Ultrasonography as an Early Evaluation Tool for Posttraumatic Osteoarthritis in Wistar Rats (Rattus norvegicus)

The aim of this study was to investigate the potential utility of ultrasound in identifying and evaluating early changes in hyaline cartilage during the development of posttraumatic osteoarthritis. To this end, the cartilages of the medial and lateral femoral condyles of the left and right hindlimbs of 42 male Wistar rats were evaluated by high-frequency ultrasound. The evaluations were carried out at 2 different times: prior to induction of osteoarthritis (US₀) and 30 d after surgical rupture of the cranial cruciate ligament (US₁) in the left stifle. The right stifle was considered the untreated control joint. Three regions of interest were measured in each cartilage, and the average value obtained was used for statistical comparison. Furthermore, ultrasound images of the left hindlimb were evaluated for the presence of changes in its structure. Cartilages of the left hindlimbs showed a significant increase in measurements obtained at US₁ when compared with US₀ measurements. On the other hand, the cartilages of the right hindlimbs, used as controla, did not show changes in thickness. Also, in US₁, 109 of 168 structural changes, such as loss of hypoechoic characteristic, irregularity in the superficial edge of the cartilage, loss of surface sharpness, and subchondral bone irregularity, were observed in the cartilages of the left medial femoral condyle and 103 of 168 in the lateral cartilages. Therefore, the present findings corroborate the potential utility of high-frequency ultrasound evaluation for detecting and quantifying initial lesions in hyaline cartilage resulting from osteoarthritis.