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Background and Objective: Lameness assessment in the gaited Icelandic horse is complex. We aimed to describe their kinematic and temporal adaptation strategies in response to forelimb lameness at walk, trot and tölt., Study Design: In vivo experiment., Methods: Ten clinically non-lame Icelandic horses were measured before and after reversible forelimb lameness induction. Upper body and limb kinematics were measured using 11 inertial measurement units mounted on the poll, withers, pelvis (tubera sacrale) and all four limbs and hoofs (Equimoves®, 500 Hz). Horses were measured on a straight line at walk and trot in-hand and at walk, trot and tölt while ridden. Linear mixed models were used to compare baseline and lame conditions (random factor = 'horse'), and results are presented as the difference in estimated marginal means or percentage of change., Results: Lameness induction significantly (p < 0.05) increased head vertical movement asymmetry at walk (HDmin/HDmax HAND : 18.8/5.7 mm, HDmin/HDmax RIDDEN : 9.8/0.3 mm) and trot (HDmin/HDmax HAND : 18.1/7.8 mm, HDmin/HDmax RIDDEN : 24.0/9.3 mm). At the tölt, however, HDmin did not change significantly (1.1 mm), but HDmax increased by 11.2 mm (p < 0.05). Furthermore, pelvis vertical movement asymmetry (PDmax) increased by 4.9 mm, sound side dissociation decreased (-8.3%), and sound diagonal dissociation increased (6.5%). Other temporal stride variables were also affected, such as increased stance duration of both forelimbs at walk, tölt and in-hand trot., Main Limitations: Only one degree of lameness (mild) was induced with an acute lameness model., Conclusions: Classical forelimb lameness metrics, such as vertical head and withers movement asymmetry, were less valuable at tölt compared to walk and trot, except for HDmax. Therefore, it is advised to primarily use the walk and trot to detect and quantify forelimb lameness in the Icelandic horse., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Blood flow restriction (BFR) has become a key rehabilitative tool for human orthopaedic conditions. With modernised technology and evolution of clinical application, patient-specific delivery of occlusion percentages is now considered the standard of care in human patients due to improved therapeutic outcomes and minimised safety risks. Safety validation and limb occlusion pressure (LOP) data for horses, however, are lacking., Objective: (1) To determine if BFR exposure resulted in forelimb biomechanical gait dysfunction as safety validation and (2) to investigate inter-horse and inter-limb LOP differences., Study Design: Controlled in vivo experiment., Methods: Daily unilateral forelimb BFR was performed in four horses over 56 days. Clinical examinations and objective gait analyses were performed on Days 0, 28 and 56. Daily LOP values were determined by Doppler evaluation to deliver 80% vascular occlusion at a walk. A linear mixed model evaluated for differences in lameness, kinetic and kinematic gait parameters., Results: There were no significant differences in forelimb lameness (range of Grades 0-2 across all forelimbs), kinematic or kinetic gait parameters over time or between BFR-exposed and control (contralateral) limbs (p > 0.05). Clinically apparent complications related to BFR such as thrombosis or dermatitis were not appreciated. Significant differences in mean LOP values between various horses (p < 0.001) and measured left (204.48 mmHg) and right (173.78 mmHg) forelimbs (p < 0.001) were observed. Mean LOP and standard deviation across all readings was 189.1 ± 22.2 mmHg., Main Limitations: Optimal BFR occlusion percentages and protocols with documented clinical efficacy are unknown. Small study population., Conclusions: Exposure to BFR did not result in forelimb biomechanical dysfunction in four horses. Applied pressures of 75-151 mmHg would likely simulate a range of 50%-80% vascular occlusion in horses, but inherent physiological variation between horses and forelimbs warrants incorporation of individual pressures., (© 2022 EVJ Ltd.)

Background: Squamate reptiles (lizards, snakes, and amphisbaenians) exhibit incredible diversity in their locomotion, behavior, morphology, and ecological breadth. Although they often are used as models of locomotor diversity, surprisingly little attention has been given to muscle development in squamate reptiles. In fact, the most detailed examination was conducted almost 80 years ago and solely focused on the proximal limb regions. Herein, we present forelimb and hindlimb muscle morphogenesis data for three lizard species with different locomotion and feeding strategies: the desert grassland whiptail lizard, the central bearded dragon, and the veiled chameleon. This study fills critical gaps in our understanding of muscle morphogenesis in squamate reptiles and presents a comparative and temporospatial analysis of muscle development., Results: Our results reveal a conserved pattern of early muscle development among lizards with different adult morphologies and ecologies. The variations that exist are concentrated in distal regions, particularly the specialized autopodia of chameleons, where differentiation of muscles associated with the digits is delayed., Conclusions: The chameleon autopod provides an example of major evolutionary modifications to the skeleton with only minor disruption of the conserved order and pattern of limb muscle development. This robustness of muscle patterning facilitates the evolution of extreme yet functional phenotypes., (© 2021 American Association for Anatomy.)

Background: Regeneration of complex patterned structures is well described among, although limited to a small sampling of, amphibians. This limitation impedes our understanding of the full range of regenerative competencies within this class of vertebrates, according to phylogeny, developmental life stage, and age. To broaden the phylogenetic breath of this research, we characterized the regenerative capacity of the Texas blind salamander (Eurycea rathbuni), a protected salamander native to the Edwards Aquifer of San Marcos, Texas and colonized by the San Marcos Aquatic Resource Center. As field observations suggested regenerative abilities in this population, the forelimb stump of a live captured female was amputated in the hopes of restoring the structure, and thus locomotion in the animal. Tails were clipped from two males to additionally document tail regeneration., Results: We show that the Texas blind salamander exhibits robust limb and tail regeneration, like all other studied Plethodontidae. Regeneration in this species is associated with wound epithelium formation, blastema formation, and subsequent patterning and differentiation of the regenerate., Conclusions: The study has shown that the Texas blind salamander is a valuable model to study regenerative processes, and that therapeutic surgeries offer a valuable means to help maintain and conserve this vulnerable species., (© 2020 Wiley Periodicals LLC.)

Hydrofoil-shaped limbs (flipper-hydrofoils) have evolved independently several times in secondarily marine tetrapods and generally fall into two functional categories: (1) those that produce the majority of thrust during locomotion (propulsive flipper-hydrofoils); (2) those used primarily to steer and resist destabilizing movements such as yaw, pitch, and roll (controller flipper-hydrofoils). The morphological differences between these two types have been poorly understood. Theoretical and experimental studies on engineered hydrofoils suggest that flapping hydrofoils with a flexible trailing edge are more efficient at producing thrust whereas hydrofoils used in steering and stabilization benefit from a more rigid one. To investigate whether the trailing edge is generally more flexible in propulsive flipper-hydrofoils, we compared the bone distribution along the chord in both flipper types. The propulsive flipper-hydrofoil group consists of the forelimbs of Chelonioidea, Spheniscidae, and Otariidae. The controller flipper-hydrofoil group consists of the forelimbs of Cetacea. We quantified bone distribution from radiographs of species representing more than 50% of all extant genera for each clade. Our results show that the proportion of bone in both groups is similar along the leading edge (0-40% of the chord) but is significantly less along the trailing edge for propulsive flipper-hydrofoils (40-80% of the chord). Both flipper-hydrofoil types have little to no bony tissue along the very edge of the trailing edge (80-100% of the chord). This suggests a relatively flexible trailing edge for propulsive flipper-hydrofoils compared to controller flipper-hydrofoils in line with findings from prior studies. This study presents a morphological correlate for inferring flipper-hydrofoil function in extinct taxa and highlights the importance of a flexible trailing edge in the evolution of propulsive flipper-hydrofoils in marine tetrapods., (© 2019 Wiley Periodicals, Inc.)

To reduce anatomically unrealistic limb postures in a virtual musculoskeletal model of a horse's forelimb, accurate knowledge on forelimb joint constraints is essential. The aim of this cadaver study is to report all orientation and position changes of the finite helical axes (FHA) as a function of joint angle for different equine forelimb joints. Five horse cadaver forelimbs with standardized cuts at the midlevel of each segment were used. Bone pins with reflective marker triads were drilled into the forelimb bones. Unless joint angles were anatomically coupled, each joint was manually moved independently in all three rotational degrees of freedom (flexion-extension, abduction-adduction, internal-external rotation). The 3D coordinates of the marker triads were recorded using a six infra-red camera system. The FHA and its orientational and positional properties were calculated and expressed against joint angle over the entire range of motion using a finite helical axis method. When coupled, joint angles and FHA were expressed in function of flexion-extension angle. Flexion-extension movement was substantial in all forelimb joints, the shoulder allowed additional considerable motion in all three rotational degrees of freedoms. The position of the FHA was constant in the fetlock and elbow and a constant orientation of the FHA was found in the shoulder. Orientation and position changes of the FHA over the entire range of motion were observed in the carpus and the interphalangeal joints. We report FHA position and orientation changes as a function of flexion-extension angle to allow for inclusion in a musculoskeletal model of a horse to minimize calculation errors caused by incorrect location of the FHA., (© 2019 Wiley Periodicals, Inc.)

