The Impact of L5 Sacralization on Fusion Rates and Clinical Outcomes After Single-level Posterior Lumbar Interbody Fusion (PLIF) at L4-L5 Level

Study Design: Retrospective review of prospectively collected data. Objective: To determine the impact of L5 sacralization on fusion rates and clinical outcomes after single-level posterior lumbar interbody fusion (PLIF) surgery at the L4-L5 level. Summary of Background Data: L5 sacralization can produce greater stress concentration at the adjacent segment (L4-L5); therefore, L4-L5 PLIF surgery in patients with L5 sacralization may negatively affect fusion rate and be associated with poor clinical outcomes. However, no study has examined the impact of L5 sacralization on fusion rates and clinical outcomes of patients who undergo L4-L5 PLIF surgery. Materials and Methods: Of 153 patients who underwent L4-L5 PLIF, data of 145 who met the study criteria were retrospectively reviewed. Among them, 31 patients had L5 sacralization (group A), whereas the remaining 114 patients did not (group B). The primary study endpoint was fusion rate evaluated using dynamic radiographs and computed tomographic scans. Secondary endpoints included (1) pain intensity in the lower back and radiating to the lower extremities on the visual analog scale; (2) clinical outcomes assessed using the Oswestry Disability Index and 12-item Short Form Health Survey; (3) surgical outcomes; and (4) complications. Results: Fusion rate evaluated using dynamic radiographs and computed tomographic scans at 6 months after surgery did not differ significantly between patients with and without sacralization (P = 0.70 and 0.81, respectively), whereas fusion rate at 1 year after surgery did (P = 0.04 and 0.04, respectively). In particular, patients with type II or III L5 sacralization had significantly lower fusion rates than those with other types of or no L5 sacralization. Pain intensity, clinical and surgical outcomes, and complications did not differ significantly between groups. Conclusions: Patients with type II or III L5 sacralization may have worse fusion rates after L4-L5 PLIF surgery than those with type I or no sacralization.