A non-invasive technique for the accurate measurement of leg length in animals

A novel, non-invasive technique for accurate measurements in animals (Kyniklometry) is presented. Kyniklometry (derived from greek ŏ kúvikloz the rabbit) determines the distance between soft tissue landmarks in conscious rabbits, in particular the rear lower leg. Each measurement consists of six subsequent and independent estimations of this distance, with a technical error of 79 microns (study I), respectively 83 microns (study II). The angle of the relaxed sitting animal's knee is approximately 45 infinity, and remains individually almost constant during subsequent measurements. The precision of the device was compared with X-ray stereophotogrammetry (technical error 30 microns). Five female New Zealand White rabbits were measured for 13 consecutive days at 24-hour-intervals both by kyniklometry and X-ray stereophotogrammetry (study I). The mean increment of 5 kyniklometric series of ten (3rd to 13th day) 24-hour-increments was 0.988 mm, the mean 24-hour-variance was 0.244 mm2. Sixty point five percent of this variance could be explained by parallel right/left leg soft tissue variation. Only 5% of the variance was explicable by the technical error. The 24-hour-correlation between kyniklometry and X-ray stereophotogrammetry was significant with r = 0.889 and p less than 0.001. Kyniklometric measurements were also performed in 5 female rabbits for 56 days at 24-hour-intervals (study II). We found spontaneous periodicity once every 8 to 14 days. There was a diurnal variation of rear lower leg increment with maxima in the early morning hours.