Mechano-acoustic diagnostic of cartilage degeneration and repair

Background: The combined use of high-frequency ultrasound and mechanical indentation has been suggested for the evaluation of cartilage integrity. In this study, we investigated the usefulness of high-resolution B-mode ultrasound imaging and quantitative mechanical measurements for the diagnosis of cartilage degeneration and for monitoring tissue-healing after autologous chondrocyte transplantation. Methods: In the first study, osteochondral samples (n = 32) were obtained from the lateral facet of a bovine patella, and the samples were visually classified as intact (n = 13) or degenerated (n = 19) and were graded with use of the Mankin scoring system. Samples were imaged with use of a 20-MHz ultrasound instrument, and the dynamic modulus (E) of cartilage was determined in unconfined compression with use of a high-resolution materials tester. In the second study, cartilage chondrocytes were harvested from the low-weight-bearing area of six-month-old porcine knee joints and cultured. A month later, a cartilage lesion was created on the facet of the femoral trochlea and was repaired with use of the autologous chondrocyte transplantation technique (n = 10). Three months later, to estimate cartilage E, the repair tissue, the adjacent cartilage, and the sham-operated contralateral joint cartilage (control) were analyzed in situ with an arthroscopic indentation instrument. Subsequently, the same sites were imaged with ultrasound. Results: All visually degenerated bovine samples (mean Mankin score = 4) and five visually normal samples (Mankin score = 1) showed reduced E