There are limited radiographic-guided injection techniques of the insertion of the distal interphalangeal joint (DIPJ) collateral ligaments. The objective of this study was to develop and evaluate a palmar/plantar radiographic-guided injection of the collateral ligament insertion in cadavers. Fifty limbs were used to develop the technique and 24 additional limbs were used to evaluate accuracy. An 18 G, 9 cm spinal needle was placed in the depression between the palmar digital neurovascular bundle and arch of the ungular cartilage with dorsodistal advancement towards the distal phalanx collateral fossa. Radiographs verified ideal needle location on the proximal border of the distal phalanx at the collateral fossa. Dye was injected. Hoof walls were partially removed and collateral ligaments were dissected with needles in place to determine needle and dye location. Accuracy of needle placement into the insertion of the DIPJ collateral ligament was 41/48 (85 per cent), with lower accuracy of dye within the ligament (34/48; 71 per cent). Dye entered the DIPJ in 2/48 injections, but dye entered periligamentous structures in 22/48 (46 per cent) injections. A palmar/plantar radiographic-guided injection of the insertion of the DIPJ collateral ligament had high accuracy rate with low injection rate of the DIPJ in cadavers., Competing Interests: Competing interests: None declared., (© British Veterinary Association 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Both pleasure and competition horses regularly exercise on surfaces such as tarmac, gravel and turf during 'hacking'. Despite this, there is limited evidence relating to the effect of these surfaces upon foot-surface interaction., Objectives: To investigate forelimb foot placement, hoof vibration and movement symmetry in pleasure horses on three commonly encountered hacking surfaces., Study Design: Quantitative gait study in a convenience sample., Methods: Six horses regularly partaking in hacking exercise were ridden in walk and trot on all surfaces. Horses were equipped with one hoof-mounted, accelerometer and four body-mounted inertial measurement units (IMUs) to measure foot impact and movement symmetry. High-speed (400 FPS) video footage of foot-placement was acquired (dorsal, palmar, lateral views). Foot-impact and movement symmetry were analysed with a mixed effects model and Bowker symmetry tests for foot-placement analysis., Results: Vibration power and frequency parameters increase as perceived surface firmness increases from grass, to gravel, to tarmac (P≤0.001). Vibration power parameters were consistently greater at trot compared with walk (P≤0.001), but the same was not true for vibration frequency (P≥0.2). Greatest movement asymmetry was recorded during grass surface trotting. No significant difference in foot-placement was detected between the three surfaces., Main Limitations: This was a field study using three commonly encountered hacking surfaces. Surface properties change easily with water content and temperature fluctuations so care must be taken when considering other similar surfaces, especially at different times of the year. Six leisure horses were used so the results may not be representative of horses of all types., Conclusions: Vibration parameters generally increase as perceived surface firmness increases. Increasing speed alters vibration power but not frequency. Further investigations are required to determine the role that this may play in the development of musculoskeletal disease in horses., (© 2018 EVJ Ltd.)

Data describing segmental masses and moments of inertia (MOI) of limb segments are required for inverse dynamic calculations. In horses, these values are usually calculated using regression equations that have been developed from a limited number of horses representing a small number of breeds. The objective of the present study was to evaluate the performance of a scaling method and a pictorial method for estimating of the values of segmental masses, lengths, and MOI in the equine limb segments by comparing their output with the standard technique involving direct measurements. Limbs of 30 horses of various breeds and sizes were disarticulated post mortem. Segmental masses, lengths, and MOI were determined using a standard method based on weighing the segments, measuring their length with calipers, and estimating the MOI from the rotational frequency of a trifilar pendulum. The scaling method used a jack-knifing procedure to avoid the need for two data sets. The pictorial method was based on digitization of two orthogonal photographs to determine segmental volumes, which were combined with published values for average segment densities to determine the inertial parameters. Scaling method and pictorial method provided comparable estimation of segmental messes and lengths, but the scaling method performed better in estimating segmental MOI. The scaling method worked well enough in the majority of horses but there were a few horses in which it was less effective. The pictorial method sometimes showed a bias correctable by regression equations but it may not warrant the additional effort unless for specific cases., (© 2018 Wiley Periodicals, Inc.)

Many dog owners allow their pets to jump out of a car boot; however, to date, there has been no study that has investigated whether this places dogs at risk of injury. The aim of this study was to investigate the relationship between height and peak vertical ground reaction force (vGRF) in static start jumps. Fifteen healthy adult dogs performed three jumps from a platform that represented common vehicle boot sill heights (0.55, 0.65, 0.75 m), landing on a single force platform. Kinetic data (mediolateral (Fx), craniocaudal (Fy) and vertical (Fz)) were normalised for body weight and analysed via a one-way repeated analysis of variance (ANOVA) and pairwise post hoc tests with a Bonferroni correction applied. There was a significant difference in peak forelimb vGRF between both the 0.55 m (27.35±4.14 N/kg) and the 0.65 m (30.84±3.66 N/kg) platform (P=0.001) and between the 0.65 and 0.75 m (34.12±3.63 N/kg) platform (P=0.001). There was no significant difference in mediolateral or craniocaudal forces between the heights examined. These results suggest that allowing dogs to jump from bigger cars with a higher boot sill may result in augmented levels of loading on anatomical structures. Further research is required to investigate the kinematic effects of height on static jump-down and how peak forelimb vGRF relates to anatomical loading and subsequent injury risk., Competing Interests: Competing interests: None declared., (© British Veterinary Association (unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Chameleon species have recently been adopted as models for evo-devo and macroevolutionary processes. However, most anatomical and developmental studies of chameleons focus on the skeleton, and information about their soft tissues is scarce. Here, we provide a detailed morphological description based on contrast enhanced micro-CT scans and dissections of the adult phenotype of all the forelimb and hindlimb muscles of the Veiled Chameleon (Chamaeleo calyptratus) and compare these muscles with those of other chameleons and lizards. We found the appendicular muscle anatomy of chameleons to be surprisingly conservative considering the remarkable structural and functional modifications of the limb skeleton, particularly the distal limb regions. For instance, the zygodactyl autopodia of chameleons are unique among tetrapods, and the carpals and tarsals are highly modified in shape and number. However, most of the muscles usually present in the manus and pes of other lizards are present in the same configuration in chameleons. The most obvious muscular features related to the peculiar opposable autopodia of chameleons are: (1) presence of broad, V-shaped plantar and palmar aponeuroses, and absence of intermetacarpales and intermetatarsales, between the digits separated by the cleft in each autopod; (2) oblique orientation of the superficial short flexors originating from these aponeuroses, which may allow these muscles to act as powerful adductors of the "super-digits"; and (3) well-developed abductor digiti minimi muscles and abductor pollicis/hallucis brevis muscles, which may act as powerful abductors of the "super-digits.", (© 2017 Wiley Periodicals, Inc.)

Background: Inertial measurement unit (IMU) sensor-based techniques are becoming more popular in horses as a tool for objective locomotor assessment., Objectives: To describe, evaluate and validate a method of stride detection and quantification at walk and trot using distal limb mounted IMU sensors., Study Design: Prospective validation study comparing IMU sensors and motion capture with force plate data., Methods: A total of seven Warmblood horses equipped with metacarpal/metatarsal IMU sensors and reflective markers for motion capture were hand walked and trotted over a force plate. Using four custom built algorithms hoof-on/hoof-off timing over the force plate were calculated for each trial from the IMU data. Accuracy of the computed parameters was calculated as the mean difference in milliseconds between the IMU or motion capture generated data and the data from the force plate, precision as the s.d. of these differences and percentage of error with accuracy of the calculated parameter as a percentage of the force plate stance duration., Results: Accuracy, precision and percentage of error of the best performing IMU algorithm for stance duration at walk were 28.5, 31.6 ms and 3.7% for the forelimbs and -5.5, 20.1 ms and -0.8% for the hindlimbs, respectively. At trot the best performing algorithm achieved accuracy, precision and percentage of error of -27.6/8.8 ms/-8.4% for the forelimbs and 6.3/33.5 ms/9.1% for the hindlimbs., Main Limitations: The described algorithms have not been assessed on different surfaces., Conclusions: Inertial measurement unit technology can be used to determine temporal kinematic stride variables at walk and trot justifying its use in gait and performance analysis. However, precision of the method may not be sufficient to detect all possible lameness-related changes. These data seem promising enough to warrant further research to evaluate whether this approach will be useful for appraising the majority of clinically relevant gait changes encountered in practice., (© 2016 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Reasons for Performing Study: Currently, there is no objective information quantifying pressures exerted by distal limb bandages., Objectives: To quantify the pressure exerted by each compression layer, a polo wrap (DLP), a compression bandage (DLC), and to measure the effect of time on sub-bandage pressure., Study Design: Longitudinal observational experiment., Methods: A DLC construct included a cotton roll compressed with brown gauze and elastic layers and the DLP construct included a pillow pad compressed by a cloth wrap. Dorsal and lateral sensors were placed on the mid-metacarpus. In healthy horses, sub-bandage pressures were recorded during application (n = 8) and at scheduled time points over the 24 (n = 9) and 96 h periods (n = 8). A generalised linear model was used to evaluate associations between pressure and sensor location, bandage type and time (P<0.05)., Results: For the DLC, dorsal and lateral sensor pressures were 187 mmHg (95% CI 185-189 mmHg) and 142 mmHg (95% CI 133-151 mmHg). Combined sensor pressure after application of the brown gauze was 80 mmHg (95% CI 75-85 mmHg) and rose to 165 mmHg (95% CI 160-170 mmHg) after the elastic layer. Combined pressure at the end of the 96 h period was 135 mmHg (95% CI 123-147 mmHg). For the DLP bandage, location but not time was significant. Combined pressures ranged between 75 mmHg (95% CI 53-97 mmHg) and 85 mmHg (95% CI 63-107 mmHg)., Conclusions: Pressure distribution was not uniform. The DLP pressures were maintained for a 24 h period. The DLC maintained high pressures for 96 h, but a significant decrease in pressure occurred between 6 and 12 h. Providing there are no other reasons to change a bandage, a 4 day interval between bandages may be appropriate if maintaining distal limb compression is the principal indication., (© 2016 EVJ Ltd.)

