This is a retrospective study. The study was conducted at a single institution between January 2009 and March 2018, and consisted of 131 patients (58 men, 73 women) who underwent PLIF with PSI (TABLE1). A total of 208 lumbar segments recorded in 131 subjects were allocated into groups A, B, and C according to the endplate changes: 1. Group A had endplates with type 2 Modic change and endplate sclerosis. 2. Group B had type 2 Modic change but without endplate sclerosis. 3. Group C had neither Modic changes nor endplate sclerosis. According to fusion potentiality at L5-S1 level would be lower than the upper lumbar levels, segments of the three groups were further divided into two subgroups: L5-S1 segment (groups A1, B1, C1) and L1-5 segments (groups A2, B2, C2). After reviewing the digital database of a radiology record system, patients meeting the following criteria were included: (1) patients age was more than 18 years; (2) patients who had been diagnosed with lumbar spondylolisthesis or lumbar spinal canal stenosis; (3) patients underwent lumbar spine surgery with pedicle screw instrumentation, and the decompressed space was implanted with cage; (4) patients had no history of adolescent scoliosis, spinal surgery, tumor, tuberculosis, infection and trauma; (5) patients had no hypertension, diabetes and heart disease. For the main purpose is to discuss the difference in fusion efficiency among patients with type 2 sclerotic Modic change or non sclerotic Modic change, a few patients with type 3 Modic change were excluded.
The research was conducted according to the principles of the Declaration of Helsinki. The ethics committee of the First Affiliated Hospital of Guangxi Medical University approved the study, and written informed consent was obtained from all patients (2019(KY-E-033)).
Patients were operated on in a prone position under general anesthesia. A midline incision was made to expose the spinous processes, laminae, and transverse processes. The initial stage involved inserting posterior transpedicular screw instrumentation (Common Spinal Fixation Device, Ltd., Li Bell, China) through a paraspinal muscle-splitting approach. The transpedicular screws were inserted under C-arm fluoroscopic guidance in all patients. The next stage involved posterior decompression (including laminectomy, medial facetectomy, and aminotomy), which was undertaken in all patients. A nearly complete discectomy was done. Intervertebral disc space spreaders were then inserted sequentially and rotated to restore the normal disc space. Next, an appropriate size of cage was inserted into the disc space directly under C-arm fluoroscopy so it would lay in the middle of the interbody space.
Modic changes were determined using MRI (GE Signa Twinspeed; GE Medical Systems, Milwaukee, WI, USA), and endplate sclerosis was detected on sagittal and coronal reconstructed CT scans (GE Light Speed Pro 16; GE Healthcare, Milwaukee, WI, USA). MRI and CT analyses included the operated lumbar levels. Endplate sclerosis was seen adjacent to the endplate and usually localized in the same area as the lumbar interbody fusion Modic change(Fig. 1). At 3 months or longer after surgery, the patients were evaluated with CT. Classification of Modic changes was based on the T1- and T2-weighted MRI results in the middle five sagittal planes. The upper and lower endplates at each disc level were graded separately regarding the presence of type 2 Modic change or absence of Modic change, as previously defined (Fig. 1a,b).Endplate sclerosis was visually evaluated from the sagittal and coronal reconstructed CT scans by comparing them with the MRI at a workstation(Fig. 1a–d). The presence of endplate sclerosis was defined as yes or no. Bony fusion was evaluated according to the postoperative sagittal and coronal reconstructed CT scans (Fig. 1c, d). CT became the preferred method for assessing interbody fusion[9–13]. Details of the bony fusion evaluation were as follows[13–15]: (1) complete fusion: evidence of bridging trabecular bone through the disc space with no cystic lucencies adjacent to the implant and no linear defects through the bridging bone; (2) partial fusion: trabecular bone seen extending from the endplate into the disc space but forming an incomplete bridge; (3) no fusion: no evidence of trabecular bone formation extending from the endplates. Because the aim of this study was to assess the bony fusion of vertebral body endplates, both complete and partial fusion were considered fusion.
Three experienced spine surgeons (JL, FZ and CZ.) who were blinded to the radiographic images independently classified the endplate changes and evaluated the images for the presence of bony fusion. If at least two of the observers agreed about the type of endplate change, the classification was carried out. The binary logistic regression analysis was used to examine the association between type 2 sclerotic Modic change and bony fusion; three binary logistic regression analysis models were inputted in turn. The models were performed as follow: a model adjusted for groups A and C (model 1); a model adjusted for groups A and B (model 2); a model adjusted for groups B and C (model 3).