Patients with spondyloarthritis (SpA) have an elevated incidence of osteoporosis and are at increased risk of pathological vertebral fracture. Evaluation of bone density by dual energy X-ray absorptiometry (DXA) has its limits in fracture prediction, already known in this population. One hypothesis is that the presence of lumbar syndesmophyte could overestimate the spine bone mineral density (BMD). Trabecular bone score (TBS) is a new texture measurement correlated with bone microarchitecture. Previous studies have shown that TBS is mildly impacted by osteoarthritis and thus could be a predictor of fracture better than spine BMD. We aimed to evaluate a male population of SpA with BMD and TBS measurement and see the impact of lumbar syndesmophytes.
Two cohorts of SpA male patients (Lausanne, Sofia) with SpA disease, clinical and bone parameters (femoral neck and total spine BMD+spine TBS) were merged. We compared BMD and TBS results regarding to the presence/absence of syndesmophytes.
Our study concerned 51 men [29 with lumbar syndesmophytes (L1 to L4,≥1), 22 without], fulfilling the European Spondyloarthropathy Study Group (ESSG) and the Assessment of SpondyloArthritis international Society (ASAS) criteria. Mean age was 52.18 years old (no difference between the 2 groups) and mean body mass index (BMI) 27.47kg/m ² (29.12±0.67 with and 25.30±0.81 without, P=0.0006). For the overall population mean BMD T-score at the spine was -0.55±1.54, mean BMD T-score at the femoral neck -1.20±0.95 and mean lumbar spine TBS was 1.26±0.13. Regarding to the presence or the absence of syndesmophytes, mean spine BMD T-score was -0.07±1.63 and -1.18±1.16 (P=0.009 and 0.250 before and after adjustment for BMI), mean femoral neck BMD T-score was -1.37±0.93 and -0.97±0.94 (P=0.14 and 0.03 before and after adjustment for BMI) and mean TBS was 1.21±0.12 and 1.33±0.11 (P=0.001 and 0.06 before and after adjustment for BMI) respectively for SpA men with and without syndesmophytes.
Our results showed that SpA men with and without syndesmophytes have lower results compared to the normal population regarding hip BMD, spine TBS and spine BMD except for men with syndesmophytes who have a normal BMD spine T-score. These results suggest that TBS is not influenced by the syndesmophytes in opposite to spine BMD and could be measured in this population in addition to the neck BMD to assess the bone fragility.