Does Systemic Administration of Parathyroid Hormone after Noninstrumented Spinal Fusion Surgery Improve Fusion Rates and Fusion Mass in Elderly Patients Compared to Placebo in Patients With Degenerative Lumbar Spondylolisthesis?

Study Design.Prospective, randomized, double-blinded, placebo-controlled clinical trial.Objective.To evaluate whether 90-day subcutaneous injections with 20 μg teriparatide increases the volume and quality of the fusion mass compared to placebo based on 12-month postop fine cut computed tomography scans. The secondary objective is to evaluate whether parathyroid hormone (PTH) increases fusion rates compared to placebo.Summary of Background Data.Few studies have investigated the effects of PTH on fusion in patients undergoing spinal arthrodesis. Early studies showed a more robust fusion mass with PTH after spinal fusion surgery. But the efficiency of PTH on noninstrumented spinal fusion surgery remains unclear.Methods.Patients with degenerative spondylolisthesis scheduled for noninstrumented posterolateral fusion were randomized to receive 90-day subcutaneous injections with 20 μg teriparatide (N = 41) or placebo (N = 46) in a 1:1 fashion. Fusion volume and quality was evaluated using 12-month postoperative fine cut computed tomography scans.Results.The two groups were comparable in terms of age, sex, and numbers of levels operated. PTH treatment was well tolerated but provided no additional benefit versus placebo. Fusion rates, the mean volume, and robustness of the fusion mass were similar between the PTH and placebo groups.Conclusion.Ninety-day subcutaneous administration of 20 μg teriparatide did not increase fusion volume or improve the quality of the fusion mass in elderly patients compared to placebo after noninstrumented spinal fusion surgery for degenerative spondylolisthesis.