Acceptable Fusion Rate of Single‐Level OLIF Using Pure Allograft Combined with Posterior Instrumentation through the Wiltse Approach: A 2‐Year Follow‐Up Study

OBJECTIVE: Autogenic bone grafts have shown successful fusion rates in the treatment of degenerative lumbar disorders, but taking too many autogenic bones may result in donor site ischemia or infection. This study aimed to evaluate the outcomes of single‐level oblique lumbar interbody fusion (OLIF) using pure allograft combined with posterior pedicle screw instrumentation through the Wiltse approach. METHODS: A retrospective case analysis was performed on a series of consecutive patients who received a single‐level OLIF procedure combined with posterior pedicle screw instrumentation through the Wiltse approach between July 1, 2017, and December 31, 2019, in which pure allogenic bone graft was used and filled in the large window of the cage. The patients were followed up as scheduled at 1 day and 3, 6, 12, 24 months after operation. Clinical outcome was assessed by multiple questionnaires, including Oswestry disability index (ODI), Japanese Orthopaedic Association (JOA) score rating system, short form‐36 health survey (SF‐36), and visual analog scale (VAS) for low back pain. Radiographic outcome was evaluated by measuring the parameters such as disc height, lumbar lordosis, and segmental angle on the standard standing lateral radiographs, and the space angle of the fusion level on the dynamic views of the lateral radiographs. Subsidence of the cage and intervertebral fusion status were evaluated on both the radiographic and CT scan images. RESULTS: A total of 34 patients were finally included in this study. At 2‐year follow‐up, the VAS for low back pain, ODI, JOA, and SF‐36 scores all had significant improvement (p < 0.001). Substantial increase of anterior and posterior disc heights was observed (p < 0.001). Both lumbar lordosis and segmental angle became larger (p < 0.05). No visible change of the space angle of the fusion level was found on the dynamic views. The 1‐year fusion rate of 73.5% on CT scans proceeded to 82.4% at 2‐year follow‐up. The fusion rate was as high as 91.2% according to Bridwell interbody fusion grading system on radiographic images. The clinical outcomes in patients with incomplete fusion were just as good as those with complete fusion. The six patients with cage subsidence had higher ODI (p < 0.001) and lower JOA (p < 0.001) and SF‐36 PCS (p = 0.011) scores than those without cage subsidence. CONCLUSION: The use of pure allograft in single‐level OLIF resulted in an acceptable fusion rate and satisfactory clinical effect at 2‐year follow‐up. Supplementation of posterior pedicle screw through the minimally invasive Wiltse approach ensured the favorable outcomes both clinically and radiographically.