Lateral parallel insertion of large footprint cages in PLIF promotes early fusion and fewer endplate cysts

Lateral lumbar interbody fusion (LLIF) allows insertion of large footprint cages, promoting stability and fusion. This study evaluated the clinical and radiological impact of a novel technique enabling large footprint cage insertion during posterior lumbar interbody fusion (PLIF). A retrospective analysis was performed on 78 patients who underwent PLIF at three institutions. Patients were classified into the LPI group (n = 20) using large footprint cages and the conventional group (n = 58). Bony union and vertebral endplate cyst formation were assessed by CT. Clinical outcomes were compared using the Japanese Orthopaedic Association (JOA) score and the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ). In IPTW-adjusted analyses, the 3-month fusion rate was significantly higher in the LPI group than in the conventional group (90.0% vs 43.1%). At 12 months, both groups achieved high fusion rates (100.0% vs 96.6%). Vertebral endplate cyst signs at 3 months were significantly less frequent in the LPI group (p = 0.006). After IPTW adjustment, the LPI group showed greater improvement at 12 months in the JOABPEQ lumbar function domain score. However, differences were limited to a single domain and were not consistently observed across other patient-reported outcomes. Early fusion was not independently associated with improvement in patient-reported outcomes. The LPI technique using a large-footprint cage in PLIF was associated with higher early fusion rates and fewer early vertebral endplate cyst signs. Clinical benefits were limited and should be confirmed in larger prospective studies.