Friday, September 28, 2018 4:05 PM–5:05 PM abstracts: new concepts: cervical spine: 242. Rigid cervical plate fixation is associated with greater restoration and maintenance of cervical lordosis compared to semi-rigid plate fixation in anterior cervical discectomy and fusion

Abstract

BACKGROUND CONTEXT Anterior cervical discectomy and fusion (ACDF) is one of the most common procedures in spine surgery. Both rigid and semi-rigid plates have been used to stabilize the anterior cervical spine after intervertebral graft application. No studies have compared the radiographic outcomes between rigid and semi-rigid cervical plate fixation over multiple level ACDF procedures. There is a lack of consensus regarding which plating modality yields superior clinical results. PURPOSE The goal of this study was to compare the long-term radiographic outcomes of patients treated with either rigid or semi-rigid plating modalities.To our knowledge, this is the largest series of patients comparing these instrumentation techniques, and as such, will help to further our understanding of the relative strengths and weaknesses of these instrumentation techniques. STUDY DESIGN/SETTING Retrospective Cohort Series. PATIENT SAMPLE We performed a retrospective cohort analysis of patients who underwent a single-level or multilevel ACDF for cervical radiculopathy or myelopathy. All of the cases were performed by one of two senior spine surgeons in the department. Patients were excluded from analysis if they were under 18 years of age at the time of surgery, had postoperative follow up less than 1 year or had an ACDF for cervical spine fracture or infection. OUTCOME MEASURES Radiographic assessments included: C2-C7 lordosis, T1 angle, levels fused, sagittal vertical axis (SVA), fusion mass lordosis, proximal and distal adjacent segment lordosis, adjacent segment degeneration (ASD), and fusion.Radiographic diagnosis of ASD was determined by the presence of new or enlarged osteophytes, endplate sclerosis, disc space narrowing >50%, and/or increased calcification of the anterior longitudinal ligament (ALL) as presented by previous published studies. Patient reported outcomes were obtained in the form of Neck Disability Index (NDI) scores and Visual Analog Scales (VAS) scores for the neck and arm. METHODS Baseline patient characteristics were compared using chi-squared analysis and independent sample t-tests for categorical and continuous data, respectively. Bivariate and multivariate regressions were subsequently used to compare clinical outcomes between procedure groups. Multivariate analyses controlled for differences in baseline patient characteristics. RESULTS There were a total of 403 patients who met our inclusion and exclusion criteria. A total of 257 patients underwent semi-rigid plating and 147 patients underwent rigid plating. Regarding demographic variables, there were statistically significantly higher proportions of smokers (24.1% vs. 10.9%; p=.001) in the semi-rigid plating group relative to the rigid group. Both plating systems successfully restore cervical lordosis with an ACDF, without significant changes in the SVA. On multivariate analysis, rigid plate fixation was associated with greater change in preoperative to postoperative overall lordosis compared to semi-rigid plating (4.5±8.6° vs. 2.5±7.6°; p=.046). Similarly, rigid plating was associated with greater change in preoperative to postoperativefusion segmentlordosis compared to semi-rigid plate fixation (8.2 ±7.2° vs. 5.4 ±5.8°; p=.002). Rigid plate fixation also maintained fusion segment lordosis from the immediate postoperative period to final follow-up better than semirigid plating (7.2±7.4° vs. 5.0±6.2; p=.014). There were no significant differences in radiographic ASD (rigid 23.1% vs. semi-rigid 26.9%; p=.525) or reoperation rates (rigid 6.8% vs. semi-rigid 3.5%; p=.134). There was no significant difference in the rate of radiographic ASD overall (semi-rigid 20.3%; rigid 21.8% p=.582). Similarly, there were no significant differences between preoperative, postoperative, or change in patient reported outcome between the two groups. CONCLUSIONS Rigid and semi-rigid plating are appropriate treatment options for patients undergoing ACDF for degenerative cervical pathology. Rigid plate fixation provides greater restoration and maintenance of cervical lordosis and fusion segment lordosis compared semi-rigid plating. Radiographic evidence of ASD is present in approximately a quarter of both groups, however re-operation rates are low. Clinical outcomes are also similar between the two groups.