Retaining intradiscal pressure after annulotomy by different annular suture techniques, and their biomechanical evaluations

BackgroundThe adverse effects of annulotomy during lumbar discectomy have been increasingly recognized, and methods are developing to repair the annular defect. Biomechanically, the repair should retain the intra-nuclear pressure, which is doubtful using the current suture techniques. Therefore, a new suture technique was designed and tested to close a simpler type of annular incision.MethodsA new suture technique, the modified purse-string suture, was introduced into a re-validated nonlinear finite element human disk model after creating a standard transverse slit incision, as well as two other suture techniques: either two simple sutures, or a horizontal crossed suture, and compared their contact pressure on the cleft contact surface. Then, porcine lumbar endplate–disk–endplate complexes with transverse slit incisions were repaired using the three techniques. Quantitative discomanometry was then applied to compare their leakage pressure, as a parameter of disk integrity.FindingsIn finite element model, the new technique created the greatest contact pressure along the suture range (the outer annulus), and generated a minimum contact pressure at the critical point, which was 68% and 55% higher than the other two suture techniques. In quantitative discomanometry, the new suture technique also had an average leakage pressure of 85% and 49% higher than the other two suture techniques.InterpretationThe modified purse-string suture can generate higher contact pressure than the other two techniques at finite element analysis and in realistic animal models, which aids in retaining intra-discal pressure, and should be encouraged in clinical practice.