The Integrity of Cartilage Hinge in Song 2/3 Lateral Humeral Condylar Fractures in Children: A Retrospective Radiological Study in Two Centers.

Objective: For pediatric lateral condylar fractures (LCFs) of the humerus, it is often hard to determine the stability of the fracture based on the Song classification, especially for those categorized as Song stages 2 and 3. This study aims to define the characteristics of cartilage injury and assess the stability of LCFs classified as Song stages 2 and 3 on post-traumatic magnetic resonance imaging (MRI).

Methods: This was a retrospective study based on imaging data, conducted with a short follow-up period. From January 2016 to May 2019, data of all patients with Song 2 and Song 3 LCFs treated at two institutions were collected. Based on the inclusion criteria, a total of 62 patients with Song stage 2/3 LCF were included. All radiographs were selected for observation and classification for comparison by two observers, both experienced pediatric orthopedic surgeons. MRIs scans for comparison were analyzed in three consecutive coronal sections and cross-sections. Patients were treated conservatively with casting or surgically with closed reduction and percutaneous pinning (CRPP).

Results: Altogether 62 cases between 1.5 to 9 years old were included. Reliability analysis revealed poor, moderate, or good agreement between the two observers (range, 0.149-0.633). Both observers showed moderate or good consistency (range, 0.413-0.611). Among the 62 patients diagnosed with Song stages 2 and 3 fractures on initial radiographs, only two patients (3%) had complete fractures with complete disruption of the cartilage hinge as seen on MRI. The hinge was generally located in the posterior-inferior region of the distal humeral cartilage as indicated on MRI. There was no significant difference between Song stages 2 and 3 with regard to ratio of hinge to total values in any cross-sections, nor was there any significant difference in the completeness of the coronal sections (P > 0.05). Of the 62 patients treated, 50 were managed conservatively with casting and 12 underwent CRPP. Forty-nine of the remaining 60 patients (97%) with incomplete fractures were managed conservatively, while the remaining 11 patients were managed with CRPP. All patients with incomplete fractures showed bone healing and no evidence of lateral condyle displacement on follow-up radiographs.

Conclusions: The Song stage 2 or 3 classification is not entirely accurate and is inadequate at guiding treatment outcomes. The cartilage hinge was most likely located posteroinferiorly within the distal humeral epiphysis. According to our findings, conservative treatment with an effective cast or splint may be sufficient for bone healing in case of incomplete cartilage fractures.