Measurement of the mechanical condition of articular cartilage with an ultrasonic probe: quantitative evaluation using wavelet transformation

Abstract

Objective. To develop a new diagnostic technology to evaluate articular cartilage quantitatively by introducing an ultrasonic probe into the knee joint under arthroscopy and analyzing the A-mode echogram by means of wavelet transformation. Design. Quantitative evaluation using comparison of two indices on the wavelet map and macroscopic evaluation using the Outerbridge classification. As the quantitative indices on the wavelet map, the maximum magnitude and the echo duration which was defined as the length of time that included 95% of echo signal were selected. Background. Quantitative evaluation of articular cartilage in situ is required for new tissue-engineered cartilage but an evaluation system that fully meets this requirement has yet to be established for clinical use. Methods. Human articular cartilage specimens were analyzed using an ultrasonic probe after macroscopic evaluation and the cartilage characteristics on the echo duration–maximum magnitude graph were examined. Results. There were significant differences between grade 1 and 3, and grade 2 and 3 in the echo duration and maximum magnitude. The cartilage specimens had a L-shaped distribution in echo duration–maximum magnitude graph. Conclusions. The present study is the new quantitative evaluation system of the articular cartilage in situ and a clinical trial under arthroscopy is presently underway. The ultrasonic measurement is highly reproducible, so we can expect this system to be suitable for in situ reliable examination under arthroscopy. Relevance Precise evaluation of articular cartilage is of particular importance for longitudinal clinical trials for determination of best surgical option or effect of new chondroprotective drugs in arthritic disease and rheumatoid arthritis.