A previous thermographic study of racehorses identified 13 regions of interest (ROIs) for monitoring the impact of training. However, that investigation did not consider the influence of breed, age, gender or training intensity level on the temperature of ROIs. The present study adopted a multivariate analysis approach to determine whether the aforementioned factors, along with ambient temperature, significantly influenced ROI temperature in the key body regions. Thermography measurements were obtained from 53 racehorses of three breeds. Horses were in regular training for over 10 months, having 13 thermographic examinations in each racing season. Backward stepwise multiple linear regression indicated that ambient temperature and breed contributed significantly to the model for predicting ROI temperature at all 13 ROIs. Training intensity level contributed significantly to the model only at the thoracic vertebrae, the left third metacarpal bone and left fetlock joint. Neither gender nor age contributed to the model significantly at any ROI. Our data suggest that ambient temperature, breed and training level affect racehorse body surface temperature in some areas of the distal parts of the forelimbs and the back. This contributes to a better understanding of the normal range of thermographic findings in racehorses undergoing intensive training., (© 2016 Japanese Society of Animal Science.)

Reasons for Performing Study: The high, repetitive demands imposed on polo horses in training and competition may predispose them to musculoskeletal injuries and lameness., Objectives: To quantify movement symmetry and lameness in a population of polo horses, and to investigate the existence of a relationship with age., Study Design: Convenience sampled cross-sectional study., Methods: Sixty polo horses were equipped with inertial measurement units (IMUs) attached to the poll, and between the tubera sacrale. Six movement symmetry measures were calculated for vertical head and pelvic displacement during in-hand trot and compared with values for perfect symmetry, compared between left and right limb lame horses, and compared with published thresholds for lameness. Regression lines were calculated as a function of age of horse., Results: Based on 2 different sets of published asymmetry thresholds 52-53% of the horses were quantified with head movement asymmetry and 27-50% with pelvic movement asymmetry resulting in 60-67% of horses being classified with movement asymmetry outside published guideline values for either the forelimbs, hindlimbs or both. Neither forelimb nor hindlimb asymmetries were preferentially left or right sided, with directional asymmetry values across all horses not different from perfect symmetry and absolute values not different between left and right lame horses (P values >0.6 for all forelimb symmetry measures and >0.2 for all hindlimb symmetry measures). None of the symmetry parameters increased or decreased significantly with age., Conclusions: A large proportion of polo horses show gait asymmetries consistent with previously defined thresholds for lameness. These do not appear to be lateralised or associated with age., (© 2015 EVJ Ltd.)

Reasons for Performing Study: Lungeing is commonly used as part of standard lameness examinations in horses. Knowledge of how lungeing influences motion symmetry in sound horses is needed., Objectives: The aim of this study was to objectively evaluate the symmetry of vertical head and pelvic motion during lungeing in a large number of horses with symmetric motion during straight line evaluation., Study Design: Cross-sectional prospective study., Methods: A pool of 201 riding horses, all functioning well and considered sound by their owners, were evaluated in trot on a straight line and during lungeing to the left and right. From this pool, horses with symmetric vertical head and pelvic movement during the straight line trot (n = 94) were retained for analysis. Vertical head and pelvic movements were measured with body mounted uniaxial accelerometers. Differences between vertical maximum and minimum head (HDmax, HDmin) and pelvic (PDmax, PDmin) heights between left and right forelimb and hindlimb stances were compared between straight line trot and lungeing in either direction., Results: Vertical head and pelvic movements during lungeing were more asymmetric than during trot on a straight line. Common asymmetric patterns seen in the head were more upward movement during push-off of the outside forelimb and less downward movement during impact of the inside limb. Common asymmetric patterns seen in the pelvis were less upward movement during push-off of the outside hindlimb and less downward movement of the pelvis during impact of the inside hindlimb. Asymmetric patterns in one lunge direction were frequently not the same as in the opposite direction., Conclusions: Lungeing induces systematic asymmetries in vertical head and pelvic motion patterns in horses that may not be the same in both directions. These asymmetries may mask or mimic fore- or hindlimb lameness., (© 2015 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Ancestral frogs underwent anatomical shifts including elongation of the hindlimbs and pelvis and reduction of the tail and vertebral column that heralded the transition to jumping as a primary mode of locomotion. Jumping has been hypothesized to have evolved in a step-wise fashion with basal frogs taking-off with synchronous hindlimb extension and crash-landing on their bodies, and then their limbs move forward. Subsequently, frogs began to recycle the forelimbs forward earlier in the jump to control landing. Frogs with forelimb landing radiated into many forms, locomotor modes, habitats, and niches with controlled landing thought to improve escape behavior. While the biology of take-off behavior has seen considerable study, interspecific comparisons of take-off and landing behavior are limited. In order to understand the evolution of jumping and controlled landing in frogs, data are needed on the movements of the limbs and body across an array of taxa. Here, we present the first description and comparison of kinematics of the hindlimbs, forelimbs and body during take-off and landing in relation to ground reaction forces in four frog species spanning the frog phylogeny. The goal of this study is to understand what interspecific differences reveal about the evolution of take-off and controlled landing in frogs. We provide the first comparative description of the entire process of jumping in frogs. Statistical comparisons identify both homologous behaviors and significant differences among species that are used to map patterns of trait evolution and generate hypotheses regarding the functional evolution of take-off and landing in frogs., (© 2015 Wiley Periodicals, Inc.)

Reasons for Performing Study: Hoof conformation, foot placement and movement asymmetry are routinely assessed as part of the lameness examination. However, to date, few studies have described these parameters, or the interplay between them, in the general horse population., Objectives: To assess foot conformation and foot placement in the forelimbs of a group of general purpose horses and investigate the relationships between foot placement, foot conformation and movement asymmetry., Study Design: Observational cross-sectional study., Methods: Forty-three horses were included in the study. Measurements were taken from photographs of each forelimb to assess foot conformation. Video footage was recorded simultaneously from perpendicular cameras at both walk and trot and used to categorise foot placement. Inertial sensor data were used to assess head movement asymmetry in trot., Results: There was a high degree of variation in foot placement between and within horses, but a 'lateral heel' placement was most common in walk and a 'lateral' placement most common in trot. Foot placement was associated with dorsal and palmar hoof angles but there was no relationship between foot placement and the other conformation parameters, nor with movement asymmetry. Moderate negative correlations were found between several of the conformation parameters and movement asymmetry., Conclusions: A relationship exists between foot conformation and movement asymmetry with decreasing hoof width and hoof length related to increasing amount of movement asymmetry. In the population of horses studied here--deemed to be 'well functioning' by their owners/riders--foot placement was found to be independent of movement asymmetry and, to a large extent, independent of foot conformation., (© 2014 EVJ Ltd.)

Reasons for Performing Study: We wished to add to the existing baseline data on impact loading of the distal limb as a precursor to assessing the potential role of impact in injury and joint disease., Objectives: To examine the effect of 3 hoof-strike conditions (toe first, flat and heel first) and 2 specimen masses (with and without a ballast of ∼2% body mass) on impact deceleration and vibration frequencies and energies at the hoof, first phalanx and third metacarpal., Study Design: Biomechanical experiments in cadaver material., Methods: Eight cadaver limbs were subjected to randomised, repeated controlled trials, in which the hoof was struck by a pendulum impact-testing machine (impact velocity, 3.55 m/s) in the 3 strike and 2 mass conditions. Data from triaxial accelerometers on the hoof, first phalanx and third metacarpal quantified, for all trials, the peak impact acceleration, frequencies in the first 6.4 ms following impact, the frequency with the most energy, 95% of the total energy and the frequency at 95% cumulative energy. The effects of the strike and mass conditions on each variable were statistically tested using repeated-measures ANOVA (α = 0.05)., Results: Signal energy reaching the third metacarpal was 6-31% of that at the hoof. A heel-first strike produced the largest peak accelerations and highest frequencies among all strike conditions, and changing the mass had no effect regardless of strike condition., Conclusions: Large accelerations that occur upon impact of the hoof with the ground are attenuated by the distal structures of the equine limb, but still carry considerable energy within the signal that could be damaging to tissue and are dependent on hoof-strike condition but not ballast. Our results suggest that impact loading on the hoof could be a factor in contributing to bone injury and joint disease in the distal limb., (© 2014 EVJ Ltd.)

