Cervical kinematics after fusion and bryan disc arthroplasty.
ABSTRACT Disc arthroplasty has been shown to provide short-term clinical results that are comparable with those attained with traditional anterior cervical discectomy and fusion. One proposed benefit of arthroplasty is the ability to prevent or delay adjacent level operations by retaining motion at the target level and eliminating abnormal adjacent activity. This paper compares motion parameters for single-level anterior cervical discectomy and fusion and disc replacement patients at the index level and adjacent segments.
Radiographic data from patients enrolled in a prospective, randomized clinical trial were selected for kinematic assessment of cervical motion. All patients received either a single-level fusion with allograft and anterior cervical plate (Atlantis anterior cervical plate, n=13) or a single-level artificial cervical disc (Bryan Cervical Disc prosthesis, n=9) at either C5/C6 or C6/C7. Flexion, extension, and neutral lateral radiographs were obtained preoperatively, immediately postoperatively, and at regular intervals up to 24-month time points. Cervical vertebral bodies were tracked on the digital radiographs using quantitative motion analysis software (QMA, Medical Metrics) to calculate the functional spinal unit motion parameters including range of motion (ROM), translation, and center of rotation. If visible, the functional spinal unit parameters were obtained at the operative level, and also the level above and the level below.
As expected, significantly (P<0.006 at 3, 6, 12, and 24 mo) more flexion/extension motion was retained in the disc replacement group than the plated group at the index level. The disc replacement group retained an average of 6.7 degrees at 24 months. In contrast, the average ROM in the fusion group was 2.0 degrees at the 3-month follow-up and gradually decreased to 0.6 degrees at 24 months. The flexion/extension ROM both above and below the operative level was not statistically different for the disc-replaced and fusion patients, however, mobility increased for both groups over time. The anterior/posterior translation that occurs with flexion/extension motion remained unchanged for the disc replacement group at the level above the target disc preoperatively and postoperatively. In contrast, the translation increased for the level above the fusion. At the 6-month follow-up, the increase in translation was significantly greater for patients that were fused (P<0.02) than for patients that received a disc replacement. This change was not significant at 12 months.
Previous studies have shown the Bryan disc to maintain mobility at the level of the prosthesis. The long-term clinical benefit of maintenance of motion is postulated to be the ability to delay or avoid adjacent level operations. This study reveals that there is no difference in flexion/extension ROM at the level above and below either a fusion or Bryan arthroplasty. There is, however, an increase in anterior/posterior translation at the cephalad adjacent level in patients with arthrodesis while the Bryan arthroplasty retains normal translation for the same amount of flexion/extension at the adjacent level.
The Bryan disc may delay adjacent level degeneration by preserving preoperative kinematics at adjacent levels.
- [show abstract] [hide abstract]
ABSTRACT: We evaluated the results of the Robinson method of anterior cervical discectomy and arthrodesis with use of autogenous iliac-crest bone graft, at one to four levels, in 122 patients who had cervical radiculopathy. A one-level procedure was done in sixty-two of the 122 patients; a two-level procedure, in forty-eight; a three-level procedure, in eleven; and a four-level procedure, in one. The average duration of clinical and roentgenographic follow-up was six years (range, two to fifteen years). The average age was fifty years (range, twenty-five to seventy-eight years). Preoperatively, 118 patients had pain in the arm, fifty-five had weakness of one or more motor roots, and seventy-seven had sensory loss. At the time of follow-up, eighty-one patients had no pain in the neck, twenty-six had mild pain in the neck, nine had moderate pain in the neck, four had mild radicular pain, and two had a combination of mild radicular pain and moderate pain in the neck. One hundred and eight patients had no functional impairment, and fourteen had a slight limitation of function during the activities of daily living. Nine of eleven patients who had symptoms related to a change at one level cephalad or caudad to the site of a previous arthrodesis had another operative procedure. Lateral roentgenograms of the cervical spine, made in flexion and extension, showed a pseudarthrosis at twenty-four of 195 operatively treated segments. Sixteen of the patients who had a pseudarthrosis were symptomatic, but only four had sufficient pain to warrant revision. The risk of pseudarthrosis was significantly greater