Analysis of meniscal hoop strain in porcine knees

Abstract

Menisci in human knee joints are two C-shaped cartilages which are predominantly made up of a network of collagen fibres. They play a very pivotal role in the biomechanics of the knee joint with their load bearing ability. As such, meniscal injuries or degeneration could lead to undesired consequences such as arthritis of the knee joint. Injuries to the meniscus are usually treated with methods such as meniscectomy or meniscal repair. However, the effectiveness of the treatments being used may be undermined without a fundamental understanding of the meniscus mechanics. The hoop stress theory suggests that the load across a knee joint are distributed into the circumferential fibres in a meniscus resulting in hoop strains being generated. The objective of this study was to measure the hoop strain that was generated at the peripheral rim of the intact meniscus and with a 90% radial tear at flexion angles of 30° to 120°. This study serves to quantify the hoop strain values measured in a porcine meniscus and analyse this animal model since porcine knees are commonly used as a substitute for human knees in various studies. A total of 4 porcine knee joints were used for this study. The specimens were mounted onto a custom-designed fixture and was subjected to a compressive of 800 N in an Instron machine. The trend of the results showed that the medial posterior recorded a higher strain than the other regions. The strain recorded in the medial posterior meniscus side was also significantly higher than that recorded in the lateral posterior (P = 0.0002) and lateral anterior (P = 0.0059) of the intact meniscus. Results seemed to indicate that the strain of the medial anterior was lower than the strain measured in the medial posterior region of the intact meniscus. From this study, it seemed to suggest that there are different hoop strains measured in different regions of the meniscus under an axial load and the strain distribution is affected by meniscal tears.