R. Weller

Comparison of radiography and scintigraphy in the diagnosis of dental disorders in the horse

Scintigraphy, with 99mTechnetium methylenediphosphonate (99mTc-MDP) and 99mTc-labelled leucocytes, was compared to radiography in the diagnosis of dental disease in the horse in a prospective case-controlled study, comprising 30 horses with clinical signs of dental disease and 30 control horses. In each case, right and left lateral, ventral and dorsal soft tissue and bone phase scintigraphic images were obtained after i.v. injection of 1 GBq/100 kg bwt 99mTc-MDP, using a gamma camera. The same views were acquired in 10 horses with clinical signs of dental disease and 12 control horses after injection of 99mTc-labelled leucocytes. Standard radiographic projections of the paranasal sinuses and of the apices of the maxillary and mandibular teeth were obtained. The scintigraphs and radiographs were assessed subjectively by 2 board-certified surgeons and one board-certified radiologist, with extensive experience of equine radiology, from who the clinical history was withheld. Sensitivity, specificity and kappa, as a measure of agreement, were calculated for the different methods. Bone phase images were also scored subjectively on a scale from 0 to 3 on the basis of isotope uptake over the teeth. Regions of interest were defined over the teeth, and normal teeth compared to diseased counterparts. Total scintigraphic counts were related to the age of the animal and to the disease process. Differences in density ratios between left and right teeth were evaluated using the Mann-Whitney Test. Dental disease was confirmed in 22 horses at surgery or postmortem examination. Horses with dental disease showed a significant increase in scintigraphic activity over the affected tooth compared to the contralateral tooth, with a typical pattern for different diseases. The sensitivity of scintigraphy with 99mTc-MDP proved to be excellent (95.5%), whereas the specificity was moderate (86.4%). In contrast, radiography had excellent specificity (95.0%) and a low sensitivity (51.5%). The greatest sensitivity and specificity were achieved by evaluating radiographs and scintigrams together. The objective scintigraphic density ratios were found to be significantly different between diseased and control horses. The results of this study suggest that, if a density ratio of 1.5 or greater between a suspected diseased tooth and its contralateral number is regarded as abnormal, only 1% false positive diagnoses and 20% false negative diagnoses will occur. In contrast, scintigraphy with 99mTc-labelled leucocytes was not very successful, due to the lack of anatomical detail provided by this technique, which made identification of the diseased tooth impossible. Accurate radiographic interpretation of dental disease presents difficulties, both in terms of missed diagnoses and mistaken diagnoses. Scintigraphy complements radiographic examination of dental structures by providing information important for accurate diagnosis and is, therefore, conceived to be essential for selection of the appropriate treatment for dental disease.

Assessment of mild hindlimb lameness during over ground locomotion using linear discriminant analysis of inertial sensor data

REASONS FOR PERFORMING STUDY Hindlimb lameness is common and can be difficult to diagnose or quantify in evaluating response to nerve blocks. An objective measure of lameness can also be used to evaluate the effectiveness of the treatments contribution to evidence-based medicine. The inertial sensor system can be used to capture 6 degree of freedom movement during over ground locomotion and here was used to quantify tuber coxae movement in nonlame and lame horses. HYPOTHESIS Tuber coxae movement is useful for discriminating between nonlame and lame horses. OBJECTIVES To measure left and right tuber coxae movement in lame and nonlame horses during over ground locomotion and to implement a linear discriminant analysis to discriminate between lame and nonlame horses. METHODS Two inertial sensors were attached to the skin over left and right tuber coxae of 21 horses (9 mildly and 12 not lame). Horses were trotted on a hard surface. A total of 1021 strides were collected. For each stride 34 features were extracted from the dorsoventral and craniocaudal movement and used in 2 different classification scenarios (lame vs. nonlame or left lame, right lame and nonlame) using linear discriminant analysis. RESULTS Six degree of freedom inertial sensors were successfully used to collect kinematic data continuously from left and right tuber coxae in horses during over ground locomotion. These data were used for an automated classification of lameness. In the first scenario, a sensitivity of 89% was achieved with a specificity of 75%. In the second scenario, all horses could be correctly assigned to the correct class in a simple 3 class reclassification test. POTENTIAL RELEVANCE A mobile system that reliably detects and quantifies hindlimb lameness in horses during unconstrained locomotion could be a valuable tool to perform an evidence-based assessment of lameness in horses in a clinical setting, e.g. before and after nerve blocks or before and after surgery.

The effect of conformation on orthopaedic health and performance in a cohort of National Hunt racehorses: preliminary results.