Reasons for Performing Study: Thus far, pressure-plate analysis has been limited to measurements on a hard surface, whereas equine athletes routinely perform on a deformable substrate., Objectives: To explore pressure-plate analysis on arena footing., Study Design: Nonrandomised crossover study using noninvasive techniques., Methods: Five sound, unshod ponies were walked and trotted over a pressure plate in 2 different conditions. In the first session, the plate was covered with only a 5 mm rubber mat, and in the second session, with an additional 50 mm layer of sand and synthetic fibres. Limb loading and timing variables (peak vertical force, vertical impulse, peak vertical pressure, hoof contact area and stance phase duration) were obtained. Toe-heel and mediolateral hoof balance of the vertical force were calculated throughout stance (126 Hz)., Results: Peak vertical force, vertical impulse, peak vertical pressure and stance phase duration were decreased on the soft substrate, while hoof contact area increased. At impact, there was more even load distribution between the toe and heel region on the soft vs. hard surface. At mid-stance, there was more loading of the toe region on the soft compared with the hard surface. At impact, there was more even load distribution between lateral and medial on the soft vs. hard surface at walk, but not at trot., Conclusions: Comparison of observed vs. expected impulse indicated that the main factor involved in the lower loading on the soft surface is the dampening effect of the soft substrate, although definitive conclusions require concurrent force-plate analysis. The pressure plate permitted quantitative evaluation of hoof balance of the vertical force on a deformable surface at the walk and trot and proved that there is more even load distribution on arena footing., (© 2013 EVJ Ltd.)

Whole body vibration (WBV) has been linked to neck and back pain, but the biomechanical and physiological mechanisms responsible for its development and maintenance are unknown. A rodent model of WBV was developed in which rats were exposed to different WBV paradigms, either daily for 7 consecutive days (repeated WBV) or two single exposures at Day 0 and 7 (intermittent WBV). Each WBV session lasted for 30 min and was imposed at a frequency of 15 Hz and RMS platform acceleration of 0.56 ± 0.07 g. Changes in the withdrawal response of the forepaw and hind paw were measured, and were used to characterize the onset and maintenance of behavioral sensitivity. Accelerations and displacements of the rat and deformations in the cervical and lumbar spines were measured during WBV to provide mechanical context for the exposures. A decrease in withdrawal threshold was induced at 1 day after the first exposure in both the hind paw and forepaw. Repeated WBV exhibited a sustained reduction in withdrawal threshold in both paws and intermittent WBV induced a sustained response only in the forepaw. Cervical deformations were significantly elevated which may explain the more robust forepaw response. Findings suggest that a WBV exposure leads to behavioral sensitivity., (© 2013 Orthopaedic Research Society.)

Moles have modified thoracic limbs with hypertrophied pectoral girdle muscles that allow them to apply remarkably high lateral out-forces during the power stroke when burrowing. To further understand the high force capabilities of mole forelimbs, architectural properties of the thoracic limb muscles were quantified in the Eastern mole (Scalopus aquaticus). Architectural properties measured included muscle mass, moment arm, belly length, fascicle length, and pennation angle, and these were used to provide estimates of maximum isometric force, joint torque, and power. Measurements of muscle moment arms and limb lever lengths were additionally used to analyze the out-force contributions of the major pectoral girdle muscles. Most muscles have relatively long fascicles and little-to-no pennation. The humeral abductor/rotators as a functional group are massive and are capable of relatively high force, power, and joint torque. Of this group, the bipennate m. teres major is the most massive and has the capacity to produce the highest force and joint torque to abduct and axially rotate the humerus. In general, the distal limb muscles are relatively small, but have the capacity for high force and mechanical work by fascicle shortening. The muscle architectural properties of the elbow extensors (e.g., m. triceps brachii) and carpal flexors (e.g., m. palmaris longus) are consistent with the function of these muscles to augment lateral out-force application. The humeral abductor/rotators m. latissimus dorsi, m. teres major, m. pectoralis, and m. subscapularis are calculated to contribute 13.9 N to out-force during the power stroke, and this force is applied in a 'frontal' plane causing abduction of the humerus about the sternoclavicular joint. Moles have several specializations of their digging apparatus that greatly enhance the application of out-force, and these morphological features suggest convergence on limb form and burrowing function between New and Old World moles., (Copyright © 2013 Wiley Periodicals, Inc.)

Reasons for Performing Study: Current literature suggests that thermographic imaging of horses should be performed in a draught-free room. However, studies on the effect of airflow on determined temperature have not been published., Objectives: To investigate effects of airflow on thermographically determined temperature of horses' forelimbs; to assess the relationship of wind velocity, rectal temperature, ambient temperature and humidity., Methods: Thermographic images were obtained for the forelimbs of 6 horses in a draught-free room. Three replicates (R) with defined wind velocities (R1, 0.5-1.0 m/s; R2, 1.3-2.6 m/s; and R3, 3.0-4.0 m/s) were conducted. Each replicate consisted of a baseline image, a 15 min phase with the wind on and a 15 min phase with the wind off. We exposed only the right leg to airflow and determined the temperature by thermography with the wind on and wind off. Temperature differences between baseline and wind on, between wind on and wind off and between different wind velocities were analysed by a general linear model, Student's paired t test and ANOVA., Results: After the onset of wind, the temperature on the right forelimb decreased within 1-3 min (by approximately 0.6°C at R1, 1.5°C at R2 and 2.1°C at R3). With the wind off, the temperature increased within 3 min (by approximately 1.2°C at R1, 1.7°C at R2 and 2.1°C at R3). With increasing wind velocity, the temperature differences between baseline and wind on and between wind on and wind off increased significantly., Conclusions: Barely noticeable wind velocities caused a decrease in thermographically determined temperatures of the forelimbs of the horse. Further research is required to assess the influence of airflow on other parts of the body and at different ambient temperatures, as well as the effect on horses with inflammatory lesions, especially of the distal limbs., Potential Relevance: It is essential for practitioners to perform thermography on horses in a draught-free environment in order to avoid false-positive or -negative diagnoses., (© 2012 EVJ Ltd.)

Reasons for Performing Study: To improve understanding of the internal structure of the proximal phalanx (P1), response of the bone to load and possible relation to the pathogenesis of fractures in P1., Objectives: To model the P1 and replicate the loads experienced by the bone in stance, walk, trot and gallop using finite element analysis., Methods: The geometry of the P1 was captured using micro-computed tomography (μCT) and was reconstructed in 3 dimensions. Values for material properties and forces experienced at stance, walk, trot and gallop were taken from the literature and were applied to the reconstructed model. Using the same total load across the proximal articular surface, the model was solved with and without loading of the sagittal groove. Biomechanical performance was then simulated with finite element analysis and evaluated in terms of von Mises stress maps., Results: Compared with the lowest force simulation equivalent to stance, the effects of the gallop force showed higher levels of stress along the sagittal groove and on the palmar surface just distal to the sagittal groove in both models, with and without the sagittal groove loaded. The results highlighted an area of bone on the dorsal aspect of P1 that experiences lower stress compared with the rest of the dorsal surface, an effect that was much more apparent when the sagittal groove was not loaded. Qualitative comparison of the models revealed minimal difference in the pattern of von Mises stress between the loaded and unloaded groove models., Conclusions: The study demonstrates a finite element model of P1 that produces results consistent with clinical observation. The simulated high stress levels associated with the sagittal groove correspond to the most common site for fractures in the equine P1., Potential Relevance: With refinement of the model and further investigation, it may be possible to improve understanding of the behaviour of P1 under loading conditions that more closely simulate those experienced in the living animal, leading to a more solid understanding of fractures of P1., (© 2012 EVJ Ltd.)

Evaluation of the relationships between muscle structure and digging function in fossorial species is limited. Badgers and other fossorial specialists are expected to have massive forelimb muscles with long fascicles capable of substantial shortening for high power and applying high out-force to the substrate. To explore this hypothesis, we quantified muscle architecture in the thoracic limb of the American badger (Taxidea taxus) and estimated the force, power, and joint torque of its intrinsic musculature in relation to the use of scratch-digging behavior. Architectural properties measured were muscle mass, belly length, fascicle length, pennation angle, and physiological cross-sectional area. Badgers possess hypertrophied shoulder flexors/humeral retractors, elbow extensors, and digital flexors. The triceps brachii is particularly massive and has long fascicles with little pennation, muscle architecture consistent with substantial shortening capability, and high power. A unique feature of badgers is that, in addition to elbow joint extension, two biarticular heads (long and medial) of the triceps are capable of applying high torques to the shoulder joint to facilitate retraction of the forelimb throughout the power stroke. The massive and complex digital flexors show relatively greater pennation and shorter fascicle lengths than the triceps brachii, as well as compartmentalization of muscle heads to accentuate both force production and range of shortening during flexion of the carpus and digits. Muscles of most functional groups exhibit some degree of specialization for high force production and are important for stabilizing the shoulder, elbow, and carpal joints against high limb forces generated during powerful digging motions. Overall, our findings support the hypothesis and indicate that forelimb muscle architecture is consistent with specializations for scratch-digging. Quantified muscle properties in the American badger serve as a comparator to evaluate the range of diversity in muscle structure and contractile function that exists in mammals specialized for fossorial habits., (Copyright © 2012 Wiley Periodicals, Inc.)

