Head and pelvic vertical displacement in dogs with induced swinging limb lameness: an experimental study

Swinging limb lameness is defined as a motion disturbance ascribed to a limb in swing phase. Little is known about its biomechanics in dogs, particularly about the body motions that accompany it, such as vertical head and pelvic motion asymmetry. The aim of this study was to describe the changes in vertical head and pelvic motion asymmetry in dogs with induced swinging limb motion disturbance, mimicking a swinging limb lameness. Fore- and hind-limb lameness was induced in ten sound dogs by placing a weight (200 g) proximal to the carpus or tarsus, respectively. Marker-based motion capture by eight infrared light emitting video cameras recorded the dogs when trotting on a treadmill. Body symmetry parameters were calculated, including differences between the two highest positions of the head (HDmax) and pelvis (PDmax) and between the two lowest positions of the head (HDmin) and pelvis (PDmin), with a value of zero indicating perfect symmetry.

Induction of swinging forelimb lameness showed significant changes in HDmax (median and range: sound 1.3 mm [- 4.7 to 3.1], in the left side - 28.5 mm [- 61.2 to - 17.9] and in the right side 20.1 mm [- 4.4 to 47.5]) and, induction of swinging hind limb lameness showed significant changes in PDmax (sound 2.7 mm [- 7.4 to 7.2], in the left side - 10.9 mm [- 22.4 to 0.5] and in the right side 8.6 mm [- 3 to 30]), as well as an increased hip movement asymmetry (sound 1.6 mm [- 8.6 to 19.9], in the left side - 18.1 mm [- 36.7 to 5.4] and in the right side 15 mm [- 20.7 to 32.1]) (P < 0.05).

Induced swinging fore- and hind limb lameness resulted in significant increased asymmetry of the maximal vertical displacement movement of the head and pelvis, due to decreased lifting of the head in forelimb lameness and of the pelvis in hind limb lameness. The results suggest that asymmetry of the maximal vertical displacement of the head and pelvis (i.e. lifting) is a key lameness sign to evaluate during examination of swinging limb lameness.