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Pediatric Imaging

E3009. Fun With the Physis: A Review of Growth Patterns, Important Pathology, and How It Changes Management

Allen H,  Nguyen J. University of Wisconsin, Madison, Madison, WI

Address correspondence to H. Allen (haileynallen@gmail.com)

Background Information: Imaging the skeleton of pediatric patients provides an excellent demonstration of how children are not simply small adults. Indeed, the musculoskeletal system is perhaps the best opportunity for the radiologist to observe the elegant process of human growth and development. The radiologic evaluation of the pediatric skeleton requires an understanding of the process of long bone growth, its wide range of normal variation, and the reasons that similar mechanisms result in different patterns of injury between skeletally mature and immature patients. A radiologist familiar with these principles knows what to look for on studies ordered on pediatric patients, and knows what the ordering provider wants to learn from the radiology report.

Educational Goals/Teaching Points: The goals of this exhibit are to review the relevant musculoskeletal embryology anatomy and normal development patterns of long bones and discuss the pathophysiology of common and a few uncommon but important congenital disorders of the skeleton and how they result in the imaging findings the radiologist will encounter. We will illustrate how traumatic injuries in the pediatric population differ from those in adults as a result of having physes in varying states of maturation and summarize how the unique injury patterns in skeletally immature patients alter their clinical management, when the effects of healing on growing bones and the preservation of future growth must be considered.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: First, we will discuss long bone embryology, anatomy, and maturation with a discussion of endochondral bone formation and the physis and centers of ossification. Second, we will review long bone growth patterns including unequal contribution to growth by different physes and the general timeline of physeal closures. Third, will illustrate abnormalities of long bone development including important normal variants, growth arrest and resumption lines, premature physeal closure, and conditions such as achondroplasia, clinodactyly, rickets, and multiple epiphyseal dysplasia. Fourth, we will discuss patterns of injury in the skeletally immature patient (Salter-Harris classification, ankle fractures [Tillaux and triplane], pivot shift injuries, slipped capital femoral epiphysis, and pediatric overuse injuries). Lastly, we will cover clinical considerations in the treatment of growing bones including the role of growth in achieving anatomic alignment of fractures, principles of utilizing hardware around open and maturing physes, and potential growth complications resulting from inappropriate treatment.

Conclusion: The slow progression from open physis to closed results in unique patterns of injury and a remarkable range of variation among normal individuals. A deeper understanding of long bone development can improve the radiologist’s ability to interpret images of the work-in-progress that is the pediatric skeleton.