OBJECTIVE To determine variance effects influencing ground reaction forces (GRFs) in a heterogeneous population of lame dogs during trotting.
ANIMALS 30 client-owned dogs with thoracic limb lameness and 31 dogs with pelvic limb lameness.
PROCEDURES GRFs, velocity, height at the dorsal aspect of the scapulae (ie, withers), and shoulder height were obtained. Each dog was trotted across a force platform at its preferred velocity. Variance effects for 12 velocity and associated relative velocity (V*) ranges were examined.
RESULTS Individual dog, velocity, V*, and limb significantly influenced GRFs. Withers height V* ranges were associated with small variance in GRFs, but all absolute and V* ranges were associated with significant effects for all 4 limbs and both types of lameness. Significant changes in lame limb GRFs and velocity in ipsilateral trials in dogs with thoracic limb and pelvic limb lameness were evident with trial repetition. Withers height V* range of 0.55 to 0.93 captured a large proportion of trials (> 90%) in dogs with thoracic limb or pelvic limb lameness, with limited effects on peak vertical force and vertical impulse.
CONCLUSIONS AND CLINICAL RELEVANCE Trial repetition caused alterations to GRFs and subject velocity that may have confounded assessment of lameness, which supported the concept that a priori selection of a velocity or V* range for force platform gait analysis should use a range that captures valid trials efficiently while minimizing GRF variance. These ranges typically would span the preferred velocity of subject dogs, such as withers height V* of 0.55 to 0.93.
Objective—To determine changes in the distal ends
of the third metacarpal and metatarsal bones (MCIII
and MTIII) of Thoroughbred racehorses that had sustained
a catastrophic condylar fracture during highspeed
Sample Population—Fractured and contralateral
MCIIIs and MTIIIs from 11 Thoroughbred racehorses
that sustained a displaced condylar fracture during
racing, both MCIIIs from 5 Thoroughbred racehorses
euthanatized because of a catastrophic injury other
than a condylar fracture, and both MCIIIs from 5 horses
of other breeds that had not been professionally
trained or raced.
Procedure—Macroscopic observations were made
of the distal ends of the bones before and after digestion
of the articular cartilage with NaOH.
Results—In all 11 racehorses with a displaced condylar
fracture, the fracture was associated with a
branching array of cracks in the condylar groove. In
this region, fracture margins were smooth, and there
was loss of subchondral bone. Comminution of the
dorsal cortex was also seen. Parasagittal linear wear
lines in the articular cartilage, erosions in the articular
cartilage of the condyles, loss of the underlying subchondral
bone, and cracking of condylar grooves were
all more severe in the Thoroughbred racehorses than
in the horses that had not been professionally trained
Conclusions and Clinical Relevance—Results suggest
that condylar fractures in horses are pathologic
fatigue or stress fractures that arise from a preexisting,
branching array of cracks in the condylar groove
of the distal end of MCIII or MTIII. (Am J Vet Res 2003;64:1110–1116)