The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject.(April 2014) |
Total disc replacement | |
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Other names | Artificial disc replacement, intervertebral disc arthroplasty |
ICD-9-CM | 80.5 |
Total disc replacement (TDR), or artificial disc replacement (ADR), is a type of arthroplasty in which degenerated intervertebral discs in the vertebral column are replaced with artificial disc implants in the lumbar (lower) or cervical (upper) spine. The procedure is used to treat chronic, severe low back pain and cervical pain resulting from degenerative disc disease. Disc replacement is also an alternative intervention for symptomatic disc herniation with associated arm and hand, or leg symptoms (radicular pain).
TDR has been developed as an alternative to spinal fusion, with the goal of pain reduction or elimination, while still allowing motion throughout the spine. Faster recoveries after surgery have also been widely reported by surgeons. [1] Another possible benefit is the prevention of premature breakdown in adjacent levels of the spine, a potential risk in fusion surgeries. [2] Recent studies have shown a strong correlation between providing motion in the spine and avoiding adjacent segment degeneration. [3]
Multiple artificial discs (or disc replacements) have been approved by the FDA for use in the US, although several have been discontinued by their manufacturers. The Charité, a mobile core device for use in the lumbar spine, was approved first, in 2004, but is no longer in use. prodisc, the longest continually used disc replacement device in the US, is a fixed core device manufactured by Centinel Spine and was approved in 2006 for the lumbar spine with a cervical device approved in 2007. The first cervical disc replacement available in the US was the Prestige, manufactured by Medtronic. There have been several Prestige cervical disc replacement designs manufactured by Medtronic, with the current design being the Prestige LP.
FDA approvals for devices are for one- or two-level use and at specific levels in the cervical or lumbar spine. Clinical studies are currently required to obtain FDA approval for disc replacements. These studies are comparative, noting differences between patients receiving a new device versus patients that receive spinal fusion or another previously-approved disc replacement. The below table illustrates currently-approved disc replacement devices, their approval dates, the number of approved levels for each device, and their current usage status.
Device | Anatomy | # Levels, (indicated levels) | Approval Date | In Current Use? |
---|---|---|---|---|
Charité [4] | Lumbar | 1 level only (L4-S1) | 10/04 | No |
prodisc L [5] | Lumbar | 1 or 2 level (L3-S1) | 8/06 | Yes |
ActivL [6] | Lumbar | 1 level only (L4-S1) | 6/15 | Yes |
Prestige [7] | Cervical | 1 level only (C3-C7) | 7/07 | No |
prodisc C [8] | Cervical | 1 level only (C3-C7) | 12/07 | Yes |
Bryan [9] | Cervical | 1 level only (C3-C7) | 5/09 | No |
Secure-C [10] | Cervical | 1 level only (C3-C7) | 9/12 | Yes |
PCM [11] | Cervical | 1 level only (C3-C7) | 10/12 | No |
Mobi-C [12] | Cervical | 1 or 2 level (C3-C7) | 8/13 | Yes |
Prestige LP [13] | Cervical | 1 or 2 level (C3-C7) | 7/16 | Yes |
M6-C [14] | Cervical | 1 level only (C3-C7) | 2/19 | Yes |
Simplify [15] | Cervical | 1 or 2 level (C3-C7) | 4/21 | Yes |
prodisc C Vivo [16] | Cervical | 1 level (C3-C7) | 7/22 | Yes |
prodisc C SK [16] | Cervical | 1 level (C3-C7) | 7/22 | Yes |
prodisc C Nova [16] | Cervical | 1 level (C3-C7) | 7/22 | Yes |
While these discs have received FDA approval, reimbursement by insurance companies is not always automatic. Effective August 14, 2007, the Centers for Medicare & Medicaid Services (CMS) does not cover, on a national basis, Lumbar Artificial Disc Replacement (LADR) for patients over the age of 60. However, individual entities (Medicare Administrative Contractors, or MACs) regulate the determination of covered use of devices in patients 60 and under, and several approve the use of LADR for these patients.[1] Approval by insurance companies is generally better for cervical disc replacements, with over 90% of the US population covered by a commercial payer that reimburses for cervical disc replacements, and over 85% for lumbar disc replacements. [17]
Many countries have their own individualized approval process for medical devices. In Europe, Regulation (EU) 2017/745 defined the Medical Device Regulation (MDR) used for reviewing, approving, and monitoring the quality of medical devices. There are a large number of total disc replacements available and approved for use in Europe, including all of those available in the US. Some other international regulatory bodies base their approvals upon regulations in third party countries, such as the EU or the US. Nearly all countries have their own approval process. The below table lists cervical disc replacement options available outside of the US.
