Assessing accuracy of measurement methods for bony fusion assessment after anterior cervical discectomy.

BACKGROUND CONTEXT: Currently, there is no universally accepted method for assessing radiological fusion shortly after anterior cervical discectomy. Five-year follow-up radiological X-rays demonstrating solid fusion or absence of fusion provided a gold standard for comparison with various assessment methods. PURPOSE: Establishing the most accurate diagnostic test for earlier bony fusion assessment by comparing different cut-off values for the difference in interspinous distance and the change in Cobb angle on dynamic radiological images against the established gold standard. DESIGN: Post-hoc analysis from the NEtherlands Cervical Kinematics (NECK) trial (NTR1289). PATIENT SAMPLE: A total of 40 patients with 1 level herniated disc that underwent anterior discectomy between 2010 and 2014 returned for a 5-year follow-up X-ray. OUTCOME MEASURES: Radiological outcome was assessed quantitatively and qualitatively by fusion on radiographic images 5 years after surgery. METHODS: Radiological dynamic X-rays were reviewed for fusion at 5-year follow-up by a senior spine surgeon. At this timepoint, bony continuity was indisputable and served as gold standard. Cobb angles and interspinous distances on flexion-extension images were measured independently by 2 investigators. Optimum agreement between the gold standard and the 2 methods was assessed, evaluating varying cut-off values, considering sensitivity, specificity, and area under the curve (AUC). RESULTS: Dynamic radiographic assessments revealed fusion in 29 out of 40 patients (mean age: 49 years ± 8; 23 women). For Cobb angle (optimal cut-off: ≤3.0°), the AUC was 0.86 with 100% sensitivity and 72.7% specificity. For interspinous distance (optimal cut-off: ≤1.5 mm), the AUC was 0.89 with 96.6% sensitivity and 81.8% specificity. The highest AUC (0.91) was observed for combined cut-off values (Cobb angle ≤3.0° and interspinous distance ≤2.0 mm), yielding 100% sensitivity and 81.8% specificity. CONCLUSION: The combination of cut-off values ≤3.0° difference for Cobb angle and ≤2.0 mm difference for interspinous distance on lateral flexion-extension X-rays was assessed to be an accurate diagnostic criterion for fusion evaluation. This tool provides a practical and easy applicable method for assessing fusion during follow-up after anterior discectomy.

Long-term results of the NECK trial-implanting a disc prosthesis after cervical anterior discectomy cannot prevent adjacent segment disease: five-year clinical follow-up of a double-blinded randomised controlled trial.

BACKGROUND CONTEXT: Motion preserving anterior cervical disc arthroplasty (ACDA) in patients with cervical radiculopathy was introduced to prevent symptomatic adjacent segment disease as compared to anterior cervical discectomy and fusion (ACDF). PURPOSE: To evaluate the long-term outcome in patients with cervical radiculopathy due to a herniated disc undergoing ACDA, ACDF or ACD (no cage, no plate) in terms of clinical outcome measured by the Neck Disability Index (NDI). Likewise, clinically relevant adjacent segment disease is assessed as a long-term result. STUDY DESIGN: Double-blinded randomized controlled trial. PATIENT SAMPLE: A total of 109 patients with one level herniated disc were randomized to one of the following treatments: ACDA, ACDF with intervertebral cage, ACD without cage. OUTCOME MEASURES: Clinical outcome was measured by patients' self-reported NDI, Visual Analogue Scale (VAS) neck pain, VAS arm pain, SF36, EQ-5D, perceived recovery and reoperation rate. Radiological outcome was assessed by radiographic cervical curvature and adjacent segment degeneration (ASD) parameters at baseline and up until five years after surgery. METHODS: To account for the correlation between repeated measurements of the same individual Generalized Estimated Equations (GEE) were used to calculate treatment effects, expressed in difference in marginal mean values for NDI per treatment group. RESULTS: Clinical outcome parameters were comparable in the ACDA and ACDF group, but significantly worse in the ACD group, though not reaching clinical relevance. Annual reoperation rate was 3.6% in the first two years after surgery, declined to 1.9% in the years thereafter. The number of reoperations for ASD was not lower in the ACDA group, while the number of reoperations at the index level was higher after ACD, when compared to ACDF and ACDA. CONCLUSIONS: A persisting absence of clinical superiority was demonstrated for the cervical disc prosthesis five years after surgery. Specifically, clinically relevant adjacent level disease was not prevented by implanting a prosthesis. Single level ACD without implanting an intervertebral device provided worse clinical outcome, which was hypothesized to be caused by delayed fusion. This stresses the need for focusing on timely fusion in future research.

Cost effectiveness of implanting a prosthesis after anterior cervical discectomy for radiculopathy: results of the NECK randomized controlled trial.

BACKGROUND CONTEXT: In the treatment of cervical radiculopathy due to a herniated disc, potential surgical treatments include: anterior cervical discectomy (ACD), ACD and fusion using a cage (ACDF), and anterior cervical disc arthroplasty (ACDA). Previous publications yielded comparable clinical and radiological outcome data for the various implants, but research on their comparative costutility has been inconclusive. PURPOSE: To evaluate the cost utility of ACD, ACDF, and ACDA. STUDY DESIGN: Cost-utility analysis. PATIENT SAMPLE: About 109 patients with cervical radiculopathy randomized to undergo ACD, ACDF, or ACDA as part of the NEtherlands Cervical Kinetics trial. OUTCOME MEASURES: Quality-adjusted life-years (QALYs) estimated from patient-reported utilities using the EuroQol-5D questionnaire and EuroQol Visual Analogue Scale (EQ VAS), measured at baseline, 2, 4, 8, 12, 26, 52, and 104 weeks postprocedure. Societal costs including admissions to hospital (related and otherwise), GP visits, specialist visits, physical therapy, medications, home care, aids, informal care, productivity losses, and out of pocket condition-related expenses. METHODS: The cost utility of the competing strategies over 1 and 2 years was assessed following a net benefit (NB) approach, whereby the intervention with the highest NB among competing strategies is preferred. Cost effectiveness acceptability curves were produced to reflect the probability of each strategy being the most cost effective across various willingness-to-pay (WTP) thresholds. Five sensitivity analyses were conducted to assess the robustness of results. RESULTS: ACDF was more likely to be the most cost-effective strategy at WTP thresholds of €20,000 to 50,000/QALY in all but one of the analyses. The mean QALYs during the first year were 0.750, 0.817, and 0.807 for ACD, ACDF, and ACDA, respectively, with no significant differences between groups. Total healthcare costs over the first year were significantly higher for ACDA, largely due to the higher surgery and implant costs. The total societal costs of the three strategies were €12,173 for ACD, €11,195 for ACDF, and €13,746 for ACDA, with no significant differences between groups. CONCLUSION: Our findings demonstrate that ACDF is likely to be more cost-effective than ACDA or ACD at most WTP thresholds, and this conclusion is robust to most sensitivity analyses conducted. It is demonstrated that the difference in costs is mainly caused by the initial surgical costs and that there are only minimal differences in other costs during follow-up. Since clinical data are comparable between the groups, it is to the judgment of the patient and surgeon which intervention is applied.