Objective To investigate and evaluate the biomechanical behaviour of tension-band-reconstruction (TBR) and ordinary titanium plates in open-door laminoplasty by finite element (FE) analysis. Methods TBR titanium plate and ordinary titanium plate were implanted into a validated finite element model of healthy adult cervical vertebrae. Among them, 5 ordinary titanium plate were used in model A, 2 TBR titanium plates and 3 ordinary titanium plates were used in model B, and 5 TBR titanium plates were used in model C. The same loading conditions was applied identically to all models. Range of motion (ROM) of the vertebral body, stress distribution of the titanium plate and intradiscal pressure (IDP) were compared in flexion, extension, lateral bending and rotation. Results The ROM of model B and C was similar in flexion and extension, and both were smaller than that of model A. The highest von Mises stress in the titanium plate appears is in model C. The IDP in C2/3 was significantly higher than that in other segments in flexion. There was no significant difference in IDP among three models in left lateral bending and left axial rotation. Conclusion Application of TBR titanium plate in open-door laminoplasty can reduced ROM in flexion, extension and axial rotation of the cervical vertebrae. But the increase of stress in TBR titanium plate could lead to higher risk of adverse events such as titanium plate deformation. Moreover, compared with complete TBR titanium plate, the combination of TBR titanium plate for C3 and C7 with ordinary titanium plate for the other vertebrae largely reduce the stress of the titanium plates by ensuring stability. The proposed FE model (C2-T1) exhibits a great potential in evaluating biomechanical behaviour of TBR titanium plate for open-door laminoplasty.

Background Previous studies have investigated the imaging changes of the paravertebral muscles (PVM) in patients with degenerative lumbar scoliosis (DLS); however, most of these studies focused on the apical vertebra (AV) level or compared with the average of the whole-segment measurement. In this study, magnetic resonance imaging (MRI) combined with surface electromyography (sEMG) was used to analyze the degenerative characteristics of the multifidus (MF) in patients with DLS at three levels of scoliosis (upper end vertebra [UEV], AV, and lower end vertebra [LEV]). Methods This is a prospective cross-sectional study. Forty patients with DLS (DLS group) and 40 healthy individuals without lumbar scoliosis (control group) were evaluated. The percentage of fat infiltration area (%FIA) and muscle relative cross-sectional area (rCSA) of the MF at the three levels of scoliosis were measured on MRI, whereas the sEMG activity of the participants in both groups was recorded during action tasks. The imaging parameters, sEMG activity, and relationship between them were analyzed. Results In the control group, there were no significant differences in the %FIA, rCSA, or sEMG activation of the MF between the bilateral sides at the three measured levels. In the DLS group, measurement of the MF at the UEV and AV levels showed that the %FIA was larger on the concave than convex side and that the rCSA was smaller on the concave than convex side, but there was no difference between the two parameters at the LEV level. In the standing flexion and extension tasks, the sEMG activation of the MF was higher on the concave than convex side. The coronal Cobb angle was correlated with the difference in the measurement data of the MF at the UEV and AV levels, but not with the difference at the LEV level. Conclusion The MF in patients with DLS has the same degenerative features at the UEV and AV levels, with the concave side showing greater degeneration; however, there are different degenerative manifestations at the LEV level. The MF degeneration at the UEV and AV levels is the result of spinal deformity, while the muscle changes at the LEV level are more consistent with natural degeneration.

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The asymmetry of paravertebral muscle (PVM) degeneration in degenerative lumbar scoliosis (DLS) patients has been extensively studied by imaging and histological examination and has not yet been verified by surface electromyography (sEMG) techniques. To study the relationship between the surface electromyography (sEMG) and degenerative characteristics of paravertebral muscles (PVMs) in patients with degenerative lumbar scoliosis (DLS). In twenty DLS patients and fifteen healthy subjects, sEMG activity of the PVMs at the level of the upper end vertebra (UEV), apical vertebra (AV) and lower end vertebra (LEV) was measured during static standing and dynamic standing forward flexion and backward extension tasks. Action segmentation was achieved according to inertial measurement unit (IMU) data. The sEMG characteristics of the PVMs on the convex and concave sides were compared, and the relationship of these data with the Cobb angle and lumbar lordotic angle (LL) was analyzed. In the DLS group, there was no difference in sEMG activity between the convex and concave sides at the UEV or AV level, but in the motion and return phases of the standing forward flexion task (P = 0.000, P = 0.015) and the maintenance and return phases of the standing backward extension task (P = 0.001, P = 0.01), there was a significant difference in sEMG activity between the convex and concave sides at the LEV level. Asymmetrical sEMG activity at the LEV level was negatively correlated with the Cobb angle (F = 93.791, P < 0.001) and LL angle (F = 65.564, P < 0.001). In the DLS group, asymmetrical sEMG activity of the PVMs appeared at the LEV level, with the concave side being more active than the convex side. This sEMG characteristics were consistent with their imaging and histological degenerative features and correlated with bone structural parameters.