Subchondral bone defects around the knee joint are uncommon in skeletally immature patients. These lesions require comprehensive management, especially if related to periarticular bacterial infections. While pediatric osteomyelitis typically affects the metaphysis of long bones, the epiphysis is also a potential site for pyogenic osteomyelitis. Long-term sequelae may include growth plate injury and articular cartilage degradation. Primary epiphyseal subacute osteomyelitis is an extremely rare condition, mainly affecting neonates or young infants, as the cartilage of the growth plate generally acts as a barrier for pathogens. Radiographically, the lesions may appear radiolucent or lytic and often demonstrate a substantial perilesional bone marrow edema in MRI studies, but do not primarily contact the articular surface. However, if diagnosis and treatment of epiphyseal infections are delayed or missed, abscess formation may spread into the knee joint and progress to septic arthritis. Approaching a distal femoral epiphyseal lesion or subsequent bone defect surgically may be limited anatomically by both the subchondral plate and articular cartilage on the distal side and the growth plate proximally. Of the few reported cases of epiphyseal osteomyelitis, most underwent non-operative treatment including antibiotic coverage, or (staged) aggressive surgical care involving open curettage, irrigation and bone grafting. We report a novel combination of arthroscopic techniques, namely "ossoscopy", bone grafting and antibiotics, to approach a large lateral femoral epiphyseal lesion with knee involvement. In this case report, we present a 5-year old male patient with subacute posttraumatic knee pain and a significant bone defect of the lateral femoral epiphysis related to pyogenic osteomyelitis. The knee joint and periarticular bone lesion were both debrided and irrigated based on arthroscopic and ossoscopic techniques.The osseous lesion was filled with bone graft. The single-stage procedure proved to be a viable treatment to restore both the large subchondral bone defect and full knee function. Over a course of two years, no recurrent symptoms, infection or growth disturbances were observed in the individual.
Keywords: epiphyseal osteomyelitis; pediatric knee; repetitive trauma; septic arthritis; subchondral defect.