Damaged articular cartilage can be substituted by porous scaffolds exhibiting tailoredmechanical properties and with a suited layer-based design. Reliable predictive modelsare able to provide a structure–property relationship in the design phase is still anopen issue which is of prominent relevance. In this paper, a bottom-up homogenizationapproach is presented having the purpose to determine the elastic properties of eachsingle layer of a osteochondral porous three-layers scaffold: a top cartilage chondral layerand two mineralized layers: an intermediate and a subchondral bone layer. For the cartilagetop layer, dry and wet conditions are considered; while, for intermediate and bonelayers only dry conditions are considered. The homogenization model is based on theporosity of each layer and on the elastic properties of the constituent materials, i.e.,water, hydroxyapatite (HA) and collagen. The elastic moduli predicted for the mineralizedlayers are compared with available literature results. The model results obtained onthe cartilage layers are validated through flat punch micro-indentation tests carried outon wet and dry samples.The results have shown that the elastic modulus of the mineralized layers is ofthe order of magnitude of few GPa; whereas, the elastic modulus of the cartilage layerwhich exhibits porosity higher than 90% is as low as 50 kPa and 300 kPa in wet and dryconditions, respectively. The above results show that the knowledge of the mechanical properties of the basic constituents which are universally known and the porosity of thelayers are sufficient information to obtain a reliable prediction of the elastic propertiesof both mineralized layers and of cartilage layers.
A Predictive Model for the Elastic Properties of a Collagen-Hydroxyapatite Porous Scaffold for Multi-Layer Osteochondral Substitutes
KON, ELIZAVETA;
2015-01-01
Abstract
Damaged articular cartilage can be substituted by porous scaffolds exhibiting tailoredmechanical properties and with a suited layer-based design. Reliable predictive modelsare able to provide a structure–property relationship in the design phase is still anopen issue which is of prominent relevance. In this paper, a bottom-up homogenizationapproach is presented having the purpose to determine the elastic properties of eachsingle layer of a osteochondral porous three-layers scaffold: a top cartilage chondral layerand two mineralized layers: an intermediate and a subchondral bone layer. For the cartilagetop layer, dry and wet conditions are considered; while, for intermediate and bonelayers only dry conditions are considered. The homogenization model is based on theporosity of each layer and on the elastic properties of the constituent materials, i.e.,water, hydroxyapatite (HA) and collagen. The elastic moduli predicted for the mineralizedlayers are compared with available literature results. The model results obtained onthe cartilage layers are validated through flat punch micro-indentation tests carried outon wet and dry samples.The results have shown that the elastic modulus of the mineralized layers is ofthe order of magnitude of few GPa; whereas, the elastic modulus of the cartilage layerwhich exhibits porosity higher than 90% is as low as 50 kPa and 300 kPa in wet and dryconditions, respectively. The above results show that the knowledge of the mechanical properties of the basic constituents which are universally known and the porosity of thelayers are sufficient information to obtain a reliable prediction of the elastic propertiesof both mineralized layers and of cartilage layers.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
