LIMB VOLUME ESTIMATES BASED ON LIMB ELLIPTICAL VS. CIRCULAR CROSS SECTION MODELS

Abstract

Limb volumes, as would be estimated bythe widely used right circular truncated conemodel (right circular frustum), were analyticallycompared to volume estimates that wouldbe obtained if limbs were represented by anelliptical cross section. A general expressionfor the ratio of circular to elliptical limbsegmental volumes was developed in terms ofthe ratio of minimum to maximum limb radialdimensions. Analytical results showed that ingeneral the elliptical representation resulted insmaller calculated limb volumes, with thedifference increasing as the ratio of minimumto maximum limb dimension became smaller.However, differences in estimated limb volumebetween circular and elliptic representationswere less than 5% if the minimum to maximumlimb dimensions at measured circumferencesites were greater than 0.64. It is concludedthat although limbs deviate from circularity,the added work of determining minimum andmaximum dimensions for each circumferencemeasured, as is needed to employ ellipticalmodels, is warranted only for extremedifferences in limb radial dimensions orpossibly for research purposes.