Evaluation of the inter-examiner reliability of myofascial trigger point identification in dogs.

Abstract

INTRODUCTION: Myofascial trigger points (MTrPs) are a source of chronic pain in humans, but their diagnosis relies on subjective manual palpation. MTrP distribution has been described in dogs, but reliability between examiners remains unknown. This prospective, blinded, clinical investigation aimed to determine the inter-examiner reliability of MTrP identification in the hindlimb musculature of dogs and to describe their distribution. METHODS: Twenty-four geriatric and retired sled dogs were assessed for MTrPs in four hindlimb muscle groups (gluteals, cranial thigh, hamstrings, and medial thigh) by two veterinarians in random order. MTrP identification was based on previous methodology defining an MTrP as a distinct, hyperactive point or nodule eliciting a pain response, known as a jump sign. Examiners were blinded to each other's findings by marking MTrPs with invisible UV ink pens. Agreement on MTrP presence or absence in a muscle group, distance between examiners' points, and the number of MTrPs per muscle group were recorded. Inter-examiner reliability was assessed using Cohen's kappa. RESULTS: In total, 380 MTrPs were identified by the two examiners across the 188 muscle groups assessed. Examiners demonstrated 81.4% agreement on MTrP presence or absence in a muscle group with a Cohen's kappa of 0.608 (95% CI: 0.491-0.724), indicating moderate to substantial inter-examiner reliability. However, the mean distance between examiners' markings for individual MTrPs was 10.6 ± 5.1 mm, suggesting a potential substantial lack of precision. The cranial thigh group contained the most MTrPs. Additionally, the more experienced examiner identified a greater number of MTrPs overall (= 0.028). DISCUSSION: This study provides the first assessment of inter-examiner reliability for MTrP identification in dogs. While examiners agreed on the general presence or absence of myofascial sensitivity within a muscle group, precise localization was unreliable. This lack of precision may be influenced by a number of factors, namely skin movement and the subjective nature of the assessment itself. This study highlights the need for further research and objective diagnostic tools for reliable, targeted MTrP identification.