Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters

Abstract

BACKGROUND CONTEXT Minimally invasive oblique lateral lumbar interbody fusion (MIS-OLIF) using a tubular retractor and pre-psoas approach has recently been gaining popularity because of its potential for minimizing para-spinal muscle damage and reducing recovery time. However, the published literature has not characterized the surgeon's learning curve with the technically demanding technique of a minimally invasive oblique lateral lumbar interbody fusion (MIS-OLIF). PURPOSE The purpose of this study is to define and analyze the learning curve for MIS-OLIF with a single spine surgeon's experience based on intra- and perioperative parameters. STUDY DESIGN/SETTING This study is retrospective analysis of single surgeon's consecutive case series in a single institution. PATIENT SAMPLE Fifty-seven consecutive patients with single or multilevel degenerative lumbar diseases who were treated by MIS-OLIF were included in the study. Surgeries were performed using oblique pre-psoas approach with a tubular retractor, and a cage was inserted using an orthogonal maneuver by a single surgeon. The corresponding segments were fixed with additional percutaneous pedicle screws. MIS-OLIF without posterior decompression was performed in 33 cases and MIS-OLIF plus posterior decompression was performed in 24 cases. OUTCOME MEASURES Corrected operative time per level, operative blood loss, postoperative drainage, transfusion rate, and ambulation recovery time were measured. Intraoperative and postoperative complication incidences were also identified. Clinical results were assessed using the visual analogue scale (VAS). METHODS The learning curve was assessed using a logarithmic curve-fit regression analysis. In the single-level OLIF group (n=21), 12 patients were defined as the “early” group (among the first 30 cases of the series), and the subsequent 9 cases were defined as the “late” group for comparison. RESULTS Corrected operative time gradually decreased as the series progressed, and an asymptote was reached after about 30 cases. Average VAS scores for lower back pain and radiating pain also significantly decreased from an average of 6.9-3.8 and 7.6-2.5, respectively. In the single-level OLIF series, operative time was significantly shorter in the late group (99±54 minutes) than the early group (141±21 minutes) and blood loss during the operation was significantly reduced in the late group (482±269 mL) compared with the early group (542±157 mL). Ambulation recovery time and VAS scores for back and leg pain did not differ between the two groups. There were two cases of retroperitoneal hematoma in the early second group requiring revision surgeries CONCLUSIONS The MIS-OLIF is a technically difficult procedure to the practicing spine surgeon with regard to unfamiliar retroperitoneal approach. Although it is not easy to master this minimally invasive technique, operative time and blood loss improved with the surgeon's experience. After the initial learning curve, this technique could be an effective and reliable option for the surgical treatment of lumbar degenerative disease. Further studies are warranted to delineate the methods to minimize the complications associated with the learning curve.