Degeneration alters the biomechanical properties and structural composition of lateral human menisci.

OBJECTIVE: Because the literature relating to the influence of degeneration on the viscoelasticity and tissue composition of human lateral menisci remains contradictory or completely lacking, the aim of this study was to fill these gaps by comprehensively characterising the biomechanical properties of menisci with regard to the degree of degeneration. DESIGN: Meniscal tissue from 24 patients undergoing a total knee replacement was collected and the degeneration of each region classified according to Pauli et al. For biomechanical characterisation, compression and tensile tests were performed. Additionally, the water content was determined and infrared (IR) spectroscopy was applied to detect changes in the structural composition, particularly of the proteoglycan and collagen content. RESULTS: With an increasing degree of degeneration, a significant decrease of the equilibrium modulus was detected, while simultaneously the water content and the hydraulic permeability significantly increased. However, the tensile modulus displayed a tendency to decrease with increasing degeneration, which might be due to the significantly decreasing amount of collagen content identified by the IR measurements. CONCLUSION: The findings of the current study may contribute to the understanding of meniscus degeneration, showing that degenerative processes appear to mainly worsen viscoelastic properties of the inner circumference by disrupting the collagen integrity.

[Anterior meniscotibial ligaments. Forces under various load conditions]. / Die anterioren meniskotibialen Ligamente. Kräfte unter verschiedenen Lastsituationen.

The main biomechanical function of the knee meniscus is to enlarge the contact area of the tibiofemoral joint leading to a reduction in articular cartilage contact stress. The meniscal attachments are essential for converting the axial load into circumferential tension in the meniscal periphery. Consequently, meniscal substitutes need sufficient anchorage to the tibial plateau to adequately restore the biomechanical function of a replaced meniscus. Therefore the aim of the present study was to investigate the loads acting on the anterior meniscotibial attachments under various joint loads.

Mechanical properties and morphological analysis of the transitional zone between meniscal body and ligamentous meniscal attachments.

In recent years, an increasing number of studies reporting on meniscal root tears have been published. While the meniscus and its ligamentous meniscal attachments have been studied before, little is known about the transitional zone between these two structures. Therefore, the aim of this study was to mechanically and morphologically characterize the transitional zone between meniscus and its meniscal attachments. Dumbbell-shaped specimens were obtained from the transitional zone between meniscus and its meniscal attachments of 6 knee joints. Samples were divided into tibial and central layers of the anterior lateral (AL), anterior medial (AM), posterior lateral (PL) and posterior medial (PM) transitional region. Testing was performed to obtain the dissipated energy during hysteresis as well as the linear modulus (Elin), the maximum strain (εmax), the maximum engineering stress (σmax,eng) and location of rupture during tensile test to failure. Two additional knee joints were used to investigate morphological differences between meniscus, transitional zone and meniscal attachments in 8µm transverse slices. The central layer of the AL, AM and PL dissipated up to 48% less energy than the tibial layer. Elin was highest in the tibial layer of the PM with 107.4±61.1MPa and lowest in the central layer of the PL with 56.0±20.5MPa. The maximum strain was higher in the central layer than in the tibial layer at the AL, AM, and PL locations. The average σmax,eng was 12.7±9.9MPa over all location and layers. 78% of the samples ruptured during tensile test to failure in the transitional zone. The morphological evaluation showed a smooth transitional zone with a transitional curve which was either linear or bell-shaped. The strength found in the transitional zone was lower than in the meniscus and the meniscal attachments, which corresponds well to clinical findings.