234 - A Comparative Study on Cage Subsidence Following Standalone Lateral In...

#234 A Comparative Study on Cage Subsidence Following Standalone Lateral Interbody Fusion

MIS Techniques and Outcomes

Poster Presented by: L. Pimenta

Author(s):

L. Pimenta (1), (2)
R. Jensen (1)
L. Marchi (1)
L. Oliveira (1)
E. Coutinho (1)
T. Coutinho (1)
C. Castro (1)
R. Amaral (1)

(1) Instituto de Patologia da Coluna, Sao Paulo, Brazil
(2) UCSD, Neurosurgery, San Diego, CA, USA

Abstract

Purpose: Previous studies on lateral lumbar interbody fusion revealed that indirect decompression of the neural structures with standard cages is feasible. But there is an important cage subsidence occurrence, which may limit ability for decompression. The influence of the cage width on indexes of surgical goals and complications is yet unknown and it is the main goal of this work.

Methods: Retrospective analysis on prospective clinical studies. Seventy-four patients (57.2 ± 14.8 y/o; BMI 24.9 ± 2.5). Standing lateral radiographs were performed preoperatively, postoperatively at 1 and 6 weeks, 3 and 12 months. Clinical outcomes were assessed by ODI and VAS up to 24 months. Standalone short-segment lateral lumbar interbody fusion was investigated. The fused segments were: 3 at L1L2, 7 at L2L3, 22 at L3L4, 66 at L4L5. Forty-six patients (56.7 ± 24.7 y/o; BMI 24.7 ± 3.1), 61 lumbar levels, were treated with standard cages (18mm) and twenty-one patients (57.2 ± 24.5 y/o; BMI 25.0 ± 2.3), 37 lumbar levels, were treated with wide cages (22mm). Radiological measurements were done regarding segmental lumbar lordosis and subsidence occurrence. Subsidence grading followed a method that estimates the percentage of the cage is inside the vertebral body: 0-24% of subsidence - grade I; 25-49%- grade II; 50-74%- grade III; 75-100%- grade IV. All patients completed 12-month follow-up evaluations.

Results: VAS and ODI scores improved equally in both groups. Although all patients had gain in segmental lumbar lordosis, wide group gain were higher than for standard group (7% for standard and 17% for wide - p= 0.0004). Difference in subsidence was evident at 6w, 3mos, and 12mos (p=0.01). At 12mos: grade I/II - 70% in standard group and 81% in wide group; grade III/IV - 30% in standard group and 14% in wide group. Subsidence was early detected on 6-week and didn't significantly progressed. Moreover, subsidence was seen to occur predominantly (68% of the cases) in the inferior endplate of the assessed intervertebral disc.

Conclusions: Wider cages have a significant impact on avoiding cage subsidence occurrence in standalone lateral interbody fusion. Better alignment correction of the lumbar spine is also achieved with this kind of implant. Moreover, cage subsidence must be carefully evaluated at early follow-up.

Subsidence comparison