Two-Year Survival of Unilateral versus Bilateral Minimally Invasive Transforaminal Lumbar Interbody Fusion

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:
The favorable clinical outcome associated with MIS TLIF is well established. To date, no published reports have addressed the differences in 2-year survivorship between unilateral and bilateral instrumentation techniques.

Aims/Objectives:
To compare the two-year survival between unilateral versus bilateral instrumentation for a single-level minimally invasive (MIS) transforaminal lumbar interbody fusion (TLIF).

Methods:
A retrospective study involving a prospectively collected registry. A consecutive series of 249 patients who underwent a primary single-level MIS TLIF for degenerative spinal pathology between 2007-2012 were identified and stratified based upon the surgical technique (Unilateral or Bilateral). Patient demographics, smoking status, Charlson comorbidity index (CCI), and one-year arthrodesis rates were assessed. The incidence and prevalence of revision surgeries at two years were calculated utilizing 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 249 patients identified, 189 (75.9%) patients and 60 (24.1%) patients were unilaterally and bilaterally instrumented, respectively. There were no significant differences in patient demographics, comorbidity burden, or smoking status between cohorts. The mean survival time after index MIS TLIF was 660.7 days in the unilateral cohort and 584.4 days in the bilateral cohort. Kaplan-Meier analysis predicted a two-year survival of 88.9% (n=168/189) and 75.0% (n=45/60) in the unilateral and bilateral cohorts, respectively. Comparison analysis demonstrated a significant difference in the survival distribution between the two cohorts (Log-Rank: Chi-square 7.84 p=0.005). The unilateral cohort had a significantly increased arthrodesis rate at one year postoperatively. (95.2% vs 86.7%, p=0.02).

Conclusions:
The unilateral instrumentation technique demonstrated superior two-year survival and 1-year arthrodesis rate compared to the bilateral instrumentation technique. Although long-term studies are warranted, this mid-term data propose the unilateral technique as a better choice with a lasting treatment effect for the management of single-level degenerative lumbar spine pathology.