Effect of bone graft granule volume on postoperative fusion after lumber spinal internal fixation: A retrospective analysis of 82 cases

Objective: To investigate the effect of bone graft volume on postoperative fusion and symptom improvement in lumbar posterior lumbar fusion and internal fixation.

Methods: A total of 82 patients receiving pedicle screw rod system internal fixation with Cage bone graft fusion in the First Hospital of Baoding City, Hebei Province were selected and randomly divided into three groups. The excised autologous laminar bones were bitten into different sizes of bone fragments. And different sizes of bone grafts were implanted during the operation. Group-A (n=28) was implanted by bone graft granule with the average volume of 0.2 cm3, Group-B (n=27) was implanted by bone graft granule with the average volume of 0.1 cm3, and Group-C (n=27) was implanted by bone graft granule with the average volume of 0.05 cm3. The bone graft granule volume, clinical effect, bone graft fusion rate and intervertebral space height were compared.

Results: The three groups had significantly different bone graft granule volumes (P<0.05), but similar intervertebral bone graft total volumes and Cage heights (P>0.05). In the final follow-up, VAS and ODI of low back pain and two lower limbs pain significantly reduced compared with those before surgery (P<0.05), but the three groups had similar results (P>0.05). The bone graft fusions of Group-B one and two years after surgery were significantly higher than those of Group-A and Group-C, and the values of Group-A exceeded those of Group-C (P<0.05). In the final follow-up, the intervertebral space height change of Group-B was significantly smaller than those of Group-A and Group-C (P<0.05).

Conclusion: Size of bone graft granule has no significant effect on postoperative symptoms. However, middle-sized volume bone graft granule (0.1 cm3/granule) showed increased postoperative intervertebral fusion rate and reduced intervertebral space height loss in our study.