Lightning Podiums: Spinal Potpourri - 803B

Presented by: L. Snyder

Author(s):

L. Snyder(1), J. Lehrman(1), R. Menon(1), J. Godzik(1), A. Newcomb(1), B. Kelly(1)

(1) Barrow Neurological Institute, Neurosurgery, Phoenix, AZ, United States

Abstract

Purpose: Minimally invasive transforaminal interbody fusion (TLIF) is a well-established procedure, but decisions on how to perform it can vary. One decision point for surgeons is whether to perform a unilateral facetectomy or bilateral facetectomy. Some surgeons perform "partial bilateral facetectomy," during which on one side a full facetectomy is performed for interbody access, while on the other side the facet capsule is drilled to loosen the facet as well as decorticate bone for arthrodesis. In this study, we sought to evaluate and compare the biomechanical benefits of a unilateral facetectomy (UF), a partial bilateral facetectomy (PBF), and a complete bilateral facetectomy (CBF) to determine which approach improved biomechanical outcomes.

Methods: 7 cadaveric specimens (L3-S1) were prepped for UF from the left with a full facet removal, hemilaminectomy, discectomy, and placement of pedicle screws (6.5X45MM) at L4-L5. With no rods in place, distraction was performed on the left side via an instrumented distractor tool (102N) and pure moment flexion (7.5Nm) test. A fixed interbody spacer was appropriately sized and placed into the specimen. Compression was then performed on the left side via an instrumented compressor tool (170N) and pure moment extension (7.5Nm) test. Rods were locked into place with bilateral compression via an instrumented compressor tool to 170N. Standard nondestructive flexibility tests (7.5Nm) were then performed to assess intervertebral range of motion (ROM) in flexion/extension (F/E), right and left lateral bending (LB), and right and left axial rotation (AR). Axial compressive loading (300N) was performed to determine compressive stiffness. Final lordosis angle was measured at the end of rod lock down after compression. Change in foraminal height was measured before and after posterior compression via compressor tool and final rod lock down. The same procedure was performed for PBF and then CBF in all 7 specimens. Data was analyzed using RM-ANOVA (P< 0.05).

Results: CBF, PBF, and UF demonstrated similar ROM in F/E, LB, and AR at the interbody fusion level L4-L5 (p>0.05). UF and CBF demonstrated greater mean compressive stiffness than PBF, but this did not reach statistical significance (p>0.9). CBF demonstrated significantly greater ROM (8.00±3.50º) in pure moment distraction than UF (7.24± 3.33º) (p=0.026) and significantly greater ROM (3.74±0.87º) in pure moment compression than both UF (2.71±1.31º) (p< 0.001) and PBF (2.97±0.99º) (p=0.001). With the compressor tool, CBF demonstrated significantly greater ROM (2.82±0.83º) than UF (2.17±1.10°) (p=0.007). Mean foraminal height did not change significantly with the compressor tool (p>0.1). However, with final rod lockdown, CBF demonstrated a significantly greater change in mean foraminal height (1.90±0.62mm) than UF (1.00±0.45mm) (p=0.037). Final lordosis achieved at the interbody level was greatest with use of CBP (3.74±0.70º), slightly less with PBF (3.11±1.22º), and the lowest with UF (2.68±1.28º), with statistical significance between all three approaches (p< 0.04).

Conclusions: CBF allows for greater ability to distract for interbody placement achieve greater lordosis angles with final screw lockdown, and increase foraminal height when compared to UF and PBF. CBF and even a PBF add time, effort, and slightly increased risk to the minimally invasive transforaminal interbody fusion, however, these may be worth it due to the potential benefit in biomechanical outcomes.