Effects of Thoracic Posture on the Nuchal Ligament in Foetal Foals

Abstract

IntroductionControversy surrounds certain head and neck postures in sport horses and their potential impact on the nuchal ligament.MethodsThree dead near‐term equine foetuses in lateral recumbency with upper‐side neck musculature removed to expose the nuchal ligament were placed in 6 head and neck positions (HNP's) between extreme hyperflexion and hyperextension, along with 3 thoracic positions: Low, Medium and High. In each of these 18 positions, the funicular length, lamella dorsoventral width at the level of C4, and craniocaudal length of the 5 major lamella bands of the nuchal ligament were measured manually.ResultsIn intermediate HNP's (HNP1, HNP2), thoracic postures significantly impacted nuchal ligament measurements. Compared to the Medium thorax position, depression and elevation of the thorax decreased lamella sheet widths by 24% (P = 0.014) and 11% (P = 0.267) respectively for HNP1, and by 8% (P = 0.01 for both depression and elevation) for HNP2. More extreme head and neck positions were not associated with any change in measurements of the nuchal ligament with changes in thoracic position.ConclusionsA decreased width suggests increased tension in an elastic structure. Hence, if the anatomical connections are similar in adults, extreme head and neck postures may reduce the effect that thoracic posture might have on the nuchal ligament in certain unnatural positions required in sport horses and may interfere with normal elastic energy storage in the nuchal ligament during movement.Ethical Animal ResearchThe study was performed on material collected during post‐mortem examination. Explicit owner informed consent for participation in this study is not stated. Sources of funding: none. Competing interests: none.