P139. Successful criteria for indirect decompression with lateral lumbar interbody fusion (LLIF)

Abstract

<h3>BACKGROUND CONTEXT</h3> Lateral lumbar interbody fusion (LLIF) is the procedure that could achieve both fusion and indirect decompression of the neural element. However, no consensus criteria have been established to select ideal candidates for this procedure. Previous studies have reported that additional direct decompression procedures were needed in many cases. In our institution, we developed the criteria to determine whether the patient is suitable for the LLIF with indirect decompression alone. <h3>PURPOSE</h3> The purposes of the study are to (1) determine the success rate following indirect decompression by LLIF with the proposed criteria applied and (2) evaluate risk factors resulting in failure (defined as persistent symptoms requiring subsequent direct decompression of the index level within 6 months after the surgery). <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study. <h3>PATIENT SAMPLE</h3> Data from 191 consecutive patients (235 fusion levels) who underwent indirect decompression with LLIF from April 2014 to June 2020 was reviewed. Inclusion criteria were patients with lumbar degenerative diseases who underwent 1-2 levels of indirect decompression with LLIF. Exclusion criteria were patients who were preoperatively planned for a combined direct and indirect decompression. <h3>OUTCOME MEASURES</h3> Patients were scheduled for a follow-up examination at 1, 3, 6, 12 and 24 months postoperatively for clinical and radiographic assessment. Demographic data including age, body mass index (BMI), bone mineral density (BMD), preoperative functional and radiographic parameters was collected. Primary outcome is the success rate following indirect decompression with LLIF without need for subsequent direct decompression. Secondary outcomes are clinical outcomes including Oswestry Disability Index (ODI), visual analog scale (VAS) of back and leg pain and radiographic outcomes including central canal diameter, foraminal height, disc height, spinal alignment and cage subsidence. <h3>METHODS</h3> Patients who underwent indirect decompression with LLIF (XLIF or OLIF) at King Chulalongkorn Memorial Hospital between April 2014 to June 2020 were enrolled. In our institution, all patients had to meet all of the following criteria before undergoing indirect decompression with LLIF. 1) Dynamic clinical symptoms (Pain developed when standing or walking but subsided more than 50% when resting in a supine position.) 2) No profound motor weakness (Patients have motor strength gr. < III.) 3) Presence of disc height discrepancy between supine and upright position (correctable disc height in a supine position) 4) No static stenosis such as facet cysts or bony lateral recess. <h3>RESULTS</h3> Of 191 patients, 13 patients (6.8%) required subsequent direct decompression after the index procedure due to persistent pain. Thus, the clinical success rate of the criteria to select surgical candidates was 92.8%. The average patient age was 66.3 years and average follow-up period was 1.21 years. The failure group has significantly lower average BMD T-score (-2.34 vs -0.75; p < 0.05). The degree of preoperative disc height discrepancy between supine and standing position in the failure group was significantly less than the success group (5.9% vs 16.5%; p < 0.05). The low postoperative disc height (< 10.2 mm), use of supplementary fixation with anterolateral plate and high-grade cage subsidence (gr. 2-3) were also identified as the significant risk factors resulting in failure. <h3>CONCLUSIONS</h3> Our study presented the criteria of patient selection to undergo indirect decompression with LLIF which resulted in a 92.8% success rate with satisfactory outcome. Risk factors of reoperation with direct decompression included low BMD, low preoperative disc height discrepancy between standing and supine position, use of supplementary fixation with anterolateral plate, low postoperative disc height and high-grade cage subsidence. Our proposed criteria and reported risk factors may provide a guidance for spine surgeons to select appropriate patients who would achieve successful results following indirect decompression with LLIF and to optimize the risk factors resulting in failure. However, further studies with larger subjects requiring subsequent direct decompression are needed to identify additional significant risk factors. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.