Unstable Joints: Cartilage Stress Anomaly and OA

            Sponsor:  Centers for Disease Control and Prevention

 

Todd O. McKinley, M.D.

Assistant Professor, Department of Orthopaedic Surgery

The University of Iowa

Iowa City, IA  52242
                        e-mail:  Todd-McKinley@uiowa.edu

 

Name

Organization

Role on Project

M. James Rudert, Ph.D.

University of Iowa

Co-Investigator

Nicole M. Grosland, Ph.D.

University of Iowa

Co-Investigator

Thomas D. Brown, Ph.D.

University of Iowa

Co-Investigator

Successful orthopaedic management of displaced intra-articular fractures, to forestall post-traumatic osteoarthritis (OA), depends on avoidance of a mechanical environment that is deleterious to articular cartilage. To date, almost no attention has been directed to the causative mechanisms by which instability induces post-traumatic osteoarthritis.  Many confounding factors, especially heterogeneity of injury, preclude systematic human clinical study of the relative importance of instability versus incongruency as causes of osteoarthritis secondary to intra-articular fractures.  We propose laboratory studies, to investigate mechanisms of how global joint instability manifests itself in terms of mechanical anomaly at the tissue and cellular level, where osteoarthritis metabolically originates.   

1.      In an established rabbit knee defect model, we modulate instability by means of partial sectioning of the anterior cruciate ligament, and document the speed/severity of the resulting secondary degenerative changes. 

  1. Using a contact finite element model of step-off incongruity that incorporates a (rate-dependent) poroelastic constitutive formulation for cartilage, we will compute internal cartilage stresses for loading and motion inputs spanning the instant of transition from (meta)stable to unstable articulation. 

If dynamic instability can be shown to be a potent determinant of post-traumatic osteoarthritis, this would strongly argue that orthopaedic management of these difficult injuries ought to prioritize attaining suitable thresholds of joint stability, rather than the presently dominant strategy of aggressive interventions to attain precise congruency in order to minimize contact stress elevations.

 

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