The severity of deformational plagiocephaly is frequently measured by cranial vault asymmetry (CVA). Cranial vault asymmetry is a simple linear proxy for the three-dimensional deformity. Different anthropometric landmarks have been suggested as the endpoints of the cross-cranial diagonals that determine CVA. One promising albeit counterintuitive set of digital landmarks is the frontozygomaticus and contralateral eurion. The validity of nondigital caliper measures associated with the diagonals defined by the frontozygomaticus and contralateral eurions has not been tested. In this study, the authors compare caliper measures against stereophotogrammetric measures that have been documented to correlate strongly with overall skull asymmetry.
Cranial vault asymmetry was assessed by direct anthropometry with 2 different measures on 36 patients. Frontozygomaticus and contralateral eurion (fz-eu) and 30 degrees off the anteroposterior diameter (30offAP). Three-dimensional photographs were obtained and also used to quantify CVA in these subjects; digital measures of fz-eu and an overall measure of plagiocephaly (Global) were calculated. Global and 30offAP obtained at 31 patient visits in 2011 were also included.
The measure best-correlated with overall Global asymmetry was digital fz-eu (R2 = 0.80). Caliper fz-eu was not strongly correlated with Global asymmetry (R2 = 0.27) or with digital fz-eu (R2 = 0.34). Differences between the digital and caliper fz-eu measures were 5 ± 4 mm (mean ± st. dev.). Differences between the caliper fz-eu and 30offAP measures were 6 ± 4 mm.
Digital fz-eu shows an excellent correlation to Global asymmetry. However, attempts to replicate this result in the clinical setting by measuring fz-eu with calipers were unsuccessful.