Abstract
INTRODUCTION AND IMPORTANCE: Floating knee injury is a rare injury that involves a simultaneous fracture of the femur and tibia. It is more common among young men and is generally caused by high-speed blows. Down syndrome is a chromosomal disorder associated with various musculoskeletal conditions. Children with Down syndrome have generalized ligamentous laxity, joint hypermobility, and hypotonia, leading to musculoskeletal conditions such as atlantoaxial instability, hip instability, and patellar instability. CASE PRESENTATION: A 10-year-old boy with Down syndrome was admitted to the emergency room due to a car accident. Radiographic examinations revealed a diaphyseal fracture of the right femur and a diaphyseal open fracture of the tibia compatible with floating knee injury Type-D, and a physeal fracture of the distal femur (Salter-Harris type 2) and a metaphyseal fracture of the proximal tibia compatible with floating knee injury Type-C. The patient underwent preoperative investigations, including a neck radiograph, cardiology evaluation, pulmonary assessment, and hematologic check. The patient underwent surgery to fix all fractures. CLINICAL DISCUSSION: The necessary investigations were carried out to perform anesthesia and measures before, during, and after the operation. Down syndrome may help the patient recover, especially the ROM, due to various musculoskeletal conditions, such as generalized ligamentous laxity, joint hypermobility, and hypotonia. CONCLUSION: Children with Down syndrome may have various musculoskeletal conditions that can complicate the treatment of other injuries such as floating knee injury. Preoperative investigations should be performed to identify any potential complications.