Effects of Different Orientations of Cage Implantation on Lumbar Interbody Fusion

Abstract

Transforaminal lumbar interbody fusion (TLIF) via a fusion cage is widely carried out to treat degenerative lumbar spinal disease, and cage implantation plays a pivotal role in buttressing the vertebrae and promoting fusion. Clinically, the cage implantation is commonly placed in 2 different orientations: oblique and traverse. Therefore, this study aimed to explore the effects of different orientations of cage implantation on lumbar interbody fusion. From January 2016 to January 2018, a retrospective study of 98 patients with lumbar degenerative disease who were treated with lumbar interbody fusion with at least 2-year follow-up was performed. According to the different positions of cage implantation, the patients were divided into 2 groups: oblique group (OG) and traverse group (TG). The clinical and radiographic outcomes were compared preoperatively, postoperatively, and at last follow-up evaluation. Radiographic measurements included the height of intervertebral (HOI) disk, segment lordosis (SL), lumbar lordosis (LL), the distance between the posterior of cage and vertebrae postoperatively (D1), the distance at final follow-up (D2), and the distance of cage move (D3). Radiographic evaluation of fusion integrity was performed based on the Bridwell interbody fusion grading system at the final follow-up. There was no significant difference between the 2 groups in terms of sex, age, surgical levels, operative time, intraoperative blood loss, time to ambulation, and length of hospital stay (P > 0.05). The HOI disk, SL, and LL in the 2 groups were noticeably improved postoperatively compared with preoperatively (P > 0.05), and there was no significant difference between the 2 groups (P > 0.05). However, at the final follow-up, HOI disk, SL, and LL in the TG were larger than those in the OG (P < 0.05). D1 and D2 in the TG were larger than those in the OG, and there was a significant difference between the 2 groups (P < 0.05). D3 in the OG was larger than that in the TG (P < 0.05). All patients achieved grade I fusion at the final evaluation. The traverse cage implantation in TLIF had the same clinical effect as oblique cage implantation, but is superior in improving sagittal alignment. Therefore, we advise that the cage should be placed in traverse orientation in TLIF.