BACKGROUND

The between-observer reliability of repeated anatomic assessments in pediatric orthopedics relies on the precise definition of bony landmarks for measuring angles, indexes, and lengths of joints, limbs, and spine. We have analyzed intra- and interobserver reliability with a new digital measurement system (TraumaCad Wizard™).

METHODS

Five pediatric orthopedic surgeons measured 50 digital radiographs on three separate days using the TraumaCad system. There were 10 anterior-posterior (AP) pelvic views from developmental dysplasia of the hip (DDH) patients, 10 AP pelvic views from cerebral palsy (CP) patients, 10 AP standing view of the lower limb radiographs from leg length discrepancy (LLD) patients, and 10 AP and 10 lateral spine X-rays from scoliosis patients. All standing view of the lower limb radiographs were calibrated by the software to allow for accurate length measurements, using as reference a 1-inch metal ball placed at the level of the bone. Each observer performed 540 measurements (totaling 2,700). We estimated intra- and interobserver standard deviations for measurements in all categories by specialists and nonspecialists. The intraclass correlation coefficient (ICC) summarized the overall accuracy and precision of the measurement process relative to subject variation. We examined whether the relative accuracy of a measurement is adversely affected by the number of bony landmarks required for making the measurement.

RESULTS

The overall ICC was >0.74 for 13 out of 18 measurements. Accuracy of the acetabular index for DDH was greater than for CP and relatively low for the center-edge angle in CP. Accuracy for bone length was better than for joint angulations in LLD and for the Cobb angle in AP views compared to lateral views for scoliosis. There were no clinically important biases, and most of the differences between specialists and nonspecialists were nonsignificant. The correlation between the results according to the number of bony landmarks that needed to be identified was also nonsignificant.

CONCLUSIONS

Digital measurements with the TraumaCad system are reliable in terms of intra- and interobserver variability, making it a useful method for the analysis of pathology on radiographs in pediatric orthopedics.