Factors Affecting the Fusion Process and Comparison of PLIF and TLIF Techniques in Lumbar Interbody Fusion.

Abstract

Retrospective cohort study. To evaluate factors affecting the fusion process and to compare radiological and clinical outcomes among different surgical techniques in patients undergoing posterior lumbar interbody fusion (PLIF). PLIF is widely performed to restore spinal stability in degenerative lumbar conditions. The rate and timing of solid fusion are influenced by multiple patient- and surgery-related factors, including age, sex, graft type, cage usage, smoking, and diabetes status. Understanding these factors is essential for optimizing surgical planning and postoperative outcomes. Seventy-three patients who underwent PLIF for degenerative lumbar pathologies with a minimum of 24 months of follow-up were retrospectively analyzed. Patients were stratified according to age, sex, smoking status, diabetes, graft type, cage usage, and surgical technique (PLIF, PLIF+facetectomy, TLIF). Fusion status was evaluated using the Bridwell fusion criteria. Radiological parameters (lumbar lordosis, sacral inclination, four-to-floor angle, disc height) and clinical outcomes (Odom's criteria) were compared. Statistical analyses were performed using SPSS v27.0; a P value<0.05 was considered significant. Female patients demonstrated significantly higher 12-month fusion rates compared to males (P<0.001). Autograft usage was associated with higher-but not statistically significant-fusion rates at 12 months (P=0.232). Cage placement resulted in significantly better preservation of disc height (P=0.019) and a significant postoperative improvement in lumbar lordosis (P=0.028). No statistically significant differences were found between surgical techniques in terms of Odom's criteria or sagittal balance parameters, although all groups showed clinical and radiological improvement. Female sex and autograft use appear to favor earlier fusion, while cage placement provides significant benefits in preserving disc height and improving lumbar lordosis. Surgical technique (PLIF, PLIF+facetectomy, TLIF) did not significantly affect long-term fusion rates or clinical outcomes, emphasizing the importance of patient-specific surgical planning and optimization of modifiable risk factors.These findings highlight that personalized surgical decision-making, rather than the choice of fusion technique alone, plays a key role in optimizing outcomes following PLIF.