The Impact of Open Lumbar Posterolateral Instrumentation and Fusion versus Minimally-Invasive Techniques: A Propensity-Matched Post-Hoc Analysis of a Randomized Controlled Trial

Introduction: Few studies have investigated primary open versus MIS 1- and 2-level lumbar fusions where the definition of MIS includes anterior (ALIF) and lateral (LLIF), as well as posterior (TLIF) approaches. Previous definitions of MIS did not include ALIF and LLIF, however, literature has shown that outpatient ALIF and LLIF have similar outcomes compared to inpatient. We devised a new definition of MIS including ALIF, LLIF, TLIF, and combined approaches and hypothesized that MIS leads to decreased postoperative pain and opioid use and increased early ambulation, but higher radiation exposure.

Methods: A propensity-matched post-hoc analysis of a randomized-controlled trial of patients undergoing primary one and two-level lumbar fusions was performed. Our definition of MIS included ALIF, LLIF, and posterior approaches with incision size < 1 inch. MIS also included combined approaches (anterior with posterior; lateral with posterior), as long as posterior incisions were < 1 inch. Preoperative and postoperative patient-reported outcome measures (PROMs) including numeric pain rating scale (NPRS), brief pain index (BPI), Oswestry disability index (ODI), and PROMs minimal clinically important difference (MCID) were assessed, along with opioid use (morphine milligram equivalents, MME), operative time, estimated blood loss (EBL), hospital length of stay (LOS), ambulation distance, urinary retention, and radiation exposure.

Results: After matching, 90 patients (30 MIS, 60 open) were included. There were no significant differences in postoperative day (POD)1 and POD3 NPRS and BPI. MIS showed lesser POD1 intravenous opioid use (p = 0.019), lower total MME POD0 - POD2 (p = 0.027) and , greater ambulation distance POD0 - POD1 (p = 0.009). The MIS cohort also showed lower EBL, shorter operative time, shorter LOS, and greater radiation exposure. There were no differences in urinary retention or preoperative ODI, but MIS had lower 2-year postoperative ODI (p = 0.003).

Conclusion : One- and two- level MIS lumbar fusion has several advantages over open fusion, including lower EBL, shorter LOS, less opioid use, and greater immediate postoperative ambulation, but greater radiation exposure. While open techniques are important in patients requiring osteotomy and/or extensive deformity correction, MIS approaches, including ALIF and LLIF, may minimize postoperative opioid usage and allow patients to ambulate sooner.