REASONS FOR PERFORMING STUDY There is a lack of scientific data and studies on the effect of conformation on performance or on orthopaedic health. OBJECTIVES To investigate the relationship between conformation, injury and performance in racehorses used for racing over fences. METHODS Over 2 years, 108 National Hunt racehorses were followed and their medical and performance data recorded. Conformation was measured in 3D with a computerised motion analysis system. Linear multiple regression models were used to evaluate the effect of conformation on measures of race performance and stepwise forward logistic regression models to assess the effect on risk of injury. RESULTS An increase in intermandibular width, flexor angle of the shoulder joint and coxal angle (the angle between the ilium and ischium) was demonstrated to have a positive effect on performance. Performance decreased with increasing girth, length of the hind digit and valgus conformation of the metacarpophalangeal joint. The risk of suffering from superficial digital flexor tendon injury increased with increasing metacarpophalangeal joint angle and with carpus valgus conformation. The risk of pelvic fracture increased with valgus conformation of the tarsus and decreased with an increasing coxal angle. CONCLUSION Valgus deformation was demonstrated to be detrimental to performance or increased risk of injury, perhaps resulting in higher loads on musculoskeletal structures. The coxal angle was the only parameter to have an effect on both risk of injury and performance. An alignment of the muscles with the axis of the pelvis may be beneficial for force transmission and decrease the bending moment of the muscles on the bones. The statistical power of this study is limited, however it provides preliminary data necessary for the planning of a larger scale study on the effect of conformation on performance and risk of injury. CLINICAL RELEVANCE Studies of the effects of conformation on performance and risk of injury may aid in identifying individuals likely to perform well on the racecourse and avoid risks of injury.

Two- and three-dimensional computed tomographic anatomy of the enamel, infundibulae and pulp of 126 equine cheek teeth. Part 1: Findings in teeth without macroscopic occlusal or computed tomographic lesions.

REASONS FOR PERFORMING STUDY Dental disorders are of major clinical importance in equine practice; however, the knowledge of normal dental anatomy, especially that of the pulp remains incomplete. Computed tomography (CT) is being used increasingly in the diagnosis of dental disease, although the normal 2- (2D) and 3-dimensional (3D) CT anatomy has not yet been fully described. OBJECTIVE To describe the 2D and 3D CT appearance of the enamel, infundibulae and pulp of normal equine cheek teeth. METHODS One-hundred-and-twenty-six cadaveric cheek teeth with eruption ages of 0.5-19 years were evaluated; CT scans of each tooth were performed after occlusal surface examination with a dental probe. Three-dimensional reconstructions of the enamel, infundibulae and pulp were created from the CT scans using greyscale thresholding and subsequent polynomial meshing. Each tooth was sectioned coronally or axially into serial slices using a band saw and the sections compared to the corresponding CT images. RESULTS The CT reconstructions enabled the systematic description of the pulpar anatomy of the mandibular and maxillary cheek teeth in 3D, which has not been described in detail previously. The number of interpulpar communications between pulp horns and the pulpar volume of each tooth was shown to decrease with increasing age. The interpulpar communications of the maxillary cheek teeth were found to be of greater complexity and variety in comparison to their mandibular counterparts. Mandibular and maxillary cheek teeth showed different, but consistent patterns in their pulpar and enamel morphology. CONCLUSIONS AND POTENTIAL RELEVANCE The detailed description of the normal 2D and 3D CT appearance of equine cheek teeth provides a reference basis for the diagnosis of dental disease with CT. Additionally, in depth knowledge of the pulpar anatomy of the equine cheek teeth is an essential prerequisite if endodontic therapy is to develop further in the future.

Cardiopulmonary effects and pharmacokinetics of i.v. dexmedetomidine in ponies

REASONS FOR PERFORMING STUDY Currently available sedatives depress cardiopulmonary function considerably; therefore, it is important to search for new, less depressive sedatives. The study was performed to assess duration and intensity of cardiopulmonary side effects of a new sedative, dexmedetomidine (DEX), in horses. OBJECTIVES To study pharmacokinetics and cardiopulmonary effects of i.v. DEX. METHODS Pharmacokinetics of 3.5 microg/kg bwt i.v. DEX were studied in a group of 8 mature (mean age 4.4 years) and 6 old ponies (mean age 20 years). Cardiopulmonary data were recorded in mature ponies before and 5, 10, 20, 30, 45 and 60 mins after administration of DEX 3.5 microg/kg bwt i.v. Data were analysed using ANOVA for repeated measures, and where appropriate Dunnetts t test was used to detect differences from resting values (P < 0.05). RESULTS Within 2 h after DEX administration, plasma levels were beyond limits of quantification (0.05 ng/ml). Mean values for kinetic parameters for mature and old ponies were: Cmax (ng/ml) 4.6 and 3.8, t 1/2 (min) 19.8 and 28.9 and AUC (ng.min/ml) 34.5 and 44.3, respectively. Heart rate, central venous pressure, pulmonary artery pressure and pulmonary capillary wedge pressure did not change significantly compared to presedation values throughout the 60 min observation period. Compared to presedation values, stroke volume and mixed venous PO2 were reduced for the first 5 mins, paralleled by an increase in systemic and pulmonary vascular resistance. Cardiac index was reduced for the first 10 mins, arterial blood pressures at 20, 30 and 45 mins and respiratory rate throughout the 60 min observation period, but no change in arterial PO2 or PCO2 occurred. CONCLUSIONS DEX administration i.v. causes similar cardiopulmonary changes to those caused by other alpha-2 adrenoceptor agonists, but of very short duration. DEX is redistributed particularly rapidly. POTENTIAL RELEVANCE DEX might be safer for sedation of horses because of its very short-lasting cardiopulmonary side effects. For long duration sedation, its kinetics favour its use as a continuous infusion.