Device | Manufacturer | Earliest Usage |
---|---|---|
Prestige-ST | Medtronic Inc | 2003 |
prodisc C | Centinel Spine | 2002 |
prodisc C Nova | Centinel Spine | 2009 |
prodisc C Vivo | Centinel Spine | 2009 |
Bryan | Medtronic Inc | 2000 |
Secure-C | Globus Medical Inc | 2006 |
PCM | NuVasive (Medtronic Inc) | 2002 |
Mobi-C | ZimmerBiomet | 2004 |
Prestige-LP | Medtronic Inc | 2004 |
Rotaio | SIGNUS Medizintechnik GmbH | 2011 |
Baguera-C | Spineart Geneva SA | 2007 |
Granvia-C | Medicrea International | 2010 |
Freedom-C | Axiomed Spine Corp | 2012 |
Discover | Centinel Spine | 2006 |
CP ESP | FH Orthopedics | 2012 |
Simplify | Simplify | 2015 |
Discocerv | Alphatec Spine Inc | 2006 |
NuNec | RTI Surgical, Inc | 2012 |
Tri-Lobe | Dymicron | 2014 |
NEOphytos | Artworld Medical | Unknown |
Activ-C | Aesculap AG | 2007 |
Rhine | K2M | 2016 |
Cadisc-C | Ranier Technology Ltd | 2012 |
Almas | NovaSpine | 2012 |
D6 | TrueMotion Spine Inc | Unknown |
ACDG5 | MAXXSPINE Ltd | 2009 |
The first artificial disc was implanted in 1959, with Swedish surgeon Ulf Fernström publishing a description of his experience implanting a stainless-steel ball bearing into an intervertebral disc space after discectomy in 1966. Fernström balls, used in approximately 250 patients, created segmental hypermobility and demonstrated a marked tendency to settle into the vertebral endplates. Reports suggest that function, while initially good, degenerated over time.
During the 1970s, a new concept was introduced: achieving mobility through articulation between the concave and convex surfaces of a multi-component device. Designs patented at that time combined metal, ceramic, or other types of elastic bearings with components made of silicone composites, rubber, polyurethane, plastics, or fluid-filled membranes. Some designs incorporated balloons, cages, pegs, wire screens, hinged plates, or springs. Springs proved to be particularly impractical because they could not withstand biomechanical fatigue tests of stress and strain. [18]
The first design with wide clinical adoption was the Charité disc replacement, designed by East German scientists: two-time Olympic champion in women's artistic gymnastics Karin Büttner-Janz and Kurt Schellnack, a doctor, engineer, and professor—both of whom were affiliated with the Charité Center for Musculoskeletal Surgery at the Medical University of Berlin[2]. First implanted in 1984, the disc had a biconvex polyethylene nucleus within a radiopaque metal ring that interfaced with two cobalt-chromium-molybdenum alloy endplates, which were coated with calcium phosphate. Approved for use in the United States in 2004, after a 4-year clinical trial, Charité was removed from the market by 2012.
The second disc replacement to achieve wide clinical use was the prodisc total disc replacement; it continues to have worldwide use today. Designed by French orthopedic spine surgeon Thiery Marnay, M.D., in the late 1980s, early implantations of the prodisc device began in 1990, with a 7-11 year follow-up published in 2005. After implementing design changes to the bone-facing endplate, and after a clinical study in the United States, the new design was made available worldwide. In October 2001, as part of the FDA trial, Jack Zigler, M.D., a spine surgeon at Texas Back Institute in Plano, Texas, performed the first prodisc L artificial disc replacement in the United States.
The US FDA requires manufacturers to conduct clinical studies to assess the safety and efficacy of disc replacements before obtaining approval to market the devices in the United States. Other devices can be approved for use with simpler non-clinical reviews. As a result, disc replacements have the highest level of clinical evidence of any spine devices. However, since this research is funded by industry, some controversy over data bias produced by the clinical studies exists [see Controversy].
