Pressure Algometry for the Detection of Mechanical Nociceptive Thresholds in Horses

SIMPLE SUMMARY: It is difficult to measure pain in horses. As animals are not able to verbalize what they feel, we are left with trying to interpret the different signs that they display when they are in pain. Many of these signs are vague (e.g., not eating their food), but some are more readily identified if the animal moves away or lifts their leg when pressure is applied to a sensitive area. Pressure algometry is a tool used to detect responses to applied mechanical stimuli within painful and nonpainful tissues. Pressure algometry has been used in many different studies, but there is no consensus on how to synthesize this information to better diagnose and treat pain in horses. The purpose of this study was to summarize the results of these studies. Based on that review, we conclude that there is good evidence that pressure algometry is a reliable and objective method to measure pain responses. This information will help to improve the diagnosis and treatment of pain in horses. ABSTRACT: The clinical assessment of pain is subjective; therefore, variations exist between practitioners in their ability to identify and localize pain. Due to differing interpretations of the signs or severity of pain equine practitioners may assign varying levels of clinical significance and treatment options. There is a critical need to develop better tools to qualify and quantify pain in horses. Palpation is the most common method to detect local tenderness or sensitivity. To quantify this applied pressure, pressure algometry has been used to gradually apply pressure over specified landmarks until an avoidance response is noted, which is defined as the mechanical nociceptive threshold (MNT). Numerous studies have used pressure algometry in different applications to measure MNTs in horses. There is an acute need to establish normative values within different body regions and to develop standardized methods of testing MNTs to better guide practitioners in the diagnosis and treatment of pain. The aim of this systematic review was to summarize the evidence for the use of pressure algometry in horses. There is good evidence that pressure algometry is a repeatable, semi-objective method that can be used in a wide array of clinical and research applications to assess MNTs in horses.