Friday, September 28, 2018 1:00 PM–2:30 PM abstracts: achieving lumbar interbody fusion: 198. The changes of volume of psoas muscle after oblique lateral interbody fusion L4-5 for treatment of degenerative lumbar disease: the observation of the effect on atrophic changes and correlation with clinical outcomes

Abstract

BACKGROUND CONTEXT Recently, minimally invasive lateral lumbar interbody fusion has gradually increased popularity as substituted method of conventional lumbar fusion.There are two methods of DLIF (direct lateral lumbar interbody fusion) and OLIF (oblique lateral interbody fusion) in lateral lumbar interbody fusion. PURPOSE In MIS-DLIF, blunt retroperitoneal and trans-psoas dissection poses a risk of injury to the psoas muscle and lumbar plexus, especially at lower lumbar level.As an alternative, MIS-OLIF uses a window between the prevertebral venous structures and psoas muscle, and gets an access to the target disc obliquely. Theoretically, MIS-OLIF preserves psoas muscle with reducing the complication of direct lateral approach. However, in most case, some psoas muscle violation cannot be avoided during the OLIF. So, the purpose of this study was to evaluate the changes of psoas muscle volume after OLIFand also to analysis whether there is a correlation between the change of psoas volume and clinical outcomes STUDY DESIGN/SETTING The study was approved by the Institutional Review Board (IRB) of our institution. Medical and radiological charts of 30 consecutive patients who underwent MIS-OLIF for various L4/L5 level pathologies and whose follow-up time exceeded 12 months (mean follow-up time 14.4 months, between July 2013 and May 2016) by a single surgeon were reviewed. PATIENT SAMPLE A total of 30 patients were included in this study. A total of 22 patients were female (73.3%). The mean age was 65.4 years, with a range from 52 to 83 years. The average follow up period among all patients was 14.4±7.2 months (range, 6.0–34.0 months). OUTCOME MEASURES Whole lumbar lordotic angles were significantly (P METHODS The clinical outcomes were assessed before surgery and postoperatively at 6 months, 1 year and 2 years by using visual analog pain scale (VAS), Oswestry disability index (ODI) score, and total time of daily walk. Radiologic outcomes were assessed with plain radiography, computed tomography (CT) and magnetic resonance imaging (MRI). We checked the radiologic datas before surgery and postoperatively at 6 months, 1 year and 2 years. Whole and segmental Lumbar lordosis, disk and foraminal height at index level were measured by using plain radiography.We used Modified Bridwell fusion criteria to define fusion rate.Both size of psoas muscles were measured with cross sectional area by axial slice of CT scan at mid point of L4/5 disc.We recorded cage subsidence postoperatively at 1 year and 2 years. RESULTS Mean age of the patients included in this study was 65.4±8.0 (52–83, Sex M: 8, F: 22) and preoperative diagnoses were Spinal stenosis/DDD in 14 patients (47%), Spondylolisthesis in 14 patients (47%) and HNP in two patients (6%). single level OLIF (L4–5) was performed in 23 patients (77%) and more than two levels OLIF (include L4–5) was performed in seven patients (23%). There was statistically significant improvement of clinical outcomes. (VAS (back, leg), ODI, walking time for 1 day, all of them p CONCLUSIONS MIS-OLIF is a relatively safe procedure without definite atrophic change or reduction of volume of psoas muscle at the first follow after surgery and overall the volume of the psoas muscle at L4-5 significantly increased postoperatively, especially in the group with good clinical outcomes.