INNOVATIVE DIAGNOSTIC TECHNOLOGIES


lameness may be more apparent when the horse is walking, but this is only because when the horse is walking, the asymmetricmotion fallswithin the normal temporal resolution of the naked human eye. The lame- ness may be easier to see at the walk than the trot, but this does not mean that the lamenesswould be easier to measure at the walk than the trot. Also, almost always, the lameness, when compared to the canter and gallop gaits, is easier to see at the trot.11 This has usually been explained as a consequence of the rather easy task of identifying asymmetry in an otherwise very symmetri- cal expected movement. This is definitely true, but this is not the only reason. When a horse transitions from trot to canter or gallop, within the range of speeds com- patible for this transition, forces on the limbs decrease. Thus, it is logical to also assume that the lameness will be less perceived or felt by the horsewhen it breaks into the canterorgallop.11 Also, options for redistributing load to spare the painful limb that are available to the horse at the trot are not so available to the horse at the canter or gallop. At transition speeds, horses with lameness will prefer to canter, especially on the non- lame limb lead. Preference for cantering or galloping on a particular lead may be informative for establish- ing the existence of lameness as a clinical sign, but specificmotion parameters that are sensitive for detec- tion of lameness (like asymmetric vertical head and pelvic motion for the trot) have yet to be objectively identified for the canter or gallop. After gradually inducing pain on the bottom of the foot in horses, lame- ness was measured at a slow trot in a straight line before it was measured at either the canter or gallop. Detection of lameness at the trot in a straight line was more sensitive at picking up lameness than at the canter or gallop.11 This may not be applicable to pain in the limb that occurs only during the swing phase of the stride. However, attempts to create lameness iso- latedonly totheswing phaseof thestridehavenot been successful, and the existence of pure swinging limb lamenesswithout pain during theweight-bearing phase of the stride has not been objectively determined to exist.


Stabilizing the Lameness


Before the availability of BMIS, it was not recognized that lameness was frequently not displayed by the horse clearly (above thresholds) and consistently (with low variability) when first examined. Clinical impression over the years has shown this to be quite common. Using horses with natural or induced lame- ness, and in following horses in the clinic with known lameness conditions as part of routine assessment of improvement, one may frequently have the opportu- nity to evaluate horses with lameness multiple times onmultiple days. Horses with known lameness condi- tions, diagnosed by previous full lameness workups, often either do not show the strongest lameness in the previously identified limb, or the lameness is not of the previously identified amplitude. When using sim- ple, subjective evaluation, there is a tendency to either not notice this or just shrug it off. It is not difficult to


342 2022 / Vol. 68 / AAEP PROCEEDINGS


raise awareness to the mistakes that can be made in theevaluation of responsetoblocks if


lameness


changes spontaneously like this. However, lameness can be “stabilized” by simply


trotting the horse back and forth a few times or lung- ing (if the horse lunges) it in both directions for a few minutes. A standard method of lameness evaluation with BMIS starts off with trotting the horse in a straight line. Then, the horse is lunged and another straight-line trial is collected. If the straight-line lameness is not stable, that is, if the lameness is not in the same limb, at the approximate same amplitude, and at an acceptable consistency (standard deviations not too much higher than the average), one should keep collecting trials until they are consistent (time permitting), have an assistant or the owner exercise the horsemore (freeing oneself up to evaluate another patient), or accept the fate that the source of lameness may have to be found some other way (limb palpation, imaging, etc.). Sometimes, the complete limb and torso evaluation stabilizes the lameness, possibly due to limb manipulation. It is not efficient to block the horse to try to discover the foci of lameness if the lameness is not stabilized. It is usually awaste of time. Some would ask if this would not, in some cases,


warmthe horse out of the lameness,making it undisco- verable. This may occur, but if the horse warms out of the lameness in such a short time, with this limited amount of exercise, then it probably is not clinically important.Understanding and taking this into consid- eration will go a long way to ameliorate some of the headaches and mistakes of interpreting objective mea- surement to evaluate blocks in horseswith lameness. Figure 7 is an example of an unstable lameness.


This first trial (left) was collected immediately before the second (right). The lame limbs are consistent, but their amplitudes are not. If the horse had been blocked immediately after Trial 1, either in the left forelimb or right hindlimb, it would have appeared that the horse improved because of the block. The real improvement occurred spontaneously. Some horsesmeasure with high variability of lame-


ness, especially in the forelimbs, because they are not trotting consistently and their adrenaline level is high and pain is masked. A small amount of sedationa will usually help, and this has been shown to be inconse- quential to the display of lameness. Lameness is often displayed strongerwithmild sedation. If one encounters a horse that does not stabilize its


lameness, or one that displays lameness of different type (impact/push off), in different limbs, or of wide variation of amplitude in different limbs, neurologic dysfunction should be more strongly considered.


Using Body-Mounted Inertial Sensors to Assess Response to Blocking


Assessing response to block as a decrease in lameness from baseline is relatively straightforward using BMIS. A positive response to block is based upon finding a change in themeasurement of lameness that is outside the 95% confidence interval for repeatability for the


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