Effect of limb position on elbow congruity with CT evaluation

Abstract

Objective: To determine if computed tomographic (CT) measurement of radio-ulnar congruence (RUC) is affected by limb position.

Study design: Prospective study.

Animals: Labrador Retrievers (n=10).

Methods: Each dog had both elbows imaged in neutral, supination, and pronation positions using helical CT acquisition, at 1 mm increments, in a transverse plane. RUC was calculated using a previously reported method and a new technique using 3-D image processing and measurements determined by a coordinate system.

Results: The limits of agreement showed that comparing any pair of elbow positions yielded large discrepancies in measurements with the previously reported technique. Better agreement between pairs of elbow positions with reduced discrepancy was achieved using the 3-D technique. Variation in antebrachium positioning did yield a difference in congruence.

Conclusions: Limb position (supination, pronation) affects elbow congruity measurements using CT analysis. Use of 3-D image processing may allow for improved elbow congruity measurements compared with other 2-D measurement techniques.

Clinical relevance: Limb position must be controlled when performing CT evaluation of elbows for incongruity. 3-D imaging appears to be less affected by limb position than conventional 2-D analysis when assessing radioulnar incongruence.