Objective: The purpose of this study was to analyze the stability and instrument-related complications associated with fixation of the lumbar spine using the Short-Rod (SR) technique.Methods: Using finite element analysis, this study assessed the stability of a bilateral lumbar fixation system when inserting the pedicle screws at angles of 10°, 15°, and 20° to the endplate in the sagittal plane. Using the most stable construct with a screw angle, the model was then assessed with different rod lengths of 25, 30, 35, and 45 mm. The optimal screw inclination angle and rod length were incorporated into the SR model and compared against traditional parallel screw insertion (pedicle screws in parallel to the endplate, PPS) in terms of the stability and risk of instrument-related complications. The following parameters were evaluated using the validated L4–L5 lumbar finite element model: axial stiffness, range of motion (ROM), stress on the endplate and facet joint, von-Mises stress on the contact surface between the screw and rod (CSSR), and screw displacement.Results: The results showed that the SR model with a 15° screw inclination angle and 35 mm rod length was superior in terms of construct stability and risk of complications. Compared to the PPS model, the SR model had lower stiffness, lower ROM, less screw displacement, and lower stress on the facet cartilage, the CSSR, and screws. However, the SR model also suffered more stress on the endplate in flexion and lateral bending.Conclusion: The SR technique with a 15° screw inclination and 35 mm rod length offers good lumbar stability with a low risk of instrument-related complications.

Objective: The purpose of this study was to analyze the feasibility of repairing a ruptured intervertebral disc using a patch secured to the inner surface of the annulus fibrosus (AF). Different material properties and geometries for the patch were evaluated.Methods: Using finite element analysis, this study created a large box-shaped rupture in the posterior-lateral region of the AF and then repaired it with a circular and square inner patch. The elastic modulus of the patches ranged from 1 to 50 MPa to determine the effect on the nucleus pulposus (NP) pressure, vertical displacement, disc bulge, AF stress, segmental range of motion (ROM), patch stress, and suture stress. The results were compared against the intact spine to determine the most suitable shape and properties for the repair patch.Results: The intervertebral height and ROM of the repaired lumbar spine was similar to the intact spine and was independent of the patch material properties and geometry. The patches with a modulus of 2–3 MPa resulted in an NP pressure and AF stresses closest to the healthy disc, and produced minimal contact pressure on the cleft surfaces and minimal stress on the suture and patch of all models. Circular patches caused lower NP pressure, AF stress and patch stress than the square patch, but also caused greater stress on the suture.Conclusion: A circular patch with an elastic modulus of 2–3 MPa secured to the inner region of the ruptured annulus fibrosus was able to immediately close the rupture and maintain an NP pressure and AF stress similar to the intact intervertebral disc. This patch had the lowest risk of complications and produced the greatest restorative effect of all patches simulated in this study.

The research aimed at discussing the analytic function of convolutional neural network (CNN) algorithm-based magnetic resonance images (MRI) in the correlation between lumbar disc herniation (LDH) and angle and irregular variation of joint (IVJ) of lumbar facet-joint (LFJ). First, CNN-based MRI (CNNM) algorithm was constructed, and Markov random field (MRF) and fuzzy C-means (FCM) algorithms were introduced for comparison. Meanwhile, all patients received MRI examination of lumbar, and CNNM algorithm was adopted in MRI images. The results showed that the sensitivity, specificity, accuracy, and precision (98.53%, 93.65%, 99.56%, and 98.74%, respectively) of the CNNM algorithm were all superior to those of MRF algorithm (90.41%, 81.11%, 91.18%, and 91.13%, respectively) and of FCM algorithm (93.14%, 82.86%, 93.23%, and 93.08%, respectively) ( P < 0.05 ). Besides, the lumbar spine angles of L3-L4, L4-L5, and L5-S1 (6.03 ± 1.34°, 7.14 ± 1.18°, and 8.96 ± 3.26°, respectively) in the experimental group was obviously less than those in the control group (6.84 ± 1.15°, 9.85 ± 1.25°, and 17.34 ± 4.79°, respectively) ( P < 0.05 ). In the experimental group, there was irregular mutation of LFJ in 78 cases, while 8 cases suffered from irregular mutation of LFJ in the control group. The proportions of protrusion in L3/4, L4/5, and L5/S1 segments (11 cases, 53 cases, and 14 cases, respectively) was higher than that in the control group (1 case, 5 cases, and 2 cases, respectively) ( P < 0.05 ). In short, the constructed CNNM algorithm had excellent performance in diagnosing lumbar MRI images and had clinical research and promotion value. Moreover, the IVJ of patients with LDH was notably increased, most of the physiological angle of the lumbar spine changed, and facet joint was correlated with the occurrence of LDH.