Biomechanical Evaluation of the Suture Anchors Used in Open-Door Laminoplasty

Study Design. A cadaveric study. Objective. To determine whether the use of suture anchors is warranted in cervical laminoplasty. Summary of Background Data. The use of suture anchors to stabilize elevated laminae has been popularized in laminoplasty. However, the validity of using suture anchors in laminoplasty has not been determined. Methods. Six intact fresh frozen cadavers were used. Open-door laminoplasty with a hinge on the cadaver's left side was performed on levels C3-C7. Elevated laminae were stabilized by suture anchors equipped with strain gauges, which were placed on C3, C5, and C7 left lateral masses. After surgery, the cervical spine was manually loaded passively, and the mechanical loads on each suture anchor during each motion were measured. Finally, the incision was opened again, and the failure loads of the suture anchors were also measured. Results. After cervical loading, all elevated laminae were confirmed to be intact without dislodgement or failure of the suture anchors. The loads during left rotation and left bending were significantly higher than those during the respective motion to the right at all levels, except in rotation at C3. The loads on the C5 anchors in flexion and left rotation and on the C7 anchors in extension were relatively high. The maximum load obtained in the present study was 14.9 N, which was one order of magnitude lower than the mean failure load of the suture anchors (131.7 N). Conclusion. Biomechanical laterality was demonstrated, reflecting the asymmetrical nature of open-door laminoplasty. The maximum load on the suture anchors was much lower than the failure load and was consistent with the stability of the suture anchors encountered in clinical cases. This may support the validity of using suture anchors in laminoplasty, although the loads during active motion may be higher than our results.