Experimental osteoarthritic articular cartilage: in vitro visualization of lesions and three-dimensional surface reconstruction using 50 MHz ultrasound microscope

This study was performed to assess the possibility to detect early osteoarthritic changes with ultrasound. A backscatter ultrasound microscope operating at 50 MHz (30 microns axial resolution) was used to image knee joints cartilage of rats in vitro. Acquisition of backscattered radio frequency signals was performed at a sampling rate of 400 MHz during the three dimensional (3D) scanning of the cartilage. Control knees and knees which have been injected with mono-iodo-acetate (MIA) were included in this study (MIA causes rapid cartilage degeneration). Patellas and tibial plateaux were obtained after sacrifice and dissection of the knee joints. As multiplanar parallel scans were performed to provide 3D information, the 3D cartilage surface (CS) could be reconstructed and displayed. The articular cartilage thickness could be measured accurately. It varies in different parts of the knee joint and ranges between 250 microns and 400 microns. We show images of cartilage lesions occurring at early stage of osteoarthritis (hypertrophic repair). Disruptions and irregularities of CS and cartilage bone interface caused by an advanced stage of the disease and corresponding to fibrillations and ulcerations are also visualized on both B-scans and 3D images. This study suggests that with further technologic improvements, intra-articular. Ultrasonography of cartilage may provide a valuable method for early defection of osteoarthritis