Background: Although urodela amphibians completely regenerate amputated limbs, the potency of limb regeneration in mammalians is very low. In mice and humans, a digit tip regenerates, but no regeneration beyond the digit joint occurs. In this article, we describe the induction of bone formation by BMPs in the forearm, a more proximal region, of neonatal mice. Distal halves of the radius and ulna were removed from limbs amputated at the wrist level in advance, and gelatin rods containing BMPs were grafted in the space of the forearm. BMP-7 and BMP-2 were effective., Results: The induction of bone formation depended on the amount of BMP-7 in grafted gelatin gels. BMP-7 at over 320 ng/limb induced long bones within 10 days. Cartilage formation was always observed before the bone formation as in the case of normal limb development. The origin of cells responsive to BMP-7 is not clear, but the formation of large bone tissues in a relatively short time suggests a wide distribution of precursor cells in the limbs. Grafting of dye-stained mesenchymal tissue fragments suggested that mesenchymal tissues other than the dermis, bone, and joint cartilage are responsive to BMP-7 and form cartilage/bone. Two long bones induced were arranged in parallel fashion in many cases like the radius and ulna. An agonist of hedgehog promoted the formation of bones in the presence of BMP-7. Furthermore, bone elements were fused to stump bones to form a single bone., Conclusions: The results suggest the potency of bone pattern regeneration in the amputated forearm of a neonatal mouse., (Copyright © 2012 Wiley Periodicals, Inc.)

Despite clinical efforts to treat growth disturbances only little is known about the growth potential of the different zones of the growth plate. The aim of this study was to investigate the growth potential of different zones of the growth plate. A total of 20 New Zealand White rabbits were used for this experiment. The right and left ulna of each animal were used resulting in a total of 40 ulnae. Animals were assigned into five groups. In groups I and II resection of the metaphyseal (n = 12) or the epiphyseal (n = 6) segment of the growth plate was performed. In group III resection of the growth plate and re-implantation was performed (n = 6). In group IV the growth plate was resected and re-implanted after a 180° rotation (n = 6). Animals in group V served as controls. Histologic and radiologic examinations were performed to evaluate the growth process at 1, 2, 4, and 12 weeks following surgery. In group I, III, and IV temporary growth disturbance which was compensated within a short time was observed. Resection of the epiphyseal part resulted in growth arrest of the distal ulna in combination with normal growth of the radius which led to and valgus deformity of the limb. The results of this study indicate the importance of the reserve zone for the functioning of the growth plate., (Copyright © 2011 Orthopaedic Research Society.)

Tree-kangaroos are a unique group of arboreal marsupials that evolved from terrestrial ancestors. The recent discovery of well-preserved specimens of extinct tree-kangaroo species (genus Bohra) within Pleistocene cave deposits of south-central Australia provides a unique opportunity to examine adaptive evolution of tree-kangaroos. Here, we provide the first detailed description of the functional anatomy of the forelimb, a central component of the locomotor complex, in the extant Dendrolagus lumholtzi, and compare its structure and function with representatives of other extant marsupial families. Several features were interpreted as adaptations for coping with a discontinuous, uneven and three-dimensional arboreal substrate through enhanced muscular strength and dexterity for propulsion, grasping, and gripping with the forelimbs. The forelimb musculoskeletal anatomy of Dendrolagus differed from terrestrial kangaroos in the following principal ways: a stronger emphasis on the development of muscles groups responsible for adduction, grasping, and gripping; the enlargement of muscles that retract the humerus; and modified shape of the scapula and bony articulations of the forelimb bones to allow improved mobility. Many of these attributes are convergent with other arboreal marsupials. Tree-kangaroos, however, still retain the characteristic bauplan of their terrestrial ancestors, particularly with regard to skeletal morphology, and the muscular anatomy of the forelimb highlights a basic conservatism within the group. In many instances, the skeletal remains of Bohra have similar features to Dendrolagus that suggest adaptations to an arboreal habit. Despite the irony of their retrieval from deposits of the Nullarbor "Treeless" Plain, forelimb morphology clearly shows that the species of Bohra were well adapted to an arboreal habitat., (Copyright © 2011 Wiley-Liss, Inc.)

The rotator cuff musculature imparts dynamic stability to the glenohumeral joint. In particular, the balance between the subscapularis anteriorly and the infraspinatus posteriorly, often referred to as the rotator cuff "force couple," is critical for concavity compression and concentric rotation of the humeral head. Restoration of this anterior-posterior force balance after chronic, massive rotator cuff tears may allow for deltoid compensation, but no in vivo studies have quantitatively demonstrated an improvement in shoulder function. Our goal was to determine if restoring this balance of forces improves shoulder function after two-tendon rotator cuff tears in a rat model. Forty-eight rats underwent detachment of the supraspinatus and infraspinatus. After four weeks, rats were randomly assigned to three groups: no repair, infraspinatus repair, and two-tendon repair. Quantitative ambulatory measures including medial/lateral forces, braking, propulsion, and step width were significantly different between the infraspinatus and no repair group and similar between the infraspinatus and two-tendon repair groups at almost all time points. These results suggest that repairing the infraspinatus back to its insertion site without repair of the supraspinatus can improve shoulder function to a level similar to repairing both the infraspinatus and supraspinatus tendons. Clinically, a partial repair of the posterior cuff after a two-tendon tear may be sufficient to restore adequate function. An in vivo model system for two-tendon repair of massive rotator cuff tears is presented., (Copyright © 2011 Orthopaedic Research Society.)

Functional MRI (fMRI) based on the blood oxygen level-dependent (BOLD) contrast is widely used in preclinical neuroscience. The small dimensions of rodent brain place high demands on spatial resolution, and hence on the sensitivity of the fMRI experiment. This work investigates the performance of a 400-MHz cryogenic quadrature transceive radiofrequency probe (CryoProbe) with respect to the enhancement of the BOLD sensitivity. For this purpose, BOLD fMRI experiments were performed in mice during electrical forepaw stimulation using the CryoProbe and a conventional room temperature surface coil of comparable dimensions. Image signal-to-noise ratio (SNR) and temporal SNR were evaluated as quality measures for individual images and for fMRI time series of images, resulting in gains (mean ± standard deviation) with factors of 3.1 ± 0.7 and 1.8 ± 1.0 when comparing the CryoProbe and room temperature coil. The CryoProbe thermal shield temperature did not affect the noise characteristics, with temporal noise levels being 63 ± 16% of the corresponding room temperature value. However, a significant effect on BOLD amplitudes was found, which was attributed to temperature-dependent baseline cerebral blood volumes. Defined local thermal conditions were found to be a critical parameter for achieving an optimal and reproducible fMRI signal. In summary, the CryoProbe represents an attractive alternative for the enhancement of image SNR, temporal SNR and BOLD sensitivity in mouse fMRI experiments., (Copyright © 2010 John Wiley & Sons, Ltd.)

Evaluating potentially analgesic effects of drugs and various treatments is critically dependent on valid animal models of pain. Since primary somatosensory (SI) cortex is likely to play an important role in processing sensory aspects of pain, we here assess whether monitoring SI cortex nociceptive C fibre evoked potentials can provide useful information about central changes related to hyperalgesia in rats. Recordings of tactile and CO(2)-laser C fibre evoked potentials (LCEPs) in forelimb and hind limb SI cortex were made 20-24h after UV-B irradiation of the heel at a dose that produced behavioural signs of hyperalgesia. LCEPs from irradiated skin increased significantly in duration but showed no significant change in magnitude, measured as area under curve (AUC). By contrast, LCEPs in hind limb SI cortex from skin sites nearby the irradiated skin showed no increase in duration or onset latency but increased significantly in magnitude after UV-B irradiation. The LCEPs in forelimb or hind limb SI cortex elicited from forelimb skin did not change in magnitude, but were significantly delayed in hind limb SI cortex. Tramadol, a centrally acting analgesic known to reduce hyperalgesia, induced changes that counteracted the changes produced by UV-B irradiation on transmission to SI cortex from the hind paw, but had no significant effect on time course of LCEPs from forelimb skin. Tactile evoked potentials were not affected by UV-B irradiation or tramadol. We conclude that altered sensory processing related to hyperalgesia is reflected in altered LCEPs in SI cortex., (Copyright © 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.)

