Journal article
Loading and Boundary Condition Influences in a Poroelastic Finite Element Model of Cartilage Stresses in a Triaxial Compression Bioreactor
The Iowa orthopaedic journal, Vol.26, pp.5-16
2006
PMCID: PMC1888601
PMID: 16789442
Appears in Diamond Open Access
Abstract
Background: We developed a poroelastic finite element (FE) model of cartilage in dynamic triaxial compression to parametrically analyze the effects of loading and boundary conditions on a baseline model. Conventional mechanical tests on articular cartilage such as confined and unconfined compression, indentation, etc., do not fully allow for modulation of compression and shear at physiological levels whereas triaxial compression does. A Triaxial Compression Bioreactor, or TRIAX, has been developed to study chondrocyte responses to multi-axial stress conditions under cyclic loading. In the triaxial setting, however, a cartilage explant's physical testing environment departs from the ideal homogeneous stress state that would occur from strict linear superposition of the applied axial and transverse pressure.
Method of approach: An axisymmetric poroelastic FE model of a cartilage explant (4 mm diameter, 1.5 mm thick) in cyclic triaxial compression was created. Axial and transverse loads (2 MPa at 1 Hz.) were applied via a platen and containment sheath. Parameters of interest included the rise time and magnitude of the applied load, in addition to the containment sheath modulus and the friction coefficient at the cartilage/platen interfaces. Metrics of interest in addition to whole explant axial strain included axial (surface normal) stress, shear stress, pore pressure, and the fluid load carriage fraction within the explant.
Results: Strain results were compared to experimental data from explants tested in the TRIAX under conditions similar to the baseline model. Explant biomechanics varied considerably over numbers of load cycles and parameter values. Cyclic loading caused an increase in accumulated strain for the various loading and boundary conditions.
Conclusions: Unlike what would be expected from linear superposition of the homogeneous stresses from the applied axial and transverse pressure, we have shown that the stress state within the TRIAX is considerably heterogeneous. Both the boundary influences (variation in the sheath modulus and friction coefficient) and the loading history (due to poroelastic material behavior) interact in a highly nonlinear manner to influence that heterogeneity.
Details
- Title: Subtitle
- Loading and Boundary Condition Influences in a Poroelastic Finite Element Model of Cartilage Stresses in a Triaxial Compression Bioreactor
- Creators
- Nicole A Kallemeyn - Department of Biomedical Engineering, The University of Iowa, Iowa City, IANicole M Grosland - Department of Orthopaedics and Rehabilitation, The University of Iowa, Iowa City, IADoug R Pedersen - Department of Orthopaedics and Rehabilitation, The University of Iowa, Iowa City, IAJames A Martin - Department of Orthopaedics and Rehabilitation, The University of Iowa, Iowa City, IAThomas D Brown - Department of Orthopaedics and Rehabilitation, The University of Iowa, Iowa City, IA
- Resource Type
- Journal article
- Publication Details
- The Iowa orthopaedic journal, Vol.26, pp.5-16
- PMID
- 16789442
- PMCID
- PMC1888601
- NLM abbreviation
- Iowa Orthop J
- ISSN
- 1541-5457
- eISSN
- 1555-1377
- Publisher
- Dept. of Orthopaedics, The University of Iowa; United States
- Language
- English
- Date published
- 2006
- Academic Unit
- Roy J. Carver Department of Biomedical Engineering; Pharmaceutical Sciences and Experimental Therapeutics; Orthopedics and Rehabilitation; Injury Prevention Research Center
- Record Identifier
- 9984040569502771
Metrics
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