Replacing diseased cartilage with tissue-engineered (TE) cartilage has promise as a treatment for osteoarthritis. It is generally believed that functional TE construct should have material properties that are similar to those of native tissue. Furthermore, determining the material properties of TE cartilage prior to implantation is thought to be important for reducing construct failure post-implantation. The purpose of this study is to develop the feasibility of both numerical and experimental approaches for the proper estimation of the material properties using destructive and non-destructive methods.
For the numerical approach, inverse analyses using finite element models were developed to calibrate the material properties of cartilage. The validation of poroelastic constitutive models under unconfined compression and indentation tests has been demonstrated. A transversely isotropic model and a depth- and strain-dependent model were established to simulate the stress relaxation process. The inverse analyses were applied by means of linear regression or constrained optimization to determine the poroelastic properties of cartilage. Results have shown that excellent estimates of mechanical properties can be obtained using coupled finite element models and constrained optimization methods. In addition, a method for determining mechanical properties of cartilage from a set of linear algebraic equations has been developed and published.
For the experimental approach, the non-destructive assessment of the depth-dependent mechanical behavior of TE cartilage in vivo was implemented using ultrasound. Conventional compression tests, like those described above, do not yield depth-dependent information about a tissue sample. Nevertheless, the material properties of TE cartilage vary in depth due to internal heterogeneities that arise from uneven rates of maturation throughout the tissue. Additionally, traditional destructive methods are undesirable for TE cartilage because they violate the sterile bioreactor environment, and tissues tested by these methods are no longer suitable for implantation. Ultrasonic elastography was developed to nondestructively estimate regional strain of inhomogeneous constructs while they reside in the sterile environment of a bioreactor. The accuracy of this approach has been validated using measurements on a well-characterized three-layered hydrogel construct and estimates of strain from a finite element model of the construct.
In this investigation, both numerical computation and nondestructive experiment can serve as guiding procedures for evaluating the functions and properties of engineered cartilage. The correlation between computations and experiments has been established. These approaches can be applied to characterize the mechanical properties of TE of articular cartilage and other tissues. It will assist the quality control of TE constructs cultured by different designs and fabrications prior to implantation.
|1995||Athanasiou KA, Agarwal A, Muffoletto A, Dzida FJ, Constantinides G, Clem M. Biomechanical properties of hip cartilage in experimental animal models. Clin Orthop Relat Res. July 1995;316:254-266.|
|2000||Guilak F, Mow VC. The mechanical environment of the chondrocyte: a biphasic finite element model of cell–matrix interactions in articular cartilage. J Biomech. December 2000;33(12):1663-1673.|
|1941||Biot MA. General theory of three‐dimensional consolidation. J Appl Phys. February 1941;12(2):155-164.|
|1980||Mow VC, Kuei SC, Lai WM, Armstrong CG. Biphasic creep and stress relaxation of articular cartilage in compression: theory and experiments. J Biomech Eng. February 1980;102(1):73-84.|
|1998||Cohen B, Lai WM, Mow VC. A transversely isotropic biphasic model for unconfined compression of growth plate and chondroepiphysis. J Biomech Eng. August 1998;120(4):491-496.|
|1991||Lai WM, Hou JS, Mow VC. A triphasic theory for the swelling and deformation behaviors of articular cartilage. J Biomech Eng. August 1991;113(3):245-258.|
|1984||Mow VC, Holmes MH, Lai WM. Fluid transport and mechanical properties of articular cartilage: a review. J Biomech. 1984;17(5):377-394.|
|1992||Mow VC, Ratcliffe A, Robin Poole A. Cartilage and diarthrodial joints as paradigms for hierarchical materials and structures. Biomaterials. 1992;13(22):67-97.|
|2004||Wilson W, van Donkelaar CC, van Rietbergen B, Ito K, Huiskes R. Stresses in the local collagen network of articular cartilage: a poroviscoelastic fibril-reinforced finite element study. J Biomech. March 2004;37(3):357-366.|
|2005||Wilson W, van Donkelaar CC, van Rietbergen B, Huiskes R. A fibril-reinforced poroviscoelastic swelling model for articular cartilage. J Biomech. June 2005;38(6):1195-1204.|
|1992||Spilker RL, Suh J-K, Mow VC. A finite element analysis of the indentation stress-relaxation response of linear biphasic articular cartilage. J Biomech Eng. May 1992;114(2):191-201.|
|1984||Armstrong CG, Lai WM, Mow VC. An analysis of the unconfined compression of articular cartilage. J Biomech Eng. May 1984;106(2):165-173.|
|1997||Khalsa PS, Eisenberg SR. Compressive behavior of articular cartilage is not completely explained by proteoglycan osmotic pressure. J Biomech. June 1997;30(6):589-594.|
|2009||Villemure I, Stokes IAF. Growth plate mechanics and mechanobiology: a survey of present understanding. J Biomech. August 25, 2009;42(12):1793-1803.|
|1986||Brown TD, Singerman RJ. Experimental determination of the linear biphasic constitutive coefficients of human fetal proximal femoral chondroepiphysis. J Biomech. 1986;19(8):597-605.|
|2001||DiSilvestro MR, Suh J-KF. A cross-validation of the biphasic poroviscoelastic model of articular cartilage in unconfined compression, indentation, and confined compression. J Biomech. April 2001;34(4):519-525.|
|1971||Hayes WC, Mockros LF. Viscoelastic properties of human articular cartilage. J Appl Physiol. October 1971;31(4):562-568.|
|1972||Hayes WC, Keer LM, Herrmann G, Mockros LF. A mathematical analysis for indentation tests of articular cartilage. J Biomech. September 1972;5(5):541-551.|
|1980||Lai WM, Mow VC. Drag-induced compression of articular cartilage during a permeation experiment. Biorheology. 1980;17(1-2):111-123.|