The recent announcement of the first posterior total disc arthroplasty in the lumbar spine is sure to shift attention from the anterior lumbar approach for motion preservation to the posterior approach.
In March, a posterior lumbar disc replacement device, the Secure-P (recently renamed Triumph Lumbar Disc, Globus Medical Inc.) was implanted in a 47-year-old woman with chronic degenerative disc disease at L4-L5. The two-piece implant is made of cobalt chrome and ultra-high-molecular-weight polyethylene. The device was implanted after a standard posterior approach and lumbar decompression.
The interview on the next page with Paul McAfee, MD, who participated in the surgery in São Paulo, Brazil, addresses several questions about this type of surgery.
Posterior total disc arthroplasty adds to the growing body of posterior solutions for achieving the goal of lumbar motion preservation, segmental load sharing and effective axial pain relief in those patients who traditionally would be treated with segmental fusions. Competing concepts include preservation of the annulus with nucleus replacements, and lumbar facet replacement technology.
Preservation of the Annulus With Nucleus Replacements
This category includes hydrogels, polycarbonate coiling spirals and metallic
devices. Case series of hydrogel implants such as the PDN device (Prosthetic
Disc Nucleus, Raymedica) have been reported. A polymer device designed to replace
the nucleus in single-level lumbar spine degenerative disc disease (DASCOR
Disc Arthroplasty System, Disc Dynamics) is currently in a prospective, multicenter
pilot study. A spherical implant available in cobalt chromium or PEEK-Optima
polymer (Satellite Spinal System, Medtronic Sofamor Danek) is cleared for use
in the United States based on a 510(k) exemption, and its safety and efficacy
have not yet been established by prospective, randomized trial data.
Lumbar Facet Replacement Technology
This category includes pedicle screw based implants such as TOPS (Impliant
Ltd.), which contains two articulating titanium components connected by a polycarbonate
urethane sleeve. The device constrains segmental motion to the neutral zone
and thus maintains normative segmental load displacement, presumably diminishing
segmental pain generation. TOPS currently is being subjected to a multicenter,
double-armed, randomized trial in the United States, and it was approved by
the European Commission this summer for use as a motion-preserving alternative
to fusion in the treatment of spinal stenosis with or without degenerative
facet arthrosis, and spondylolisthesis.
Total Facet Arthroplasty System (Archus Orthopedics) is conceptually similar to the TOPS system. It is based on a pedicle fixation design and constrains segmental motion. In this system, however, pedicle fixation is accomplished with polymethylmethacrylate, PMMA, cement. A prospective randomized trial is currently enrolling patients in more than 20 centers.
Dynamic Stabilization Systems
Dynamic stabilization systems are becoming increasingly available and compete
in the same market as the above devices by constraining segmental motion at
abnormal, pain generating spinal segments rather than using traditional rigid
fixation and segmental arthrodesis. These systems include the Graf ligament,
Dynesys Dynamic Stabilization System (Zimmer Spine), Isobar TTL (Scient’x),
and Stabilimax NZ Dynamic Spine Stabilization System (Applied Spine Technologies).
Despite the resources being devoted to the development of posterior lumbar
motion preservation technology and its clinical trials, it remains uncertain
whether this is just an alternative to the standard segmental lumbar fusion
with similar patient clinical outcomes or whether this is a superior approach
to the treatment of segmental lumbar disease by virtue of motion preservation.
In large part this answer depends on two factors:
- whether the premature failure of a motion segment adjacent
to a fusion is a consequence of rigid arthrodesis or if it represents the
natural history of lumbar degenerative disease; and
- whether the natural history of premature adjacent motion segment failure, regardless of etiology, is corrected by motion preservation surgery.
Patrick W. McCormick, MD, FACS, MBA, is a partner in Neurosurgical Network Inc., Toledo, Ohio. He is associate editor of AANS Neurosurgeon.The author reported no conflicts for disclosure.
| A Surgeon’s Experience With Posterior Total Disc Arthroplasty
In this interview, Patrick McCormick, MD, questions Paul McAfee, MD, a surgeon who participated in the first posterior total disc arthroplasty in the lumbar spine using the Secure-P device. Dr. McAfee is a consultant with and receives research funding from Globus Medical Inc. What is the degree of difficulty in placing the implant? Is it comparable
to the time and effort required for a posterior lumbar interbody fusion with
fixation? Are precise positioning and sizing of the implant critical to the
success of the surgery, or is the implant designed to be more forgiving in
this regard? How does this implant stack up against the anterior lumbar disc prostheses
that are currently approved or under trial in the United States? What additional insights and thoughts do you have regarding the prospects
for a posterior total disc replacement system becoming a routine option for
surgical treatment of lumbar disc disease? |