When cervical total disc arthroplasty (cTDR) was introduced, many questioned its efficacy over anterior cervical discectomy and fusion (ACDF). Clinical adjacent segment pathology (CASP) was considered to be part of natural history, and many thought that cTDR would not reduce CASP. Others disagreed based on the evidence available at the time. In vitro studies showed increased stress on the adjacent levels after ACDF in comparison with cTDR. Increased stress was thought to cause accelerated disc degeneration that was seen on imaging studies. CASP does not appear “in a vacuum”; it is preceded by radiographic adjacent segment pathology. Therefore, the logical conclusion was that ACDF increases CASP, and with longer follow-up, adjacent level surgery will be greater with ACDF than with cTDR. Longer-term outcomes from randomized controlled trials show that as a group, cTDR patients do as well or better than ACDF patients, and that CASP is reduced with cTDR. Good outcomes with cTDR have also been confirmed in real-world practice and cost-effectiveness studies.1
One criticism has been that US Investigational Device Exemption studies, although randomized, are not reliable due to the fact that they are industry-sponsored and conflicts of interest may exist. Each study must be scrutinized separately as to its value,2 but longer-term outcomes have shed light on many previously unanswered questions. Before we celebrate, however, there are issues relevant to cTDR that need to be considered. Placing an artificial disc is not the same as placing an implant to achieve fusion. With cTDR, the preparation of host bone endplates and the placement of an artificial disc must be more meticulous and precise. Cervical prostheses can migrate or subside after implantation. Heterotopic ossification may lead to spontaneous fusion, and postoperative kyphosis may develop. Peri-prosthetic osteolysis may occur many years after the surgery, and these patients may need much longer follow-up.
Randomized controlled trials have led to better understanding of cervicogenic headaches. Headaches are a very common accompanying symptom for those with cervical degenerative disc disease. Anterior cervical spine surgery, both cTDR and ACDF, led to headache reduction with durable outcomes.3
1. Ament JD, Yang Z, Nunley P, et al. Cost utility analysis of the cervical artificial disc vs fusion for the treatment of 2-level symptomatic degenerative disc disease: 5-year follow-up. Neurosurgery
2. Ament JD, Mollan S, Greenan K, et al. Understanding United States investigational device exemption studies-clinical relevance and importance for healthcare economics. Neurosurgery
3. Liu JJ, Cadena G, Panchal RR, et al. Relief of cervicogenic headaches after single-level and multilevel anterior cervical diskectomy: a 5-year post hoc analysis. Global Spine J