Reasons for Performing Study: Mechanical characterisation of the high speed gallop has significant importance for animal welfare and basic biology. Kinematic parameters such as the velocity of each foot at contact can inform theories of why animals gallop, and supplant epidemiological investigation into the mechanisms of musculoskeletal injury., Objective: To determine the velocity at which the fore and hind hooves of elite galloping horses impact the surface., Methods: High speed videography was used to measure the horizontal and vertical velocity of the hoof immediately prior to impact, and the subsequent sink (vertical) and slip (horizontal) distances travelled by the hoof into the surface. Horse speed ranged from 11-19 m/s. In total 170 forelimb and 168 hindlimb foot falls from 89 horses were analysed., Results: Horizontal and vertical hoof velocity increased with speed (P<0.001). Horizontal hoof velocity was significantly greater in the hindlimbs compared to the forelimbs (P<0.001) and was greater in the nonlead limbs compared to the lead limbs (P<0.001). Vertical hoof velocity was significantly greater in the lead limb than the nonlead limb (P<0.001). Overall, forelimbs contacted the ground with a more acute velocity vector angle than hindlimbs (P<0.001). Lead limbs contacted the ground at more acute angles than nonlead limbs (P<0.001). Vertical and horizontal velocities were highly correlated to sink and slip distance., Conclusion: Hindlimbs impact the surface at higher velocity than forelimbs, which is likely to result in higher peak impact forces in the hindlimbs. This runs counter to the finding of lower incidence of injury in hindlimbs., Potential Relevance: Explanations consistent with these findings include the hindlimbs more effectively dampening peak impact forces, or that other injury mechanisms, such as limb vibration and limb load at mid stance, play an important role in injury., (© 2010 EVJ Ltd.)

Reasons for Performing Study: Simple objective assessment tools are essential to monitor the clinical efficacy of therapeutic interventions used in equine orthopaedics and rehabilitation. In human medicine, goniometry is a validated tool to quantify restrictions in joint range of motion (ROM); however, the technique is not validated in horses., Objectives: To validate 2 different goniometry techniques for the measurement of passive flexion of the fetlock, carpus and hock by examining; 1) the intra- and inter-tester reliability; 2) the differences between 2 goniometry techniques and 3) differences between standing and anaesthetised horses., Methods: The study is composed of three parts: 1) the intra- and inter-tester reliability was examined on 10 horses, where each horse was assessed by 5 pairs of testers measuring ROM with a universal goniometer; 2) the differences between 2 goniometry techniques were examined on 14 horses, each assessed by 2 investigators (either working in pairs with one investigator holding the limb and the other measuring the joint angle, or working individually at the same time holding and measuring); 3) on 6 horses, the differences between standing and anaesthetised horses were assessed by 2 investigators with the same techniques as described above. Nonparametric tests (Mann-Whitney, Wilcoxon sign-rank) and Intraclass Correlation Coefficient (ICC) were used for statistical analysis (P < 0.05)., Results: 1) The intra-tester reliability was high to excellent (ICC 0.8-1) and the inter-tester reliability low to average (ICC 0.1-0.5); 2) significant differences in joint ROM were registered in carpus and hock when measuring in pairs compared to singly and 3) significant differences in joint ROM were registered measuring anaesthetised compared to standing horses., Conclusions: As shown in human studies, goniometry is a promising tool in documenting passive flexion of fetlock, carpus and hock, if used by the same investigator. However, additional studies are needed for further validation., (© 2010 EVJ Ltd.)

Reasons for Performing Study: Biomechanical events of the distal limb during the landing phase of a jump have been proposed to be risk factors for injury, indicating need for further characterisation of the landing and the hoof-surface interaction. This is essential also for valid testing of arena surfaces when simulating actual conditions., Objectives: To investigate the hoof landing characteristics for different limbs of elite showjumping horses during the landing phase when jumping 1.30-1.50 m competition fences on 2 different arena surfaces., Materials and Methods: A single, fixed high speed camera (1000 frames/s) was aimed at landing spots after different fences during 2 competitions. A total of 64 hoof landings were recorded on one sand and one turf surface (using studs on the turf). Hoof movements were tracked from calibrated video sequences. Landing velocities, landing angles, maximal vertical and horizontal deceleration and timing of maximal deceleration peaks were calculated and compared between leading/trailing fore-/hindlimbs. All outcomes were analysed for limb, using generalised linear models and controlling for effects of surface and obstacle., Results: Landing speed differed among limbs (P < 0.02 for all speeds and models). The leading hoof approached the ground more acutely angled to the horizontal plane than the trailing comparing fore- (P < 0.001) and hindlimbs (0.05 ≥ P > 0.01), respectively. Differences in landing and braking kinematics were also found between surfaces and obstacles; however, these effects were hard to separate because of the nonexperimental design., Conclusions: The landing and braking characteristics of the hooves varied substantially between hind-, fore-, trailing and leading limbs. Developing mechanical testing devices for arena surfaces, this fairly wide range of biomechanical events must be considered, in order to simulate the horse-surface interaction., (© 2010 EVJ Ltd.)

Reasons for Performing Study: Bending of the equine metacarpal bones during locomotion is poorly understood. Cantilever bending, in particular, may influence the loading of the metacarpal bones and surrounding structures in unique ways., Hypothesis: We hypothesised that increased amounts of sagittal-plane cantilever bending may govern changes to the shape of the metacarpal bones of Thoroughbred racehorses during training. We hypothesised that this type of bending would require a linear change to occur in the combined second moment of area of the bones for sagittal-plane bending (I) during race training., Methods: Six Thoroughbred racehorses were used, who had all completed at least 4 years of race training at a commercial stable. The approximate change in I that had occurred during race training was computed from radiographic measurements at the start and end of training using a simple model of bone shape., Results: A significant (P < 0.001), approximately linear pattern of change in I was observed in each horse, with the maximum change occurring proximally and the minimum change occurring distally., Conclusions: The pattern of change in I was compatible with the hypothesis that sagittal-plane cantilever bending governed changes to the shape of the metacarpal bones during race training., (© 2010 EVJ Ltd.)

Reasons for Performing Study: Gait analysis parameters are sensitive to alterations in velocity. For comparison of nonspeed-matched data, the velocity dependency needs to be known., Objectives: To describe the changes in gait pattern and determine the relationships between stride duration, vertical impulse, contact time and peak vertical force within a range of walking and trotting speeds., Methods: Thirty-eight nonlame Warmblood horses were subjected to an incremental speed test. The spans of speed were adjusted individually to each horse and ranged from 1.1-2.1 m/s at walk and from 2.5-5.8 m/s at trot. Time, force and spatial parameters of each limb were measured with an instrumented treadmill and analysed with regression analysis using velocity as the independent variable., Results: At a slow walk the shape of the force curve was generally single-peaked in the fore- and trapezoidal in the hindlimbs. With increasing speed, the curves turned into the typical double-peaked shape with a higher second peak in the fore- and a higher first peak in the hindlimbs. With increasing velocity, stride duration, stance durations and limb impulses of the fore- and hindlimbs decreased in both gaits (r2 > 0.92). Increasing speed caused a weight shift to the forehand (walk: from 56 to 59%; trot: from 55 to 57%). Despite decreasing limb impulses, peak vertical forces increased in both gaits (r2 > 0.83). The suspension duration of the trot increased with faster velocities and reached a plateau of around 90 ms at the highest speeds. At a slow trot, the forelimbs impacted first and followed the hindlimbs at lift-off; with increasing speed, the horses tended to impact earlier with the hindlimbs. Contralateral symmetry indices of all parameters remained unchanged., Conclusions: Subject velocity affects time, force and spatial parameters. Knowing the mathematical function of these interdependencies enables correction of nonspeed-matched data., (© 2010 EVJ Ltd.)

Reasons for Performing Study: Although the main cause of injury to the superficial digital flexor tendon (SDFT) is assumed to be high intensity loading of the tendon, to date the forces exerted on the SDFT during cantering have never been measured., Objective: To measure the force exerted on the SDFT at walk, trot and canter on a treadmill., Methods: Arthroscopically implantable force probes (AIFP) were implanted in the SDFT of the left and right forelimbs of 8 Thoroughbred horses (480-565 kg). The output of the AIFP was calibrated using the SDFT force calculated by inverse dynamics and an in vitro model of the lower forelimb at trot. The AIFP output was recorded at 1000 Hz at the walk, trot and canter (9 m/s) on a flat treadmill., Results: AIFP data were analysed successfully in 13 measurement sessions at the walk and trot, in the leading forelimb in 8 sessions at canter and in the trailing forelimb in 5 sessions at canter. The mean ± s.d. maximal force in the SDFT was 3110 ± 1787 N at the walk, 5652 ± 2472 N at the trot, 7030 ± 2948 N in the leading forelimb and 6453 ± 2940 N in the trailing forelimb at canter., Conclusions: The force in the SDFT increases with running speed from the walk to the canter. The force in the SDFT could not be measured at the gallop. Further study is needed to determine the force in the SDFT at high speed, because it is important for preventing injuries to the SDFT to limit overloading of this tendon., (© 2010 EVJ Ltd.)

