A TRANSVERSELY ISOTROPIC BIPHASIC MODEL FOR UNCONFINED COMPRESSION OFGROWTH-PLATE AND CHONDROEPIPHYSIS

Using the biphasic theory for hydrated soft tissues (Mow et al., 1980) and a transversely isotropic elastic model for the solid matrix, an a nalytical solution is presented for the unconfined compression of cyli ndrical disks of growth plate tissues compressed between two rigid pla tens with a frictionless interface. The axisymmetric case where the pl ane of transverse isotropy is perpendicular to the cylindrical axis is studied and the stress-relaxation response to imposed step and ramp d isplacements is solved. This solution is then used to analyze experime ntal data from unconfined compression stress-relaxation tests performe d on specimens from bovine distal ulnar growth plate and chondroepiphy sis to determine the biphasic material parameters. The transversely is otropic biphasic model provides an excellent agreement between theory and experimental results, better than was previously achieved with an isotropic model, and can explain the observed experimental behavior in unconfined compression of these tissues.