[Comparison of different methods to quantify the volume of horse limbs]

Measuring the leg volume of horses is useful for diagnostic and treatment of different diseases in relation to swollen legs. In the present study different methods to quantify the limb volume are compared, the water displacement method, an optoelectronic 2-dimensional body scanner, the so-called perometer and calculation of volume by applying the disc model. As reference method the golden standard of human medicine - the water displacement method was used. We took volume measurements from different tall horses in a defined section of the forelegs between the coronary band and the carpal joint. All applied methods are easily reproducible. The optoelectronic method has a higher intra-class correlation coefficient (ICC) of 0.90 than the water displacement method (ICC = 0.84). Pairwise comparison delivers strong linear relationship with coefficients of correlation > or = 0.972 and comparing the absolute values delivers coefficients of concordance > or = 0.962. In comparison to the water displacement method, the volumes taken by the disc model using a measuring tape tend to underestimate the volume by approximately 8%. The volume taken by the perometer agrees well in the range of measuring accuracy (-0.6 +/- 4.4%), but tends to slightly overestimate the volume (0.6%). Due to the linear relationship, the different methods are easily interchangeable using a conversion factor. The only methods applicable in clinical practice are the disc model and the perometer. The water displacement method is strongly limited due to its lacke of acceptance by horses. In comparison with all the above-mentioned methods the results taken by the disc model are the least accurate. However, when viewed in comparison their reliability is in many applications satisfying. The best method to quantify the limb volume of a horse is the contactless optoelectronic measurement by the perometer. This is quite expensive, but it is found to be acceptable to horses and established results that are nearly one to one when compared to the golden standard. The examiner gets much more information (volume-time diagrams) due to different options and not only the pure result of volume.