DISC PROTHESIS

  • HISTORY


    The concept of disc replacement has been around for more than 60 years.

    Since the late 1950s, several dozens of materials or implants have been studied to restore the viscoelasticity of the intervertebral disc. The vast majority of these products will never be used in clinical practice.

    In 1955, David Cleveland first replaced intervertebral discs with cement balls. This technique evolved as a result of the work carried out by Fernström, which led to the implantation of stainless steel balls. The first artificial disc was invented in 1958 by Hoogland and was never implanted in a patient.

    The first prosthetic design to be widely adopted is the Charité prosthesis, designed by Karin Büttner-Janz, an East German neurosurgeon, and was implanted for the first time in 1984. Three generations of implants enabled the prosthesis to evolve for more than 25 years and become the most implanted prosthesis in the world, until 2011, when its production stopped. In parallel with this experience, in the late 1980s, in Montpellier, Dr. Thierry Marnay was able to complete his independent work on the development of a semi-constrained disc prosthesis: the Prodisc.

    The first generation of prosthesis was implanted in the early 1990s, in 60 patients. Dr. Thierry Marnay and his team then waited for 7 years to ensure the long-term outcome of this prosthesis and in 1999, the quality of the results and the rate of patient satisfaction allowed the development of a second generation of prosthesis, which was widely used throughout Europe.

    The Prodisc-L was approved by the Food and Drug Administration for implant in the United States in 2006. It is currently the only disc replacement prosthesis to be authorized in the United States. Many other implants have emerged in recent years, confirming the interest in intervertebral disc replacement surgery.



  • FUNCTION


    The aim of a surgical procedure on a joint affected by a degenerative disease is to relieve pain and to restore, as close as possible, the natural mechanics of this joint.

    The spine has 3 main functions that the disc replacement surgery will respect:

    >> Stability and ability to support the weight of the body

    The disc prosthesis is anchored between the vertebra using a central keel and its porous surface allows it to be recolonized by the surrounding bone. The materials comprising it (metal alloy and polyethylene) are perfectly inert and are the same as those of hip and knee prostheses used in surgery for more than 50 years.

    >> Biomechanics and mobility

    The principle of the disc prosthesis is that of a ball joint, which allows rotational movements in the 3 planes of space, to reproduce the mobility of a normal disc as closely as possible. The disc prosthesis will assist with the movements of the spine, while maintaining stability between the vertebrae. In a static position (standing, sitting, or lying down), the prosthesis will automatically place itself in the position that allows the best balance for the spine and will relieve all other discs.

    >> Protection of the central nervous system

    The nerve roots, an extension of the spinal cord in the spine, are located in a canal, behind the discs and the vertebral bodies. During the placement of a disc prosthesis, the surgeon will have previously removed almost all of the diseased, oftentimes pinched, disc. In case of associated bulging disc or herniated disc, this will also be removed in its entirety, to allow the release of the compressed nerve roots. The initially collapsed space between the 2 vertebrae will then be restored, creating maximum space for the nerves until they exit the spine at the foramina. The prosthesis is then put in place and will maintain this increased space in all positions, including during movement.



  • SYMPTOMS


    definition and causes

    While common lumbago (back pain) can have multiple causes (muscle, ligament, joint, psychological), severe, chronic, and disabling lumbago is almost always disc-related; it is lumbar discopathy, i.e., progressive degeneration of one or more intervertebral discs.

    course of the disease

    Discopathy can occur through acute low back pain (lumbago), which often occur after a “wrong move”, or after physical exertion. The episode naturally tends to heal in a few days, or sometimes a few weeks. While in most people these episodes will remain isolated, or at least very spread out over time, in 5% of cases, the low back pain will intensify, occur with less and less significant exertion, until they become permanent. The disc will tear, dry out, and gradually pinch. Sometimes, a fragment of this disc is expelled and compresses the nerve roots located immediately behind it: this is the phenomenon of a herniated disc, responsible, among other things, for sciatic pain in the legs. In some cases, this herniated disc occurs suddenly at the outset of the discopathy, in people with absolutely no back pain up to that point, while in other cases the hernia appears after a long history of back pain. It must also be understood that the more the disc is pinched, the narrower the space around the nerve roots will become. Therefore, sometimes the simple removal of a herniated disc is not enough to completely release a compressed root.

    Symptoms

    lumbar discopathy can be responsible for two major types of symptoms: back pain (lumbago) and pain in the legs (sciatica or cruralgia). Somewhat briefly, it is the degeneration of the entire disc that is responsible for low back pain, and the herniated (or bulging) disc that can compress the nerve roots and trigger sciatica. In case of a disc that is very pinched, very bulging or very inflammatory, sciatica may appear even when there is no hernia. Lumbago related to lumbar discopathy corresponds to band-like pain in the lower back. Remaining seated or standing for a prolonged time quickly becomes very painful. The pain is very sensitive to physical exertion, and often forces the sufferer to reduce his/her sports or professional activities. There is often morning pain and stiffness that requires a warm-up period before the start of daily activities. Worsening occurs in some people through increased frequency, duration, and intensity of episodes of acute low back pain. The pain can then become permanent, day and night. The impact on social and family life is often very substantial, and can lead the sufferer to experience feelings of failure or even depression. Sciatic pain is described in the herniated disc paragraph.

  • SURGERY


    Lumbar disc replacement surgery is not performed through the back, like a simple herniated disc surgery, but through the abdomen, to exert minimal tension on the nerve roots located at the back of disc. This is a minimally invasive technique, since in a thin subject, the disc prosthesis will be placed through a 5 to 7 cm incision. Disc replacement is a very demanding surgical technique, which requires the joint action of a spinal surgeon and a vascular surgeon specialized in this type of surgical approach. The anesthetic techniques must also be adapted to this surgery. Post-operative pain is managed by the anesthesiology team, using epidural catheters (like an “epidural” during childbirth), which allow the dissemination of a local anesthetic and an analgesic directly in contact with the surgical area. This catheter is left in place for 3 to 4 days following the procedure. The patient who underwent surgery can then get up, with no immobilization or brace, and will then be autonomous for everyday tasks. The average duration of stay at the clinic is 6 days.

    POST-OPERATIVE RECOMMENDATIONS

    At the clinic: Patients generally first get up the third or fourth day after the procedure, under the supervision of the physical therapist. The physical therapist teaches you and supervises the actions you will have to perform throughout your recovery: how to get up, lie down, bend down, pick up objects on the floor, and perform personal hygiene. During your stay at the clinic, you will regain some autonomy for these everyday tasks. Prescriptions for changes of dressing, pain medications, and medical leave until the follow-up consultation will be given to you at discharge.

    RECOVERY TIME

    Discharge can be directly to home or to a rehabilitation center for a 2- to 3-week stay. Transfer is by medical transport service in both cases. Management at the center will be multidisciplinary (rehabilitation specialist, pain specialist, physical therapist, ergotherapist). The total recovery period extends for at least 6 weeks after the surgery and in some cases may last for 3 to 6 months. Based on the severity of symptoms before the procedure, this period may last even longer. Recovery is not synonymous with bed rest. Physical exertion, carrying loads, and car trips must be limited during this period. Walking is often beneficial. Recurrence of pain during recovery is often the result of too much activity and will tend to disappear with rest. Follow-up consultations with your surgeon will be scheduled at regular intervals during the first two years after the surgery