CT for Patellar Evaluation in Pediatric Patients: A Step-By-Step Approach for the Radiologist

Patellofemoral instability is a clinical syndrome of high prevalence in young patients. It is multifactorial in origin due to the complexity of the knee joint. Adequate radiologic and clinical evaluation is necessary to determine best treatment to prevent joint overload, cartilage deterioration, and subsequent osteoarthritis, as these may lead to early disability in young populations. Computed tomography improves risk factor analysis, providing objective information on bone parameters and relevant data to aid the clinician in determining the best possible treatment. The need for CT compels for the development of optimized tomographic acquisition protocols with minimal radiation dosages that consider the ALARA principle for the diagnosis of patellofemoral instability in the pediatric population. This article focuses on the most practical and useful angles and measurements associated with patellofemoral instability in the pediatric population to help with the surgical decision making. Using an 8-step approach, we establish an evaluation algorithm that considers measurements and parameters most used by the orthopedist to choose among treatment options. Finally, we propose a structured report model that encompasses these useful tomographic findings, facilitating image interpretation for residents and radiologists and easing interpretation for other specialists. By applying this fast and interactive reading method the reading time of these studies will be reduced with noticeable improvements in the concluded results and in the interobserver agreement.