Assessment of Osteoporosis Treatment on Spine Bone Strength Using a Novel Finite Element Analysis

Introduction: Osteoporosis (OP) is an important risk factor for mechanical complications post-surgery. Using a novel Finite Element Analysis we studied the pedicle screw-bone connection in pullout test and physiological spinal loads with different OP treatments, including romosozumab, teriparatide and alendronate.

Methods: This retrospective secondary analysis used lumbar spine computed tomography (CT) data from postmenopausal women with low BMD or OP in the imaging substudies of the romosozumab Phase 2 (NCT00896532) and Phase 3 ARCH (NCT01631214) trials. For the Phase 2 study, treatment groups were: Romo 210 mg QM, placebo [Pbo], or teriparatide [TPTD] for 12 months. In ARCH, treatment groups for this analysis were: Romo or alendronate [Aln] for first 12 months, then Aln for all for a second 12 months. For each patient, CT scans at baseline (BL) and follow-up (6, 12, and/or 24 months), were used to create a finite element model at each timepoint for the patient’s L1 vertebra, virtually implanted with a pedicle screw, in a “shear pullout” configuration. Percent changes from BL in shear bone strength (N), volume of failed tissue (cm3) associated with shear bone loading related to weak bone, and periprosthetic BMD (mg/cm3) were compared by analysis of covariance models adjusting for baseline covariates.

Results: Data were analyzed for 79 patients from each study (Phase 2: Romo, 24; Pbo, 27; TPTD, 28; ARCH: Romo/Aln, 44; Aln/Aln, 35). BL characteristics were similar across treatment groups within each study. In the Phase 2 study, compared to Pbo and TPTD, Romo significantly increased shear bone strength, decreased volume of failed tissue, and increased periprosthetic BMD. In ARCH, at M6 and M12 compared to Aln, Romo significantly increased shear bone strength, decreased volume of failed tissue, and increased periprosthetic BMD, and these changes were maintained at M24 after switching from Romo to Aln.

Conclusion : For both studies, compared to its respective comparators, Romo significantly increased shear bone strength and periprosthetic BMD and lowered the amount of failed tissue around virtual screw. These data demonstrate Romo’s greater efficacy vs TPTD or Aln in improving spine bone density and strength.