Geometry, time-dependent and failure properties of human meniscal attachments

Meniscectomies have been shown to lead to osteoarthritis and the success of meniscal replacements remains questionable. It has been suggested that the success of a meniscal replacement is dependent on several factors, one of which is the secure fixation and firm attachment of the replacement to the tibial plateau at the horn locations. To aid in the development of meniscal replacements, the objectives of the current study were to determine the time-dependent and failure properties of human meniscal attachments. In contrast to the time-dependent tests, during uniaxial failure testing a charge-coupled video camera was used to document the local strain and linear modulus distribution across the surface of the attachments. The lateral attachments were statistically smaller in cross-sectional area and longer than the medial attachments. The anterior attachments were statistically longer and had a smaller cross-sectional area than the posterior attachments. From the stress relaxation tests, the load and stress relaxation rates of the medial anterior attachment were statistically greater than the medial posterior attachment. There were no significant differences in the creep, structural properties or the ultimate stress between the different attachments. Ultimate strain varied between attachments, as well as along the length of the attachment. Ultimate strain in the meniscus region (10.4+/-6.9%) and mid-substance region (12.7+/-16.4%) was smaller than the bony insertion region (32.2+/-21.5%). The lateral and anterior attachments were also found to have statistically greater strain than the medial and posterior attachments, respectively. The linear modulus was statistically weaker in the bony insertion region (69.7+/-33.7MPa) compared to the meniscus region (153+/-123MPa) and mid-substance region (195+/-121MPa). Overall the anterior attachments (169+/-130MPa) were also found to be statistically stronger than the posterior attachments (90.8+/-64.9MPa). These results can be used to help design tissue-engineered replacement menisci and their insertions and show the differences in material properties between attachments, as well as within an attachment.