Class 2/3 Obesity Leads to Worse Outcomes Following Minimally Invasive Transforaminal Lumbar Interbody Fusion.

Abstract

Background context: There is lack of evidence regarding the impact of class 2/3 obesity (body mass index, BMI ≥35) on outcomes following minimally invasive transforaminal lumbar interbody fusion (MI-TLIF).

Purpose: To analyze clinical outcomes, return to activities, fusion rates, and complication/reoperation rates following MI-TLIF in class 2/3 obese patients and compare them with other BMI groups.

Study design: Retrospective cohort PATIENT SAMPLE: Patients who underwent primary single-level tubular MI-TLIF for degenerative conditions of lumbar spine and had a minimum of 1-year follow-up were included. Patients were divided into 4 cohorts based on their BMI: normal (BMI 18.5 to <25), overweight (25 to <30), class 1 obesity (30 to <35), and class 2/3 obesity (BMI ≥35).

Outcome measures: 1) operative variables: operative time, estimated blood loss (EBL), postoperative length of stay (LOS); 2) patient reported outcome measures (PROMs) (Oswestry Disability Index, ODI; Visual Analog Scale, VAS back and leg; 12-Item Short Form Survey Physical Component Score, SF-12 PCS); 3) global rating change (GRC), minimal clinically important difference (MCID), and patient acceptable symptom state (PASS) achievement rates; 4) return to activities; 5) fusion rates; and 5) complication and reoperation rates. Two postoperative timepoints were defined: early (<6 months) and late (≥6 months).

Methods: Differences between the 4 BMI cohorts in demographics and outcome measures were analyzed with appropriate statistical tests. Subgroup analyses were performed to compare outcomes between a) class 2 and class 3 obesity groups and b) patients with and without metabolic syndrome. Regression analyses were performed to analyze the relationship of BMI groups and metabolic syndrome with PASS achievement.

Results: 390 patients were included (119 normal, 160 overweight, 67 class 1 obesity, 44 class 2/3 obesity). There was no significant difference in intraoperative variables. Although no significant difference was seen between the groups in PROMs at <6 months, class 2/3 obesity group had significantly worse PROMs, lower PASS achievement rates, and lower MCID achievement rates in VAS leg and SF-12 PCS at ≥6 months. There were no significant differences in the MCID achievement rates in ODI and VAS back and responses on the GRC scale. Although class 2/3 obesity group had a lower fusion rate (67% vs. >87% in other groups), this difference was not statistically significant. Class 2/3 obesity group had significantly higher postoperative LOS (62 hours vs. <50 hours in other groups) and took significantly greater number of days to return to driving (74 days vs. <40 days in other groups). No significant difference was found in return to work and discontinuation of narcotics. The groups had similar complication and reoperation rates. On subgroup analysis, postoperative PROMs did not show any difference between a) class 2 and class 3 obesity groups and b) patients with and without metabolic syndrome. On regression analysis, class 2 and class 3 obesity groups showed a significant negative relationship with PASS achievement. Class 2 obese patients were 3.7 times and class 3 obese groups were 5 times less likely to achieve PASS.

Conclusions: Class 2/3 obese patients undergoing MI-TLIF had significantly worse PROMs and lower MCID and PASS achievement rates at ≥6 months. They took longer to be discharged from the hospital and return to driving following surgery. Class 2 obese patients were 3.7 times and class 3 obese groups were 5 times less likely to achieve an acceptable symptom state after surgery.