Use of the inertial measurement unit to assess normal and abnormal equine hoof kinematics
Date
2013
Authors
Moorman, Valerie J., author
Kawcak, Christopher E., advisor
McIlwraith, C. Wayne, committee member
Reiser, Raoul F., II, committee member
Haussler, Kevin K., committee member
Journal Title
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Volume Title
Abstract
Lameness is a major medical concern and results in a large economic impact for both horse owners and the equine industry. In addition, subtle to mild lameness can result in poor performance, which can result in decreased competition winnings. While the subjective lameness examination is the most common tool for lameness evaluation, its sensitivity and repeatability have been shown to be poor, especially for subtle and mild lameness. This has led to the development of objective methods to supplement the subjective lameness examination, including stationary force platform analysis, optical kinematics, and horse-based inertial sensor systems. Several of these methods have been shown to be sensitive in identifying lameness. However, stationary force platform and optical kinematics are largely confined to experimental settings, are expensive and time-consuming, and require expertise for collecting and analyzing data. Horse-based systems have become widely investigated, as the components are small, light-weight, telemetric, and can be more easily used in a clinical setting. One specific system with poll and pelvis-mounted sensors, allows for real-time identification of asymmetry, which objectively supplements the subjective lameness examination. While this inertial-sensor system has been shown to be sensitive enough to detect subtle lameness at the trot, it cannot accurately detect bilateral forelimb lameness at the trot and has not been investigated for use evaluating other gaits. As previous optical methods have shown that distal limb kinematics are altered with moderate lameness and the hoof is an ideal place to rigidly mount a small sensor, the kinematics of the hoof should also be investigated to determine if mild lameness can also be detected in this manner. Inertial measurement units (IMU) combine a three-dimensional accelerometer, three-dimensional rate gyroscope, three-dimensional magnetometer, and thermostat. By the integration of these signals, these sensors allow determination of linear and angular kinematics in a global coordinate system. IMUs have been investigated for their use in assessing equine locomotion, by attaching them to the body of a horse. However, an IMU has not been previously utilized on the hoof of the horse. As emerging IMUs are small, light-weight, and often wireless, they have appropriate characteristics to measure hoof kinematics and may be a useful method of also objectively determining abnormal hoof kinematics associated with lameness. As optical methods are currently the gold standard for assessing distal limb kinematics, we used these as a standard to which to compare both linear and angular kinematics determined by an IMU. In the first experiment, optical methods were used to validate the IMU in five clinically normal horses. Walk and trot data were collected on a single forelimb and hind-limb, as the horse was led over-ground, and three-dimensional linear and angular kinematics were compared between the two systems. In the second experiment, three grades of lameness were induced in a single forelimb in six clinically normal horses, and following the most severe lameness, peri-neural anesthesia of the medial and lateral palmar nerves was performed to alleviate the lameness. Using optical kinematics, intra- and inter-limb comparisons were made at the walk and trot at baseline, and following lameness and peri-neural anesthesia. Linear variables were assessed in the cranial-caudal and vertical directions, as well as sagittal plane orientation (Θ). Intra-limb changes to three-dimensional orientation were assessed in the lame forelimb with the IMU. In the first study, the IMU was found to produce similar, yet not identical, kinematics to the optical system. While the IMU produced highly correlated data in the sagittal plane, the linear and angular profiles in the other planes showed similar trends to the optical system. In the second set of experiments, multiple linear and angular variables of the hoof were altered following induction of lameness, using both kinematic methods. The optical and IMU systems both identified significant changes in sagittal plane (Θ) orientation with lameness. In addition, hoof kinematics were significantly altered in mild lameness at the trot and when no lameness could be visually assessed at the walk. The IMU also detected significant changes in the frontal and transverse planes of rotation following lameness. After peri-neural anesthesia, the IMU detected a significant increase in variance in Θ orientation. Overall, it was demonstrated that the IMU can be mounted on the hoof to measure both normal kinematics and detect significant orientation changes following both lameness and peri-neural anesthesia. The IMU appeared to be a sensitive device to evaluate hoof kinematics even when lameness is mild or undetectable to the human eye. While its usefulness on clinical lameness has yet to be determined, the IMU should be further investigated for its use in a non-research setting.
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Subject
equine
IMU
gait analysis