Cervical disc arthroplasty compared with arthrodesis for the treatment of myelopathy. Surgical technique.

BACKGROUND: Although there have been case reports describing the use of cervical disc arthroplasty for the treatment of myelopathy, there is a concern that motion preservation may maintain microtrauma to the spinal cord, negatively affecting the clinical results. As we are not aware of any studies on the use of arthroplasty in this scenario, we performed a cross-sectional analysis of two large, prospective, randomized multicenter trials to evaluate the efficacy of cervical disc arthroplasty for the treatment of myelopathy.

METHODS: The patients in the current study were a cohort of patients who were enrolled in the United States Food and Drug Administration Investigational Device Exemption studies of the Prestige ST and Bryan disc replacements (Medtronic, Memphis, Tennessee). The inclusion criteria were myelopathy and spondylosis or disc herniation at a single level from C3 to C7. Clinical outcome measures were collected preoperatively and at six weeks, three months, six months, twelve months, and twenty-four months postoperatively.

RESULTS: A total of 199 patients were included in the present study; 106 patients (53%) underwent arthroplasty, whereas ninety-three (47%) underwent arthrodesis. The Neck Disability Index, Short Form-36 scores, and specific arm and neck pain scores improved significantly from baseline at all time points. Patients in all four groups had improvement in the postoperative neurological status and gait function; at twenty-four months after surgery, 90% (95% confidence interval, 77.8% to 96.6%) of the patients in the arthroplasty group and 81% (95% confidence interval, 64.9% to 92.0%) of those in the arthrodesis group had improvement in or maintenance of the neurological status in the Prestige ST trial and 90% (95% confidence interval, 75.8% to 97.1%) of the patients in the arthroplasty group and 77% (95% confidence interval, 57.7% to 90.1%) of those in the arthrodesis group had improvement in or maintenance of the neurological status in the Bryan trial.

CONCLUSIONS: We found that patients in both the arthroplasty and arthrodesis groups had improvement following surgery; furthermore, improvement was similar between the groups, with no worsening of myelopathy in the arthroplasty group. While the findings at two years postoperatively suggest that arthroplasty is equivalent to arthrodesis for the treatment of cervical myelopathy for a single-level abnormality localized to the disc space, the present study did not evaluate the treatment of retrovertebral compression as occurs in association with ossification of the posterior longitudinal ligament, and we cannot comment on the treatment of this condition.