Spondylotic Cervical Myelopathy Treated Using an Artificial Disc
Postoperative Course and Case Discussion
Postoperatively, the patient was mobilized on the first day postop without a collar. Dynamic x-rays of the cervical spine this stage showed maintenance of motion at the level of the decompression (see Figure 10).
Figure 10: Postoperative flexion extension x-rays show satisfactory placement of the prosthesis with motion maintained at the instrumented segment.
The patient was discharge on the 2nd day after surgery. He had no neck pain or discomfort and returned to work the following week. The patient was reviewed 6 weeks postoperatively and had improved symptomatically from his myelopathy. His hand function had improved and he no longer had a positive Lhermitte's phenomenon. There was no neck discomfort and he had returned to work. Imaging at this stage was satisfactory. He has been followed for 3 months and continues to improve.
This case illustrates the management of single level cervical myelopathy through anterior decompression and disc replacement. This patient has had an excellent short-term result with improvement in myelopathic symptoms, maintenance of motion, and reduced surgical morbidity.
Cervical myelopathy is a relatively common spinal condition and is generally managed either from an anterior or posterior approach. Single level disease is usually caused by anterior osteophytic compression or disc protrusion. The current standard of care for this is anterior cervical discectomy, usually with an iliac crest autograft, with or without plating. Some surgeons use cages or allograft but the overall goal is aimed at achieving arthrodesis at the involved level. Because anterior cervical fusion has been performed for many years, it is now being realised that there is an incidence of adjacent segment disease, with accelerated wear and tear at levels above and below. The risk of requiring surgery at those adjacent levels may be as high as 30% at 10 years. Consequently the placement of a disc prosthesis is attractive from the point of view of maintaining motion and trying to prevent adjacent segment disease. Coupled with this, no orthosis is required, and iliac crest grafting, which has a morbidity of up to 20%, is avoided.
When looking at a patient as a potential candidate for disc replacement, patient selection, as in most surgical interventions, is the key. This case, and subsequent cases we have performed, have illustrated that the thought processes are different when deciding to use this new technology, from standard surgical procedures. Cervical disc replacement is currently only appropriate for single level disease and trials are underway on 2 level disease. It is not appropriate if there is significant dorsal disease. It is not appropriate for correcting deformity, and indeed may lead to accelerated prosthesis wear if used in kyphotic patients. Also, the foramina are not distracted by the surgery and meticulous foraminal decompression must be performed at the time of surgery, as distraction is not typically prominent.
Cervical disc replacement is becoming available throughout the world, and is currently available in Belgium and Australia. Trials are beginning in the North America. Not all patients are suitable for this technology. The procedure is technically more demanding and more time consuming than current surgical options. The long-term sequelae of these implants are not known although at 25 million cycles in vivo, little wear is seen, the equivalent of 25 years of neck movements.
This case illustrates a new and exciting technique used in the management of cervical myelopathy. It is gratifying to see the patient leave hospital with no collar and no hip grafting. Just as in large joint surgery, fusion is giving way to joint replacement and this procedure may become commonplace in the management of cervical spine disease in the near future.