Effect of vertebral rotation on adjacent segment degeneration after the early stage of lumbar fusion surgery.

Objective: Related studies have shown that the torsional vertebral after fused significantly increase adjacent disc stress and accelerate degeneration. This suggests that vertebral rotation (VR) may accelerate adjacent segment degeneration (ASD). To investigate: (1) the correlation between VR and radiographic adjacent segment degeneration (rASD) after the early stage of lumbar fusion (2), the incidence of rASD with different VR degrees (3), whether the incidence of rASD can be reduced by surgically reducing instrumented vertebrae (IV) rotation.

Methods: A retrospective analysis was conducted on the cases of 195 patients with lumbar degenerative disease (LDD) who were selected based on inclusion and exclusion criteria. The grade and angle of VR were measured for accurate analysis. The final follow-up evaluated the clinical improvement of the patients and the rASD. The impact of various factors on rASD was observed using univariate and multivariate logistic regression analyses. With different VR grades, Kaplan-Meier survival analysis was used to describe the incidence of rASD at various follow-up intervals.

Results: The results indicate that preoperative adjacent vertebrae (AV) rotation (OR = 1.852, 95% CI = 1.064-3.224, P = 0.029) and IV rotation at final follow-up (OR = 2.748, 95% CI = 1.458-5.177, P = 0.002) are the independent risk factors for rASD. The results of the Kaplan-Meier analysis showed that with different VR grades, the follow-up period was different when the cumulative incidence of rASD reached 50%. The AV rotation decreased in the patients whose IV rotation decreased after the operation (P < 0.001), and the incidence of rASD was also lower (P = 0.004), especial in the fused to S1 group.

Conclusions: VR is a risk factor for rASD at the early stage of lumbar fusion surgery. Reducing VR during surgery can alleviate the speed of ASD and reduce the incidence of rASD in fused to S1.