Variation in conformation in a cohort of National Hunt racehorses

REASONS FOR PERFORMING THE STUDY Assessment of conformation is commonly used in the selection of horses for performance purposes. Little information is available on the normal range of conformational traits within the Thoroughbred population. OBJECTIVES To describe variations in conformation in a cohort of racing Thoroughbreds in order to provide a set of baseline standards within which conformational traits can be considered normal. MATERIALS AND METHODS Ninety-eight conformational parameters were measured in a cohort of 108 National Hunt racehorses using a digital motion analysis system. The measurements consisted of segment lengths, joint angles in 2D and 3D, inclinations, deviations and circumference measurements. The differences between left and right sides were determined to obtain a measure of asymmetry. Conformational parameters were related to each horses country of origin, preferred race distance and race type. RESULTS The majority of parameters followed a normal distribution with the biggest relative variation in hoof related measurements and in stifle and coxal angle. All circumference measurements and the majority of the length measurements were significantly correlated with the height of the horse at the withers. No underlying pattern of combinations of conformational parameters was identified. Twenty-five per cent of the parameters showed a significant difference between left and right-sided measurements. A significant difference in girth and intermandibular width was observed between Irish and French horses. CONCLUSIONS Thoroughbreds differ from other breeds, not only with regard to segment lengths but also with regard to joint angles and deviations. Variation in conformational parameters was relatively small and no distinct pattern of combinations of conformational traits identified. CLINICAL RELEVANCE The variation in conformational measurements in Thoroughbred racehorses establishes a set of baseline measurements of conformational range against which individual horses can be assessed.

Reliability of conformational measurements in the horse using a three-dimensional motion analysis system

REASONS FOR PERFORMING STUDY The importance of a reliable method for conformation studies is generally acknowledged, but there are only limited data on the accuracy and precision of current assessment methods. OBJECTIVES To assess (1) the accuracy and repeatability of marker placement, (2) influence of stance of the horse on conformational parameters, (3) practicality of a computerised motion analysis system and (4) to compare the computerised motion analysis system to photographic systems of assessment. METHODS Twenty-eight reflective markers placed over anatomical landmarks were located in 3D using a computerised motion analysis system and their coordinates used to calculate segment lengths and joint angles. Four experiments, involving a cadaver study, a series of repeated measures on a single Thoroughbred and repeat measurements on 108 racehorses were performed. RESULTS Identification of anatomical landmarks was found to introduce the biggest variation in the measurements for proximal conformation parameters with the interoperator being larger than intraoperator variation. Length measurements were least influenced by stance, with distal interphalangeal and metacarpo/metatarsophalangeal joint angles being the most variable. In some measurements, the variation between stances within a horse proved to be almost as large as between horses, rendering these parameters less useful as predictors of performance or orthopaedic health. CONCLUSIONS A computerised motion analysis system allows 3D assessment of conformation with high accuracy and precision. It eliminates 3 major sources of error associated with photography-based methods and increases accuracy of conformational assessment by allowing repeat measurements in a relatively short period. POTENTIAL RELEVANCE Studies on conformation should be viewed in the light of the limitations of the measurement technique used. The presented method maximises accuracy and precision and is a valuable basis for future studies investigating the effect of conformation on performance or orthopaedic health.

Medetomidine-ketamine anaesthesia induction followed by medetomidine-propofol in ponies: infusion rates and cardiopulmonary side effects.

