A peer-reviewed literature search was performed through December 2010.
In 2009, Phillips et al. reported a manufacturer-sponsored study on TFAS that assessed the kinematics of implanted and adjacent lumbar segments in nine human lumbar spines (L1 to sacrum). Specimens were tested as follows: intact, after L3 laminectomy with L3-L4 facectomy, after L3-L4 pedicle screw fixation, and after L3-L4 TFAS implantation. The author’s conclusions were that the “TFAS restored range and quality of motion at the operated segment to intact values and restored near-normal motion at the adjacent segments”.
Two Phase III clinical trials, both sponsored by the device developers were found as follows:
The ACADIA™ Facet Replacement System (AFRS®, NCT00401518) is an actively recruiting U.S. multicenter randomized controlled trial with a primary objective to evaluate the overall success rate in patients with spinal stenosis when compared to a posterior spinal fusion. The study began in 2006, is expected to enroll around 300 subjects, and has an estimated completion of 2013. Specific inclusion criteria are patients between 21 and 85 years of age with lateral, lateral recess and/or central canal stenosis, disc height measuring ≥ 4 mm at the operative level, with persistent leg, thigh and/or buttock symptoms, including pain, numbness, burning, or tingling with a minimum leg pain score of 40-mm as measured by the Visual Analogue Scale (VAS) refractory to at least six months of conservative treatment, candidate for a decompression with full facetectomy at the operative level, candidate for a posterior lumbar fusion. Study participants will be randomly assigned in a 2:1 ratio into treatment with the investigational artificial facet replacement device (TFAS®) or with standard posterior instrumented fusion.
The Total Facet Arthroplasty System® (TFAS®, NCT00418197) is a randomized controlled trial listed as ongoing but not currently recruiting. The study began in 2005, is expected to enroll around 450 subjects, and has no estimated date of completion. It is designed for patients with moderate to severe lumbar spinal stenosis requiring neural decompression with facetectomy at L3-L4 or L4-L5, Grade I degenerative spondylolisthesis with objective evidence of neurologic impairment, and degenerative disease of the facets, with or without instability. Specific inclusion criteria are patients between 50 and 85 years of age with degenerative spinal stenosis, central or lateral, at spinal levels L3-L4 or L4-L5, with persistent leg symptoms, including pain, numbness, burning, or tingling that are refractory to at least six months of conservative treatment, no greater than Grade I degenerative spondylolisthesis at the index level, and no more than three levels of degenerative lumbar spinal stenosis requiring decompression. Study participants will be randomly assigned in a 2:1 ratio into treatment with the investigational artificial facet replacement device (TFAS®) or with standard posterior instrumented fusion.
Pending publication of these trials and subsequent FDA approvals, available evidence is insufficient to evaluate the effect of facet arthroplasty on health outcomes. Therefore, facet arthroplasty is considered experimental, investigational and unproven.