Endoprostheses for cervical spinal discs have only been available for about ten years. Those prostheses have been developed to maintain mobility in the segment affected. They are an alternative to spinal fusion.
By Philipp Grätzel von Grätz
It doesn't have to be lifting the proverbial heavy weight - sudden severe pain in the back or the small of the back can occur during many day-to-day activities.
One of several possible causes is a prolapsed disc. Parts of the intervertebral disc slide into the adjoining spinal canal, i.e. into the space containing the spinal cord, where they irritate the spinal cord and the efferent nerves. This irritation is painful and can cause dysaesthesia and even paralysis.
Disc prolapse is a major topic at the Medica in Düsseldorf, the world's largest medical trade fair with parallel congress. Five renowned experts on spinal discs will meet at a seminar chaired by senior lecturer Jörg Herdmann from St. Vinzenz‘ hospital in Düsseldorf, Germany, to discuss the possibilities of modern treatment for disc prolapse.
"In cases of prolapsed discs it is important first of all to conduct an exact neurological examination," Herdmann stresses. If there are relevant neurological deficits or the threat of paraplegia, there is no alternative to an emergency operation by a spinal surgeon. However, the great majority of patients with disc prolapse "only" have pain, such as pain radiating from the lumbar spine into the leg, and rather mild neurological symptoms. "If medication is not sufficient to give these patients a satisfactory quality of life, an invasive treatment should be advised," Herdmann says.
Microsurgery using a modern operating microscope. Nerve tissue can be identified precisely. Photos (3): PD Jörg Herdmann
The first option to be mentioned at this point is microtherapy, a minimally invasive approach that will be presented in detail at the Medica seminar by Professor Dietrich Grönemeyer from Bochum, Germany. "Microtherapy means that the areas affected are infiltrated with a cocktail of a local anaesthetic and a corticoid," Herdmann explains. The local anaesthetic provides immediate relief from the pain. The effects of the corticoid include reduction of tissue swelling, which in turn reduces the pressure on the nerve. "In an ideal situation this can even alleviate mild paralysis," Herdmann says. In order to achieve the best results, many microtherapists now work with imaging technology: they use either a radiological image converter or a computed tomography scanner to pinpoint precisely the structures that are causing the symptoms.
If the patient has severe paralysis, or microtherapy proves insufficient to relieve the symptoms, operative procedures may be used. These aim to remove the parts of the prolapsed disc pressing on the roots of the efferent nerves. The challenge associated with operations close to the nerve roots is to be as exact as possible, because the numerous nerve structures close to the site of the operation must on no account be damaged.
In principle there are two possible operative procedures: microsurgery, in which microscopes are used, and endoscopy. "The current standard is definitely still the microscope-assisted operation, i.e. microsurgery," emphasises Dr. Sebastian Rütten from St. Anna's hospital in the town of Herne. But surgeons are also using endoscopy more and more often, which means that they operate through tube-like instruments.
According to Rütten, the advantages of endoscopy include above all the less invasive procedure, which keeps down the postoperative costs and makes sometimes necessary follow-up interventions simpler. "Nowadays we can operate endoscopically on many prolapsed discs in the lumbar spine and even some in the cervical spine," says Rütten. In early 2008 he published the results of two randomised controlled studies comparing the endoscopic procedure with microsurgery in patients with prolapsed discs in the cervical or lumbar spine. They showed that the clinical results of the two procedures do not differ. Endoscopy certainly has advantages in cases of prolapsed discs with sequestered pieces of the discs close to where the lumbar spine meets the pelvis and with very laterally prolapsed discs, as Herdmann reports. However, he also points out that there is a certain learning curve associated with the procedure: "Not every one who has an endoscope can actually perform the procedure well."
The disc prosthesis by Link was implanted here between the 5th and 6th cervical vertebrae.
For operating on the cervical spine, which is very much more mobile than the lumbar spine, for decades spinal surgeons have been using yet another procedure, the fusion of neighbouring vertebrae. It is very safe and brings good clinical results, but harbours the problem that the adjacent segments of the spinal column are subject to a greater load after this type of procedure. "For this reason disc endoprostheses have been developed that maintain mobility in the segment affected and thus also enable patients to move their necks as normally as possible after the operation," Herdmann explains. He sees a disc endoprosthesis indicated primarily in younger patients under fifty. The procedure does not preclude the option of fusion later on.
"It is not widely known that the interventions on the cervical spine are just as safe as, and possibly even safer than, those on the lumbar spine," stresses Herdmann. We do not yet have long-term results because disc endoprostheses for the cervical spine were introduced only about ten years ago. Incidentally, the pioneer in disc prostheses was a German company. "The first prosthesis was developed by the company Link in Hamburg together with the Charité teaching hospital in Berlin," Herdmann says.
Waldemar Link GmbH & Co. KG, Barkhausenweg 10, 22339 Hamburg, Germany, Tel.: +49 40 53995-0, Fax: +49 40 53869-29 Internet: www.linkhh.de, E-Mail: firstname.lastname@example.org, Medica: Hall 13, C37