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Retaining intradiscal pressure after annulotomy by different annular suture techniques, and their biomechanical
Yueh-Feng Chiang1, Chang-Jung Chiang, Chih-Hong Yang
1Department of Orthopaedic Surgery, Buddhist Tzu Chi General Hospital, Taichung Branch, No. 66 Sec. 1 Fongsing Road, Tanzih Township. Taichung County, Taiwan.
Background:
The 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.
Methods:
A 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.
Findings:
In 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.
Interpretation:
The 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.