2015 Outstanding Paper Winner: Surgical ScienceTotal disc arthroplasty versus anterior cervical interbody fusion: use of the Spine Tango registry to supplement the evidence from randomized control trials
Introduction
The neurologic symptoms and neck pain associated with disc degeneration of the cervical spine can be treated surgically using either the established standard procedure of anterior interbody fusion (AIF) or the more recently introduced total disc arthroplasty (TDA). The evidence regarding the comparative effectiveness of these surgical procedures has been summarized recently in a Cochrane Review [1]. The review included nine randomized controlled trials (RCTs), five of which were considered to have a low risk of bias [2], [3], [4], [5], [6]. It identified evidence for a small but statistically significant difference between the treatments in the alleviation of arm pain, neck-related function, and neurologic outcome, all in favor of arthroplasty [1]. Although statistically significant, the effect sizes were not clinically relevant. Based on these results, the reviewers concluded that at this point in time both treatments could be considered valid therapeutic options. They also cautioned that, as the available RCTs only included follow-up periods of up to 2 years, the hypothesis that TDA results in a reduced incidence of secondary symptoms at adjacent levels would require evaluation in future updates of the review once the results of long-term studies were available.
Randomized control trials have an important limitation in that they often define narrow admission criteria which may not be applicable to daily clinical practice. For instance, some studies only recruited patients younger than 60 years [7], [8], limited the treated segments to C3–C7 [2], [3], [7], [8], [9], [10], [11], [12], or excluded marked spondylosis [2], [10], [11], trauma [5], [7], [8] or spondylolisthesis, which are sometimes considered contraindications for TDA. Such restrictions are common for RCTs in an effort to examine treatment effects under ideal circumstances. Although these trials provide evidence about the relative efficacy of treatments in selected patients, additional studies may be needed that measure the relative effectiveness of the treatments in broader populations [13], [14]. In doing so, they serve to assess the external validity of the results of RCTs.
The purpose of this study is to demonstrate how data from a surgical registry can be used to supplement the evidence from RCTs with regard to the outcomes after different types of surgery for degenerative cervical spine disease. The Spine Tango registry collects real-world data of patients undergoing surgery of the spine, without the restrictions inherent in RCTs, and some participating clinics follow their patients for a long period of time. Using such prospective cohorts, well designed and carefully executed observational studies can help to answer clinical questions that go beyond the evidence presented by RCTs [15], [16]. Spine Tango collects detailed clinical data of patients undergoing TDA and AIF, among other treatments. With the careful application of matching algorithms, a quasi-experimental comparison of the two surgical groups can be achieved to confirm (or refute) RCT results [17]. Registry-based observational studies can also serve to describe the surgical outcome of a broader spectrum of patients outside the narrow admission criteria of RCTs. Finally, the registry gives us the opportunity to perform longer-term effectiveness studies of the surgical treatments.
The aims of this paper were threefold. In a first study we applied the admission criteria used in the available RCTs and conducted a propensity score-adjusted outcome analysis to evaluate whether this design produces short-term results similar to those of the RCTs, for the comparison of TDA and AIF. We then analyzed the comparative clinical outcome (for TDA vs. AIF) of patients typically excluded from the RCTs published to date, but present in the registry. Third, we evaluated the mid to long-term effects of TDA versus AIF in all patients with follow-up longer than 2 years.
Section snippets
Spine Tango forms and study cohort
The physician-based surgery form of the registry contains detailed information on diagnosis, the surgical procedure, and surgical and general complications. In addition to these surgical records, patients are asked to complete the self-reported Core Outcome Measures Index (COMI) questionnaire which includes two graphic rating scales (GRS 0–10 points) for neck pain and arm pain [18]. The COMI form is the official patient-reported outcome instrument of the Spine Tango registry [18], [19] .
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Results
Out of a total of more than 75,000 Spine Tango surgery forms in the registry, the selection process for the present study resulted in a cohort of 987 patients undergoing TDA or AIF surgery. Fig. 1 shows the study profile of the included patients. Overall, 35 hospitals from 8 countries (Australia, Belgium, Germany, Poland, Slovenia, Switzerland, UK, and the USA) contributed their data to this study. TDA was documented in 30 hospitals from 8 countries. AIF was documented in 16 hospitals from 5
Summary of results
In this analysis of surgical outcomes after TDA and AIF we demonstrate how data from the Spine Tango registry can be used to present evidence that both complements and supplements that provided by RCTs. The first study, a matched comparison of patients who were representative of the type recruited into the RCTs published to date, showed that the outcomes for TDA were slightly but statistically significantly superior to those for AIF. Our second study examined patients that are typically
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FDA device/drug status: Not applicable.
Author disclosures: LPS: Nothing to disclose. CRy: Nothing to disclose. CRö: Nothing to disclose. AFM: Nothing to disclose. JGJ: Nothing to disclose. MA: Nothing to disclose. EA: Nothing to disclose.