Roles of the Fibrous Superficial Zone in the Mechanical Behavior of TMJ Condylar Cartilage

• Published in: Annals of biomedical engineering Vol. 43; no. 11; pp. 2652 - 2662
• Main Authors: Ruggiero, Leonardo, Zimmerman, Brandon K., Park, Miri, Han, Lin, Wang, Liyun, Burris, David L., Lu, X. Lucas
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.11.2015; Springer Nature B.V
• Subjects: Animals; Biochemistry; Biological and Medical Physics; Biomedical and Life Sciences; Biomedical Engineering and Bioengineering; Biomedicine; Biophysics; Cartilage; Cartilage, Articular - physiology; Classical Mechanics; Collagen Type I; Compressive Strength; Female; Finite element method; Friction; Male; Mathematical analysis; Mechanical properties; Nonlinearity; Sliding; Stress, Mechanical; Surgical implants; Swine; Temporomandibular Joint - physiology; Tensile Strength; Friction coefficient; Heterogeneous; Finite element model; Interstitial fluid pressurization; Tension–compression nonlinearity; Biphasic theory
• ISSN: 0090-6964; 1573-9686
• DOI: 10.1007/s10439-015-1320-9

In temporomandibular joints (TMJs), the cartilage on the condylar head displays a unique ultrastructure with a dense layer of type I collagen in the superficial zone, different from hyaline cartilage in other joints. This study aims to elucidate the roles of this fibrous zone in the mechanical behaviors, particularly lubrication, of TMJ under physiological loading regimes. Mechanical tests on porcine condylar cartilage demonstrated that the superficial and middle-deep zones exhibit tension–compression nonlinearity. The tensile and compressive moduli of the superficial zone are 30.73 ± 12.97 and 0.028 ± 0.016 MPa, respectively, while those for the middle-deep zone are 2.43 ± 1.75 and 0.14 ± 0.09 MPa. A nonlinear finite element model of condylar cartilage was built to simulate sliding of a spherical probe over the articular surface. The presence of the superficial zone significantly promoted interstitial fluid pressurization (IFP) inside the loaded cartilage and reduced the friction force on the surface, compared to the case without the superficial zone. Finite element simulations showed that IFP depends on sliding speed but not normal load, which matches the experimental results. This study revealed the presence of the fibrous zone can significantly reduce the deformation of condylar cartilage under compression and the friction force on its surface during sliding.