Ontario Veterinary College researcher, Dr. Mark Hurtig, is developing a new non-invasive way to assess cartilage health, which could improve veterinarians’ ability to diagnose injuries and hard to pinpoint lameness, such as early osteoarthritis. While current technologies, including physical exams, diagnostic injections, x-ray images and ultrasound, are limited, Dr. Hurtig has found that using electroarthrography can provide valuable information about the quantity of articular cartilage.
Electroarthrography (EAG), developed by human medicine researchers at the Université de Montréal and École Polytechnique, employs dime-sized electrodes, placed on the skin, to record electrical signals produced by joint cartilage when loaded and unloaded.
The researchers reasoned that these electrical signals might be measured on the skin surface similar to electrocardiography (ECG) for the heart. They discovered that people with knee arthritis had lower electrical potentials than those with healthy knee joints. Thus, the concept of EAG was born.
Dr. Hurtig, and his team of postdoctoral fellows and graduate students, is applying the technique to horses by performing validation studies in cadaveric limbs, in which electrical signals are pulsed through the limbs to assess cartilage quality. “We thought that the fetlock might be a good place to start in the horse, since the cartilage surface is close to the skin without any bulky muscles overlying the joint,” he explained.
Preliminary data from cadaveric forelimbs of horses under simulated weight bearing has shown that EAG signals can be easily recorded from the fetlock and are altered by damaged or osteoarthritic cartilage. Further, when the cartilage is deliberately damaged with an enzyme like those found in osteoarthritic cartilage, lower EAG signals are produced. Once the validation study is complete, the next phase is to apply EAG to normal and lame horses.
In a preliminary live-animal test, electrical signals were recorded from fetlock joint cartilage as the horse was being pushed side-to-side while standing on a platform that times and measures weight distribution (similar to using a Nintendo Wii gaming platform). The strength of the EAG signals under the same weight indicates the status of cartilage health. In an eroded or damaged cartilage surface, the water and protein content changes resulting in a decline of electrical signals.
An instrumented horse boot capable of recording weight bearing information while EAG signals are recorded is currently being developed by other collaborators in the University of Guelph, School of Engineering, in order to make this diagnostic tool portable.
Dr. Hurtig has high hopes for the use of EAG as a diagnostic tool. “If we are successful,” he said, “it could mean that we can diagnose cartilage damage years before conventional methods.”