Do Chronic Oral Glucocorticoids Preferentially Decrease Bone Mineral Density of the Anterior Lumbar Vertebral Body?

Introduction: A recent Nature study has demonstrated unique anterior and posterior lineages of vertebral skeletal stem cells (vSSCs), distinct from long bone stem cells, in mice and humans. Murine models suggest that the anterior lineage may be more sensitive to glucocorticoid-induced osteoporosis. We analyzed anterior and posterior bone mineral density (BMD) of L1 and L2 vertebral bodies in glucocorticoid-exposed (GC) and naive (control) patients. We hypothesized that the anterior vertebral body will have lower BMD than posterior vertebral body in GC patients.

Methods: Patients > 18 years with preoperative lumbar computed tomography (CT) within 6 months of any surgery were included. The GC cohort included patients with > 6 months oral GC prior to imaging. BMD were measured using QCT Pro densitometry software, Version 6.1 (Mindways Software). L1 and L2 were selected due to their lower probability of degenerative changes compared to lower levels. Four volumetric measurements were made per level (upper and lower anterior; upper and lower posterior); cortical bone, areas of sclerosis/Modic changes, Schmorl nodes, and cysts were avoided. Total anterior BMD at a given level was the average of upper and lower anterior; posterior BMD was similarly calculated.

Results: 382 patients (GC = 110; control = 272) were included. There were no differences in age, sex, or body mass index. Posterior BMD was greater than anterior at L1 (p < 0.001) and L2 (p < 0.001) for the control cohort and GC (p = 0.003, p = 0.002, respectively) cohorts. Comparing anterior L1 (p < 0.01), posterior L1 (p < 0.01), anterior L2 (p < 0.05), and posterior L2 (p < 0.05), between GC versus control, the control cohort had greater BMD in all cases. Current or former smoking status decreased BMD at L1 and L2 in both cohorts compared to non-smokers (p < 0.05).

Conclusion : While chronic oral glucocorticoids do not appear to preferentially impact anterior vertebral BMD in the lumbar spine, posterior BMD was consistently greater than anterior in both GC and control cohorts. These findings may be important for spine surgeons when considering anterior screw fixation (e.g. standalone anterior lumbar interbody fusion) versus posterior screw fixation.