Annular Defects Impair the Mechanical Stability of the Intervertebral Disc

Abstract

Study Design: A biomechanical study. Objectives: The purpose of this study was to investigate the effects of cruciform and square incisions of annulus fibrosus (AF) on the mechanical stability of bovine intervertebral disc (IVD) in multiple degrees of freedom. Methods: Eight bovine caudal IVD motion segments (bone-disc-bone) were obtained from the local abattoir. Cruciform and square incisions were made at the right side of the specimen’s annulus using a surgical scalpel. Biomechanical testing of three-dimensional 6 degrees of freedom was then performed on the bovine caudal motion segments using the mechanical testing and simulation (MTS) machine. Force, displacement, torque and angle were recorded synchronously by the MTS system. P value <.05 was considered statistically significant. Results: Cruciform and square incisions of the AF reduced both axial compressive and torsional stiffness of the IVD and were significantly lower than those of the intact specimens ( P < .01). Left-side axial torsional stiffness of the cruciform incision was significantly higher than a square incision ( P < .01). Neither incision methods impacted flexional-extensional stiffness or lateral-bending stiffness. Conclusions: The cruciform and square incisions of the AF obviously reduced axial compression and axial rotation, but they did not change the flexion-extension and lateral-bending stiffness of the bovine caudal IVD. This mechanical study will be meaningful for the development of new approaches to AF repair and the rehabilitation of the patients after receiving discectomy.

Recent advances in the repair of degenerative intervertebral disc for preclinical applications

“…AF sutures maintain IVD height and lumbar stability but do not provide high mechanical loading for long periods. Moreover, suture manipulation is difficult with larger defects ( Heuer et al, 2008 ; Rickers et al, 2018 ; Li et al, 2020 ; Ren et al, 2020 ; Chen et al, 2023 ). In the last decades, tissue-engineered biological repairs, such as hydrogels and scaffolds, has shown great advantages.…”

Species variation in the cartilaginous endplate of the lumbar intervertebral disc

“…At present, several animal models such as mice, 13 rats, 14 rabbits, 15 pigs, goats, 16 , 17 , 18 dogs, and nonhuman primates 19 , 20 have been extensively used for studying the reparative treatments to IVD‐related disorders; additionally, bovine coccygeal IVD has been frequently utilized as an organ culture model in vitro. 21 , 22 In these species, the rodents, rabbits, pigs, goats and dogs had the structure of vertebral growth plates that persisted through adulthood, and this structure was not seen in adult humans. 23 In some studies that used rodents as an animal model, the growth plate was mistakenly identified as the CEP; 24 it thus became meaningless to extrapolate the results found in the animals to the human CEP.…”

Is annular repair technique useful for reducing reherniation and reoperation after limited discectomy?

“…Nowadays, a "limited" discectomy, even microendoscopic discectomy, which excises only fragments with minimal invasive exposure, was widely used to minimize the influence of segmental stability (3). However, the reoperation incidence persists at 13% to 25% after the limited discectomy procedure, mainly due to the symptomatic recurrent disc herniation presenting as the primary contributor (4)(5)(6). The annular defect because of the primary LDH or discectomy, especially for large and massive defect (≥ 6 mm), is considered the main reason for recurrent disc herniation (7)(8)(9).…”