Bryan cervical disc prostheses: preservation of function over time

Preserving the function of cervical disc prostheses, even over the short term, is a matter of concern among surgeons. Our case series highlights our results and protocol for increasing the probability of continued device function. Twenty-five consecutive patients with a mean (±SEM) age of 44.3 ± 8.3 years underwent 29 cervical total disc arthroplasties for disc herniations. Three patients underwent primary bilevel arthroplasty, and one patient underwent a second arthroplasty for another herniation 2 years after the first. Prosthesis ranges of motion were measured using dynamic plain X-ray studies and compared to the ranges of motion of adjacent segments. At follow-up, all prostheses were in the correct location and without subsidence. All displayed firm secondary stability. One segment had fused. Twenty-eight of 29 devices were mobile an average of 9.5° ± 4.7° (range 3° to 20°) (for all 29 devices the average movement angle was 9.2° ± 5°; range 0° to 20°), 25 upper adjacent segments were mobile an average of 10.9° ± 4.5° (range 2° to 20°) (excluding the fused prosthesis: 11° ± 4.6°) and 15 lower adjacent segments were mobile an average of 9.8° ± 6° (range 1° to 21°). With our protocol, 28 of 29 cervical disc prostheses in 25 consecutive patients were mobile after an average of 22.3 ± 9.4 months. Prosthesis motion was physiological and very similar to that of the healthy adjacent segments. Long-term studies including larger numbers of patients are required to validate our initial observations.