S. Corr

Functional anatomy of the cheetah (Acinonyx jubatus) hindlimb.

The cheetah is capable of a top speed of 29 ms−1 compared to the maximum speed of 17 ms−1 achieved by the racing greyhound. In this study of the hindlimb and in the accompanying paper on the forelimb we have quantified the musculoskeletal anatomy of the cheetah and greyhound and compared them to identify any differences that may account for this variation in their locomotor abilities. Specifically, bone length, mass and mid‐shaft diameter were measured, along with muscle mass, fascicle lengths, pennation angles and moment arms to enable estimates of maximal isometric force, joint torques and joint rotational velocities to be calculated. Surprisingly the cheetahs had a smaller volume of hip extensor musculature than the greyhounds, and we therefore propose that the cheetah powers acceleration using its extensive back musculature. The cheetahs also had an extremely powerful psoas muscle which could help to resist the pitching moments around the hip associated with fast accelerations. The hindlimb bones were proportionally longer and heavier, enabling the cheetah to take longer strides and potentially resist higher peak limb forces. The cheetah therefore possesses several unique adaptations for high‐speed locomotion and fast accelerations, when compared to the racing greyhound.

High speed galloping in the cheetah (Acinonyx jubatus) and the racing greyhound (Canis familiaris): spatio-temporal and kinetic characteristics.

SUMMARY The cheetah and racing greyhound are of a similar size and gross morphology and yet the cheetah is able to achieve a far higher top speed. We compared the kinematics and kinetics of galloping in the cheetah and greyhound to investigate how the cheetah can attain such remarkable maximum speeds. This also presented an opportunity to investigate some of the potential limits to maximum running speed in quadrupeds, which remain poorly understood. By combining force plate and high speed video data of galloping cheetahs and greyhounds, we show how the cheetah uses a lower stride frequency/longer stride length than the greyhound at any given speed. In some trials, the cheetahs used swing times as low as those of the greyhounds (0.2 s) so the cheetah has scope to use higher stride frequencies (up to 4.0 Hz), which may contribute to it having a higher top speed that the greyhound. Weight distribution between the animals limbs varied with increasing speed. At high speed, the hindlimbs support the majority of the animals body weight, with the cheetah supporting 70% of its body weight on its hindlimbs at 18 m s–1; however, the greyhound hindlimbs support just 62% of its body weight. Supporting a greater proportion of body weight on a particular limb is likely to reduce the risk of slipping during propulsive efforts. Our results demonstrate several features of galloping and highlight differences between the cheetah and greyhound that may account for the cheetahs faster maximum speeds.

Endogenous analgesia in the chicken

Endogenous analgesia has been identified in mammals, but little is known about suppression of tonic pain following trauma or disease. Birds suffer from gouty arthritis which can be induced experimentally by intra-articular injection of sodium urate (SU) crystals. SU injection into the ankle joint of the chicken tested in cages resulted in pain-coping behaviour (one-legged standing, sitting) together with severe lameness. Birds kept and tested in large pens showed significantly less pain-coping behaviour, while birds tested in novel pens showed either complete analgesia or marked hypoalgesia, together with a significant reduction in lameness. Complete analgesia was observed during pre-laying behaviour. These results demonstrate a remarkable ability of birds to suppress such severe tonic pain as SU arthritis.

Functional anatomy of the cheetah (Acinonyx jubatus) forelimb: Functional anatomy of the cheetah

Despite the cheetah being the fastest living land mammal, we know remarkably little about how it attains such high top speeds (29 m s−1). Here we aim to describe and quantify the musculoskeletal anatomy of the cheetah forelimb and compare it to the racing greyhound, an animal of similar mass, but which can only attain a top speed of 17 m s−1. Measurements were made of muscle mass, fascicle length and moment arms, enabling calculations of muscle volume, physiological cross‐sectional area (PCSA), and estimates of joint torques and rotational velocities. Bone lengths, masses and mid‐shaft cross‐sectional areas were also measured. Several species differences were observed and have been discussed, such as the long fibred serratus ventralis muscle in the cheetah, which we theorise may translate the scapula along the rib cage (as has been observed in domestic cats), thereby increasing the cheetah’s effective limb length. The cheetah’s proximal limb contained many large PCSA muscles with long moment arms, suggesting that this limb is resisting large ground reaction force joint torques and therefore is not functioning as a simple strut. Its structure may also reflect a need for control and stabilisation during the high‐speed manoeuvring in hunting. The large digital flexors and extensors observed in the cheetah forelimb may be used to dig the digits into the ground, aiding with traction when galloping and manoeuvring.

