Ten-year Absolute Fracture Risk and Hip Bone Strength in Canadian Women with Systemic Lupus Erythematosus

Objective. Women with systemic lupus erythematosus (SLE) are at risk of osteoporosis (OP) and fractures because of SLE or its treatments. We aimed to determine in women with SLE (1) the prevalence of low bone mass (LBM) in those 50 years of age; (2) the 10-year absolute fracture risk in those > 40 years of age using the Canadian Fracture Risk Assessment Tool (FRAX); (3) bone quality using hip structural analysis (HSA); and (4) the associations between HSA and age, SLE duration, and corticosteroid exposure. Methods. Women without prior OP fractures were eligible. Bone mineral densities at the hip, spine, and femoral neck were determined using dual-energy x-ray absorptiometry. OP was determined using World Health Organization definitions for participants aged ≥ 50 years (32.8%), and LBM was defined as Z-scores ≤ −2.0 for those aged < 50 years. For those aged ≥ 40 years (63.5%), the 10-year probabilities of a major fracture (FRAX-Major) and hip fracture (FRAX-Hip) were calculated. FRAX-Major ≥ 20% or Hip ≥ 3% was considered high risk. HSA was done in a subgroup (n = 81) of patients. Results. The study group was 271 women. Mean (SD) age was 43.8 (13.1) years and SLE duration was 11.6 (10.4) years. OP was diagnosed in 14.6% and LBM in 8.8%. FRAX-Major ≥ 20% was seen in 9 patients (5.3%), of whom 6 were taking OP medications. FRAX-Hip ≥ 3% occurred in 16 patients (9.4%), of whom 9 were taking OP medications. Buckling ratio at the left hip narrow neck was positively correlated with FRAX-Major, FRAX-Hip, SLE duration, and duration of corticosteroid use. Conclusion. LBM is prevalent in women with SLE who are < 50 years of age. FRAX may identify those at higher risk of fractures while HSA can assess bone structure noninvasively.