Effect of a Focal Articular Defect on Cartilage Deformation during Patello-Femoral Articulation

The objective of this study was to determine cartilage strains near, and in apposition to, a focal defect during patello femoral articulation Bovine osteochondral blocks from the trochlea (TRO) and patella (PAT) were apposed compressed 12%, and subjected to sliding under video microscopy Samples, lubricated with synovial fluid, were tested intact and then with a full thickness defect in PAT cartilage Shear (E-xz) axial (E-zz) and lateral (E-xx) strains were determined locally for TRO and PAT cartilage For articulation with a focal defect the strain amplitudes of PAT cartilage near the surface were similar to 2-8x lower in E-xz and similar to 1 4x higher in -E-zz than intact PAT cartilage At 20% depth, E-xz and E-xx for PAT cartilage with a focal defect were similar to 2x and similar to 10-25x higher than intact PAT, respectively For TRO articulating against a focal defect, E-xz and -E-zz near the surface and at 20% depth were similar to 2-4x lower than that for articulation against intact cartilage The results elucidate dramatic region specific changes in strain due to lateral motion In these regions, such altered cartilage mechanics during knee movement may cause focal defects to extend by induction of damaging levels of strain to bordering regions of cartilage (c) 2010 Orthopaedic Research Society Published by Wiley Periodicals, Inc J Orthop Res 28 1554-1561 2010