The next step
Next, we had to determine what it is about this vertical motion that is characteristic of lameness. Study of the hundreds
of motion signals collected over the years and consultation with engineers at the University of Missouri suggested that this
was a fault detection problem, or, more specifically to engineers, a vibrational analysis for fault detection. When a horse
is sound, the pattern of the vertical movement of its torso (at a trot) is a simple, symmetrical pattern. When a horse is
lame, the vertical movement of its torso becomes more complex and asymmetrical with multiple possible patterns. This complexity
and asymmetry of movement could be quantified.
In the year 2000, this approach to equine lameness evaluation was not entirely new, but it was impractical. Completing evaluations
of horses trotting on treadmills, marked with reflective markers and filmed with high-speed cameras, was tedious and difficult
work. No one was going to take the time and energy necessary using this method to evaluate a single horse. So, what good was
it for a practitioner, where the ultimate need resides? Fault analysis of the vertical motion of the torso to detect lameness
in horses was a curiosity, of interest at bioengineering or equine locomotion conferences but not to those on the front lines
of equine lameness — equine practitioners.
However, further study suggested that the different patterns of vertical torso motion seen with various forms of lameness
might mean something. In other words, there was untapped relevant information in the pattern of vertical torso motion. Different
lameness foci resulted in different vertical torso movement patterns. Lameness with peak pain during impact or the first part
of the stance phase of the stride, when the horse is coming down on the limb, may result in a vertical torso movement pattern
different from lameness with peak pain during pushoff or the second part of the stance phase of the stride, when the horse
is thrusting itself upward and forward by extending the limb. Also, compensatory patterns of head movement in hindlimb lameness
and of pelvic movement in forelimb lameness contained additional information helpful to isolating lameness in horses.
The tool begins to take shape
Since 2000, the University of Missouri, in collaboration with engineers in Japan at the Hiroshima Institute of Technology,
has been concentrating on developing this concept into a tool equine practitioners can use. The core belief was that this
approach could be adapted to the field by using body-mounted inertial sensors and wireless transmission. First attempts were
crude and impractical, employing large sensors with wires running to cell-phone-like devices strapped to a horse's back. Besides
the incompatibility of horses and wires, the range was too short to be practical. Errors in translating the inertial sensor
signals into forms compatible for the fault detection approach were too large. Transmission interference was significant.
Much more work was needed.
At last, a practical tool
Our quest to provide a clinically useful tool is now complete. Equine veterinarians and engineers at the University of Missouri
have reached the point where they feel that computer-assisted lameness detection is a real possibility for practicing equine
veterinarians. Years of development and validations have resulted in a body-mounted inertial sensor system specifically designed
as a diagnostic aid to practicing equine veterinarians.
This tool involves noninvasively instrumenting the horse with three small (28-g) inertial sensors—one on the head, one on
the pelvis and one on the right forelimb—in a process that takes about two minutes. The horse is then trotted in hand or ridden
while movement data are collected. Movement data are transmitted at 200 Hz in real time to a hand-held computer at ranges
up to 150 meters (Figure 1). The data are then analyzed using the aforementioned fault detection approach. The veterinarian
is given information on lameness severity, single or multiple limb involvement, timing of lameness (impact or pushoff), and
compensatory movement patterns common with equine lameness, as well as on the reliability of the data collected (Figure 2).
Presently, 18 of these body-mounted inertial sensor systems are out in the field in the United States, Europe and Canada,
being tested and now used clinically by practicing equine veterinarians to evaluate lameness (see Table 1). Many of the suggestions
for improvement from these early adopters have been incorporated into what is now called the Lameness Locator™. Current users range from solo ambulatory practitioners evaluating a few lameness cases a week to large referral hospitals
with a lameness-predominant caseload and institutional veterinary teaching hospitals. Current users of the Lameness Locator
find that it is most helpful under the following circumstances:
1. Evaluating horses with mild lameness
2. Evaluating horses with apparent multiple limb lameness
3. Evaluating horses with apparent compensatory lameness
4. Quantifying the effectiveness of peripheral nerve and joint blocks
5. Confirming the incidental nature of equivocal imaging abnormalities
6. Developing a further diagnostic approach based on type of the lameness (impact, pushoff)
7. Documenting musculoskeletal soundness in cases of poor performance
8. Monitoring convalescence or improvement after treatment.
As with any other diagnostic test or piece of medical equipment, there is a slight learning curve for most effectively using
the Lameness Locator; the system will not suddenly turn a novice into an expert lameness evaluator. There is no substitute
for dedicated experience and for performing a thorough physical and limb examination. Concentrating on the computer without
looking at the horse is a sure way to miss something or disappoint the client. The inventors of the Lameness Locator stress
that it is a valuable aid for practicing equine veterinarians, not a substitute. Most will find it easy to incorporate into
their normal lameness evaluations. The Lameness Locator is a medical device and will only be made available to equine veterinarians.
Editor's note: The Lameness Locator is licensed by the University of Missouri to Equinosis LLC, a faculty-startup company
launched in 2008 with the mission to assist and equip equine practitioners by developing wireless sensor solutions to collect
biological data useful for the diagnosis of equine disease. Equinosis LLC is an angel-investor and Missouri Innovation Center-backed
company with headquarters in Columbia (Missouri Life Sciences Incubator at Monsanto Place) and St. Louis (The Incubation Factory),
Mo., with support from the National Science Foundation's Small Business Technology Transfer Research (STTR) program. The first
commercial version of the Lameness Locator will be on display at the 2009 American Association of Equine Practitioners meeting
in December in Las Vegas, Nev. Further information can be found at
Dr. Kevin G. Keegan is an associate professor, Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri,