Medical Student Case Western Reserve University School of Medicine Cleveland Heights, Ohio, United States
Introduction: Range of motion (ROM) preserving devices such as the Premia Spine TOPS System facet replacement implant and the Dynesys Dynamic Stabilization System offer a potential alternative to fusion surgery in patients with degenerative spondylolisthesis or lumbar spinal stenosis. By preserving segmental motion, these devices aim to reduce adjacent segment disease (ASD) rates compared to traditional fusion surgery. Loosening of pedicle screws following surgery can be indicated by radiolucency and may indicate incomplete fixation in fusion operations, but the implication of screw loosening in motion-preserving surgeries is not clear. This study examines data from the TOPS Investigational Device Exempt (IDE) Trial to determine the impact of screw loosening on patient outcomes.
Methods: The TOPS IDE trial included 209 patients who received the TOPS System and 96 who underwent a fusion surgery. A modified intention-to-treat analysis was conducted with clinical outcomes reported from Zurich Claudication Questionnaire (ZCQ), Visual Analog Scale (VAS) for pain, and Oswestry Disability Index (ODI).
Results: In the TOPS cohort, 7 patients (3.3%) were identified as having screw loosening with 2 undergoing re-operation (0.97%) compared to 1 re-operation in the fusion group for screw loosening (1.08%). Patients in the TOPS cohort with screw loosening had a significant reduction in VAS for pain at 12 months postoperatively in worst leg (p-value < 0.001) and low back (p-value = 0.03) with no significant difference in VAS reduction compared to those without screw loosening. Likewise, there was significant improvement in ODI from preoperative baseline to 12 month postoperative in the loose screw population (p-value = 0.001) and no significant difference in the number of patients who achieved a minimum of 30% improvement in ODI score from baseline. Overall ZCQ success following surgery (meeting at least 2 individual ZCQ success criteria) was seen in 6 of the loose screw patients (85.7%) and was not significantly different from the non-loose screw population.
Conclusion : Screw loosening was not associated with worse clinical outcomes in patients undergoing facet replacement with the TOPS System. Improvements in pain, disability, and overall surgery success were significant in patients who underwent facet replacement regardless of loose screw status.
