Injury to the palmar supporting structures of the fetlock alters limb stiffness and fetlock angle.

BACKGROUND: In vivo measurement of limb stiffness and conformation provides a non-invasive proxy assessment of superficial digital flexor tendon (SDFT) and suspensory ligament (SL) function. Here, we compared it in fore and hindlimbs and after injury. OBJECTIVES: To compare the limb stiffness and conformation in forelimbs and hindlimbs, changes with age, and following injury to the SDFT and SL. STUDY DESIGN: Retrospective cohort study. METHODS: Limb stiffness was calculated using floor scales and an electrogoniometer taped to the dorsal fetlock. The fetlock angle and weight were simultaneously recorded five times with the limb weight-bearing and when the opposite limb was picked up (increased load). Limb stiffness of both limbs was calculated from the gradient of the regression line of angle versus load. Fetlock angle when the weight was zero was extrapolated from the graph and used as a measure of conformation. Limb stiffness was measured in uninjured forelimbs (n = 42 limbs), hindlimbs (n = 19 limbs), forelimbs with SDFT injury (n = 18) and hindlimbs with SL injury (n = 5). RESULTS: Limb stiffness correlated with weight in forelimbs as shown previously (p < 0.001) but also in hindlimbs (p = 0.006). When normalised to the horse's weight (503 kg, IQR 471.5-560), forelimb stiffness was significantly higher (22.3 [±4.5] × 10-3 degree-1) than for the hindlimb (16.4 [±4.0] × 10-3 degree-1; p < 0.001). While there were no significant differences between forelimb and hindlimb conformation in unaffected or SDFT injury, both limb stiffness and conformation was significantly greater in limbs with SL injury (p = 0.009 and p = 0.002, respectively). MAIN LIMITATIONS: Small sample size, lack of clinical data including lameness and quantification of injuries. CONCLUSIONS: Injury to the forelimb SDFT does not alter limb stiffness or conformation in the long-term, while hindlimb SL injury simultaneously increases limb stiffness and fetlock angle, suggesting an increase in SL length following injury.

Validation of a novel clinical tool for monitoring distal limb stiffness.

Objective: To validate a novel technique to measure limb stiffness in a clinical setting. Animals: Three horses and three ponies owned by the Royal Veterinary College. Procedures: Limb stiffness indices for both forelimbs were first derived using the gold standard of kinematic analysis. Using the same animals, limb stiffness indices were then calculated using portable floor scales to record weight and an electrogoniometer to record changes in metacarpophalangeal joint angle. The two techniques were then assessed for correlation and repeatability. Results: The repeatability of limb stiffness measurement using the novel clinical tool was considered to be good based on a small coefficient of variation (5.70%). The correlation of limb stiffness as derived by both methods was high (r = 0.78, p < 0.01). Limb stiffness was positively correlated with the mass of the subject (r = 0.85, p < 0.01), with heavier horses having greater limb stiffness. Clinical relevance: This study has compared a novel method to measure distal forelimb stiffness non-invasively in a clinical setting to kinematic analysis in six equids. It has demonstrated that limb stiffness increases in a linear fashion with body mass consistent with the role of forelimbs providing energy storage. Because in vivo limb stiffness has been shown previously to alter with injury to the superficial digital flexor tendon, it is hypothesized that this technique will offer a practical technique for the clinician to assess limb stiffness in clinical cases. Further study will be necessary to determine its clinical usefulness in such cases.

Inter- and intra-observer agreement for grading radiographs of thoracolumbar spinous processes in healthy horses during a pre-purchase examination.

BACKGROUND: There is wide variability in radiographic grading systems in thoracolumbar spinous processes in horses. The aim of this study was to determine the agreement of grading different parameters, and combinations of those, in radiographs of the spinous processes of the equine thoracolumbar spine in the scope of a pre-purchase examination. We hypothesized that agreement is variable and interpretation of these radiographs is difficult. METHODS: Radiographs of the thoracolumbar spine of healthy horses (N = 100) were assessed by three observers. Spinous processes were separately graded for interspinous space width, modelling, radiopacities, radiolucencies and isolated opacities dorsally. Inter- and intra-observer agreement was assessed for individual and combinations of parameters. RESULTS: Agreement (inter- and intra-observer) was good for the following parameters: interspinous space width, isolated opacities dorsally, beak-shaped formations craniodorsally and modelling cranioventrally. The agreement increased slightly for a sum of specific parameters such as radiopacities, modelling, dorsal abnormalities and related abnormalities involving increased opacity, modelling and osseous cyst-like lesions. Agreement for the total radiographic abnormalities per back was moderate. CONCLUSIONS: Grading of thoracolumbar radiographs in horses without back pain showed good inter- and intra-observer agreement for specific parameters and these should be used in future grading of spinous processes. Limitations should be considered in pre-purchase examinations.

The Impact of Horse Age, Sex, and Number of Riders on Horse Performance in British Eventing Horse Trials.

Limited research has been undertaken to determine the impact of horse age, sex, and number of riders on horse performance in British Eventing (BE) horse trials. Improved understanding of this can aid professionals in planning a competition horse's career. To investigate the impact of age, sex, and number of riders on the peak performance of horses at each of the main levels of BE competitions. The best score from each horse competing in BE horse trials in the years 2008-2018 was recorded, and principal component and hierarchical cluster analysis was performed. Basic data analysis was used to identify variables associated with particular better-performing clusters of horses. The interplay of the combinatory variables was then used to map out the trends in career trajectory for horses competing at each level of competition in the best-performing and worst-performing clusters. The peak performance of mares was worse than geldings and stallions at all levels. At Novice to Advanced, stallions did not perform as consistently with multiple riders as geldings. The age at which the best-performing groups peaked was similar for mares and geldings in all classes, although stallions peaked at an older age than mares and geldings at Novice and Intermediate level. All horses were a minimum of 4-years-old at the time of competition, as per BE rules.

Effect of horse sex status on British Eventing competition performance: an observational study between 1998 and 2016.

To test the hypothesis that gender affects horse scores in eventing competition, data on the scores and points awarded to 681 horses was collected from the British Eventing website. Equal numbers of mares, geldings and stallions were used, all foaled during or after 1994 and aged 4-10 years. The study included five levels of competition (BE90, BE100, Novice, Intermediate and Advanced) and investigated differences in mean phased scores, total scores and rank in competition. Additionally, the mean and median 'BE points per competition' of each gender were compared. Significant differences in performance between genders were found at all levels except Advanced. Differences were highlighted in average phased and total scores, rank and median points per competition. There was an overall pattern of stallions and geldings outperforming mares, though this was not found to be true at all levels. The only area in which mares were found to perform significantly better than geldings or stallions was showjumping time penalties at BE90.