LAUSR

hen cervical total disc arthroplasty (cTDR) was W 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 costeffectiveness studies. 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