Biomechanical evaluation of traditional posterior versus anterior spondylolisthesis reduction in a cadaveric grade I slip model

Radiological Outcomes of Reduction Surgery for Degenerative Lumbar Spondylolisthesis Using Long Arm Pedicle Screws

Objective

Until now, the spondylolisthesis reduction technique has relied on posterior instrumentation using long arm pedicle screws. In this way, the segments will be brought into alignment with the other vertebrae with the pedicle mats being tightened. The aim of this study is to acknowledge whether reduction surgery for degenerative lumbar spondylolisthesis (DLS) using long arm pedicle screws is able to correct the listhesis and spinopelvic parameters.

Methods

We carried out a retrospective study of patients with degenerative lumbar spondylolisthesis who went through reduction surgery using long arm pedicle screws in our institutions from January 2019 to March 2022. Preoperative and postoperative radiological outcomes consisting of listhesis and spinopelvic parameters were assessed.

Results

We found a statistical difference between the magnitude of listhesis immediately after surgery and preoperatively (p<0.001), with a successful correction of 85.85%. There was significant decrease in the value of pelvic tilt (p=0.044) and increase in the value of sacral slope (p=0.008) after surgery.

Conclusion

Reduction surgery using long arm pedicle screws for DLS was able to reduce the listhesis effectively up to 85.5%, and also to restore the parts of spinopelvic parameters, the pelvic tilt and sacral slope, approaching normal values.

Biomechanical analysis of reduction technique for lumbar spondylolisthesis: anterior lever versus posterior lever reduction method

BACKGROUND

Reduction of lumbar spondylolisthesis during spinal fusion surgery is important for improving the fusion rate and restoring the sagittal alignment. Despite the variety of reduction methods, the fundamental mechanics of lumbar spondylolisthesis reduction remain unclear. This study aimed to investigate the biomechanical behavior while performing spondylolisthesis reduction with the anterior and posterior lever reduction method.

METHODS

We developed an L4-L5 spondylolisthesis model using sawbones. Two spine surgeons performed the simulated reduction with a customized Cobb elevator. The following data were collected: the torque and angular motion of Cobb, displacement of vertebral bodies, change of lordotic angle between L4 and L5, total axial force and torque applied on the model, and force received by adjacent disc.

RESULTS

Less torque value (116 N-cm vs. 155 N-cm) and greater angular motion (53o vs. 38o) of Cobb elevator were observed in anterior lever reduction. Moreover, the total axial force received by the entire model was greater in the posterior lever method than that in the anterior lever method (40.8 N vs. 16.38 N). Besides, the displacement of both vertebral bodies was greater in the anterior lever method.

CONCLUSIONS

The anterior lever reduction is a more effort-saving method than the posterior lever reduction method. The existing evidence supports the biomechanical advantage of the anterior reduction method, which might be one of the contributing factors to successfully treating high-grade lumbar spondylolisthesis with short-segment instrumentation.