after a multiple-level arthrodesis than after a single-level arthrodesis (p < 0.01). At the time of the most recent follow-up, fifty-three of the fifty-five patients who had had a motor deficit had had a complete recovery, and the two remaining patients had had a partial recovery. Seventy-one of the seventy-seven patients who had had a sensory loss had regained sensation. None of the patients had an increased neurological deficit postoperatively. Our results suggest that the Robinson anterior cervical discectomy and arthrodesis with an autogenous iliac-crest bone graft for cervical radiculopathy is a safe procedure that can relieve pain and lead to resolution of neurological deficits in a high percentage of patients.The Journal of Bone and Joint Surgery 09/1993; 75(9):1298-307. · 3.23 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: We studied the incidence, prevalence, and radiographic progression of symptomatic adjacent-segment disease, which we defined as the development of new radiculopathy or myelopathy referable to a motion segment adjacent to the site of a previous anterior arthrodesis of the cervical spine. A consecutive series of 374 patients who had a total of 409 anterior cervical arthrodeses for the treatment of cervical spondylosis with radiculopathy or myelopathy, or both, were followed for a maximum of twenty-one years after the operation. The annual incidence of symptomatic adjacent-segment disease was defined as the percentage of patients who had been disease-free at the start of a given year of follow-up in whom new disease developed during that year. The prevalence was defined as the percentage of all patients in whom symptomatic adjacent-segment disease developed within a given period of follow-up. The natural history of the disease was predicted with use of a Kaplan-Meier survivorship analysis. The hypothesis that new disease at an adjacent level is more likely to develop following a multilevel arthrodesis than it is following a single-level arthrodesis was tested with logistic regression. Symptomatic adjacent-segment disease occurred at a relatively constant incidence of 2.9 percent per year (range, 0.0 to 4.8 percent per year) during the ten years after the operation. Survivorship analysis predicted that 25.6 percent of the patients (95 percent confidence interval, 20 to 32 percent) who had an anterior cervical arthrodesis would have new disease at an adjacent level within ten years after the operation. There were highly significant differences among the motion segments with regard to the likelihood of symptomatic adjacent-segment disease (p<0.0001); the greatest risk was at the interspaces between the fifth and sixth and between the sixth and seventh cervical vertebrae. Contrary to our hypothesis, we found that the risk of new disease at an adjacent level was significantly lower following a multilevel arthrodesis than it was following a single-level arthrodesis (p<0.001). More than two-thirds of all patients in whom the new disease developed had failure of nonoperative management and needed additional operative procedures. Symptomatic adjacent-segment disease may affect more than one-fourth of all patients within ten years after an anterior cervical arthrodesis. A single-level arthrodesis involving the fifth or sixth cervical vertebra and preexisting radiographic evidence of degeneration at adjacent levels appear to be the greatest risk factors for new disease. Therefore, we believe that all degenerated segments causing radiculopathy or myelopathy should be included in an anterior cervical arthrodesis. Although our findings suggest that symptomatic adjacent-segment disease is the result of progressive spondylosis, patients should be informed of the substantial possibility that new disease will develop at an adjacent level over the long term.The Journal of Bone and Joint Surgery 04/1999; 81(4):519-28. · 3.23 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: This study presents the 5-9-year follow-up after anterior cervical fusion and osteosynthetic stabilization anterior plating for fractures and/or dislocations of the cervical spine in 25 patients. Adequate bony fusion was obtained in all patients within 1 year postoperatively. There were no problems of late screw loosening. Fracture of the osteosynthetic plate occurred in one patient. Late degenerative changes of the cervical spine at the disc levels adjacent to the fusion area were radiologically detected in 15 of the 25 patients (60%) and were related to the following situations: fusion on more than one disc level, fusion on a lower cervical segment, Frankel class A-C at admission, and hyperflexion injuries. However, these late degenerative changes had no subjective or clinical repercussions, at least until now. From a neurological point of view all patients remained stable postoperatively and no patients had late deterioration.Journal of Spinal Disorders 01/1996; 8(6):500-8; discussion 499. · 1.21 Impact Factor