Pediatric musculoskeletal ultrasound of the elbow: a pictorial review

The elbow is a complex joint consisting of three separate articulations: ulnotrochlear, radiocapitellar, and proximal radioulnar. Collectively, these allow movements including flexion, extension, supination, and pronation. The developing pediatric elbow can be challenging to assess due to the predominance of cartilaginous epiphyseal and apophyseal structures, which are not evident on radiographs. Although MRI provides a comprehensive assessment of elbow anatomy, it can also be technically challenging. In a supine position with the arm to the side, the off-center position of the elbow can lead to decreased image quality due to magnetic field inhomogeneity with low signal-to-noise ratio (SNR) and poor fat suppression. Positions that attempt to bring the elbow to the MR iso-center can be uncomfortable in children suffering from elbow pain, leading to motion artifact. Furthermore, many of the soft tissue pathologies in the elbow are dynamic in nature and are best assessed using dynamic maneuvers. Ultrasound (US) is an ideal imaging modality for both static and dynamic assessment of the pediatric elbow joint and its soft tissue stabilizers. Additionally, comparison with the US of the contralateral elbow can serve as an internal control in the assessment of skeletally immature patients. In this narrative review, we describe the ultrasound technique for evaluating the pediatric elbow, the normal sonographic anatomy, and the common pathologies that may be encountered in practice.