AN IMPROVED TECHNIQUE FOR MEASURING IN-VIVO INTERVERTEBRAL MOTION IN THE CANINE

Study Design. An experimental animal study using an established techni que for measuring in vivo motion in canines was designed to improve me asurement techniques and to eliminate the effects of the instrument mo unting technique on the tissue and subsequently on the motion being me asured. Objectives. The purpose of this study was to improve a techniq ue for measuring in vivo intervertebral motion in canines, so that the measuring technique did not affect the motion being measured. Summary of Background Data. Biplanar radiography has been used to measure in vivo intervertebral motion, but involves radiation exposure and expens ive equipment. Electromecahanical devices have been used more recently but have had significant effects on the motion over extended time per iods. Methods. Intervertebral motion was measured using an instrumente d spatial linkage in eight adult canines divided into two groups that differed regarding the method of ''mounting pin'' placement. Group I h ad open surgical placement of the pins and Group II had pins placed in to the spinous processes. After pin implantation, the instrumented spa tial linkage was attached and motion data were recorded during walking . This testing sequence was repeated 3 weeks later. Animals were kille d and intervertebral and facet motion were calculated from the experim ental data and compared statistically. Results. Facet motion decreased 1 to 3 weeks after pin implantation or animals of group I (3.4 +/- 0. 2 mm to 1.1 +/- 0.3 mm), whereas the facet excursion of animals in Gro up II showed no change (3.0 +/- 0.2 mm and 3.1 +/- 0.3 mm). Conclusion s. A new method of measuring in vivo intervertebral motion in canines has been developed and shown to have no significant affect on the segm ent mechanics.