Assessing Bone Age with Knee MRI

When treating pediatric knee conditions that require an MRI, obtaining an additional left-hand radiograph to assess bone age is unnecessary, according to study results presented in Scientific Poster P263, on display in Academy Hall.

The authors write that accurate bone age assessment is critical for managing many pediatric knee diseases and conditions. The purpose of their study was to determine if an accurate skeletal age could be assessed from knee MRIs alone, ruling out the need for a left-hand radiograph.

The researchers retrospectively reviewed 846 knee MRIs from pediatric patients (females = 413; males = 433) obtained for pain or trauma between 2007 and 2015. Patients with radiographic evidence of tumors, infections, skeletal dysplasia, or systemic processes affecting the physes were excluded. Between 20 and 25 MRIs were assessed for each age group and each sex. The researchers documented the chronologic age, sex, and presence or absence of radiographic features specific to the patella, tibia, fibula, and femur for each patient. 

After statistical analysis, the researchers determined that the patella, tibia, fibula, and femur undergo a consistent and reproducible sequence of skeletal maturation and ossification. For example, the patella provides the best age assessment in early childhood, while ossification of the tibial spines followed by ossification of the tibial tubercle are of particular importance between the ages of 6 and 12 years. MRI features of the fibula, particularly ossification of the styloid and closure of the physis, are more important for age assessment later in skeletal maturity. The researchers note that the femur was unique in that it is the last knee bone to ossify and its physis is the last to disappear.

The authors conclude that the predictable ossification and maturation pattern of the patella, tibia, fibula, and femur enable accurate bone age calculations to be determined from knee MRIs, making an additional left-hand radiograph unnecessary.                    

Authors of “Bone Age Assessment Utilizing Knee MRI” are Andrew Tennant Pennock, MD, and James Bomar.

Details of the authors’ disclosure as submitted to the Orthopaedic Disclosure Program can be found in the Final Program; the most current disclosure information may be accessed electronically at www.aaos.org/disclosure

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