Comparison of clinical and radiological results of dynamic and rigid instrumentation in degenerative lumbar spinal stenosis
Authors: Varol Eyup , Etli Mustafa Umut , Avci Furkan , Yaltirik Cumhur Kaan , Ramazanoglu Ali Fatih , Onen Mehmet Resid , Naderi Sait 
Published: September 2022

Objective
Lumbar spinal stenosis is defined as a clinical syndrome characterized by neurogenic claudication or radicular pain due to the narrowing of the spinal canal or neural foramen and the compression of its neural elements. Surgical treatment is applied to decompress the neural structures. In some cases, transpedicular instrumentation and fusion may also be applied. In this study, we aimed to investigate and compare the preoperative and postoperative, clinical and radiological aspects of patients with lumbar spinal stenosis who underwent lumbar instrumentation using a polyetheretherketone (PEEK) rod or a titanium rod.

Materials and Methods:
In this study, the files of 293 patients who underwent posterior lumbar transpedicular stabilization between January 2015 and February 2018 in the Neurosurgery Clinic of Ümraniye Training and Research Hospital were reviewed retrospectively. Patients who did not meet the study criteria were excluded, and 127 patients who met the criteria and underwent posterior lumbar transpedicular stabilization due to lumbar spinal stenosis and/or lumbar degenerative disc disease were retrospectively reviewed. The patients were divided into two groups, dynamic and rigid, according to the rod types used. The two groups were compared using various postoperative clinical and radiological parameters.

Results:
The demographic data, surgical data, Visual Analog Scale-Oswestry Disability Index (VAS-ODI) data, and radiological data of both groups were carefully examined. There were 63 patients in the rigid group and 64 patients in the dynamic group. The age range in both groups was from 30 to 78 years, with a mean age of 56.44 years; 99 of the cases were female and 28 were male. The analysis of the participants' demographic data showed no significant differences between the two groups. Compared with the preoperative data, the postoperative evaluations revealed a significant decrease in VAS and ODI, but no significant difference was observed between the two groups. There was no difference between the two groups in terms of duration of surgery, follow-up time, operating distances, hospitalization duration, pseudoarthrosis, or fusion. Regarding the total and segmental range of motion, the affection was less in the dynamic group, which allowed for more movement. While there was no difference in disc height index between the two preoperative groups, it was observed that it was better maintained in the rigid group in the postoperative long term. Regarding foraminal height (FH), there was no difference between the two groups in the preoperative and early postoperative periods, but in the long term, FH was better maintained in the dynamic group. The long-term follow-ups revealed that adjacent segment disease (ASD) had developed in 19 patients in the rigid group, whereas ASD developed in only nine patients in the dynamic group. Based on these results, the probability of developing significant ASD in the rigid group was higher.

Conclusion:
Previous experience with PEEK rod systems has demonstrated physiological spine movement, increased fusion rates, minimal complications, reduction in adjacent segment degeneration, and biomechanical compatibility. Although further long-term studies are needed and the cost of PEEK systems is likely to be a barrier, the results of the present study support the use of PEEK rods and other dynamic systems in spinal surgery.