Level 1 and level 1a studies (the highest quality levels: see Hierarchy of Evidence) have shown safety and efficacy for both lumbar and cervical discs, and have become the de facto standard of care for appropriate patients outside of the United States. [19] [20] All prospective, randomized clinical studies that have been run in the United States have shown lumbar and cervical disc replacements to provide faster recovery, better long-term patient satisfaction, and fewer incidents of adjacent segment degeneration than comparative spinal fusion options. [19] [20]
A few non-industry funded studies also exist. In addition to the previously mentioned 7-11 year followup study on prodisc conducted by Thiery Marnay, M.D., [21] a Norwegian study published in The Spine Journal in 2017 compared total disc replacement and multidisciplinary rehabilitation with an eight-year follow up. The study was randomized, controlled, multi-center and not funded by industry. 77 patients randomized to surgery and 74 patients randomized to rehabilitation responded at eight-year follow-up. The study found a statistically significant benefit in favor of surgery. [22]
The AAOS states that disc replacement requires a high level of technical skill for accurate placement and has a significant level of risk if revision surgery is needed. [23]
Members of AAOS and the American Association of Neurological Surgeons joined together as the Association for Ethics in Spine Surgery, formed to raise awareness of the ties between physicians and device manufacturers. [24]
Aetna rescinded its positive coverage for single level lumbar ADR after merger with Coventry in 2013. [25] There is currently (in 2022) a class-action lawsuit against Aetna Life Insurance for denying patients seeking lumbar disc replacement surgery in the United States alleging that patients are being harmed by denials since Aetna has declared them 'experimental or investigational’. [26]
Despite published meta-analyses (the highest-level clinical evidence) that have illustrated that total disc replacement seems to be superior to fusion in most clinical parameters, new studies have identified concerns regarding long-term durability of some of these devices. One such recent study identifies a large “midterm failure rate” related to the M6-C. It recommends that “patients implanted with the M6-C prosthesis should be contacted, informed, and clinically and radiologically assessed”. [27] Unfortunately, catastrophic failure of the M6-C prosthesis has also been reported. [28]
Orthopedic surgery or orthopedics is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat musculoskeletal trauma, spine diseases, sports injuries, degenerative diseases, infections, tumors, and congenital disorders.
Spondylosis is the degeneration of the vertebral column from any cause. In the more narrow sense it refers to spinal osteoarthritis, the age-related degeneration of the spinal column, which is the most common cause of spondylosis. The degenerative process in osteoarthritis chiefly affects the vertebral bodies, the neural foramina and the facet joints. If severe, it may cause pressure on the spinal cord or nerve roots with subsequent sensory or motor disturbances, such as pain, paresthesia, imbalance, and muscle weakness in the limbs.
Degenerative disc disease (DDD) is a medical condition typically brought on by the normal aging process in which there are anatomic changes and possibly a loss of function of one or more intervertebral discs of the spine. DDD can take place with or without symptoms, but is typically identified once symptoms arise. The root cause is thought to be loss of soluble proteins within the fluid contained in the disc with resultant reduction of the oncotic pressure, which in turn causes loss of fluid volume. Normal downward forces cause the affected disc to lose height, and the distance between vertebrae is reduced. The anulus fibrosus, the tough outer layers of a disc, also weakens. This loss of height causes laxity of the longitudinal ligaments, which may allow anterior, posterior, or lateral shifting of the vertebral bodies, causing facet joint malalignment and arthritis; scoliosis; cervical hyperlordosis; thoracic hyperkyphosis; lumbar hyperlordosis; narrowing of the space available for the spinal tract within the vertebra ; or narrowing of the space through which a spinal nerve exits with resultant inflammation and impingement of a spinal nerve, causing a radiculopathy.
Bone morphogenetic proteins (BMPs) are a group of growth factors also known as cytokines and as metabologens. Professor Marshall Urist and Professor Hari Reddi discovered their ability to induce the formation of bone and cartilage, BMPs are now considered to constitute a group of pivotal morphogenetic signals, orchestrating tissue architecture throughout the body. The important functioning of BMP signals in physiology is emphasized by the multitude of roles for dysregulated BMP signalling in pathological processes. Cancerous disease often involves misregulation of the BMP signalling system. Absence of BMP signalling is, for instance, an important factor in the progression of colon cancer, and conversely, overactivation of BMP signalling following reflux-induced esophagitis provokes Barrett's esophagus and is thus instrumental in the development of esophageal adenocarcinoma.
Klippel–Feil syndrome (KFS), also known as cervical vertebral fusion syndrome, is a rare congenital condition characterized by the abnormal fusion of any two of the seven bones in the neck. It can result in a limited ability to move the neck and shortness of the neck, resulting in the appearance of a low hairline. Most people only have one or two of those symptoms so it may not be noticeable without medical imaging.
Spinal fusion, also called spondylodesis or spondylosyndesis, is a surgery performed by orthopaedic surgeons or neurosurgeons that joins two or more vertebrae. This procedure can be performed at any level in the spine and prevents any movement between the fused vertebrae. There are many types of spinal fusion and each technique involves using bone grafting—either from the patient (autograft), donor (allograft), or artificial bone substitutes—to help the bones heal together. Additional hardware is often used to hold the bones in place while the graft fuses the two vertebrae together. The placement of hardware can be guided by fluoroscopy, navigation systems, or robotics.
Failed back syndrome or post-laminectomy syndrome is a condition characterized by chronic pain following back surgeries. Many factors can contribute to the onset or development of FBS, including residual or recurrent spinal disc herniation, persistent post-operative pressure on a spinal nerve, altered joint mobility, joint hypermobility with instability, scar tissue (fibrosis), depression, anxiety, sleeplessness, spinal muscular deconditioning and even Cutibacterium acnes infection. An individual may be predisposed to the development of FBS due to systemic disorders such as diabetes, autoimmune disease and peripheral blood vessels (vascular) disease.
