Incongruity-dependent changes of contact stress rates in human cadaveric ankles.

Cartilage biosynthetic transduction and injury characteristics have been shown to be particularly sensitive to changes in contact stress rates. This study investigated incongruity-associated changes in contact stress rates that resulted from an articular surface stepoff of the distal tibia in human cadaveric ankles. Ten human cadaveric ankles were subjected to quasi-physiologic stance-phase motion and loading and instantaneous contact stresses were captured at 132 Hz over the entire articular surface using a custom-fabricated stress transducer.

Contact stress transients during functional loading of ankle stepoff incongruities.

Cartilage deformation demonstrates viscoelastic behavior due to its unique structure. However, nearly all contact studies investigating incongruity-associated changes in cartilage surface stresses have been static tests. These tests have consistently measured only modest increases in contact stresses, even with large incongruities.

Pathomechanic determinants of posttraumatic arthritis.

The etiology of posttraumatic arthritis is poorly understood. One possible mechanism involves a mechanical insult to the cartilage matrix that affects chondrocyte function. To better understand the etiology of posttraumatic arthritis, pathomechanic changes in articular contact mechanics resulting from injury during physiologic motion and loading need to be determined.

Incongruity versus instability in the etiology of posttraumatic arthritis.

The etiology of posttraumatic arthritis is understood poorly but it clearly has a pathomechanical component. Posttraumatic arthritis likely results from irreversible cartilage damage sustained at the time of injury and chronic cartilage overloading resulting from articular incongruity and instability. However, the relative importance of instability and incongruity is unknown.