Objective evaluation of chronic orthopedic pain in a carpal groove model in Shetland ponies

Abstract

Chronic orthopedic pain in horses is one of the most common conditions the equine vet is confronted with in the daily practice. This type of pain is different from the more acute occurring (often visceral) pain and has become a growing area of research during the past few years. This study evaluates the use of a composite pain scale developed for chronic equine pain (CPS) and the Equine Utrecht University Scale for Facial Assessment of Pain (EQUUS-FAP) in ponies with induced orthopedic pain. Eight Shetland ponies were grooved in the radiocarpal and intercarpal joints of one front limb prior to an eight week treadmill exercise program. The ponies were scored real-time during rest (CPS and FAP scores) and during training (FAP training) and objective gait analysis was performed.

The CPS showed a high inter-observer reliability (ICC: 0.799, P<0.005) whilst the FAP in rest and during training had fair inter-observer reliabilities (ICC: 0.478 and 0.508 respectively, P<0.005). Pain scores at the end of the study period were significantly higher than baseline scores for all scoring systems (P<0.01). No clear trends in lameness deterioration during the study period was found through objective gait analysis.

Especially the CPS, but also the FAP and FAP training could develop into reliable tools in order to assess chronic orthopedic pain in horses. Facial pain recognition during training should be recognized as an important part of pain recognition in chronic pain circumstances in horses.