Object: Total disc replacement is an alternative to lumbar fusion, but patients with spinal stenosis, spondylolisthesis, and facet arthropathy are often excluded from this procedure because increased adjacent-segment motion can exacerbate dorsal spondylotic changes. In such cases of degenerative spondylolisthesis with stenosis, decompression and fusion remain the gold standard of treatment. To avoid attendant loss of motion at the treated segment, the TOPS system is a novel total posterior arthroplasty prosthesis that allows for an alternative dynamic, multiaxial, three-column stabilization and motion preservation. The purpose of this study is to report preliminary surgical data and clinical outcomes in patients treated with the TOPS lumbar total posterior arthroplasty system.
Methods: Twenty-nine patients were enrolled in a nonrandomized, multicenter, prospective pilot study outside the US. All patients had spinal stenosis and/or spondylolisthesis at L4-5 due to facet arthropathy. Radiographs and scores on outcome measures including the visual analog scale (VAS) for pain, Oswestry Disability Index (ODI), Short Form-36, and Zurich Claudication Questionnaire were prospectively recorded before surgery and at 6-week, 3-month, 6-month, and 1-year intervals after surgery. Prior to instrumentation, a bilateral total facetectomy and laminectomy at L4-5 or L3-4 was performed via a standard midline posterior approach. After decompression, the TOPS screws were inserted into four pedicles to achieve maximal purchase with triangulating bicortical trajectories. An appropriately sized TOPS arthroplasty implant was then applied. The mean surgical time was 3.1 hours, and patients' clinical status improved significantly following treatment with the TOPS device. The mean ODI score decreased compared with baseline by 41% at 1 year, and the 100-mm VAS score declined by 76 mm over the same time period. Radiographic analysis showed that lumbar motion was maintained, disc height was preserved, and no evidence of screw loosening was found. No device malfunctions or migrations and no device-related adverse events were reported during the study.
Conclusions: The TOPS total posterior arthroplasty system represents a novel, dynamic, posterior arthroplasty device that provides multiaxial stability in flexion, extension, rotation, and lateral bending after total facetectomy and neural decompression. The surgical data indicate that it can be safely applied via a traditional approach with low surgical morbidity and excellent 1-year functional and radiographic outcomes in patients with degenerative spondylolisthesis accompanied by stenosis and back pain.