The challenge of implant integration in partial meniscal replacement: an experimental study on a silk fibroin scaffold in sheep

Abstract

Purpose To restore meniscal function after excessive tissue damage, a silk fibroin implant for partial meniscal replacement was developed and investigated in an earlier sheep model. After 6 months implantation, it showed promising results in terms of chondroprotection and biocompatibility. To improve surgical fixation, the material was subjected to optimisation and a fibre mesh was integrated into the porous matrix. The aim of the study was the evaluation of this second generation of silk fibroin implants in a sheep model. Methods Nine adult merino sheep received subtotal meniscal replacement using the silk fibroin scaffold. In nine additional animals, the defect was left untreated. Sham surgery was performed in another group of nine animals. After 6 months of implantation macroscopic, biomechanical and histological evaluations of the scaffold, meniscus, and articular cartilage were conducted. Results Macroscopic evaluation revealed no signs of inflammation of the operated knee joint and most implants were located in the defect. However, there was no solid connection to the remaining peripheral meniscal rim and three devices showed a radial rupture at the middle zone. The equilibrium modulus of the scaffold increased after 6 months implantation time as identified by biomechanical testing (before implantation 0.6 ± 0.3 MPa; after implantation: 0.8 ± 0.3 MPa). Macroscopically and histologically visible softening and fibrillation of the articular cartilage in the meniscectomy- and implant group were confirmed biomechanically by indentation testing of the tibial cartilage. Conclusions In the current study, biocompatibility of the silk fibroin scaffold was reconfirmed. The initial mechanical properties of the silk fibroin implant resembled native meniscal tissue. However, stiffness of the scaffold increased considerably after implantation. This might have prevented integration of the device and chondroprotection of the underlying cartilage. Furthermore, the increased stiffness of the material is likely responsible for the partial destruction of some implants. Clinically, we learn that an inappropriate replacement device might lead to similar cartilage damage as seen after meniscectomy. Given the poor acceptance of the clinically available partial meniscal replacement devices, it can be speculated that development of a total meniscal replacement device might be the less challenging option.

Total meniscus replacement with a 3D printing of network hydrogel composite scaffold in a rabbit model

“…The most striking outcome of this study was the PG-Pg scaffold's ability to progressively enhance mechanical strength, and reduce cartilage deterioration after 6 months of implantation in rabbit knees. Several clinical studies have demonstrated that meniscal substitutes previously used in clinical practice exhibit varying degrees of decrease in biomechanical properties as tissue infiltration and scaffold degradation occur in vivo [8,16,20,25,27,32]. The PG-Pg scaffold exhibited similar initial mechanical properties to the same material used to replace the rabbit meniscus [32], but their initial mechanics changed as the size of the PG-Pg scaffold changed.…”

Applications of Tissue Engineering in Meniscus Repair

“…From the experimental results, silk fibroin transplantation did not show obvious repair, but still the stent and tissue can not bind tightly and produce inflammation defects. The study of silk fibroin scaffolds still needs to be improved and perfected, but it can not be denied that silk fibroin scaffolds transplantation is still a promising means of meniscus injury repair [18].…”

Engineering Anisotropic Meniscus: Zonal Functionality and Spatiotemporal Drug Delivery

“…CMI® and Actifit®, are indeed hybrid materials. Collagen Meniscus Implant (CMI®, Ivy Sports Medicine, Germany), commercialized in Europe since 2016, is based on purified bovine collagen I and glycosaminoglycans; whereas Actifit® (Orteq Ltd., UK) contains polycaprolactone and polyurethane [61][62][63] . Moreover, NUsurface® (Active Implants Israel Ltd., Israel), made of polyethylene and polycarbonateurethane, is in the process of FDA approval for total meniscus replacement 61 .…”