Relationships of Body Weight,Body Size,Subject Velocity,and Vertical Ground Reaction Forces in Trotting Dogs

Objective: To evaluate the relationship of body weight (BW) and size, dog velocity, and vertical ground reaction forces (GRF) from a large number of dogs of various sizes. Study Design: Clinical research. Animals: Orthopedically healthy dogs (n=129) Methods: BW and dog size, represented as height at the withers (WH), were obtained. Stance times (ST), vertical impulses (VI), and peak vertical forces (PVF) of thoracic and pelvic limbs were measured on a force plate at controlled trotting speed. They were evaluated against BW and WH using linear regression analysis in absolute (nonnormalized) values, and when normalized to BW and/or body size according to the theory of dynamic similarity. Relative velocities were calculated for each dog. Results: Absolute ST, VI, and PVF showed strong positive correlations with BW and/or body size. When GRFs were normalized to BW, correlations with body size were markedly reduced, but remained positive for VI, and turned negative for PVF. Normalizing the time‐dependent variables (ST and VI) also to WH eliminated most size influence. A small dependency of fully normalized GRF on body size remained that was because of differences in relative velocity between dogs of different sizes. Reference values for the fully normalized data are given. Conclusions: The inherent relationship between BW, body size, dog velocity, and vertical GRF was demonstrated. Clinical Relevance: BW, body size, and relative dog velocity must be accounted for when wanting to obtain GRF variables that are comparable between different dogs.     

Effects of Shortening Breakover at the Toe on Gait Kinematics at the Walk and Trot

Point of breakover, defined as the portion of the hoof last in contact with the ground during the terminal stance phase of a limb, can be influenced by many factors including craniocaudal placement of the shoe. Shortening the point of breakover has been suggested to decrease strain on the deep digital flexor tendon and navicular bone as well as to improve the alignment of the second and third phalanx. The current experiment involved eight sound horses fitted with aluminum plates adhered to their front hooves, which were drilled and tapped to allow additional aluminum plates of various lengths to be attached (the longest plate was placed flush with the toe, while the shortest plate was moved 3.81 cm caudal to the toe). Horses were recorded on video while at the walk and trot over a distance of 70 meters for six repetitions to determine differences in gait kinematics. Results of this study show significant changes in stride kinematics caused by shortening the point of breakover. Retraction of the forelimbs was greatest when breakover was moved 1.27 cm back from the toe (P < .05), and minimum height of the fetlock at the trot was higher on all treatments where the breakover point was moved caudally (P < .05). Some improvements in gait quality were observed when breakover was shortened, although extreme caudal placement of the shoe (negative placement in relation to P3) resulted in a decrease in gait quality as seen by decreased retraction of the forelimb (P < .05) coupled with hoof height occurring earlier in the stride (P < .05).     

Linear and Temporal Kinematics of the Walk in Warmblood Foals

Kinematic variables of the walk in adult horses have been well described in the literature, but few studies have investigated growth-associated changes in these parameters. The objective of this study was to quantify linear and temporal walk patterns in Warmblood foals during the preweaning growth period. Nine foals were videotaped at the walk at 3, 11, and 21 weeks of age. Repeated-measures analyses were used to compare trait means between age groups. No significant effects owing to gender were found. Although stride length and stride duration increased as foals aged, neither differed across age groups when adjusted for wither height or velocity. Most kinematic variables did not differ across age groups when adjusted for Froude number. Overstride distance decreased by more than 40% in a linear manner from 3 to 21 weeks, and had an inverse relationship with distance between diagonal limbs during stance phase. Diagonal stance duration was greater than lateral stance duration for all age groups, indicating foals did not achieve an even, four-beat rhythm by the end of the study period. Changes in walk kinematics over time were independent of differences in velocity and increasing height during growth, and may indicate the need to account for body length or other morphometrics when assessing gait parameters in growing animals. Further research is needed during postweaning growth to determine when kinematic variables become consistent with those of adult horses.     

Muscle Contractures in the Limbs of Dogs and Cats

Muscle contractures causing varying degrees of lameness commonly occur from skeletal muscle fibrosis, the result of injury such as that caused by circulatory insufficiency, infection, autoimmune reaction, or trauma. Quadriceps contracture, whether congenital or acquired, is treated by sectioning the cordlike fibrotic muscle group by "Z" plasty, resulting in lengthening it enough to allow the knee to assume a normal standing angle. Adhesion of the muscle group to a large femoral callus (muscle tie down) may occur and require additional surgical correction. Infraspinatus contracture results in a typical foreleg deformity and change in gait. Surgical repair by tenotomy is usually followed by rapid return to normal. Gracilis contracture, though common in racing greyhounds, is not commonly reported in pet dogs. Surgical excision of the entire affected muscle mass is curative.     

