Geometry Parameters among Black and White Women with SLE.

Alele2,  Jimmy D., Kamen2,  Diane L., Hunt2,  Kelly J., Gilkeson1,  Gary S., Ramsey-Goldman3,  Rosalind

Med Univ of South Carolina, Charleston, SC
Medical University of South Carolina, Charleston, SC
Northwestern University, Chicago, IL

Purpose:

Recent studies reported an increased prevalence of osteoporotic fractures among patients with systemic lupus erythematosus (SLE). While the prevalence of low bone mineral density (BMD) is higher among these subjects than the general population, this finding does not fully account for increased fracture rate. The purpose of this study was to determine if SLE status was associated with bone geometry parameters that predict increased skeletal fragility among black and white women.

Methods:

Study subjects included 153 women who had participated in the Study of Lupus Vascular and bone Long Term Endpoints (SOLVABLE) (69% white, 31% black) and 4920 controls from the third National Health and Nutrition Examination Survey (NHANES III) (59% white, 41% black). Dual energy x-ray absorptiometry (DXA) scans from SOLVABLE (Hologic DQR-4500), and NHANES III (Hologic DQR-1000) were analyzed using the Hip Structure Analysis (HAS) program to derive BMD and bone geometry parameters (section modulus, buckling ratio, outer diameter and cross-sectional area) at the femoral neck, intertrochanter and proximal femoral shaft. Linear regression was used to examine differences (SLE vs. NHANES) in bone density and geometry in blacks and whites after adjusting for age and body mass index.

Results:

NHANES participants were older than SLE subjects, and were more likely to smoke. We detected significant BMD and bone geometry differences (SLE vs. non-SLE, black and white subjects) at the intertrochanter as follows and per table below:

1) BMD (g/cm2) was lower among both black and white SLE subjects (0.80 vs. 0.94, p<0.0001 and 0.82 vs. 0.86, p<0.01 respectively).

2) BMD reduction was associated with reductions of cross sectional area (cm2) among black and white SLE subjects (3.76 vs. 4.61 and 4.05 vs. 4.35 respectively, p<0.0001), suggesting that low BMD among SLE patients was a result of reduced total bone quantity.

3) Section modulus (cm3) was also reduced among SLE subjects in both races (3.03 vs. 3.81, p<0.0001 and 3.54 vs. 3.76, p<0.01 respectively), suggesting reductions in bending resistance among SLE patients.

4) Reductions in section modulus were accompanied by reductions in outer skeletal diameter (cm) among both black and white SLE subjects (4.98 vs. 5.20, p<0.0001 and 5.19 vs. 5.31, p<0.001, respectively), suggesting reduced subperiosteal apposition.

5) Finally, buckling ratio was increased among black patients vs. NHANES (9.49 vs. 8.58, p<0.01), suggesting increased tendency for local cortical buckling among black patients at this location. Similar findings were detected at the narrow neck and proximal shaft.

Table. Age and BMI-adjusted mean (95% CI) bone mineral density and bone geometry parameters stratified by race and SLE status.

 WhitesBlacks
 NHANES (n = 2916)SLE (n = 105)NHANES (n = 2004)SLE (n = 48)
Intertrochanter Region
BMD (g/cm2)0.86 (0.86, 0.87)0.82 (0.79, 0.85)*0.94 (0.93, 0.94)0.80 (0.75, 0.84)‡
Section Modulus (cm3)3.76 (3.74, 3.79)3.54 (3.40, 3.68)*3.81 (3.78, 3.85)3.03 (2.81, 3.24)‡
Cross Sectional Area (cm2)4.35 (4.32, 4.37)4.05 (3.91, 4.20)‡4.61 (4.58, 4.65)3.76 (3.55, 3.97)‡
Width (cm)5.31 (5.30, 5.32)5.19 (5.13, 5.26)†5.20 (5.18, 5.22)4.98 (4.89, 5.08)‡
Bucking Ratio9.25 (9.17, 9.32)9.27 (8.88, 9.66)8.58 (8.49, 8.67)9.49 (8.90, 10.1)*
P-values are for comparisons within racial group between NHANES participants and individuals with SLE:
*p-value < 0.01
†p-value < 0.001
‡p-value < 0.0001.

Conclusion:

Our study suggests that SLE is associated with BMD and bone geometry profiles that predict increased skeletal fragility among both black and white women. These skeletal differences probably result from the inflammatory nature of SLE and common therapies, especially steroids.

To cite this abstract, please use the following information:
Alele, Jimmy D., Kamen, Diane L., Hunt, Kelly J., Gilkeson, Gary S., Ramsey-Goldman, Rosalind; Bone Geometry Parameters among Black and White Women with SLE. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :960
DOI: 10.1002/art.28727

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