REASONS FOR PERFORMING STUDY To search for long-term total i.v. anaesthesia techniques as a potential alternative to inhalation anaesthesia. OBJECTIVES To determine cardiopulmonary effects and anaesthesia quality of medetomidine-ketamine anaesthesia induction followed by 4 h of medetomidine-propofol anaesthesia in 6 ponies. METHODS Sedation consisted of 7 microg/kg bwt medetomidine i.v. followed after 10 min by 2 mg/kg bwt i.v. ketamine. Anaesthesia was maintained for 4 h with 3.5 microg/kg bwt/h medetomidine and propofol at minimum infusion dose rates determined by application of supramaximal electrical pain stimuli. Ventilation was spontaneous (F(I)O2 > 0.9). Cardiopulmonary measurements were always taken before electrical stimulation, 15 mins after anaesthesia induction and at 25 min intervals. RESULTS Anaesthesia induction was excellent and movements after pain stimuli were subsequently gentle. Mean propofol infusion rates were 0.89-0.1 mg/kg bwt/min. No changes in cardiopulmonary variables occured over time. Range of mean values recorded was: respiratory rate 13.0-15.8 breaths/min; PaO2 29.1-37.9 kPa; PaCO2 6.2-6.9 kPa; heart rate 31.2-40.8 beats/min; mean arterial pressure 90.0-120.8 mmHg; cardiac index 44.1-59.8 ml/kg bwt/min; mean pulmonary arterial pressure 11.8-16.4 mmHg. Recovery to standing was an average of 31.1 mins and ponies stood within one or 2 attempts. CONCLUSIONS In this paper, ketamine anaesthesia induction avoided the problems encountered previously with propofol. Cardiovascular function was remarkably stable. Hypoxaemia did not occur but, despite F(I)O2 of > 0.9, minimal PaO2 in one pony after 4 h anaesthesia was 8.5 kPa. POTENTIAL RELEVANCE The described regime might offer a good, practicable alternative to inhalation anaesthesia and has potential for reducing the fatality rate in horses.

The 3D anatomy of the cervical articular process joints in the horse and their topographical relationship to the spinal cord

UNLABELLED REASONS FOR STUDY: Detailed anatomy of the equine cervical articular process joints (APJs) has received little attention in the literature and yet disorders of this joint have been linked to spinal cord compression resulting in severe clinical signs such as ataxia and weakness. This study aimed to describe the 3D anatomy of the APJ in relation to the spinal cord in the horse. HYPOTHESIS Artificial distension of the APJ causes the joint pouches to extend into the vertebral canal, with the potential for APJ effusion to cause spinal cord compressive disease. METHODS Six cadaveric necks (C1-C7) of clinically normal horses were used in this study. Computed tomography scans of the cervical APJ were acquired after injection of a negative contrast agent to maximal distension. The resulting images were semi-automatically segmented using greyscale thresholding and reconstructed in 3D by polygonal surface meshing. The 3D reconstructions were used to assess the topographic anatomy of the APJ in relation to the spinal cord and to measure joint volume at each cervical vertebra in relation to vertebrae size. RESULTS Joint volume varied significantly between joint location (P<0.0001) and was positively correlated to the vertebral site (from cranial to caudal) (r = 0.781, P<0.0001). After distension, the medial outpouch of the APJ extended towards the vertebral canal from a dorsolateral location but in none of the 6 horses was there apparent compression of the dura mater surrounding the spinal cord. There was no significant difference in the extent of medial outpouch at any vertebral level (P = 0.104). Flexion of the neck resulted in minor changes to the shape of the APJ but did not result in the medial outpouch encroaching any closer to the spinal cord. CONCLUSIONS From this study, it appears that in the absence of any other soft tissue or bony changes an effusion of the APJ is unlikely to cause spinal cord compression. However, given that the APJ and spinal cord are in close approximation, in the presence of other anatomical changes, an effusion may have the potential to cause compression. POTENTIAL RELEVANCE This study confirms that the APJ extend into the dorsolateral aspect of the vertebral canal in a ventromedial direction, suggesting that oblique myelographic views are recommended for the diagnosis of spinal cord compression when pathology of the APJ is suspected.

Kinetics of jump landing in agility dogs

A recent survey reported an increased risk of injury in dogs participating in agility, a competitive canine sport involving different jumping activities. The aim of this study was to quantify the kinetic parameters during jump landing for commonly used obstacle types. It was hypothesised that with increasing obstacle height, the vertical force and vertical and accelerative horizontal impulse will increase as a result of a lengthened aerial phase, a more acute landing angle and the need to convert potential into forwards kinetic energy. Simultaneous kinetic and kinematic data were recorded from 11 competition agility dogs jumping over obstacle combinations of different height and inter-obstacle distance. Speed and landing angle of the second of the two consecutive jumps were successfully controlled by obstacle height and distance between obstacles. Statistical analysis showed differences between obstacles for peak vertical force, vertical impulse and accelerative horizontal impulse (increasing values with more acute landing angles). Extremely high peak vertical force was observed in the forelimbs (4.5 times bodyweight) when landing from a hurdle jump at high speed. Further detailed studies into the consequences for internal limb structures are warranted in order to clarify how this might be related to injury.