Intraoperative Conversion of Primary Cervical Total Disc Replacement to Fusion: Incidence and Reasons

Introduction: Cervical total disc replacement (TDR) currently offers an alternative treatment with results similar or superior to anterior cervical discectomy and fusion (ACDF). Once individual surgeons become comfortable using a device, they will typically expand indications for its use, however, patient safety must remain at the forefront. In order to reduce reoperations, surgeons must use strict selection criteria to determine which patients are most appropriate to receive TDR. Despite those criteria, situations may arise when surgeons convert from TDR to ACDF intraoperatively. The purpose of the study was to determine the incidence and reasons of intraoperative conversion from planned cervical TDR to ACDF.

Methods: A comprehensive surgery log was reviewed to identify cases of planned TDR converted intraoperatively to ACDF. All cases were performed at a single institution by 28 attending surgeons beginning with the first case experience in November, 2003 and ending with cases performed in November, 2023. Retrospective chart review was performed to collect demographic data and determine reasons for conversion.

Results: During the 20-year period, a total of 2,092 consecutive cases of planned TDR were examined. The total number of planned TDR levels was 2,807. There were 7 cases of intra-operative conversion to ACDF and one additional case where the procedure was aborted at one level prior to discectomy due to the location of a large vein in the operative area. The rate of intraoperative conversion of TDR to ACDF was 0.38% (8/2,092 cases), 95% confidence interval 0.20% - 0.70%. With respect to the number of operated levels, the intraoperative rate of conversion was 0.36% (10/2,807 levels), 95% confidence interval 0.20-0.60%. The most common reason for conversion was related to the shape or erosion of the vertebral body endplate (n=3). Other reasons included inadequate bone quality (n=1), severe osteophytes (n=1, need for conversion anticipated prior to surgery), and dural tear (n=1).

Conclusion : There was a very low incidence of intra-operative conversion of cervical TDR to ACDF. However, surgeons performing this procedure should be prepared for the possibility of intraoperative conversion from TDR to ACDF and educate patients of this possibility.