The Effect of Proton Pump Inhibitors on Bone Formation in a Rat Spinal Arthrodesis Model

Study Design. Rat posterolateral arthrodesis model. Objective. Quantify the impact of administration of a proton pump inhibitor on spine fusion. Summary of Background Data. Proton pump inhibitors (PPIs) are widely used for gastrointestinal disorders and for ulcer prophylaxis in patients taking non-steroidal anti-inflammatory drugs. PPIs cause chronic acid suppression which has been found to result in decreased bone mineral density, increased fracture risk, and impaired fracture healing. Despite advances in surgical techniques, pseudarthrosis still occurs in up to 24% of patients requiring revision surgery following spinal fusion procedures. Thus, there are likely many unidentified risk factors. While PPIs have been hypothesized to impact fracture healing, no study has evaluated their effect on spine arthrodesis rates. Methods. Thirty-eight female rats underwent posterolateral lumbar spinal fusion. Rats were divided into two groups: normal saline control and pantroprazole, which was administered by daily intraperitoneal injections. At 8 weeks postoperative spines were evaluated with manual palpation, microCT, histologic analysis, and biomechanical testing. Results. Fusion rates of the control group and PPI group were not significantly different (100% vs. 94%). Average fusion scores were significantly lower in the pantoprazole group. New bone formation identified on microCT imaging of bilaterally fused specimens demonstrated a lower average volume of newly generated bone in the PPI group, but this difference was not significant. Biomechanical testing demonstrated no significant difference in strength or stiffness of the fusion mass between the groups. Conclusion. This study demonstrates that administration of PPIs does not inhibit fusion rates, bone formation, or affect biomechanical integrity of fusion. However, lower fusion scores in the PPI group suggest that a negative impact may still exist. Future studies will explore growth factor and protein expression in the fusion masses as well as utilize higher doses of PPI to fully discern their effect on spine fusion.