Anterior cervical discectomy and fusion (ACDF) is a surgical procedure to treat nerve root or spinal cord compression by decompressing the spinal cord and nerve roots of the cervical spine with a discectomy, followed by inter-vertebral fusion to stabilize the corresponding vertebrae. This procedure is used when other non-surgical treatments have failed.
Manipulation under anesthesia (MUA) or fibrosis release procedures is a multidisciplinary, chronic pain-related manual therapy modality which is used for the purpose of improving articular and soft tissue movement. This is accomplished by way of a combination of controlled joint mobilization/manipulation and myofascial release techniques. MUA is used by osteopathic/orthopedic physicians, chiropractors and specially trained physicians. It aims to break up adhesions on or around spinal joints or extremity joints to which a restricted range of motion can be painful and limit function. Failed attempts at other standard conservative treatment methods, over a sufficient time-frame, is one of the principal patient qualifiers.
Jack Elliot Zigler is a Board Certified orthopedic surgeon specializing in spine surgery at the Texas Back Institute in Plano, Texas. He is best known for being the first surgeon to perform a ProDisc artificial disc replacement surgery in the United States, on October 3, 2001.
An artificial facet replacement is a joint prosthesis intended to replace the natural facets and other posterior elements of the spine, restoring normal motion while providing stabilization of spinal segments. It is typically used as an adjunct to laminectomy, laminotomy, neural decompression, and facetectomy, in lieu of standard lumbar fusion. The prosthesis is indicated for back and leg pain caused by central or lateral spinal stenosis, degenerative disease of the facets with instability, and grade 1 degenerative spondylolisthesis with objective evidence of neurological impairment.
Hip resurfacing has been developed as a surgical alternative to total hip replacement (THR). The procedure consists of placing a cap, which is hollow and shaped like a mushroom, over the head of the femur while a matching metal cup is placed in the acetabulum, replacing the articulating surfaces of the person's hip joint and removing very little bone compared to a THR. When the person moves the hip, the movement of the joint induces synovial fluid to flow between the hard metal bearing surfaces lubricating them when the components are placed in the correct position. The surgeon's level of experience with hip resurfacing is most important; therefore, the selection of the right surgeon is crucial for a successful outcome. Health-related quality of life measures are markedly improved and the person's satisfaction is favorable after hip resurfacing arthroplasty.
Pulsed electromagnetic field therapy, also known as low field magnetic stimulation (LFMS) is the use of electromagnetic fields in an attempt to heal non-union fractures and depression. By 2007 the FDA had cleared several such stimulation devices.
An interbody fusion cage is a prosthesis used in spinal fusion procedures to maintain foraminal height and decompression. They are cylindrical or square-shaped devices, and usually threaded. There are several varieties: the Harms cage, Ray cage, Pyramesh cage, InterFix cage, and lordotic LT cage, all of which are made from titanium; the Brantigan cage, made from carbon fibre; and the Cortical Bone Dowel, which is cut from allograft femur. The cages can be packed with autologous bone material in order to promote arthrodesis. Such implants are inserted when the space between the spinal discs is distracted, such that the implant, when threaded, is compressed like a screw. Unthreaded implants, such as the Harms and Pyramesh cages have teeth along both surfaces that bite into the end plates.
Metallosis is the medical condition involving deposition and build-up of metal debris in the soft tissues of the body.
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 onset and improve with leaning forward. Severe symptoms may include loss of bladder control, loss of bowel control, or sexual dysfunction.
Richard N.W. Wohns is a neurosurgeon who is the founder and president of NeoSpine, LLC. He has been listed one of the 50 Spine Surgeons and Specialists to Know by Becker's ASC Review. He currently practices and teaches medicine in the Puget Sound Region of Washington, United States.
Due to the many regulations in the industry, the design of medical devices presents significant challenges from both engineering and legal perspectives.
Thomas Schuler, M.D., F.A.C.S is an American spinal surgeon, researcher and educator in the treatment of neck and low back conditions. He was an early adopter of stem cell therapy, biologics, robotics, laser and hybrid surgery and augmented reality for spinal surgery. Schuler specializes in cervical and lumbar disc replacement procedures, minimally invasive spine surgery and robotic spine surgery. He performed the first hybrid multi-level cervical artificial disc replacement with spinal fusion in the country. He founded a practice that has performed some of the first robotic and augmented reality spinal surgeries in the world. In 2002 he created and currently serves as President of the National Spine Health Foundation, a national non-profit focused on education, research and patient advocacy of neck and back health.
The total posterior spine or TOPS system is an FDA-approved mechanical implant that serves as an alternative to lumbar interbody fusion surgery after decompression. It was developed by Impliant and commercially launched by Premia Spine.