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The most common surgical procedure for the treatment of cervical disk disease resulting in radiculopathy or myelopathy is the combination of anterior cervical diskectomy and fusion (ACDF). Although it is effective for relieving symptoms of neural compression, questions still remain about the effect of cervical fusion on cervical biomechanics and subsequent adjacent segment disease. Therefore, the main goal for the development of a cervical total disk arthroplasty (TDA) system is to preserve motion while maintaining spinal stability to minimize adjacent segment disease. Other advantages of TDA over other conventional surgical procedures may include quicker return to activities of daily living and improved acceptance by patients. Other motion-preserving procedures such as cervical laminoplasty and anterior and posterior cervical foraminotomies are discussed elsewhere in the textbook.
The history of current cervical TDA can be linked back to the development of lumbar spine arthroplasty systems. The original purpose for the development of lumbar TDA was to address lumbar axial diskogenic pain while providing the benefit of motion preservation. In selected cases, when conservative measures have failed, lumbar TDA may be of benefit in the management of lumbar degenerative disk disease. Since their development, the lumbar disk systems have been extensively studied biomechanically. However, as lumbar TDA has become more extensively used and investigated, several questions remain unanswered, including questions about in vivo wear rates, revision strategies, and payer acceptance.
Several differences exist between cervical and lumbar TDA systems, however. Biomechanically, the load demand on TDA in the cervical spine is less than in the lumbar spine. Furthermore, identifying acceptable motion of the instantaneous axis of rotation may be more important and position sensitive in cervical TDA design in comparison with lumbar TDA. Perhaps most fundamentally different is that the indication for cervical TDA is the management of radiculopathy and myelopathy and not axial diskogenic pain, in contrast to the indication for lumbar disk arthroplasty. Therefore, as for all surgical procedures, the best results of cervical TDA require careful patient selection and precise surgical technique.
Currently, cervical TDA is indicated and approved in the United States, depending on the implant selected for patients with single-level or two-level disease causing cervical radiculopathy or myelopathy, or both. Unlike in lumbar arthroplasty, cervical diskogenic pain is not an indication.
Patients should be evaluated with a minimum of a cervical spine radiographic series including flexion and extension views to assess for radiographic evidence of instability. Magnetic resonance imaging should be obtained to help confirm the surgical level and to correlate with the clinical examination. In some cases, a computed tomography scan may also be of benefit to determine the extent of facet arthropathy and cervical spondylosis and the presence or absence of ossification of the posterior longitudinal ligament. A bone mineral density scan may help in assessing patients with suspected osteoporosis.
Although several contraindications to placement of cervical TDA exist, particular attention should be paid to both clinical and radiographic evidence of moderate to severe facet arthropathy. The presence of facet arthropathy is believed to be a contraindication to cervical TDA because motion preservation at the operated level may aggravate or even result in pain within the arthritic facet joints. Other contradictions include cervical instability, osteoporosis, and a history of cervical spine infections. A complete list of contraindications is listed in Box 32-1 .
Cervical instability
>11 degrees of angulation
>3 mm of segmental translation
Multilevel disease
Radiographic evidence of severe facet joint degeneration
Radiographic evidence of severe osteoarthritis with loss of normal disk space height >80%
“Hard disk” disease
Lack of motion of target disk space on preoperative radiographs
Postlaminectomy status with kyphotic deformity
Osteoporosis
Metabolic bone disease
Rheumatoid arthritis, ankylosing spondylitis
Ossification of the posterior longitudinal ligament or diffuse hyperostosis
Infection (past or present)
Malignant disease
Known hypersensitivity to cobalt, chromium, molybdenum, titanium, or polyethylene
Traumatic injury
Pregnancy or possible pregnancy within 3 years of implantation
Therefore, careful review of the indications for and contraindications to placement of cervical TDA reveals that most patients have limited degenerative problems and are physiologically younger than patients typically undergoing ACDF. Regardless, all patients selected for cervical TDA should be informed preoperatively that if intraoperative findings dictate, the TDA procedure may have to be converted to ACDF.
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