Comparison of Clinical and Perioperative Outcomes in Patients Undergoing MIS-TLIF in Outpatient vs Inpatient Setting: Matched Cohort Analysis

Background The most common technique utilized for lumbar arthrodesis in an outpatient setting is minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). While prior studies have assessed this technique’s feasibility in an outpatient setting, there is a paucity of literature comparing long term clinical outcomes of MIS-TLIF in an outpatient versus inpatient setting. This study investigates the differences in clinical outcomes between these two settings through comparison of patient-reported outcome measures (PROMs) and minimum clinically important difference (MCID) achievement. Methods Primary, elective, single-level MIS-TLIF procedures performed between 2005 and 2021 for degenerative spinal pathology were identified in a surgical database. Patient demographics, perioperative characteristics, and PROM scores were collected. PROMs measuring physical function, back pain, leg pain, and disability were administered at preoperative and 6-week, 12-week, 6-month, 1-year, and 2-year postoperative time-points. Patients were grouped into two cohorts, depending on whether a patient underwent surgery in an inpatient setting or in an outpatient setting at an ambulatory surgery center (ASC) where the patient was discharged within 23 hours. Coarsened exact match was carried out to control for significant demographic differences between cohorts. Demographic and perioperative characteristics were compared among groups using chi-square and Student’s t-test for categorical and continuous variables, respectively. Mean PROM scores were compared between cohorts at each time point utilizing a two-sample t-test. Postoperative PROM improvement from preoperative baseline within each cohort was calculated with use of paired t-test. Achievement of Minimum Clinical Important Difference [MCID] was determined by comparing ΔPROM scores to previously established threshold values. Rates of MCID achievement were compared among groups using simple logistic regression. Results After coarsened exact matching, 227 patients were excluded and final patient cohort consisted of 391 patients – 339 patients in the Inpatient MIS-TLIF cohort and 52 patients in the Outpatient MIS-TLIF cohort ( Table 2 ). Mean estimated blood loss (EBL), postoperative length of stay (LOS), and postoperative narcotic consumption on days 0 and 1 were observed to be significantly lower in Outpatient MIS-TLIF cohort (p<0.041, all) ( Table 3 ). Preoperative and postoperative mean PROM scores were not significantly different for all PROMs collected ( Table 5 ). Both cohorts demonstrated significant improvement for PROMIS-PF, SF-12 PCS, VAS back, and VAS leg at 2-year time-point from preoperative baseline ( Table 4 ). Patients in the Inpatient MIS-TLIF cohort demonstrated greater proportion achieving MCID for overall SF-12 PCS and overall VAS back (p<0.022, all) ( Table 6 ). No significant differences for MCID achievement rates were noted between cohorts at specific postoperative time points ( Table 6 ). Inpatient cohort demonstrated significantly higher rates of postoperative nausea and vomiting (p=0.001) ( Table 4 ). Conclusion After careful patient selection, patients undergoing MIS-TLIF in an outpatient setting demonstrated similar long term clinical outcomes for back pain, leg pain, physical function, and disability as defined by PROMs and MCID achievement. Additionally, patients in outpatient cohort demonstrated reduced postoperative narcotic consumption. Results from our study would suggest patient safety and outcome quality is not compromised from undertaking MIS-TLIF in an outpatient setting.