Posterior femoral condylar separation: Is it a particular type of osteochondritis dissecans in adolescents?
Authors: Semenov A. V. , Chmykhova A. M. , Isaev I. N. , Koroteev V. V. , Tarasov N. I. , Lozovaya Yu. I. , Vybornov D. Yu. 
Published: December 2022

Introduction. Dissecting osteochondritis (RO) is based on damage to the subchondral bone, leading to its detachment and sequestration separately or together with articular cartilage with the possible formation of a free bone-cartilage fragment. The disease occurs more often in adolescents, accompanied by an increased risk of early arthrosis of the knee joint. Chronic traumatization of the subchondral bone leads to insufficient blood supply to a certain area of the growth zone of the secondary point of ossification of the femoral epiphysis, to ischemia and subsequent necrosis of the subchondral bone, which, according to modern literature, is the leading cause of the formation of the lesion. The typical localization of the RO focus is the lateral part of the medial condyle of the femur along the supporting surface. The present clinical analysis presents cases of atypical localization of dissecting osteochondritis with clinical features, specific signs on MRI, as well as various tactical approaches to treatment.Material and methods. This clinical review presents 3 cases of sequestration of the posterior lateral condyle of the femur in adolescents. Despite the similarity of the clinical picture and the MRI data, the features of the foci of RO were found in all children, which determined the need for an individual approach to therapeutic tactics. All children required surgical treatment, which was performed in the Department of Traumatology and Orthopedics of the N.F. Filatov DGKB in different volumes in each case: from transchondral osteoperforations and fixation of an osteochondral fragment with a screw to debridement of a fragmented focus with removal of osteochondral fragments.Results. All 3 clinical cases are united by atypical localization of the focus in the posterior lateral condyles of the femurs, the clinical course of the disease in the form of a low-intensity long-term pain syndrome, as well as the results of MRI of the knee joint. Most researchers adhere to the classical multifactorial etiological theory of dissecting osteochondritis, according to which the main mechanism of the origin of the lesion is mechanical overload of the subchondral bone with subsequent disruption of blood supply in it at the border with the secondary point of ossification of the femoral epiphysis. However, there is also data in the literature on congenital ossification disorder in the cartilaginous part of the growth zone of the secondary ossification point as the morphological basis of dissecting osteochondritis. The presented clinical cases cast doubt on the generally accepted model of primary damage to the subchondral bone as the only possible cause of the formation of the focus of RO, since patients have, among other things, signs of impaired ossification of the secondary ossification point of the femoral condyle, in one of whom a violation of ossification of the secondary ossification center was also determined in the patella in the form of patella bipartita.Conclusion. Inspite of all similarities connecting these cases there is still lack of data to judge about separate type of the OCD because every separate type of disease usually have particular morphological basis. There is a need of partial biopsy of these lesions to confirm or refute our hypothesis of posterior condylar separation being separate type of OCD. However these cases undoubtedly require particular managementwith special attention to timing of appropriate diagnostic procedures and surgical management to perform in time prior to osteochondral fragment separation. In case of the absence of any complaintswith particular MRI appearance of fragmented bone in the lesion with impaired ossificationindividual treatment planneeds to be defined.