The morphology of the calcaneus is important for the rearfoot because it influences the static and dynamic aspects of walking.
Three characteristic angles are shown by a lateral radiograph of the foot: The Fowler-Philip (FPA), calcaneal pitch (CPA), and total calcaneal (TCA) angles.
Some authors define the TCA as the sum of the FPA and the CPA.
The authors sought to study these angles in healthy paediatric and adolescent populations to determine whether differences existed in these angles compared with those of an adult population.
A total of 141 feet were studied by the authors; lateral weightbearing radiographs of each foot were conducted following standard techniques.
The FPA values of 44 degrees to 69 degrees are considered normal, and one degree greater than 75 degrees is considered a pathologic abnormality.
The authors found that more than 90% of adolescents had FPA values within the reference range. For individuals whose values were outside the reference FPA range, 1.5% had FPA values less than 45 degrees and 8% had values greater than 70 degrees.
A reference CPA value is 15 degrees to 21 degrees, and it reflects the height of the medial longitudinal arch.
Only 26% of the patients tested had CPA values within the reference range; of the patients who had CPA values outside the reference range, 33% had angles less than 15 degrees (flat feet) and 10% had angles greater than 25 degrees (cavus feet).
The TCA is considered normal at 64 degrees to 89 degrees, and is abnormal at values greater than 89 degrees; 97% of the adolescents had normal TCA values and only 3% had angles greater than 89 degrees.
With more variation found in the CPA values, and the mean values of the FPA, CPA and TCA being similar in both the paediatric and adult populations, the authors concluded that the TCA could be a useful radiographic clinical reference value because it does not change with age and it incorporates the FPA and CPA measurements.
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