An artificial facet replacement is a joint

prosthesis In medicine, a prosthesis (plural: prostheses; from grc, πρόσθεσις, prósthesis, addition, application, attachment), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through trau ...

intended to replace the natural

facets A facet is a flat surface of a geometric shape, e.g., of a cut gemstone. Facet may also refer to: Arts, entertainment, and media * ''Facets'' (album), an album by Jim Croce * ''Facets'', a 1980 album by jazz pianist Monty Alexander and his tri ...

and other posterior elements of the spine, restoring normal (or near-normal) motion while providing stabilization of spinal segments. It is typically used as an adjunct to

laminectomy A laminectomy is a surgical procedure that removes a portion of a vertebra called the lamina, which is the roof of the spinal canal. It is a major spine operation with residual scar tissue and may result in postlaminectomy syndrome. Depending ...

laminotomy A laminotomy is an orthopaedic neurosurgical procedure that removes part of the lamina of a vertebral arch in order to relieve pressure in the vertebral canal. A laminotomy is less invasive than conventional vertebral column surgery techniques, ...

, neural decompression, and

facetectomy Facetectomy is a surgical procedure which involves decompression of a spinal nerve root. For example, it can be performed in severely resistant cases of cervical rhizalgia, where the cervical nerve roots within the intervertebral foramina ...

, in lieu of standard lumbar

fusion Fusion, or synthesis, is the process of combining two or more distinct entities into a new whole. Fusion may also refer to: Science and technology Physics *Nuclear fusion, multiple atomic nuclei combining to form one or more different atomic nucl ...

. The prosthesis is indicated for back and leg pain caused by central or lateral

spinal stenosis Spinal stenosis is an abnormal narrowing of the spinal canal or neural foramen that results in pressure on the spinal cord or nerve roots. Symptoms may include pain, numbness, or weakness in the arms or legs. Symptoms are typically gradual in on ...

, degenerative disease of the facets with instability, and grade 1 degenerative

spondylolisthesis Spondylolisthesis is the displacement of one spinal vertebra compared to another. While some medical dictionaries define spondylolisthesis specifically as the forward or anterior displacement of a vertebra over the vertebra inferior to it (or t ...

with objective evidence of neurological impairment.

History

Patents related to facet replacement have been around since the 1980s; more intense research into artificial facet replacement as an effective and marketable prosthesis has been ongoing since the mid-2000s. Prominent researched options include: * ACADIA: a facet replacement implant "designed to reproduce facet motion while restoring normal stability and motion," first tested in 2006; also known as the Anatomic Facet Replacement System (AFRS);

clinical trial Clinical trials are prospective biomedical or behavioral research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, dietar ...

s still ongoing as of September 2015 * TOPS: a total posterior arthroplasty system first tested in January, 2005; clinical trials completed in 2011 * TFAS: the Total Facet Anthroplasty System, a nonfusion spinal implant originally developed by Archus Orthopedics in 2005; clinical trial status unknown since February 2009, when the company was dissolved but then acquired by Facet Solutions, then Globus medical; status unknown

Current status and efficacy

In 2011, in a retrospective and future analysis of the technology in the ''International Journal of Spine Surgery'', Serhan et al. opined that artificial facet replacement still had much to prove:

In the future, facet replacement devices will require a substantial amount of validation testing and numerous clinical studies before they can be considered a viable treatment option for the treatment of spinal disorders. To date, most pathophysiologic research and thus surgical treatments have been focused on the disc as a pain generator. A more comprehensive focus on re-establishing the structure and function of the human functional spinal unit may include facet replacement. A better understanding of facet function and facet-mediated pain, possibly through classification of facet degeneration, may be needed to support the use of such devices.

More recently, an August 2014 critique in the journal ''Neurosurgery'' has suggested that research aside, at least in the United States the regulatory process has led to "time lag inherent in the design, development and implementation of new technologies" such as artificial facet replacement, noting that both ACADIA and TOPS were still not

FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food s ...

-approved within the U.S. In the short-term, study literature has provided "insufficient support" for the prosthesis, with pessimal results for the procedure. However, more long-term results (such as those from the seven-year follow-up on TOPS implants) have been encouraging, albeit limited by patient sample size.

History

Current status and efficacy

See also

References

Further reading