Humeroradioulnar Synostosis in a Patient with Underlying Congenital Scoliosis: A Case Report.

Introduction: Synostoses, or fusions, of the bones of the elbow are rare orthopedic occurrences that result from abnormal segmentation of the humerus, radius, and/or ulna during fetal development. The upper extremity begins as a single cartilage anlage in utero that segments into a distinct humerus, radius, and ulna and when disrupted, synostoses of the elbow occur. The most uncommon synostosis reported is the humeroradioulnar synostosis, in which all three bones of the elbow are fused. These synostoses often occur in conjunction with other orthopedic anomalies, as well as defects of other body systems due to their simultaneous development in utero. There are only six previous reports of humeroradioulnar synostoses. These reports describe additional concurrent orthopedic anomalies; however, anomalies of the ipsilateral shoulder or wrist, or scoliosis of any kind have not been reported. This report adds to the limited body of literature surrounding this rare orthopedic anomaly and presents additional skeletal manifestations not previously reported. Case Report: This patient is a 17-year-old male with a history of congenital scoliosis previously treated with Mehta casting, and no other known medical diagnoses. He presented to our orthopedic clinic with concerns about his worsening spinal deformity and moderate back pain. On imaging and clinical exam, he was found to severe thoracic and thoracolumbar curves, as well as a fixed deformity of the right elbow, due to a humeroradioulnar synostosis. He was also found to have deformities and limited motion of the ipsilateral shoulder, wrist and hand. The patient's scoliosis was treated with posterior spinal fusion after a course of halo traction, and he has decided to forgo any further evaluation or treatment for his right humeroradioulnar synostosis. The patient has been able to maintain a high level of function, participate in daily activities and even cook as a hobby. Conclusion: Humeroradioulnar synostosis is an exceedingly rare orthopedic condition that results from abnormal segmentation of the bones of the elbow during fetal development. Only six reports of this anomaly were found in our literature review. This report is of a 17-year-old male with a humeroradioulnar synostosis and is the first to describe this anomaly in a patient with defects of the ipsilateral shoulder and wrist with underlying congenital scoliosis. He has been able to maintain a high level of function, enjoy hobbies, such as cooking, and go to school, and is thus being treated conservatively with observation for this issue.