Evaluation of ankle joint synovitis in diabetic neuroosteoarthropathy in relation to an inflammatory phase of chronic osteomyelitis

Diabetic neuroosteoarthropathy complicated by osteomyelitis is one of the severe conditions of the ankle joint in patients with diabetes. The role of the synovium in the pathogenesis of this disease remains poorly understood. Purpose To identify structural changes in the synovium of the Charcot ankle depending on the inflammatory phase of chronic osteomyelitis. Material and methods The synovium and osteochondral fragments of the ankle were studied in 33 patients. Paraffin sections stained according to the three-color Masson method, hematoxylin and eosin, and semi-thin sections stained with methylene blue and basic fuchsin were studied using an AxioScope. A1 microscope with an AxioCam digital camera (Carl Zeiss MicroImaging GmbH, Germany) and Zenblue software (Carl Zeiss MicroImaging GmbH, Germany). The phase of the inflammatory process of chronic osteomyelitis was assessed according to the HOES of Tiemann et al (2014) and synovitis according to Krenn et al (2006). Results Full-thickness articular cartilage defects, synovial pannus, foci of osteonecrosis in the subchondral zone, bone microsequesters, osteoclastic resorption of the subchondral bone plate, replacement of bone marrow structures with granulation tissue, the severity which depended on the inflammatory stage of chronic osteomyelitis, were recorded in the process of studying osteochondral fragments. In 82 % of patients, the inflammatory phase of chronic osteomyelitis was characterized as active and subacute. In all the cases, hyperplasia, hypervascularization and hyperemia of the synovium with the presence of bone and cartilage fragments were observed, as well as inflammatory infiltrate, synovial pannus invading the articular cartilage. The vessels featured a pronounced narrowing of the lumens or their complete closure. The severity of synovitis correlated positively with the inflammatory phase of chronic osteomyelitis; Spearman's correlation coefficient of 0.76 indicated high relationship. Conclusions In diabetic osteoarthropathy of the ankle joint complicated by chronic osteomyelitis, the irreversible structural changes revealed in the synovium contribute to the formation of synovial pannus and the progression of destruction of the articular cartilage and subchondral bone. The severity of synovitis positively correlates with the inflammatory phase of chronic osteomyelitis.