Heat hypersensitivity at a site proximal to a surgically induced osteochondral fracture in horses. (May 2021)

• Record Type: Journal Article
• Authors: Lizarraga, Ignacio; Panizzi, Luca; Gieseg, Michael A.; Riley, Christopher B.; Chambers, J Paul
• Is Part Of: Veterinary anaesthesia and analgesia. Volume 48:Number 3(2021)
• Page Start: 461
• Page End: 469
• Publication Date: 2021-05
• Subjects: horse -- nociception -- osteoarthritis model -- thermal threshold; Veterinary anesthesia -- Periodicals; 636.089
• DOI: 10.1016/j.vaa.2020.11.008
• Languages: English
• ISSNs: 1467-2987

Abstract

Abstract: Objective: To evaluate thermal nociceptive thresholds (TNTs) before and after inducing a standardized radiocarpal bone osteochondral fracture (OCF) in horses. Study design: Prospective, controlled, randomized, masked study. Animals: A group of 10 Thoroughbred fillies aged 2 years. Methods: Skin temperature and TNTs were measured on the skin over the triceps brachii muscle in both the thoracic limbs before (week 0) and weekly (weeks 1–8) after unilateral arthroscopic induction of a radiocarpal OCF ( n = 4) or sham surgery ( n = 6) followed by a standardized exercise programme. The contralateral, non-operated thoracic limb was used as a control within each horse. Percentage thermal excursion (%TE) defined as %TE = 100 ∗ (TNT – skin temperature)/(cut-off temperature – skin temperature) was calculated. Data were analysed with a mixed-effects model followed by Dunnett's and Tukey's tests for within and between-limbs comparisons, respectively; p < 0.05 was considered significant. Results: Skin temperature in the control limb of OCF horses was significantly higher at week 7 than at week 0 ( p = 0.0125). At week 1, TNTs and %TE values in operated limbs of OCF horses were significantly reduced compared with their baseline values at week 0 ( p ≤ 0.0153) and their values in contralateral control limbs ( p ≤ 0.0024) and operated limbs of sham-operated horses ( p ≤ 0.0162). At week 2, TNTs and %TE values in operated limbs of OCF horses remained significantly reduced compared with values in operated limbs of sham-operated horses ( p ≤ 0.0248). Conclusions and clinical relevance: Creation of an OCF in a radiocarpal bone induced transitory (<2 weeks) ipsilateral heat hypersensitivity proximal to the surgery site (skin over the triceps brachii muscle) in horses. Surgically induced OCF may cause somatosensory abnormalities consistent with secondary thermal hyperalgesia.