Degenerative lumbar changes have a statistically significant but small effect on trabecular bone score (TBS)-adjusted fracture risk (FRAX)

Abstract

Trabecular bone score (TBS) assesses trabecular microarchitecture at the lumbar spine and was shown to improve fracture risk prediction compared to bone mineral density (BMD) alone. We investigated whether lumbar degenerative changes (DC) affect TBS and TBS-adjusted 10-year fracture risk assessment (tool) (FRAX) estimates. All patients who underwent BMD and TBS measurements via dual-energy X-ray absorptiometry at our institution between 1/7/2020 and 1/10/2020 were retrospectively evaluated. We identified all patients who had DC in 1 or 2 vertebrae (out of L1–L4) with a BMD T score > 1 unit higher than the remaining 2 to 3 adjacent vertebrae. TBS and BMD were compared between the vertebrae with and without DC. Change in TBS as well as FRAX estimates for major osteoporotic (MOP) and hip fractures after exclusion of the degenerative vertebrae were also determined. Of the 356 eligible patients, 94 met the inclusion criteria. The mean TBS of vertebrae without DC was not significantly different from that of L1 to L4 (1.31 ± 0.12 vs 1.32 ± 0.12, respectively, P = .11). The FRAX estimates after exclusion of the degenerative vertebrae were statistically significantly higher than for L1 to L4 for both MOP and hip fractures (P = .04 and P = .01, respectively). However, the differences were very small. The mean 10-year MOP FRAX estimate after exclusion of degenerative vertebrae was 7.67% ± 4.50% versus 7.55% ± 4.36% for L1 to L4 and the mean 10-year hip FRAX estimate after exclusion of degenerative vertebrae was 2.06% ± 2.01% versus 2.02% ± 1.98% for L1 to L4. Lumbar DC have a statistically significant but only small effect on TBS-adjusted FRAX making it unnecessary to exclude the degenerative vertebrae when computing TBS.