The study was a post-hoc review of data acquired from 2 Food and Drug Administration (FDA) -approved Investigational Device Exemption (IDE) trials. For a study, researchers sought to assess disc space heights near the level to be treated with a total disc replacement (TDR). They also sought to examine cervical disc space heights to be replaced with TDR and investigate the utilization of a reduced height TDR when one was available. Cervical TDR offers comparable results or better than anterior cervical discectomy and fusion. While restoring the height of a collapsed, degenerative disc was a surgical goal, over distracting the section with an implant could cause complications. Radiographs from the 1-level Simplify Cervical Artificial Disk IDE experiment assessed disc heights, yielding results for 259 levels adjacent to the treated level and 162 treated levels. The device was offered in 3 heights: 4, 5, and 6. The 4 mm height was only available after the single-level trial had reached 13% completion and was available throughout the 2-level trial. Of 259 adjacent levels, 55.2% of disc spaces had a height of less than 4 mm, and 82.7% of operating levels were less than 4 mm. When a 4 mm TDR was available, it was utilized in 38.4% of 1-level and 54.3% of 2-level operating levels. TDRs of greater heights may potentially over distract disc space since 55.2% of non-operated levels were of height of 4 mm. Surgeons chose the 4 mm TDR in 49.4% of all implanted levels, indicating a preference for lower TDR height. More research was needed to see if the lower height implants were linked to clinical and radiographic results.