Reasons for Performing Study: Conformation in horses is often considered an indicator of athletic ability, performance and resistance to orthopaedic disease. Evaluation is performed in the standing horse and repeatability influenced by stance. Ground reaction forces increase in the moving horse as speed increases., Objectives: To determine the effect of locomotion on equine carpus, tarsus, metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints in the frontal plane., Hypothesis: Valgus/varus angulation will change when moving., Materials and Methods: Kinematic data were collected standing, walking and trotting for 2 groups of horses. The change in angle for carpus, tarsus, MCP and MTP joints was calculated standing and midstance for each stride. Comparison of joint angles between left and right limbs, standing, walking and trotting were made. Inter- and intrahorse variations were investigated., Results: Significant differences were observed between groups of horses and left and right forelimbs. Between walk and trot, the MCP joint changed from valgus to varus, and the tarsus and MTP joints increased in valgus deformity. Between standing and walk the carpus increased in valgus deformity. Interhorse variation was significantly different, intrahorse variation was not. Variation in measurements between gaits was minimal., Conclusions: This study validates the measurement of joint angles from the front in the walking and trotting horse using kinematic data, interhorse variation in joint angle measurements exceeding intrahorse variation. The increases in joint angles between standing and walking, and walking and trotting warrant further investigation., (© 2010 EVJ Ltd.)

Reasons for Performing Study: Whereas the effect of heel configuration on the tension of the suspensory apparatus is well documented in the literature, there are few reports of joint contact force components in the equine distal forelimb., Objectives: To improve understanding of the effect of heel configuration on equine digit joint loading, a sensitivity analysis was performed to compare the effect of a raised heel on joint contact force components in the coffin and fetlock joints during the stance phase of the trot., Materials and Methods: Four Warmblood horses were used. An inverse dynamic analysis was carried out using kinematic and kinetic data. Taking into account the tendon wrapping forces (WF) around the sesamoid bones in the calculations, the joint contact forces (CF) were estimated for the coffin and fetlock joints during the trot stance phase (4 m/s). To test the sensitivity of the results to heel configuration changes, calculations were performed repeatedly for different heel configurations (raised by 0, 6 and 12°). A one-way ANOVA with repeated measures was used to test the effect of heel configuration (at the 3 levels) (α = 0.05; P < 0.05; post hoc testing: Bonferroni)., Results: For heel configurations raised from 0-12°: whereas the tension of the deep digital flexor tendon decreased and the tension of the superficial digital flexor tendon increased, for the coffin joint the peak WF (1.4 ± 0.25 bwt; 1.2 ± 0.2 bwt; 0.95 ± 0.1 bwt) and the peak CF (2.45 ± 0.25 bwt; 2.2 ± 0.2 bwt; 2 ± 0.1 bwt) decreased significantly (P < 0.05). For the fetlock joint, the peak WF (3.8 ± 0.7 bwt; 4.1 ± 0.3 bwt; 4.4 ± 0.25 bwt) and the peak CF (4.35 ± 0.7 bwt; 4.7 ± 0.35 bwt; 5 ± 0.3 bwt) increased, but not significantly., Conclusion: This analysis suggests that the coffin joint loading and fetlock joint loading are strongly connected. The heel configuration may influence both coffin joint and fetlock joint contact force components., (© 2010 EVJ Ltd.)

Reasons for Performing Study: Although beach training is commonly used in horses, limb loading on beach sand has never been investigated. A dynamometric horseshoe (DHS) is well adapted for this purpose., Objectives: To compare ground reaction force (GRF) and fetlock kinematics measured in harness trotters on 2 tracks of beach sand with different water content., Methods: Two linear sand tracks were compared: firm wet sand (FWS, 19% moisture) vs. deep wet sand (DWS, 13.5% moisture). Four French trotters (550 ± 22 kg) were used. Their right forelimb was equipped with a DHS and skin markers. Each track was tested 3 times at 7 m/s. Each trial was filmed by a high-speed camera (600 Hz); DHS and speed data acquisition was performed at 10 kHz on 10 consecutive strides. All recordings were synchronised. The components Fx (parallel to the hoof solar surface) and Fz (perpendicular) of the GRF were considered. For 3 horses the fetlock angle and forelimb axis-track angle at landing were measured. Statistical differences were tested using the GLM procedure (SAS; P < 0.05)., Results: Stance duration was increased on DWS compared to FWS. Fzmax and Fxmax (oriented, respectively, downwards and forwards relatively to the solar surface) and the corresponding loading rates, were decreased on DWS and these force peaks occurred later. Fxmin (backwards) was not significantly different between both surfaces; the propulsive phase (Fx negative) was longer and the corresponding impulse higher, on DWS compared to FWS. The forelimb was more oblique to the track at landing and maximal fetlock extension was less and delayed on DWS., Conclusions: This study confirms that trotting on deep sand overall reduces maximal GRF and induces a more progressive limb loading. However, it increases the propulsive effort and likely superficial digital flexor tendon tension at the end of stance, which should be taken into account in beach training., (© 2010 EVJ Ltd.)

Reasons for Performing Study: Desmopathies of the suspensory ligament are relatively frequent and vary in prevalence over different anatomical regions. This variation may be because of regional differences in tissue characteristics., Objective: To characterise different regions of healthy forelimb suspensory ligaments (SLs) by means of biochemical, biomechanical and histomorphological techniques., Hypothesis: There is substantial topographical heterogeneity in the SL with respect to structural, compositional and functional characteristics., Methods: SLs were harvested from 38 limbs and used for biochemical (n = 20), biomechanical (n = 14) and histomorphological (n = 4) evaluation. Sulphated glycosaminoglycan (S-GAG), DNA and collagen content, degree of lysyl hydroxylation and numbers of enzymatic and nonenzymatic cross-links were determined in 7 regions of the SL: lateral and medial part of the origin (OM, OL), mid-body (MB), axial and abaxial parts of the lateral and medial branches (ILAX, ILAB, IMAX and IMAB, respectively). Passive resistance to tensile loading was measured in 5 regions of the SL (all except OL and OM)., Results: DNA content was lower in OL and OM than in all other parts. GAG content was also lower in OL and OM and highest in ILAB and IMAB. Collagen content was lower in OL/OM and highest in ILAX/IMAX. Pentosidine levels were highest in OL and significantly lower in the lateral insertion (ILAX/ILAB). There were no differences in hydroxylysylpyridinoline (HP) cross-links or lysyl hydroxylation. Stiffness (P<0.01) and modulus of elasticity (P<0.01) were substantially higher in the MB region than in all other regions except for IMAB. Strain at failure was lower in the MB region (P<0.0001), resulting in a comparable force at rupture as in the other regions., Conclusions: Matrix composition differs to a relatively limited extent between different regions of the SL. The mid-body of the ligament is stiffer than the branches, which have similar properties and relevance and mechanical differences between mid-body and branches/origin may explain some use-related differences in the prevalence of lesions., (© 2010 EVJ Ltd.)

Reason for Performing Study: Foot stance in grazing significantly influences hoof conformation and development from foal to yearling age., Objectives: To conduct a longitudinal study to establish if the relationship between motor laterality and uneven front feet persisted in 3-year-old horses at the time of studbook selection and to investigate if such laterality and unevenness might influence the horses' ability to perform symmetrically while trotting, cantering and free jumping., Methods: Seventeen clinically sound but untrained (with only minimal experience of handling) and sound Warmblood horses that had participated in a previous study were assessed as per the protocol reported. Laterality was tested in a preference test (PT) and z-values were calculated for analysis purposes. Laterality and hoof unevenness were related to both relative limb length and relative head size, while the ability to perform symmetrically was tested in free trot-canter transitions and free jumping exercises. Differences in performance between horses with and without a limb preference in the PT and those with 'uneven' and 'even' feet were tested for differences in performance metrics using Students' t test, while linearity was tested using a regression analysis (P<0.05)., Results: Significant laterality was still present in 24% of the 3-year-old horses and the relationship between laterality and uneven feet pairs was stronger than at foal and yearling stages. Horses with significant motor laterality had almost 4 times more unevenness, a smaller head and longer limbs and the relationship between body conformation and laterality was still present. There was a strong linear relation between unevenness, laterality and a bias or side preference for trot-canter transitions. However, this relationship was not significant during the free jumping exercise., Conclusion: Motor laterality and uneven feet pairs were still present and significantly related in the 3-year-old horses and both variables were also strongly related to sidedness in trot-canter transitions., Potential Relevance: Warmblood studbooks should include quantitative data on laterality at the time of studbook admission as part of the selection criteria.

Reconstruction of limb posture is a challenging task in assessing functional morphology and biomechanics of extinct tetrapods, mainly because of the wide range of motions possible at each limb joint and because of our poor knowledge of the relationship between posture and musculoskeletal structure, even in the extant taxa. This is especially true for extinct mammals such as the desmostylian taxa Desmostylus and Paleoparadoxia. This study presents a procedure that how the elbow joint angles of extinct quadruped mammals can be inferred from osteological characteristics. A survey of 67 dried skeletons and 113 step cycles of 32 extant genera, representing 25 families and 13 orders, showed that the olecranon of the ulna and the shaft of the humerus were oriented approximately perpendicular to each other during the stance phase. At this angle, the major extensor muscles maximize their torque at the elbow joint. Based on this survey, I suggest that olecranon orientation can be used for inferring the elbow joint angles of quadruped mammals with prominent olecranons, regardless of taxon, body size, and locomotor guild. By estimating the elbow joint angle, it is inferred that Desmostylus would have had more upright forelimbs than Paleoparadoxia, because their elbow joint angles during the stance phase were approximately 165 degrees and 130 degrees , respectively. Difference in elbow joint angles between these two genera suggests possible differences in stance and gait of these two mammals., (Copyright 2009 Wiley-Liss, Inc.)

