Impact of the Cage Height, Diameter, and Positioning on Clinical and Radiographic Outcome of the Extreme Lateral Interbody Fusion

Abstract

Introduction Extreme lateral interbody fusion (ELIF) is a novel technique for anterior spinal fixation and indirect decompression of neural elements. The aim of this study was to determine certain parameters of the interbody cage that would result in better radiographic and clinical outcomes. Patients and Methods We performed a retrospective analysis of 145 ELIFs in 90 patients. Intervertebral disc height, foraminal height, cage position, and lumbar lordosis were determined on preoperative, postoperative, and the latest follow-up studies. Clinical outcomes were evaluated by Oswestry Disability Index and Visual Analogue Scale. Results At the time of last follow-up (17.7 ± 1.1 months), two of the following factors determined restoration of foraminal height: the amount of increase in the disc height (implant height—preoperative disc height) and the footprint of the intervertebral spacer. Cages that had increased the disc height by 6 to 9 mm yielded in significantly greater restoration of foraminal height compared with the grafts that had increased the disc height by 0 to 3 mm ( p < 0.01) or 3 to 6 mm ( p < 0.05). In addition, 22 mm spacers allowed for a significantly higher increase in the foraminal height compared with 18 mm spacers ( p < 0.001). Interestingly, neither cage position nor posterior instrumentation had statistically significant influence on restoration of foraminal height. Both, lordotic and nonlordotic cages allowed for increased lumbar lordosis on postoperative imaging. Clinical evaluation revealed a mean ODI, VAS back, buttock, and leg pain improvements of 21.1%, 3.7, 3.6, and 3.7 points, respectively. Conclusions In ELIF, cage width and height but not cage position, determine restoration of foraminal height.