Introduction/Purpose: Lumbosacral angle measurements in flexion and extension positions have been published as a method for estimating lumbosacral range of motion in dogs. However, angle measurement and patient positioning methods have differed among published studies. Aims of this study were to compare lumbosacral angle measurements obtained using two previously published computed tomographic (CT) techniques, and to estimate variation in canine lumbosacral angle measurements within standardized extension and flexion positions.
Methods: A cross-sectional study was conducted using CT scans of the lumbosacral region that had been acquired for a previous prospective study. The study included 39 military working dogs, all purebred Labrador Retrievers. All scans were acquired using the same scanner at the Military Working Dog Hospital located at the Lackland Joint Base in San Antonio, Texas during the period of July 10, 2013 to July 17, 2013. All dogs were positioned by the same operators, a board certified veterinary radiologist and a licensed veterinary technician. For each dog, the first scan was acquired with maximal extension of the hind limbs and the second scan was acquired with maximal flexion. Imaging analysis software was used to create triplicate measures of each dog’s lumbosacral angle in extension and flexion using two techniques. For technique 1 the markers were placed cranial of the L7 vertebral body, caudal of the L7 vertebral body, and caudal of the S1 vertebral body and for technique 2, the marker was placed cranial of the L7 vertebral column, cranial of the S1 vertebral column, and caudal of the S1 vertebral column. We compared averages of lumbosacral angle measurements for technique 1 and technique 2 in each of flexion and extension positions using matched pairs tests and estimated the variation of lumbosacral angle measurements.
Results: The mean lumbosacral angle measurement using technique 1 in flexion was 1.23 degrees greater than the mean lumbosacral angle measurements in technique 2 in flexion and the difference between the two techniques was significant (p=0.005). The mean lumbosacral angle measurements using technique 1 in extension were 2.03 degrees greater than the mean lumbosacral angle measurements using technique 2 in extension, which was also statistically significant (p<0.001).
Discussion/Conclusions: Findings indicate that two published CT methods for quantifying lumbosacral angle yield different results. This should be taken into consideration for future studies quantifying lumbosacral range of motion using lumbosacral angle differences between standardized flexion and extension positions.