Reasons for Performing Study: Data are required to confirm that strain gauges recording high bone strains in Thoroughbred racehorses provide an accurate record of bone strain., Objective: To test the accuracy and reliability of very high in vivo strain recordings made during fast exercise in Thoroughbred racehorses., Methods: Strains were recorded during exercise from rosette gauges implanted onto the mid-shaft dorsal cortex of each third metacarpal bone (MC3) in 6 yearling and 6 mature Thoroughbreds in a previous experiment. Bulk elastic modulus (E(US)) was calculated from ultrasound speed and single photon absorptiometry measures. Each cleaned MC3 with the original gauge in situ and new gauges placed in a region of strain similarity (as shown by photoelastic coating) was loaded in a materials testing system (MTS) and strains recorded during loading. Elastic moduli were calculated from strain measures from new rosette gauges on the medial, dorsal, lateral and palmar surfaces (E(m); E(d); E(El); E(p), and bulk moduli calculated from the displacement of the MTS machine heads during loading (Ebt). Peak loads were increased incrementally to failure., Results: Of 14 original gauges tested against new gauges, 11 recorded strains from 80-115% of the new gauges and 3 showed reduced function (31-40%). Ebt were similar to E(m), and E(US) were similar to E(l) and not significantly different from Ed. Maximum strains at yield were recorded by the medial gauges and ranged from -7500 to -16,000 microepsilon., Conclusions and Clinical Relevance: Similarities between recordings from gauges used in vivo and new gauges confirmed the reliability and likely accuracy (or possible underestimate) of very high strains (exceeding -6000 microepsilon) recorded in exercising Thoroughbred racehorses. The similarity between E(bt) and E(m) confirms that the gauges measured the true distortion of the bone in the MTS. These results confirm that mammalian bone may withstand much greater compressive loads than -4000 microepsilon under some conditions at least.

Reasons for Performing Study: Although track surfaces are a risk factor of tendon injuries, their effects on tendon loading at high speed are unknown. Using a noninvasive ultrasonic technique, it is now possible to evaluate the forces in the superficial digital flexor tendon (SDFT) in exercise conditions., Objectives: To compare the effects of an all-weather waxed track (W) vs. a crushed sand track (S), on the SDFT loading in the trotter horse at high speed., Methods: Two trotter horses were equipped with the ultrasonic device (1 MHz ultrasonic probe, fixed on the palmar metacarpal area of the right forelimb). For each trial, data acquisition was made at 400 Hz and 10 consecutive strides were analysed. In each session, the 2 track surfaces were tested in a straight line. The speed was imposed at 10 m/s and recorded. The right forelimb was also equipped with a dynamometric horseshoe and skin markers. The horse was filmed with a high-speed camera (600 Hz); all recordings were synchronised. Statistical differences were tested using the GLM procedure (SAS; P < 0.05)., Results: Maximal tendon force was significantly lower on W compared with S. In addition to maximal force peaks around mid-stance, earlier peaks were observed, more pronounced on S than on W, at about 13% (horse 2) and 30% (both horses) of the stance phase. Comparison with kinematic data revealed that these early peaks were accompanied by plateaux in the fetlock angle-time chart. For high tendon forces, the tendon maximal loading rate was significantly lower on W than on S. CONCLUSIONS AND POTENTIAL CLINICAL RELEVANCE: The all-weather waxed track appears to induce a lesser and more gradual SDFT loading than crushed sand. The SDFT loading pattern at high speed trot suggests proximal interphalangeal joint movements during limb loading.

Reasons for Performing Study: Radial strain in normal hooves has been found to vary with strain gauge location, limb posture and sample limb but reported magnitudes were considered to be low. More accurate measurement of radial strain may enhance the understanding of hoof function., Objectives: To explore in vitro radial hoof strain in relation other kinetic and kinematic variables that may be related., Methods: Five normal forelimbs were removed at the proximal articular surface of the third metacarpal bone (McIII). The limbs were loaded using a modified Instron test machine. Six calibrated infrared cameras captured movement from markers on the hoof and bone fixed markers on the second and first phalanxes and McIII, whilst radial hoof strain was measured using a calibrated instrumented plug. Change in strain, joint angle and load were found at simulated walking postures and bivariate correlations were used to compare the relationships between them., Results: Radial strain was moderately correlated with proximal interphalangeal joint (PIPJ) rotation (r = -0.519). Large reductions in radial strain were found in loading and midstance with 10 degrees of heel lift postures., Conclusions and Potential Relevance: PIPJ rotation has previously been linked to the magnitude of deep digital flexor tendon (DDFT) loads and it is therefore suspected that these loads may have the greatest influence on radial strain magnitudes. Further investigation of radial strain is needed to describe the patterns fully during the stance phase in vivo.

Reasons for Performing Study: Insight into the loading pattern of the articular cartilage surface during the complete stride is important as biomechanical factors play a pivotal role in the pathogenesis of joint trauma and osteoarthritis (OA)., Objectives: To determine the loading pattern in the equine MCP articulation in vitro during simulated walk., Methods: Eight cadaveric limbs from mature Dutch Warmblood horses were loaded in a pneumatic loading device in 6 different positions (A1-A6). The pressure distribution on the articular surface of the proximal phalanx (P1) was measured at 7 sites (S1-7) using intra-articularly placed pressure sensitive films, which were analysed by scanning and densitometry., Results: Pressures recorded after mid-stance (A4, 5, 6) were significantly (P < 0.05) higher than those before (A1, 2, 3) and showed the biphasic loading pattern of the walk at all sites, except for the site halfway along the sagittal groove (S7). At S7, there was a linear increase in pressure during the progress of the stance phase of the stride in most horses. Medially (S4, 5, 6) the pressure was significantly higher than laterally (S1, 2, 3) (P < 0.05)., Conclusions and Potential Relevance: The heavier medial loading coincides with the location where articular cartilage degeneration in the process of OA in the equine MCP joint is known to start. The discrepancy between the loading of the central groove and the other parts of the joint may result in large stress differences at the end of the stance phase, which might be related to the pathogenesis of stress fractures in the first phalanx and distal third metacarpal bone.

Reasons for Performing Study: Inadequate track surfaces are believed to be a risk factor in the occurrence of musculoskeletal injuries, but quantification of the shocks and vibrations provoked by hoof impact on different ground surfaces (including new synthetic tracks) has been insufficiently documented in trotters under high-speed training conditions., Objectives: To test the reliability and sensitivity of an accelerometric device to discriminate between the biomechanical effects of 2 different tracks at high speed., Methods: Three French Trotters were used and their right front hooves were equipped with one triaxial accelerometer. Two different track surfaces (crushed sand track: S and all-weather waxed track: W) were tested when horses were trotting in a straight line. For each session of measurements, trials were repeated 3 times in a Latin square design. The speed of the runs was set at 10 m/s, controlled by the driver and recorded synchronously. Sample rate was set at 6 kHz. Acceleration of the hoof (resultant vector and 3D components), power spectral density at impact and variability (between strides, trials, sessions and horses) were analysed. Statistical differences were tested using a GLM procedure (SAS). Least square mean differences were used for comparisons between tracks (P < 0.05)., Results: Results showed that the deceleration of the hoof (magnitude of the resultant vector) was statistically different between the 2 tracks with an attenuation of the shock of about 50% on the all-weather waxed track. Magnitude of the power spectral density was reduced at higher frequencies on W., Conclusions and Clinical Relevance: These preliminary results demonstrate the sensitivity of the tool to discriminate between the different behaviours of the hoof on the different track surfaces at high speed. Deceleration and vibration of the hoof at impact were reduced on W compared to S, suggesting a better shock-absorbing quality of this track.

Reasons for Performing Study: Warmblood horse studbooks aim to breed horses with a conformation that will enable elite future sports performance, but reduce the risk of early retirement due to lameness. Negative conformational traits, such as asymmetrical or 'uneven' forefeet may possibly shorten the career of sporthorses., Objectives: To investigate the significance of foot conformation at young age to duration of the career of sporthorses., Methods: Databases of the Royal Dutch Warmblood Studbook (KWPN) and of the Royal Dutch Equestrian Sports Federation (KNHS) were matched and resulted in a dataset comprising 23,116 records of horses for which their conformation scores and duration of their sports career were available. Survival analysis was used to determine which of the conformation traits had a significant effect on duration of sports career in dressage and jumping at basic and elite level., Results: Duration of competitive life was shorter for jumping than for dressage. A different set of risk factors was found for each level and discipline. The trait 'uneven feet' tended to shorten the competitive life in dressage, but was a significant risk factor at the elite level of jumping., Conclusions: Limb conformation and, in particular, the conformation of the distal limb, are important for duration of competitive life. From the prevalence of uneven feet in sports disciplines, it may be concluded that this is an undesirable trait, particularly at the elite level of jumping, since uneven feet have a detrimental effect on the duration of competitive life in a sporthorse population., Potential Relevance: This study provided evidence that the conformation trait uneven feet has a negative effect on Warmblood jumping performance and, therefore, breeders should be encouraged to avoid this phenomenon at foal age.