Weekly Teriparatide Administration and Preoperative Anterior Slippage of the Cranial Vertebra Next to Fusion Segment < 2 mm Promote Osseous Union After Posterior Lumbar Interbody Fusion.

<bold>Study Design: </bold>A multicenter case-control study.<bold>Objective: </bold>The aim of this study was to investigate the independent predictors of osseous union after posterior lumbar interbody fusion (PLIF).<bold>Summary Of Background Data: </bold>PLIF is usually performed to treat lumbar degenerative diseases in elderly patients. Some patients exhibit intervertebral pseudoarthrosis.<bold>Methods: </bold>We analyzed 66 elderly patients with osteoporosis who underwent PLIF from 2011 to 2014 (all women, mean age 71 years, follow-up period ≥6 months). Patients were randomly allocated to receive either treatment with weekly teriparatide, starting at 1 week postoperatively, or no teriparatide. Preoperative lumbar spine radiographs were obtained, and the amount of anterior slippage was measured. Osseous union was assessed by computed tomography at 6 months postoperatively.<bold>Results: </bold>Thirty-three patients (50%) showed complete osseous union, while 33 did not. Teriparatide was administered in 20 (61%) patients of the union group and in 9 (27%) patients of the nonunion group (P < 0.01). The preoperative anterior slippage of the cranial vertebra next to fusion segment < 2 mm was observed in 16 (49%) and 4 (12%) patients in the union and nonunion groups, respectively (P < 0.01). Multivariate regression analysis showed that teriparatide administration (odds ratio, 4.75; 95% confidence interval: 1.51-14.90; P < 0.01) and preoperative anterior slippage of the cranial vertebra next to fusion segment < 2 mm (odds ratio, 5.90; 95% confidence interval: 1.53-22.70; P < 0.01) were independently associated with osseous union within 6 months after PLIF. At 6 months postoperatively, the mean femoral neck bone mineral density significantly increased by 1.1% in the union group and decreased by 1.3% in the nonunion group (P < 0.05).<bold>Conclusion: </bold>Weekly teriparatide administration and preoperative anterior slippage of the cranial vertebra next to fusion segment < 2 mm were independent predictors of osseous union within 6 months after PLIF. Our findings suggest that biological and mechanical factors may influence the improvement of spinal fusion.<bold>Level Of Evidence: </bold>4. [ABSTRACT FROM AUTHOR]