Porcine treadmill gait: 2D analysis as a functional outcome measure of peripheral nerve regeneration
Matthew Wordsworth, MA, MRCS1,2; Nicholas Robbins, DO1; Erik K Weitzel, MD3; Warren Breidenbach, MD4; Andrew Hart, MD, PhD5; Rory Rickard, FRCS, PhD6; (1)59th Medical Wing, San Antonio, TX, (2)Academic Deparment of Military Surgery and Trauma, Birmingham, United Kingdom, (3)Institute of Surgical Research, San Antonio, TX, (4)Department of Surgery, Division of Reconstructive and Plastic Surgery, United States Army Institute of Surgical Research, San Antonio, TX, (5)University of Glasgow, Glasgow, United Kingdom, (6)Academic Department of Military Surgery and Trauma, Birmingham, United Kingdom
There is a need for a well-defined large animal model of peripheral nerve regeneration. Traditional small animals cannot model large nerve gaps or long regeneration distances and have significant anatomical and physiological differences to humans. There is a growing experience of the pig as an animal model both in neurological disease and in trauma research. The functional recovery of nerve injury is the most clinically important aspect of nerve regeneration but functional outcomes are difficult to objectively measure in animal models. There is a need for a pig model of peripheral nerve trauma with functional recovery as the primary outcome measure. Gait is the primary complex co-ordinated function of the limb in animals and gait analysis can be used to objectively quantify pig limb function.
In this study 6 Yucatan swine were trained to walk on a treadmill. The gait of the forelimb was analysed using 125fps video 2D motion capture with reflective sensors affixed to the skin over the joints of the forelimb. Normal forelimb pig gait has a characteristic pattern with maximal hoof flexion (mean 48¡) and extension (mean 53¡) at the mid point of the swing and stance phase respectively. The angle of change velocity in the hoof was over 365¡/s at normal walking speeds. The forelimb gait was symmetrical with no statistically significant difference between left and right in all animals. There were no significant inter-test differences in gait parameters in the same animal at a given speed but consistent differences intra animal and at differing treadmill inclinations and speeds.
The gait studies were repeated after ultrasound guided 0.5% bupivacaine anaesthetic blockade of the median, ulnar and radial nerves at defined levels. The efficacy of the block was confirmed with a nerve stimulator before pigs were returned to the treadmill. This enabled determination of the effects of specific nerve blocks on the specifics of gait.
A pig model of peripheral nerve injury and regeneration provides an opportunity for peripheral nerve research. The in vivo monitoring of nerve regeneration observed via gait disturbance facilitates research to enhance nerve regeneration in a clinically relevant large animal model. 
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