Accuracy of computerized tomographic evaluation of canine radio-ulnar incongruence in vitro

OBJECTIVE: To evaluate the accuracy of linear measurements obtained from computer tomography (CT) images of staged radio-ulnar incongruence in a canine cadaver forelimb model. STUDY DESIGN: CT evaluation of induced progressive radio-ulnar incongruence in canine cadaveric forelimbs. SAMPLE POPULATION: Eight cadaveric canine left forelimbs. PROCEDURE: A type 2 external skeletal fixator (ESF) with linear motors was attached to the radius in 8 cadaveric left canine forelimbs. Contiguous incremental and helical CT images of the proximal radio-ulnar articulation were acquired in the transverse, sagittal and dorsal planes. The radius was shortened by 1, 2, and 4 mm increments and scanning protocols were repeated at each increment. Digital caliper and CT image analysis measured the progressive change in distance between 2 marking spheres and the epiphyseal bone surfaces of the radio-ulnar articulation. Statistical analysis of measurements from incremental and helical CT acquisitions, and direct and reformatted images were compared with inter-sphere distance using Pearson product moment correlation coefficients. RESULTS: The reformatted incremental acquisition series at the mid-coronoid in the oblique plane had the highest correlation coefficient (r-value) at 0.908. The mid-coronoid in the dorsal plane had the second highest r-value (0.856). The coronoid incisure in the sagittal plane had an r-value of 0.826. The reformatted incremental acquisition series at the coronoid incisure in the oblique plane had the lowest r-value, 0.592. CONCLUSION: Measurement of radioulnar incongruence may be best performed using reformatted incremental acquisition CT in the mid-coronoid region in an oblique plane. CLINICAL RELEVANCE: Use of the technique reported in this study may enable determination of the association, if any, between radioulnar incongruence and developmental diseases of the canine elbow.