Introduction: A randomized control trial (RCT) comparing outcomes after discectomy and after discectomy with a bone-anchored annular closure device (ACD) showed that the implant reduced reherniation and reoperation rates by 41% and 29%, respectively at five-years. Laminectomy and laminotomy are both procedures performed during discectomy to allow for access to the disc space for appropriate nerve root decompression. Data collected in the RCT included the amount of bone removed from the lamina and was evaluated for both the discectomy group and the ACD group. Results showed that, when compared to the surgeon’s typical discectomy patient, 50.7% of ACD subjects had an “above average amount of bone removal” as compared to 23.4% of Control patients. Investigate the effects of increased bone removal.in the implant group.
Methods: This post-hoc analysis of a 554 patient RCT, which investigated the use of a bone-anchored annular closure device (ACD). During surgery, laminotomy was completed, and the surgeon qualitatively scored the amount of bone removal relative to their average discectomy procedure. Potential responses were above average, average, or below average bone removal. Correlations were evaluated between the amount of bone removal and 1) the subject’s segmental instability assessed via rotational and translational (A-P) range of motion (ROM) during flexion-extension and change in spondylolisthesis; and 2) disability assessed through VAS leg, VAS Back, ODI, and reoperation to treat instability.
Results: Above average bone removal occurred in 50.7% of ACD subjects. When comparing five-year outcomes of subjects with “above average” bone removal to subjects with “equal to or less than average” bone removal, radiographic instability, pain, and disability scores were not found to be statistically different. (Radiographic Stability – Flexion-Extension Change in Angular ROM: p=0.74, Change in Translational ROM: p=0.17. Disability – VAS leg: p=0.56, VAS Back: p=0.50, ODI: p=0.35). Fewer reoperations were performed for segmental instability in subjects with “above average” bone removal (p=0.03).
Conclusion : Bone-anchored ACD has previously been shown to significantly reduce reherniation and reoperation rates. This study showed that, although ACD patients require more bone removal compared to a typical discectomy, these patients did not suffer from a long-term increase in instability or disability.