Effect of Different Head-and-Neck Positions on Nuchal Ligament Dimensions in Fetal Foals

Abstract

Controversy surrounds certain head-and-neck positions (HNPs) in sport horses and their potential impact on the nuchal ligament (NL). This study measured the effects of six different HNPs on NL dimensions in five fetal cadavers, specifically funicular length, lamellar width at C4, and the lengths of the five individual lamellar bands. Normalized mean percentage changes in NL dimensions in HNP-2 to HNP-6 were compared with the NL dimensions in HNP-1. The lengths of the funicular and lamellar bands (C2–C6) decreased when the head and neck were raised (HNP-2, HNP-3, and HNP-5), in proportion to the degree of elevation, and increased when the head and neck were lowered (HNP-4 and HNP-6). Not all cervical segments were affected in the same way nor to the same degree. Lamellar width significantly decreased an average of 46% with HNP-4 (rollkur) and 29% with HNP-6 (long and low). Exaggerated poll flexion, as in HNP-3 and HNP-4, showed uneven stretching suggesting that the NL was not working as an integrated unit in these postures. Overall, the results suggest that certain HNPs impose limitations on the cycling of strain energy from head and neck movements during locomotion. Some positions may be associated with an increased chance of damage to either the NL or associated muscles.