General Session: Tumor, Trauma, Infection, Image

Presented by: L. Pimenta - View Audio/Video Presentation (Members Only)

Author(s):

L. Marchi(1), R. Amaral(1), F. Fortti(1), L. Oliveira(1), E. Coutinho(1), R. Jensen(1), L. Pimenta(1,2)

(1) Instituto de Patologia da Coluna, Sao Paulo, Brazil
(2) USCD, Neurosurgery, San Diego, CA, United States

Abstract

Introduction: Less invasive fusion approaches, such as mini-anterior lumbar anterior fusion (mini-ALIF), have proliferated. Historically, there were no agreement about the stability of stand-alone ALIF cage. Recently, interbody cages with locking screws have been introduced to avoid the use of posterior fixation. Biomechanical tests have demonstrated acceptable stability for clinical use, but few reports have assessed fusion rates of these constructions. The hypothesis of this study is that is possible to achieve solid fusion with anterior lumbar interbody fusion in a standalone montage using self-blocking cage. To answer that, it was studied the fusion and nonunion rates at 12-month follow-up following mini-ALIF with a stand-alone construction using interbody cages with locking screws.

Methods: Single-center radiological and clinical study, with consecutive enrollment. Inclusion criteria: cases that underwent mini-ALIF procedures for L5S1 using a self-blocking interbody cage (two cranial screws, one caudal hollowed screw) due to either DDD with stenosis/ instability and/or low-grade spondylolisthesis. Exclusion criteria: cases that received posterior or anterior additional supplementation, or lack of 12-month evaluation. Forty-four cases with 12-month data versus 87 cases enrolled; minimum follow-up of 12 months. The primary outcome was fusion status assessed in CT scans, secondary outcomes was revision surgery due micro motion, device migration or pseudoarthrosis. Mini-ALIF procedures were performed through a retroperitoneal anterior approach, using interbody cage with 3/4 locking screws in direction to the adjacent vertebral endplates, and packed with synthetic bone grafts (calcium phosphate). No additional supplementation was done. 12-month CT scans and lateral fexion/extension lumbar radiographs were analyzed. Fusion status was defined according to Bridwell and Lenke classification.

Results: Forty-four L5S1 cases were included in this study. Complete or ongoing fusion was found in thirty-nine cases (87%).Thirty-three of the 44 levels (77%) were judged completely fused by CT after 12 months of the surgery. Six levels (14%) had ongoing bone ingrowth, two levels (5%) displayed lucent lines around the cage, and two levels (5%) had lucent lines and subsided. Posterior supplementation was necessary for two cases (5%) - one with subsidence and slippage progression (at 12 months) and other with symptomatic micro motion (at 6 months). Any device expulsion occurred.

Conclusion: Mini-ALIF using a stand-alone construction with locking screws can achieve reasonable bone fusion rate and low reoperation rate in a mid-term analysis for degenerative disc conditions in L5S1.

CT images showing bone fusion