No 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.

Age-related changes in neuromuscular function may have adverse effects on hamstring reflex activity and may impair knee joint stability. The aim of this study was to investigate whether increasing age affects hamstring short latency responses (SLR), medium latency responses (MLR), and anterior tibial translation. In 40 healthy subjects ranging from 20 to 70 years of age we assessed hamstring muscle latencies and integrals for both hamstring reflex components (SLRs and MLRs) as well as anterior tibial translation in order to quantify knee joint stability in response to induced tibial translation during stance. The results showed no significant differences within the subject population in hamstring SLR and MLR latencies and integrals or anterior tibial translation. More precisely, regression analysis did not reveal any correlation between age and the aforementioned parameters. Our findings suggest that functional knee stability in terms of anterior tibial translation appears to be unaffected from people 20 to 70 years of age. Thus, as compared with younger people, older people - at least those under 70 years of age - do not appear to have a higher risk of ligamentous knee injuries associated with hamstring dysfunction. Further studies should be conducted to assess whether the present findings also apply to dynamic real-world situations. This would improve the understanding of the relationship between knee stability and ageing.