Columbus, OH - January 2016
Magnetic resonance imaging (MRI) is increasingly used to evaluate patellofemoral disorders in the knee, and as a result, more exact and reliable measurements of the patellofemoral joint are possible. The morphology of the joint has now been standardized for adults, leading to a better understanding of the disorders. Data has been lacking, though, in the pediatric population.
Recent research from Nationwide Children’s Hospital published in Pediatric Radiology has changed that. Doctors have found that the same MRI measurement techniques used in adults can be applied to children, and they have used those techniques to describe standard morphology by age and sex for the pediatric patellofemoral joint.
“We frequently encounter patellar instability in the pediatric population,” says Kevin E. Klingele, MD, chief of Orthopaedics at Nationwide Children’s and senior author of the study. “We think that with early identification of normal and abnormal patellofemoral anatomy, patient outcomes can be improved.”
Researchers examined 144 normal or near normal MRIs in 131 pediatric patients who were 1 to 16 years old (the upper age limit was 14 for females because of anticipated physeal closure). Six measurements were made using the MRIs: lateral trochlear inclination, trochlear facet asymmetry, trochlear depth, tibial tuberosity-trochlear groove distance, sulcus angle and patellar height ratio. Each measurement was made by two different data recorders to assess interobserver reliability, and 30 randomly selected measurements were repeated by the same data recorder to assess intraobserver reliability.
The researchers found high reliability and reproducibility for all six measurements. Trochlear depth and patellar height ratio showed significant differences in sex after adjusting for age. But after adjusting for sex, all measurements except lateral trochlear inclination showed statistically significant differences in age. Those measurements suggest that morphology should not be compared across all ages.
Tables of the normative values by age and by sex were published as part of the article in Pediatric Radiology. Establishing normative pediatric data may now allow doctors to consider an age-based approach to patellofemoral evaluation, according to Dr. Klingele.
“We hope this will be a foundation for future studies regarding early morphological changes associated with patellar instability and the effect of early intervention on these knees in children,” he says.
Mundy A, Ravindra A, Yang J, Adler BH, Klingele KE. Standardization of patellofemoral morphology in the pediatric knee. Pediatric Radiology. 2015 Sep 17. [Epub ahead of print]