A comparison of outcomes following tibial plateau levelling osteotomy and cranial tibial wedge osteotomy procedures

The objective of this study was to determine whether clinical outcomes were superior and complication rates were lower in dogs that had had a cranial cruciate ligament rupture treated by tibial plateau levelling osteotomy (TPLO), compared to those dogs that had been treated using the original cranial tibial wedge osteotomy (CTWO) procedure. Thirty-seven client-owned dogs with cranial cruciate ligament rupture were included in the study: 19 dogs underwent a TPLO procedure, and 18 dogs underwent a CTWO procedure. The study was retrospective, with the data being obtained from medical records and a review of radiographs. The long-term outcome was assessed by means of an owner questionnaire using a visual analogue scale. For the majority of factors that were reviewed, there was not a significant difference in outcome between the dogs that had a TPLO or those that had undergone a CTWO. All of the dogs showed a rapid return to weight bearing after surgery, and at the six week re-examination, the majority of the dogs did not have any pain on stifle palpation. They displayed a good stifle range of motion and significantly lower lameness scores than those prior to surgery. The complication rates did not differ between the procedures, however, within this small sample of dogs, complications following a CTWO were more likely to require revision surgery.

The gait dynamics of the modern broiler chicken: A cautionary tale of selective breeding

SUMMARY One of the most extraordinary results of selective breeding is the modern broiler chicken, whose phenotypic attributes reflect its genetic success. Unfortunately, leg health issues and poor walking ability are prevalent in the broiler population, with the exact aetiopathogenesis unknown. Here we present a biomechanical analysis of the gait dynamics of the modern broiler and its two pureline commercial broiler breeder lines (A and B) in order to clarify how changes in basic morphology are associated with the way these chickens walk. We collected force plate and kinematic data from 25 chickens (market age), over a range of walking speeds, to quantify the three-dimensional dynamics of the centre of mass (CoM) and determine how these birds modulate the force and mechanical work of locomotion. Common features of their gait include extremely slow walking speeds, a wide base of support and large lateral motions of the CoM, which primarily reflect changes to cope with their apparent instability and large body mass. These features allowed the chickens to keep their peak vertical forces low, but resulted in high mediolateral forces, which exceeded fore–aft forces. Gait differences directly related to morphological characteristics also exist. This was particularly evident in Pureline B birds, which have a more crouched limb posture. Mechanical costs of transport were still similar across all lines and were not exceptional when compared with more wild-type ground-running birds. Broiler chickens seem to have an awkward gait, but some aspects of their dynamics show rather surprising similarities to other avian bipeds.

The effects of selective breeding on the architectural properties of the pelvic limb in broiler chickens: a comparative study across modern and ancestral populations

