Detection of Posttraumatic Cartilage Lesions using Magnetic Resonance Imaging (MRI): An experimental Study on Canines

Abstract

Purpose: The investigation of cartilage lesions in knee joints after knock injuries with Magnetic Resonance Imaging (MRI) over a time period of six months. Materials and Methods: A controlled force form a drop-tower was applied to one knee of 12 normal adult beagle dogs to produce a subchondral bone bruise and soft tissue compression without visible bone fracture. MR images of both knees were acquired at a magnetic field strength of 1.5 T immediately after this defined knock-trauma and again after six months. The images were based on sagittal T1-weighted spin-echo sequence, a T2-weighted turbo-spin-echo sequence with spectral fat-suppression, and a fat suppressed 3D spoiled gradient echo sequence (FLASH®, SPGR). The traumatized joints underwent an arthroscopy immediately after the second MR examination and biopsies of the cartilage were performed. The biopsies were scored histologically (Mankin score of degenerative cartilage lesions). Results: Six months after trauma, ten out of the twelve canines had circumscribed cartilage lesions in the traumatized area of the affected knee joint and nearly all dogs had joint effusions in the affected knee joints. Furthermore, the knees with the most extending bone marrow edema developed high-grad cartilage lesions. All control scans and cartilage biopsies of the contralateral knee joints showed normal findings. Conclusion: Joint trauma causes focal cartilage defects. The described animal model supports the hypothesis that subchondral traumatic lesions such as bone bruises are an important risk factor for early development of osteoarthritis in (knee) joints. Within a few months, severe osteoarthritis could be induced by subchondral bone bruises. Potential etiogenic mechanisms are the damage of subchondral nutrition of hyaline cartilage or changes in the biochemical composition or biomechanic properties of the cartilage.