Chronic changes in the articular cartilage and meniscus following traumatic impact to the lapine knee

Abstract

The objective of this study was to induce anterior cruciate ligament (ACL) and meniscal damage, via a single tibiofemoral compressive impact, in order to document articular cartilage and meniscal changes post impact. Tibiofemoral joints of Flemish Giant rabbits were subjected to a single blunt impact that ruptured the ACL and produced acute meniscal damage. Animals were allowed unrestricted cage activity for 12 weeks before euthanasia. India ink analysis of the articular cartilage revealed higher degrees of surface damage on the impacted tibias (p=0.018) and femurs (p<0.0001) compared to controls. Chronic meniscal damage was most prevalent in the medial central and medial posterior regions. Mechanical tests revealed an overall 19.4% increase in tibial plateau cartilage thickness (p=0.026), 34.8% increase in tibial plateau permeability (p=0.054), 40.8% increase in femoral condyle permeability (p=0.029), and 20.1% decrease in femoral condyle matrix modulus (p=0.012) in impacted joints compared to controls. Both the instantaneous and equilibrium moduli of the lateral and medial menisci were decreased compared to control (p<0.02). Histological analyses revealed significantly increased presence of fissures in the medial femur (p = 0.036). In both the meniscus and cartilage there was a significant decrease in GAG coverage for the impacted limbs. Based on these results it is clear that an unattended combined meniscal and ACL injury results in significant changes to the soft tissues in this experimental joint 12 weeks post injury. Such changes are consistent with a clinical description of mid to late stage PTOA of the knee.

An optimized transversely isotropic, hyper-poro-viscoelastic finite element model of the meniscus to evaluate mechanical degradation following traumatic loading

“…The observed decreases in the α (or stiffness) term from control to impacted menisci were not surprising, as the experimental data utilized for this study showed decreases in in meniscal instantaneous and equilibrium moduli (Fischenich et al, 2014a), while a similar study of an OA transection model also found decreased indentation stiffness (Fischenich et al, 2014b). Our results show that in addition to decreases in stiffness, the time dependent mechanical properties of the menisci were altered following tibiofemoral impact.…”

“…Changes to the GAG content could therefore disrupt tissue permeability. Previous work shows a decrease in GAG content in menisci at twelve weeks post injury (Fischenich et al, 2014a; Fischenich et al, 2014b). Increases in permeability could lead to an overloading of the solid matrix and fibers, resulting in further degradation of these solid constituents.…”

“…Following anesthesia (2% isoflurane and oxygen), a 1.75 kg mass was dropped from 70 cm in height onto the distal femur with the right tibiofemoral joint at 90° flexion, causing ACL rupture and acute damage to surrounding tissues (Fischenich et al, 2014a; Fischenich et al, 2014b). Left limbs remained non-impacted as paired controls.…”

“…Two critical components of OA research are developing models that mimic degradation in humans and characterizing changes to the tissue as a result of OA. Experimental animal models have been used extensively to simulate osteoarthritic changes within the knee, but very few have investigated meniscal changes (Adams et al, 1983; Fischenich et al, 2014a; Fischenich et al, 2014b; Hellio Le Graverand et al, 2001). The majority of these studies have used a traditional anterior cruciate ligament transection (ACLT) model.…”

“…Directly evaluating mechanical properties from experimental data provides useful insight into tissue behavior, but often yields limited results such as elastic modulus (Fischenich et al, 2014a; Fischenich et al, 2014b; Proctor et al, 1989) and testing procedures can be destructive in nature (Mansour and Mow, 1976). Inverse finite element (FE) approaches are an effective method to evaluate a range of material properties through parameter optimization (Korhonen et al, 2002; Lei and Szeri, 2007; LeRoux and Setton, 2002) and can be utilized with non-destructive experimental analyses.…”