Intensive artificial selection has led to the production of the modern broiler chicken, which over the last few decades has undergone a dramatic increase in growth rate and noticeable changes in body conformation. Unfortunately, this has been associated with musculoskeletal abnormalities which have altered the walking ability of these birds, raising obvious welfare concerns, as well as causing economic losses. Here we present a comparative study of ancestral and derived muscle anatomy in chickens to begin to tease apart how evolutionary alterations of muscle form in chickens have influenced their locomotor function and perhaps contributed to lameness. We measured the muscle architectural properties of the right pelvic limb in 50 birds, including the Giant Junglefowl, a commercial strain broiler and four pureline commercial broiler breeder lines (from which the broiler populations are derived) to identify which features of the broiler’s architectural design have diverged the most from the ancestral condition. We report a decline in pelvic limb muscle mass in the commercial line birds that may compromise their locomotor abilities because they carry a larger body mass. This greater demand on the pelvic limb muscles has mostly led to changes in support at the hip joint, revealing significantly larger abductors and additionally much larger medial rotators in the broiler population. Differences were seen within the commercial line bird populations, which are likely attributed to different selection pressures and may reflect differences in the walking ability of these birds. In addition, Junglefowl seem to have both greater force‐generating capabilities and longer, presumably faster contracting muscles, indicative of superior musculoskeletal/locomotor function. We have provided baseline data for generating hypotheses to investigate in greater depth the specific biomechanical constraints that compromise the modern broiler’s walking ability and propose that these factors should be considered in the selection for musculoskeletal health in the chickens of the future. Our new anatomical data for a wide range of domestic and wild‐type chickens is useful in a comparative context and for deeper functional analysis including computer modelling/simulation of limb mechanics.

Canine and feline obesity: a One Health perspective

Recent years have seen a drastic increase in the rates of overweight and obesity among people living in some developed nations. There has also been increased concern over obesity in companion animals. In the latest article in Veterinary Records series on One Health, Peter Sandøe and colleagues argue that the relationship between obesity in people and in companion animals is closer and more complex than previously thought, and that obesity should be treated as a One Health problem

Retrospective study of Achilles mechanism disruption in 45 dogs.

Forty-five cases of canine Achilles mechanism disruption were reviewed, mostly involving medium-sized dogs, among which dobermanns, labradors and border collies were most commonly represented. Most cases were acute in onset (66.7 per cent), and were usually closed injuries (75.6 per cent). In the majority of cases, the damage involved all tendons (26.7 per cent), all tendons except the superficial digital flexor tendon (22.2 per cent), or the gastrocnemius alone (20 per cent). Damage most commonly occurred at the tendo-osseous junction (60 per cent), with injury occurring less commonly at the musculotendinous junction (20 per cent) or in the body of the tendon (13.3 per cent). A plantigrade posture was not predictive of involvement of specific tendons, but was more likely if the injury involved the musculotendinous junction. The most common method of treatment was a primary tendon repair using polydioxanone suture in a locking-loop pattern, with placement of a temporary calcaneotibial screw and cast. The outcome was not significantly influenced by whether the injury was open or closed, the duration of the injury, the tendons involved, or the method of repair. Complications were recorded in 16 cases (35 per cent), of which 10 were minor and six major. Complications were significantly more likely if the damage involved the body of the tendon. Long-term follow-up was available for 19 dogs; the outcome of surgery was considered to be good to excellent in 18 dogs.

Canine stifle positive contrast computed tomography arthrography for assessment of caudal horn meniscal injury: a cadaver study

OBJECTIVE To investigate the use of computed tomography (CT) arthrography in cadaveric canine stifles with particular emphasis on the diagnosis of meniscal injury. STUDY DESIGN Prospective cadaver study. SAMPLE POPULATION Pelvic limbs from adult Beagles (n=10). METHODS After survey CT scan of each stifle oriented in the dorsal plane, positive contrast stifle CT arthrogram (CTA) was performed using the same slice orientation. Each stifle was then randomly allocated into 1 of 2 treatment groups: group A--arthrotomy, cranial cruciate ligament (CCL) transection and simulated injury to the caudal horn of the medial meniscus; group B--arthrotomy and CCL transection only. CT scan was repeated as before and post-arthrotomy images were interpreted by a radiologist unaware of treatment grouping. RESULTS The cranial and caudal cruciate ligaments, medial and lateral menisci, menisco-femoral ligament, and long digital extensor tendon were all identifiable on CTA images. CTA was 90% sensitive and 100% specific for diagnosing simulated caudal horn meniscal injury. CONCLUSIONS Stifle CTA enables identification of intra-articular structures within the stifle and is a reliable method for identifying simulated meniscal injuries in a cadaver model. CLINICAL RELEVANCE CTA imaging of the canine stifle has potential clinical value for detection of meniscal injury.