Risk factors for pathological fractures of simple bone cysts of the humerus in children: a retrospective cohort study

Background: Simple bone cysts (SBCs) are common osteolytic lesions in children, which often lead to pathological fractures of the non-weight-bearing bone (humerus) in patients. Cyst index is a classic index to evaluate the risk of pathological fracture, but the reliability of this index is reduced due to the deviation of cyst area in the frontal and lateral position and the subjectivity of the determination of cyst area. MRI can clearly show the cyst boundary, the appointment cycle is long, and children need to be examined under sedation, which cannot be judged by clinicians in time. Therefore, it is necessary to find a basic and simple imaging evaluation index in clinic. The purpose of this study is to retrospectively analyze the risk factors of pathological fracture of simple bone cyst of humerus in children. Methods: The medical records and plain films of patients with SBCs from January 2014 to December 2021 were retrospectively analyzed. Patients were divided into a fracture group (35 cases) and a non-fracture group (10 cases). The relationship between pathological fractures and the children's age, gender, and cyst index was analyzed. The presence of the pectoralis major and the link to the tendon insertion site of ectopectoralis and anconeus lateralis (TEAL) of the lesion were also examined. Perform binary logistic regression analysis. Results: Binary logistic regression analysis was performed on the age, gender, and cyst index, and whether the lesion was located in the TEAL. The results demonstrated that the TEAL was an independent risk factor for fractures [odds ratio (OR) =21.423, 95% confidence interval (CI): 2.409-190.539; P=0.006]. Conclusions: SBCs of humerus in children is often accompanied by pathological fracture. The lesion is located at TEAL, so we should be alert to the risk of pathological fracture.