Disc Replacement

The Charité is a prosthesis system consisting of two endplates made of high quality cobalt chromium alloy with an ultra high molecular weight polyethylene sliding core placed between them. Both of these materials are well tolerated by the body and are the same standardized implant materials that have been used in artificial hip and knee prostheses for the last 30 years.

The endplates are attached to the vertebral bodies by means of anchoring teeth along their edge. The polyethylene sliding core is placed between these articulating endplates and is designed to allow near normal physiological movement. Much like an artificial hip or knee that relies on metal and plastic bearing surfaces to replicate normal movement of those joints, the Charité is designed to closely mimic the normal function of a healthy disc.

The surgical procedure for the Charité requires placement of the implant using an anterior (front) approach with a small incision just below the belly button. The degenerative disc is removed at the affected level and the Charité Artificial Disc is placed into the disc space.

The Charité has received the CE mark and is commercially available outside of the United States in over 25 countries throughout Europe, Asia, Canada, Australia, Africa and Latin America.

Artificial discs, conceived in the 1960s, but later developed in the 1980s by German surgeons Kurt Schellnack, M.D., and Karin Buttner-Janz, M.D., have been in clinical use outside of the United States for more than 14 years. Over 4,000 patients in some 25 countries throughout Europe, Asia, Canada, Australia, Africa, and Latin America have benefited from the devices, which relieve the back pain associated with herniated or collapsed discs and varying types of degenerative disc disease (DDD).

A 1997 study conducted in France by Lemaire et al reviewed 105 cases undergoing SB Charité III prosthetic disc replacement. After eight years of post-operative follow-up, the study reported that 79 percent of the patients had excellent results and 87 percent returned to work. A 1997 independent study, conducted by the Texas Back Institute and the Institutes for Spine and Biomedical Research, followed 67 patients who underwent intervertebral disc replacement with the SB Charité III device in Europe. After a six-year follow-up period, the study reported that 70 percent of the patients decreased or discontinued use of pain medication following the procedure. Comparing pre and postoperative analog pain scores, it was noted that patients experienced significant pain relief. Additionally, 46 percent of patients reported an increase in activity level, with 67 percent able to return to work at the same or a modified physical level.

Differing from the common surgical method for relieving pain associated with DDD, total disc replacement is intended to retain motion at the operative level once the damaged disc has been removed. Additionally, total disc replacement theoretically protects the discs at adjacent levels by sharing or distributing the stress through the lower back during normal flexion and extension.

The goal of the procedure is to restore the intervertebral disc height and neuroforaminal height while restoring physiologic motion. The surgery is approached from the front, with a small incision in the abdomen below the belly button. Organs are gently moved to the side so that the surgeon can visualize the spine while protecting important anatomic structures. The collapsed degenerated disc is removed and the SB Charité III prosthesis is implanted. First the two endplates are pressed into the vertebrae above and below the disc space; teeth along the border of the endplate grip the bone. A polyethylene core is then placed between the endplates. The artificial disc stays in place by the spinal ligaments and remaining part of the annulus of the disc, as well as the compressive force of the spine. Bending X-rays of patients after the surgery show that the motion of the artificial disc (flexion, side bending and rotation) can closely approximate the normal motion of a healthy disc.

Artificial discs have been highly successful in Europe and elsewhere in the world. Currently the FDA has only approved the technology for use in the USA in a carefully monitored clinical trial. The clinical trial currently underway for the artificial lumbar disc has completed enrollment and is expected to receive FDA general marketing clearance in two years.

Facet Joint implants have been designed and patented but are currently undergoing medical testing but have not yet started clinical trials.