Morphometrics of nuchal ligament in greyhound in different neck and body positions

Abstract

This study was conducted to describe the morphometrics of nuchal ligament and investigate the effects of different neck and body positions on the nuchal ligament in greyhounds. Nine adult greyhounds cadavers without any locomotion abnormalities were dissected through the neck musculature on the left side to expose the nuchal ligament. Three pins were placed to mark regions of interest on the nuchal ligament: at one cm cranial to the site of origin (the most dorsal point of the spinous process of the first thoracic vertebra), at the midpoint of the nuchal ligament and one cm caudal to the nuchal ligament site of insertion (close to the caudal aspect of the spinous process of the axis). Each cadaver was positioned on a masonite board and placed on a table on the floor in their lateral recumbency and seven different standardized body positions; P1-P7 were mimicked using goniometers and metal wires. Photographs were taken by positioning and fixing the camera above the nuchal ligament region. The length and widths (W1, W2 and W3) of nuchal ligament were measured using Image Pro software (Image-Pro Express version 5.0) on standardized photographs of each of seven different body and neck positions. The length of nuchal ligament in relation to the neutral position (P1) was less (- 7%, p>0·05) in P6 (neck elevated) and increased in all other positions (+1%, p>0·05 for P2, +19%, p<0·05 for P3, +37%, p<0·05 for P4, +1%, p>0·05 for P5, +40%, p<0·05 for P7). Nuchal ligament width at the middle (W2) decreased significantly with P4 (- 26%, p<0·05), and P7 (- 32%, p<0·05). Also, nuchal ligament width at the site of origin (W3) decreased significantly with P4 (- 24%, p < 0·05) and P7 (-35%, p<0·05). These findings reflect the need for clinical and biomechanical studies to describe in-depth the gross anatomy of the nuchal ligament in greyhounds. They suggest that different neck and body positions change the shape, and hence, the function of the nuchal ligament during movement.