Survival Analysis of Minimally Invasive Lumbar Diskectomy in Obese Patients

Presented at SMISS Annual Forum 2014
By Islam Elboghdady
With Kern Singh MD, Sreeharsha Nandyala BA, Alejandro Marquez-Lara MD, Eric Sundberg MD, Abbas Naqvi BS, Hamid Hassanzadeh MD, Anton Jorgensen MD, Khaled Aboushaala MD, Blaine Manning BS,

Disclosures: Islam Elboghdady None Kern Singh MD A; CSRS Resident Grant. B; DePuy, Zimmer, Stryker, CSRS, ISASS, AAOS, SRS, Vertebral Column - ISASS. D; Avaz Surgical, LLC, Vital 5, LLC. F; Zimmer, Stryker, Pioneer, Lippincott Williams & Wilkins, Th, Sreeharsha Nandyala BA None, Alejandro Marquez-Lara MD None, Eric Sundberg MD None, Abbas Naqvi BS None, Hamid Hassanzadeh MD None, Anton Jorgensen MD None, Khaled Aboushaala MD None, Blaine Manning BS None,

Introduction:
Obesity is associated with worsened outcomes and higher rates of reoperation following lumbar decompression surgery. However, the rate of revision surgeries associated with MIS lumbar diskectomy techniques in obese patients is not well described in the published literature.

Aims/Objectives:
To analyze the one-year survivorship, with revision surgery as the end-point, of minimally invasive (MIS) lumbar diskectomy in obese and non-obese patients.

Methods:
201 patients who underwent a primary 1 or 2 level MIS lumbar diskectomy for degenerative spinal pathology between 2007-2013 by a single surgeon were retrospectively analyzed. Patients were stratified based upon their body mas index (Obese: BMI>30Kg/m2) and assessed with regards to demographics, and Charlson comorbidity index (CCI). The incidence and prevalence of revision surgeries at 12-months were calculated by the Kaplan-Meier method. Survival distributions were analyzed with the Log-Rank comparison test and a p-value of <0.05 was utilized to denote statistical significance.

Results:
Of the 201 cases analyzed, 74 (36.8%) were performed on obese patients (mean BMI: 36.0±5.5). There were no significant differences in patient age (40.8±14.1 vs 42.1±11.2, p=0.52), and comorbidity burden (CCI: 1.44±1.82 vs 1.26±1.35, p=0.55) between the two cohorts. Kaplan-Meier analysis predicted a one-year survival of 85.1% (n=63/74; mean survival in days: 341.9) for obese patients and 87.2% (n=102/117; mean survival in days: 337.3) for non-obese patients. Patient BMI did not significantly impact the one-year survival distribution (Log-Rank: Chi-square 0.11, p=0.74) or type of revision surgery (decompression vs laminectomy, p=0.39).

Conclusions:
This retrospective analysis of MIS lumbar dikectomies demonstrated no differences in the rates and times to reoperation between obese and non-obese patients. The invariable surgical exposure achieved by MIS instrumentation, regardless of body habitus, may play a role in reducing the risk of revision surgery and worsened outcomes associated with obese patients.