Abstract
Aims: Clinical methods do not provide direct quantitative information about cartilage functional properties. We have developed a novel handheld ultrasound indentation instrument for the diagnosis of articular cartilage degeneration. This study investigates the feasibility and reproducibility of the instrument to evaluate cartilage properties in situ. Methods: Osteochondral blocks (n=18) were prepared from lateral patellar groove (LPG), medial condyle (FMC) and medial tibial (MTP) of bovine knee. In ultrasound indentation, cartilage is indented with an ultrasound transducer. For the determination of cartilage dynamic modulus, tissue thickness and deformation are calculated using ultrasound and stress is measured with strain gauges. High-resolution material tester was used for reference mechanical tests. Cartilage glycosaminoglycan (GAG) content was determined using digital densitometry. Results: Cartilage dynamic modulus was efþciently detected with the novel instrument (r=0.913 with reference values). Dynamic modulus was signiþcantly (p< 0.05) higher at LPG (10.14±3.11 MPa) than at FMC (4.63±1.32 MPa) or MTP (2.92±1.38 MPa). Ultrasound reßection coeff. from the articular surface was signiþcantly smaller at MTP (2.04±0.73%) than at FMC (4.22±0.88%) or LPG(4.43±0.83%). Reproducibility (standardized coeff. of variation) was 3.0%, 5.2% and 1.7% for thickness, dynamic modulus and ultrasound reßection coeff. Cartilage GAG content correlated positively with dynamic modulus (r=0.678) but it was not related with the ultrasound reßection coeff. (r=0.294, p=0.24). Conclusions: Manual measurements were reproducible and the instrument can be used in situ to detect topographical variation of cartilage mechano-acoustic properties. This study establishes a step towards clinical arthroscopic use.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
