Error in the estimation of periosteal and endosteal contours from micro-CT scans for nonadult tibiae and humeri.

OBJECTIVES

This article summarized errors obtained by diverse techniques used for the derivation of cross-sectional contours in nonadult humeri and tibiae.

MATERIALS AND METHODS

We analyzed cross-sectional contours in a total sample of 62 humeral and 75 tibial diaphyses in the age between birth and 12 years divided into three age groups. Long bone 35% (humeri) and midshaft (tibiae) cross-sections were taken on micro-CT images and analyzed by EPJMacro in FIJI. Properties were extracted from contours derived by manual, automatic, spline, and ellipse techniques. Agreement between techniques was assessed using manually extracted properties such as the true value using percent prediction error (%PE), reduced major axis regression, and ±95% limits of agreement.

RESULTS

The lowest measurement errors were obtained for total areas, moderate errors for cortical areas and section moduli, and the highest errors for medullary areas for both bones. Derivation of humeral nonadult cross-sectional properties is less sensitive to the technique used for derivation of periosteal and endosteal contours, reaching mean %PEs below 5%. In contrast, tibial nonadult cross-sectional properties are more sensitive to the technique used and exceed 5% for some combinations.

DISCUSSION

Automatic techniques provide reasonably high agreement with manually extracted contours for nonadult humeri but low agreement for tibiae. Semiautomatic approaches-spline and ellipse techniques-may reduce the error for all studied properties in tibiae, especially when combined with manually traced periosteal contours. The positive effect of the semiautomatic technique on measurement error is low for humeri.