To investigate the characteristics and causes of endplate injury in the oblique lateral interbody fusion for the treatment of lumbar diseases, and summarize the precaution of endplate injury.

Thirty-five cases of endplate injury were observed, which were originally treated with oblique lateral interbody fusion with or without pedicle screw fixation from October 2014 to December 2017. There were 7 males and 28 females, and the age ranged from 51 to 78 years old (averagely 62.8±8.13 years). There were 2 cases of lumbar disc degeneration, 10 cases of lumbar canal stenosis, 17 cases of lumbar degenerative spondylolisthesis, 2 cases of lumbar spondylolysis with or without spondylolisthesis, and 4 cases of lumbar degenerative scoliosis. Lesion sites contained L_3,4 in 2 cases, L_4,5 in 21 cases, L_2-4 in 3 cases, L_3-5 in 4 cases, L_2-5 in 3 cases and L_1-5 in 2 cases. Preoperative bone mineral density examination revealed there were 7 cases of T>-1 SD, 24 cases of -2.5 SD<T<-1 SD and 4 cases of T<-2.5 SD. There were 5 cases of high iliac crest. There were 25 cases of single segment, 5 cases of double segment, 3 cases of three segments, and 2 cases of four segments. Endplate injury occurred in all cases, and a total of 40 endplates occurred in 39 intervertebral spaces, of which the upper and lower endplates of 1 intervertebral space were injured, and the rest were single endplate injuries. There were 35 cases of upper endplate injury, 5 cases of lower endplate injury and 3 cases combined with vertebral fracture. The cage location where the endplate injury occurred: 3 cases in zone Ⅰ-Ⅱ, 31 cases in zone Ⅱ-Ⅲ and 5 cases in zone Ⅲ-Ⅳ. The main observation indicators were Visual Analog Scale (VAS) for low back pain, Oswestry disability index (ODI), intervertebral space height, and position of cage.

The reasons for endplate injury were: osteopenia or osteoporosis 28 cases, improper surgical steps 9 cases, high iliac crest 5 cases, endplate anatomical morphology variation 5 cases, obvious stenosis of the intervertebral space 4 cases, large cage 3 cases and mixed factors 12 cases. The follow-up time was 18.5±8.1 months. There was no pedicle screw loosen during the follow-up. There were 3 cases of lateral displacement of cage, including 1 case of Stand-alone OLIF, 2 cases of OLIF combined with pedicle screw fixation. In all cases, different degrees of cage subsidence occurred. Among them, 7 cases of Stand-alone OLIF were supplemented with posterior pedicle screw fixation. The intervertebral height of diseased segment was well restored postoperatively, which was statistically significant compared with preoperative. But there was significant loss during the follow-up, and the difference was statistically significant at the last follow-up. The low back pain VAS score was from 6.6±2.2 preoperative to 1.3±0.74 at the last follow-up, which was statistically different. The ODI was from 36.3%±7.4% preoperative to 9.6%±3.5% at the last follow-up, which was statistically different. Except 3 cases, the remaining had well interbody fusion, with the fusion rate of 91.4%.

The incidence of endplate injury during oblique lateral interbody fusion is high. The reasons of endplate injury include both the patient's factors and the surgical factors. Endplate injury is closely related to the decreased intervertebral space height during the follow-up period, as well as the settlement or displacement of cage. Some cases may require reoperation. The prevention of endplate injury should be strengthened. Once it occurs, timely and effective treatment should be taken, and follow-up should be done closely.

Lumbar vertebrae; Spinal fusion; Intraoperative complications; Reoperation