title: Minimally invasive versus open transforaminal lumbar interbody fusion: comparison of clinical outcomes among obese patients.
abstract: OBJECTIVE
  Minimally invasive (MI) transforaminal lumbar interbody fusion (TLIF) has been demonstrated in previous studies to offer improvement in pain and function comparable to those provided by the open surgical approach. However, comparative studies in the obese population are scarce, and it is possible that obese patients may respond differently to these two approaches. In this study, the authors compared the clinical benefit of open and MI TLIF in obese patients.
  
  
  METHODS
  The authors conducted a retrospective cohort study based on review of electronic medical records at a single institution. Eligible patients had a body mass index (BMI) ≥ 30 kg/m(2), were ≥ 18 years of age, underwent single-level TLIF between 2007 and 2011, and outcome was assessed at a minimum 6 months postoperatively. The authors categorized patients according to surgical approach (open vs MI TLIF). Outcome measures included postoperative improvement in visual analog scale (VAS), Oswestry Disability Index (ODI), estimated blood loss (EBL), and hospital length of stay (LOS).
  
  
  RESULTS
  A total 74 patients (21 open and 53 MI TLIF) were studied. Groups had similar baseline characteristics. The median BMI was 34.4 kg/m(2) (interquartile range 31.6-37.5 kg/m(2)). The mean follow-up time was 30 months (range 6.5-77 months). The mean improvement in VAS score was 2.8 (95% CI 1.9-3.8) for the open group (n = 21) and 2.4 (95% CI 1.8-3.1) for the MI group (n = 53), which did not significantly differ (unadjusted, p = 0.49; adjusted, p = 0.51). The mean improvement in ODI scores was 13 (95% CI 3-23) for the open group (n = 14) and 15 (95% CI 8-22) for the MI group (n = 45), with no significant difference according to approach (unadjusted, p = 0.82; adjusted, p = 0.68). After stratifying by BMI (< 35 kg/m(2) and ≥ 35 kg/m(2)), there was still no difference in either VAS or ODI improvement between the approaches (both unadjusted and adjusted, p > 0.05). Complications and EBL were greater for the open group than for the MI group (p < 0.05).
  
  
  CONCLUSIONS
  Obese patients experienced clinically and statistically significant improvement in both pain and function after undergoing either open or MI TLIF. Patients achieved similar clinical benefit whether they underwent an open or MI approach. However, patients in the MI group experienced significantly decreased operative blood loss and complications than their counterparts in the open group.
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan;
authors.forename: Samuel W
authors.initials: SW
authors.lastname: Terman
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Yee
authors.forename: Darryl
authors.initials: D
authors.lastname: Lau
authors.forename: Adam A
authors.initials: AA
authors.lastname: Khan
authors.forename: Frank
authors.initials: F
authors.lastname: La Marca
authors.forename: Paul
authors.initials: P
authors.lastname: Park
mesh_terms: D000328:Adult; D016063:Blood Loss, Surgical / Q000706:statistics & numerical data; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures; D009765:Obesity / Q000150:complications*; D010147:Pain Measurement; D011183:Postoperative Complications / Q000453:epidemiology; D020127:Recovery of Function; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000379:methods*; D016896:Treatment Outcome
keywords: BMI = body mass index; EBL = estimated blood loss; IQR = interquartile range; LOS = length of stay; MI = minimally invasive; ODI = Oswestry Disability Index; TLIF; TLIF = transforaminal lumbar interbody fusion; VAS = visual analog scale; minimally invasive; obesity; spine surgery; transforaminal lumbar interbody fusion