Evaluation Of An Anterior Lumbar Interbody Fusion Approach To Degenerative Spondylolisthesis

Presented at SMISS Annual Forum 2014
By Sun Keegan Lee Bachelor of Medicine
With Prashanth Rao Bachelor of Medicine/Bachelor of Surgery,

Disclosures: Sun Keegan Lee Bachelor of Medicine None Prashanth Rao Bachelor of Medicine/Bachelor of Surgery None,

Introduction:
Debate continues over the optimal approach for fusion of isthmic and degenerative spondylolisthesis. We favour anterior lumbar interbody fusion (ALIF) as it permits liberal discectomy and placement of a large, lordotic device which restores disc height and sagittal balance, reduces slip and decompresses exiting nerve roots. There are only a few papers in literature looking at the degree of reduction and the durability over time in patients undergoing ALIF with spondylolisthesis.

Aims/Objectives:
This study aims to assess the initial degree of reduction achieved with ALIF for patients with isthmic and degenerative spondylolisthesis. Subsequent analysis of the degree of regression on follow up radiological images will assess the durability of the reduction following ALIF instrumentation.

Methods:
Radiographic analysis of prospectively collected data was conducted. All patients with lumbar spondylolisthesis who underwent ALIF between 2009 and 2013 by a single surgeon RJM were included. Radiologic analysis of slip percentage and disc height preoperative and on immediate postoperative and latest follow up imaging was carried out with Surgimap Spine software. Demographic factors, surgical data and radiological results were compared.

Results:
Average patient age was 63 yrs (range 36-84) with 19 females and 15 males. There were 35 levels treated with 20 at L4/5, 14 at L5/S1 and one at L3/4. Mean listhesis was 16% which immediate postoperatively reduced to 2.3% but at latest follow up was reduced to 58% of original value. Of note, these analysis of these measurements showed a high degree of inter- and intra-class correlation. Mean follow up was 17 months. Average disc height increase of 184% was observed postoperatively. The overall radiological fusion rate was 91%. Only 3 patients required subsequent posterior instrumentation, which will be discussed.

Conclusions:
ALIF achieves disc height restoration and indirect listhesis reduction in isthmic and degenerative spondylolisthesis. Although this reduction may regress over time it is still reduced by about 50% at latest follow up. Only 10% of them required further strengthening by posterior pedicle screw fixation.