Non-physiologic loading of the carpal bones is believed to result in osteochondral fractures, ligament rupture and axial instability in the equine forelimb; however, the mechanism of carpal damage due to non-physiologic loading of the carpus is largely unknown. To investigate carpal stability (alignment and direction of carpal bones’ movement) under load and during flexion, some previously described carpal parameters were measured on radiographs obtained from 24 equine cadaver limbs (aged 10.71±4.15 years). The limbs were transected at the antebrachial midshaft, axially loaded in a commercial press and serially radiographed under a range of incremental loads (extension) and 2 flexion positions. The extensions were measured by a 10° decrease in the dorsal fetlock angle (DFA) from 160° to 110° (DFA160 to DFA110) using the jacking system of the press; and flexions at palmar carpal angle of 45° and 90° (PCA45 and PCA90). As loading increased from DFA160 to DFA110 there was a progressive significant increase in Third Carpal bone Palmar Facet Angle (C3PalFCA: 86.46±2.54° to 88.60±2.51°) but a decrease in Dorsal Carpal Angle (DCA: 173.03±3.47° to 159.65±4.09°); Medial Carpal Angle (MCA: 186.31±1.90° to 184.61±2.26°); and Groove width of the Cr-Ci intercarpal ligament (GW.Cr-Ci ICL: 9.35±1.20° to 8.83±1.13°) while no significant differences were observed for Distal Radial Slope Carpal Angle (DRSCA) and Intermediate carpal bone Proximal Tuberosity-Radial Angle (CiPxTRA). A generalised medio-distal directional displacement in the carpal bones’ movement were observed. In conclusion, increased load on the forelimb (carpus) produced carpal hyperextension with measurable radiographic changes in the position and alignment of the carpal bones. The non-stretching (strain) or shortening of the Cr-Ci ICL during loading, indicated by the decrease in GW.Cr-Ci ICL, suggests a relaxed intercarpal ligament within a confined space which appears to absorb compressional load transferred from carpal bones and redistribution of concussion forces within the carpal joint during loading thereby providing a useful mechanism to minimise carpal damage.

Carpal conformation is often considered as a contributory factor to performance and lameness in the horse; however, few attempts have been made to objectively measure radiographic variations of carpal conformation in horses due to insufficient measurable carpal parameters. This pilot study used carpal radiographic images acquired from 10 cadaveric equine forelimbs transected at the antebrachial midshaft from 7 adult horses (7.2 ± 2.6 years), positioned at ‘zero lateromedial’ (ZLM) and ‘zero dorsopalmar’ (ZDP) views, to investigate the anatomy of the equine carpus and develop parameters that could be objectively used to assess carpal conformation in horses. Dorsal carpal angle (DCA: 176.61 ± 0.66º), distal radial slope carpal angle (DRSCA: 145.59 ± 2.19º), intermediate carpal bone proximal tuberosity‐radial angle (CiPxTRA: 115.69 ± 3.15º) and third carpal bone palmar facet angle (C3PalFCA: 84.43 ± 1.13º) were all developed from the ZLM view while medial carpal angle (MCA: 183.34 ± 1.02º), disto‐dorsal slope angle of the third carpal bone (C3DDSA: 8.27 ± 0.92º) and width ratio of distal radius to proximal metacarpus (WDR:WPM = 1.13±0.03) were 3 of the 10 parameters developed from the ZDP view. Easy to identify and measurable parameters will help to provide quantitative assessment of carpal conformation in the horse with potential of eliminating subjective observational variation errors between clinicians. These newly developed parameters will be useful in further studies to measure variations in the conformation of the equine carpus in live horses and comparison between subjective visual assessment and objective radiographic evaluation methods.

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.

Generally, joints can be classified based on their structure and function. The structural classification focuses on the nature of the material binding the bones together and whether a joint cavity is present or not, while the functional classification is based on the type and amount of movement allowed at the joint (Getty, 1975a). The equine carpal joint is structurally a synovial joint and functionally a composite joint, consisting of both freely movable (diarthrotic) joints such as the antebrachiocarpal and middle intercarpal joints; slightly movable (amphiarthrotic) joints such as the carpometacarpal joint and the many intercarpal joints between adjacent carpal bones; and non-movable (synarthrotic) joints such as the fused joints between the proximal ends of the second (MC2),

Radiographs required for morphological studies should be of remarkably high quality (Abdunnabi, 2011;Oheida et al., 2016). They should clearly show all the anatomical features used as landmarks for each parameter being measured. However, the conditions under which radiographs are often taken in the field are less desirable due to potential horse movements, postural tilts of horse's limbs, rotations of radiographic plate holder and/or cassette and the angle of projection of the X-ray beam. These rotations (variables) could make maintaining the focal object distance and alignment between the X-ray beam, the object and the cassette a major challenge. Usually, 3