In this society focused on evidence-based medicine, there is also a push toward cost-effectiveness of surgical interventions. For degenerative disk disease, there are no prospective studies investigating the financial implications of nonoperative versus operative intervention; however, multiple studies have investigated the cost differences between fusion and TDR in retrospective reviews. Examining solely hospital charges, Patel and colleagues46 compared the costs for single- level TLIF, anterior-posterior fusion, anterior standalone fusion, and TDR. No fusion procedures used BMPs, which would have added significantly to the hos- pital charges in the fusion cases. Patel and colleagues found that TLIF, anterior fusion, and TDR incurred similar costs, whereas AP fusion was significantly more expensive. Levine and associates47 also showed that for single-level degenerative disk disease, circumferential fusion was significantly more expensive than TDR ($46,280 vs. $35,593). Taking into consideration both the direct medical costs of the index procedure and costs incurred in the first 2 years postoperatively, Guyer and co-workers48 showed that TDR was no more expensive than fusion proce- dures. Based on these retrospective economic evaluations, the choice between fusion and TDR has no significant economic repercussions in terms of direct medical costs.
COMMENTARY
The advent of TDR marks a movement toward motion-preserving technology in treatment of the spine, analogous to the situation in the 1960s and 1970s when peripheral joint arthroplasty supplanted fusion in the treatment of functionally dis- abling degenerative joint disease of the hip and knee. Preservation of motion is intuitively desirable. TDR has been shown to maintain motion at the index level and lessen the stress at adjacent-level disks44; this forms the biomechanical foundation from which TDR has evolved. In the laboratory, based on cadaveric preparations as well as computer models using finite element analysis, TDR has been shown to protect the adjacent-level disk better than fusion. This finding is clinically mirrored in long-term data from Level III studies in Europe showing a rate of degeneration in adjacent levels of less than 3%,35 compared with long-term data for fusions that report adjacent-level disease rates nearing 40% at 10 years.43,49
As with any new technology, ongoing scrutiny is mandatory. Postmarket surveil- lance has been required by the FDA for both the ProDisc-L and Charité single-level devices. A mechanism for extremely high capture of real-life complication rates is thereby in place.
A thorough review has been presented of the surgical options and evidence- based decision making that justify the opinion that motion preservation is equal if not superior to fusion for the particular patient described in the Case Presentation.
Medium-term follow-up is now available in Level I studies that support this view. It should be stressed that appropriate patient selection and meticulous surgical tech- nique are paramount in obtaining successful clinical outcomes. TDR would also be a viable option at the L3-4 level and the L5-S1 level. Since March 2000, the surgical group at the Texas Back Institute has implanted over 1000 lumbar TDR devices from L3 to S1. Their unpublished data show a revision rate of less than 2% for all TDR devices implanted, whereas the rate of reoperation in fusion patients nears 17% in the 5-year data from the FDA IDE.39 Based on this experience, and on the available best evidence as discussed in this chapter, TDR appears to be equivalent and possi- bly superior to fusion with regard to clinical outcomes, radiographically determined success, complication profiles, and cost-effectiveness. With secondary findings of earlier and more frequent return to work and decreased medication usage in the arthroplasty patient cohorts, indirect costs for arthroplasty may prove to be signifi- cantly better in the intermediate stages. If a decrease in adjacent-level disease is demonstrated in coming years, resulting in a less frequent need for transition-level reoperation (the holy grail of arthroplasty), the choice of arthroplasty may be over- whelmingly favored.
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