Based on transversely isotropic theory, a finite element model for three-dimensional solid-liquid coupling defect repair of articular cartilage was established. By studying stress state of host cartilage near the restoration interface, we identified deformation type of cartilage and discussed the cause of restoration interface cracking. The results showed that the host cartilage surface node near the restoration interface underwent compression deformation in the condition of surface layer defect repair. When the middle layer, deep layer or full-thickness defect were repaired, the node underwent tensile deformation. At this point, the radial dimension of cartilage increased, which might cause restoration interface cracking. If elastic modulus of the tissue engineered cartilage (TEC) was lower (0.1 MPa, 0.3 MPa), the host cartilage surface layer and middle layer mainly underwent tensile deformation. While elastic modulus of TEC was higher (0.6 MPa, 0.9 MPa), each layer of host cartilage underwent compression deformation. Therefore, the elastic modulus of TEC could be increased properly for full-thickness defect repair. This article provides a new idea for evaluating the effect of cartilage tissue engineering repair, and has a certain guiding significance for clinical practice.
ObjectiveTo evaluate long-term radiographic and clinical effectiveness of total cervical disc replacement (TDR) with Prodisc-C prosthesis at a minimum of 10 years follow-up.MethodsThe clinical data of 118 patients with cervical disc degeneration disease (CDDD) treated with TDR by using Prodisc-C prosthesis between December 2005 and April 2008 were retrospectively analyzed. There were 66 males and 52 females, with the age of 25-62 years (mean, 46.8 years). There were 38 cases of cervical spondylotic radiculopathy, 28 cases of cervical spondylotic myelopathy, and 52 cases of mixed cervical spondylotic myelopathy. The operative segments were C3-7, including 90 cases of single segment, 20 cases of continuous double segments, and 8 cases of continuous three segments. A total of 154 Prodisc-C prostheses were used during the operation. The clinical effectiveness was evaluated by pain visual analogue scale (VAS) score, neck disability index (NDI), Japanese Orthopaedic Association (JOA) score, and Odom grade before and after operation. Imaging evaluation indicators included range of motion (ROM), sagittal lordosis angle, intervertebral disc height (IDH), and prosthesis displacement, subsidence, loosening, locking, and heterotopic ossification (HO), adjacent segment degeneration (ASD), and other complications. Patients were grouped according to whether HO or ASD occurred or not, the ROM of surgical segment was compared.ResultsAll patients were followed up 121-150 months (mean, 135.8 months). No revision operation was performed during the follow-up period. The VAS, NDI, JOA scores and Odom grades were significantly improved at 1 week after operation and last follow-up when compared with preoperative ones (P<0.05); VAS and NDI scores were further improved at last follow-up than those at 1 week after operation (P<0.05); there was no significant difference in JOA scores and improvement rates between at 1 week after operation and at last follow-up (P>0.05). The ROM of the whole cervical spine and the operative segment decreased at 1 week and 10 years after operation when compared with preoperative ones (P<0.05), but there was no significant difference in the other time points (P>0.05); there was no significant difference in the ROM between the upper adjacent segment (UAS) and the lower adjacent segment (LAS) at each time point after operation (P>0.05). There was no significant difference in sagittal lordosis angle of cervical spine before and after operation (P>0.05); the sagittal lordosis angle of operative segment increased significantly at 1 week, 6 months, 1 year, and 2 years after operation (P<0.05). The IDH of operative segment was significantly improved at each time point after operation (P<0.05), but there was no significant difference in IDH between UAS and LAS at each time point after operation (P>0.05). No prosthesis displacement, subsidence, or loosening occurred at each time point after operation. There was no significant difference of the prosthetic displacement and subsidence distance between all time points after 6 months after operation (P>0.05). At last follow-up, the incidence of prosthetic locking/fusion was 10.4%, showing no significant difference when compared with 6 months (1.9%) (P<0.05). The incidence of upper ASD and lower ASD was 1.3% and 2.6% respectively at 1 week after operation. The incidence of upper ASD and lower ASD increased gradually with time prolonging, and there were significant differences between different time points (P<0.05). The ROM of operative segment in ASD group was lower than that in non-ASD group at each time point after operation, but there was no significant difference (P>0.05). HO appeared in 58.4% of the segments at 6 months after operation, and the incidence of HO increased significantly with time, which was significantly different from that at 6 months after operation (P<0.05). The ROM of operative segments in HO group was significantly lower than that in non-HO group at 6 months, 2 years, 5 years, and 10 years after operation (P<0.05).ConclusionTDR has little effect on adjacent segments, although there are some imaging complications, it has no significant effect on the improvement of overall clinical effectiveness. Prodisc-C prosthesis can provide long-term, safe, and definite clinical effectiveness in the treatment of CDDD.
A solid-liquid two-phase finite element model of articular cartilage and a microscopic finite element model of chondrocytes were established using the finite element software COMSOL in this study. The purpose of the study is to investigate the mechanics environment and the liquid flow field of the host cartilage chondrocytes in each layer by multi-scale method, under physiological load, with the different elastic modulus of artificial cartilage to repair cartilage defect. The simulation results showed that the uniform elastic modulus of artificial cartilage had different influences on the microenvironment of different layer chondrocytes. With the increase of the elastic modulus of artificial cartilage, the stress of the shallow surface layer and the intermediate layer chondrocytes increased and the stress of deep layer chondrocytes decreased. The flow field direction of the middle layer and the bottom layer of cartilage can also be changed by artificial cartilage implantation, as well as the ways of nourishment supply of the middle layer and underlying chondrocytes change. A barrier to underlying chondrocytes nutrition supply may be caused by this, thus resulting in the uncertainty of the repair results. With cross-scale finite element model simulation analysis of chondrocytes, we can quantitatively evaluate the mechanical environment of chondrocytes in each layer of the host cartilage. It is helpful to assess the clinical effect of cartilage defect reparation more accurately.
Melanin nanoparticles (MNPs) not only retain the inherent characteristics of melanin (metal ion chelation, photothermal conversion property, etc.), but also can exhibit more excellent properties, such as high dispersion stability, good biocompatibility and biodegradability, etc. Furthermore, these performances can be enhanced to target the specific sites and treat diseases by the surface modification or combination with functional substance. In this paper, the characteristics, preparation methods and applications of MNPs were reviewed. It provides a reference for further development of application for MNPs, and theoretical basis for practice in biology, medicine and so on.