Advanced diagnostics for orthopedic & sports related injury (Proceedings)
Identifying the cause of forelimb and hind limb lameness in dogs can be a challenge. Until recently, diagnostics in small animal orthopedics included visual gait analysis and radiographs. With advanced diagnostics becoming more readily available (objective gait analysis, CT scan, MRI, ultrasound, nuclear scintigraphy, arthroscopy, etc) clinicians can now obtain a definitive diagnosis to those challenging conditions.
Quantitative analysis of animal motion can provide unique insight into normal and abnormal limb function. This information is useful clinically for the diagnosis of disease and as a measure of outcome following treatment intervention. Historically, gait analysis has been cumbersome and time-consuming. Dramatic computational and equipment improvements over the past ten years, however, have made these techniques readily available for routine assessment of gait in a modern-day hospital. Perhaps the most attractive draw to gait analysis is that many methods produces objective data of limb function.The most common techniques used to measure outcomes in veterinary medicine are visual observation of gait and force platform gait analysis (measuring of ground reaction forces) Other, less frequently used, methods of analyzing gait in animals include the use of 2D or 3D kinematics, accelerometers, electromyography, electrogoniometry, roentgenographic and magnetic coupling methods. Some of these methods are practical for clinical use, others are not.
Visual Observation of Gait
The entire gait cycle lasts for only one second thus; a systematic and disciplined approach must be used to clinically evaluate a patient's gait. To document this in the medical record one could semiquantify the findings by using a visual analog scale or numerical rating scale. Regardless of what mechanism two important facts are that visual observation of gait is subjective and the scientific literature would strongly suggest it is unreliable. For example, in one publication when the sensitivity of visual observation of gait was compared to that of force platform gait analysis, visual observation was found to be vastly inferior. In this comparison they evaluated 148 adult Labrador Retrievers, 17 were free of orthopedic and neurologic abnormalities and 131 were 6-months after surgery for unilateral CCL injury. The observer was blinded to the dog's group assignment. Of the 17 normal dogs the observer correctly identified all as having no gait abnormality, as did the force platform. However, the observer only identified 15 of 131 dogs' 6-months after knee surgery as not being normal. Using ground reaction forces from force platform gait analysis, 75% of 131 dogs failed to achieve GRFs consistent with sound Labradors. In this paper if a dog looked lame it was lame, but if it looked normal by the observer it may in fact have been very abnormal. In another recent publication that tried to validate clinician observation of gait neither trained or untrained (first semester veterinary students) observers could reliably identify lameness, there were large disagreements between individuals and that untrained observers had the same visual acuity for dog lameness as boarded surgeons. (Waxman et al. 2008). The only saving grace was a finding that trained clinicians provided repeatable data; i.e. they consistently made the same mistake. This would allow a clinician to compare groups over time, but not necessarily comment success or failure of an individual dog. It should not be surprising that a computational gait analysis is more sensitive than our powers of observation. This fact should be remembered when we inform an owner that a dog, "has returned to normal" after a clinical exam.
Pedometers and Accelerometers
The greatest limitation to data that is collected at a veterinary hospital is that it measures a moment in time, not the day to day level of activity of the dog at home. Use of a pedometer or accelerometer can be used to measure patient activity level at home over an extended period of time. In one study pedometers were successfully used to measure physical activity in dogs over a 14 day period. Pedometer accuracy varied depending upon the patient's size (overestimated walking in large dogs and underestimated walking in small dogs), but correlated well to overall reports of the dogs activity level at home and the dog's condition body score. Accelerometers are a bit more sophisticated in that some can measure changes in acceleration in the x-, y- and z- axis. Thus, body movement in any direction is measured. In one study that determined variability in accelerometer data in companion dogs it was reported that large day-to-day and even week-to-week variations occurred in dogs but within dogs, a full 7-day comparison of total activity counts from one week to the next provided the least variable estimate of the dogs' activity. They also reported that accelerometers may be most useful for documenting changes in the dog's activity over time. Given the limitations both pedometers and accelerometers have in their estimates of a patient's activity level these methods are probably suited for use in studies that wish to compare large groups of dogs that have similar body size and shape. To the authors knowledge these methods have not been applied to dogs after RCCL surgery and their use would be beneficial for outcome comparisons.