Aspects of Magnetic Resonance in the surgical treatment of osteochondral lesions of the knee

AIM: To assess the magnetic resonance (MR) appearance of knee cartilage chondroplasty procedures and their evolution in order to evaluate the usefulness of the method in monitoring postoperative rehabilitation. MATERIALS AND METHODS: Sixty-two patients treated with knee chondroplasty for high-grade cartilage injuries (Noyes' stages II and III) were examined with MR. Forty patients were treated with abrasion chondroplasty, fifteen with osteochondral graft in the injury site and seven with the matrix-induced autologous chondrocyte transplant technique. All patients were operated on by the same orthopaedic team and examined with the same MR protocol. The MR follow-up was performed six months and one year after surgery in the patients treated with abrasion chondroplasty and osteochondral graft, and one week, three months and one year after surgery in the patients treated with cartilage transplant. In the patients treated with abrasion chondroplasty we assessed the fibrocartilage repair and the subchondral bone features, in the patients treated with osteochondral graft we examined the cartilage, the subchondral bone and the graft borders, while in the patients treated with cartilage transplant we evaluated the features and the evolution of the transplant and the subchondral bone. Arthrosynovitis was assessed in all patients. In seven patients a cartilage repair biopsy was performed in arthroscopy. RESULTS: In all the patients MR imaging proved useful in monitoring the chondroplasty. In the patients treated with abrasion chondroplasty the cartilage repair appeared as a hypointense non-homogeneous irregular strip of tissue that replaced the articular surface. The subchondral bone was sclerotic with some geodes. In the later examination the repair was unchanged. In the patients treated with osteochondral graft the articular cartilage was similar to the adjacent hyaline cartilage, although more non-homogeneous. The subchondral bone was sclerotic and in three cases oedematous. In four cases the graft extended beyond the articular border. In the cartilage transplant the matrix appeared as a hypointense stripe after a week due to hydration and it had thinned with signal reduction in the later follow-ups. In the cases with unfavourable clinical evolution the subchondral bone was oedematous and sclerotic in the later examinations. In the cases with unfavourable clinical evolution there was moderate arthrosynovitis, regardless of the chondroplasty technique performed. CONCLUSIONS: MR imaging is useful for monitoring the maturation and the integration of knee chondroplasty and can be proposed as a replacement of arthroscopy for the assessment of postoperative rehabilitation.