Effect of Degenerative Lumbar Changes on Trabecular Bone Score (TBS) in Patients Assessed for Osteoporosis in Routine Clinical Practice

Introduction: Trabecular bone score (TBS) assesses trabecular microarchitecture at the lumbar spine and its combination with lumbar spine bone mineral density (BMD) has been shown to improve fracture risk prediction compared to BMD alone. The aim of this investigation is to determine whether TBS is affected by lumbar degenerative changes in routine clinical practice.

Methods: All patients who underwent BMD and TBS measurements via DXA at our institution between 1/7/2020 and 1/10/2020 were retrospectively evaluated. We identified all patients who had degenerative changes in one or two vertebrae (out of L1–L4) with a BMD T score >1 unit higher than the remaining 2-3 adjacent vertebrae. TBS and BMD were compared between the vertebrae with and without degenerative changes. Change in TBS classification (i.e., normal, partially degraded, degraded) after exclusion of the degenerative vertebrae was also determined.

Results: Of the 356 patients who fulfilled the entry criteria, 120 patients had the above-defined degenerative changes in one (n=75) or two (n=45) vertebrae. The TBS of the vertebrae without was significantly lower than the TBS of the vertebrae with degenerative changes (1.30 ± 0.12 vs. 1.33 ± 0.14, respectively, P=0.001) and L1-L4 (1.30 ± 0.12 vs. 1.31 ± 0.12, respectively, P=0.01) in the same patients. There was no change in TBS classification in 97/120 patients (80.8%) after exclusion of the degenerative vertebrae. However, in 19 patients (15.8%), this exclusion resulted in a less favorable classification: from normal to partially degraded in 10 (8.3%) and from partially degraded to degraded in 9 (7.5%). In only 4 patients (3.3%) did the exclusion of the degenerative vertebrae result in a more favorable TBS classification.

Conclusions: Degenerative lumbar changes do not affect lumbar TBS measurement in the majority of patients. However, excluding the degenerative vertebrae can result in significantly lower TBS values and unfavorable TBS classification in a considerable proportion of patients with potential implications for patient management.