[Digital speckle correlation method: a technique to evaluate the tensile property of articular cartilage]

To establish a new technique for evaluation of the tensile property of articular cartilage using digital speckle correlation method (DSCM).

Three specimens of whole layer articular cartilage of the size of 10 mm x 4 mm were prepared from the cartilage of head of femur replaced from a 52-year-old male suffering from fracture of neck of femur (old control), the amputated tibia plateau of a 16-year-old female suffering from osteosarcoma (young control), and the cartilage of head of femur of a 19-year-old female suffering from spondyloepiphyseal dysplasia tarda with progressive arthropathy (SEDT-PA) and then underwent DSCM in U and V fields.

The specimens of the 2 controls showed a smooth surface of cartilage and homologous deformation while the specimen of the SEDT-PA patient showed a rough surface of cartilage and deformation with increased undulation. Under a changed loading of 3.3 N the values of average strain of cartilage were 3800, 8800, and 9500 micro epsilon, and the values of tensile elastic modularity were 227.23, 89.59, and 127.25 MPa respectively for the old control, young control, and SEDT-PA patient. The numbers of pixel in U field after 20 pixels were moved in the X direction were significantly different between the old control subject and the SEDT-PA patient (0.101 +/- 0.022 vs 0.220 +/- 0.053, P = 0.023). The numbers of pixel in V field after 20 pixels were moved in the Y direction were significantly different among the old control subject and the SEDT-PA patient. Differences were also significant among the three kinds of cartilage (0.055 +/- 0.018, 0.196 +/- 0.057 vs 0.658 +/- 0.144, both P < 0.05).

DSCM is a reliable technique to measure the tensile property of articular cartilage, especially for evaluation of small specimens. SEDT-PA is characterized by a dramatic decrease of tensile property, causing destruction and loss of the articular cartilage.