Vertical Frontlimb Ground Reaction Forces of Sound and Lame Warmbloods Differ From Those in Quarter Horses

Lameness is a highly prevalent condition in horses and is the principal cause of removal from athletic activity in this species. In evidence-based veterinary medicine studies to evaluate non-setoidal anti-inflammatory drug (NSAID) therapies, force plates are commonly used to objectively assess improvement of lameness. The objective of this study was to determine whether breed differences would influence force plate measurements in sound and lame riding horses. Force plate measurements of lame (n = 20) and sound (n = 18) Warmblood and lame (n = 15) and sound (n = 8) Quarter Horses were compared. Lameness was visually scored using the grade 0–5 American Association of Equine Practitioners (AAEP) lameness scale. Trotting sound Warmbloods loaded their frontlimbs with 118% body weight (BW) and their hindlimbs with 96% BW, whereas Quarter Horses only used 101% BW in the front and 92% BW in the hindlimbs (P < .05). Furthermore, it appeared and was estimated that, at trot, front-limb-lame Warmblood horses showed higher peak vertical force (PVF) values (grade 2: 89% BW; grade 3: 69% BW), than front-limb-lame Quarter Horses with similar lameness scores (grade 2: 78% BW; grade 3: 66% BW). In conclusion, peak vertical forces (PVF expressed in % BW) of either lame or sound horses seem to be influenced by breed differences between Warmblood and Quarter Horse riding horses. Possible conformation and gait differences enabled trotting Quarter Horses to demonstrate lower absolute PVF values than Warmbloods, whereas trotting lame Warmbloods showed a relatively larger decrease in frontlimb loading and thus in PVF than lame Quarter Horses at a trot. Thus, in studies in which objective lameness observations are recorded, breed differences should be taken into account when specific grades of lameness of a group of horses are to be objectively compared with another group.     

The ligamentum olecrani of the Elbow Joint in Dogs and Cats

The olecranon ligament ( ligamentum olecrani ) is described as an elastic ligament of the elbow joint in carnivores that tenses the caudomedial part of the joint capsule. The aim of the study was to compare the course and the microscopic structure of the ligament in dogs and cats. The elbow regions of 25 dogs and 15 cats were dissected to examine the topography of the ligament in extension and flexion. Furthermore, the olecranon ligaments of five dogs and five cats were studied using routine histological methods. Additional sections were stained with Resorcin–Fuchsin and Orcein to detect elastic fibres. In both species the olecranon ligament originates at the lateral surface of the epicondylus medialis humeri and inserts at the cranial crest of the olecranon extending distally to the roof of the processus anconeus . Tension of the ligament only occurs when the elbow joint is flexed maximally. This tension is increased by a slight supination of the forearm, which takes place automatically in this joint position. In dogs the ligament is long (30–40 mm in medium sized breeds) and relatively slim (approx. 2–4 mm). In cats the ligament is short (10–12 mm) and relatively strong (5–8 mm). The histological examination of the olecranon ligament shows all signs of a tight collagenous ligament with a negligible amount of elastic fibres. The olecranon ligament helps to limit the maximal flexion of the elbow joint. In addition, it controls a slight lateral movement of the processus anconeus during the automatic supination of the antebrachial bones in extreme flexion of the elbow joint.     

The Pharmacokinetics of a Long-acting Oxytetracycline Formulation in Healthy Dogs and in Dogs Infected with Ehrlichia canis

The pharmacokinetic properties of oxytetracycline were studied following a single injection of a long-acting formulation (20 mg/kg body weight) into the semimembranosus muscle of healthy dogs and of dogs that had been experimentally infected with Ehrlichia canis. The disposition curves of the long-acting oxytetracycline formulation before and after infection were best described by a bi-exponential decline after a first-order absorption. The mean maximum serum concentration (C _max) following infection was significantly lower and the time taken to attain this concentration (t _max) was significantly shorter than that in the healthy dogs. The mean apparent elimination half-life (t _1/2) was significantly increased following infection. The corresponding rate constant () was significantly decreased. The absorption half-life (t _1/2ab) was significantly decreased after infection. The volume of distribution at steady state (V _dss) increased significantly following infection. It was concluded that the pharmacokinetic behaviour of a long-acting oxytetracycline in dogs after intramuscular administration is characterized by a two-compartment model with a slow elimination phase. This could be due to flip-flop kinetics. The febrile reaction in experimental E. canis infection affected some pharmacokinetic parameters of oxytetracycline.     

Postoperative Examination of the Biceps Femoris Muscle Sling Used in Excision of the Femoral Head and Neck in Dogs

Twenty-four dogs underwent unilateral excision of the femoral head and neck. An adjunctive biceps femoris muscle sling procedure was done in 16 dogs. In eight dogs (controls), the flap was dissected and returned to its original position. Four dogs with muscle slings were euthanatized on days 2, 5, 30, and 60, respectively. Four control dogs were euthanatized on day 2 and four dogs on day 5. Limb function did not differ consistently between dogs with muscle slings and control dogs. There was marked swelling and edema of the affected limb in half the dogs with muscle slings but not in the controls. Postoperative temperature elevations were significantly higher in dogs with muscle slings on days 1 and 2 (p less than 0.05). Infection was documented in four dogs with muscle slings. Flaps from control dogs had only minor gross and histologic abnormalities. On days 2 and 5, flaps from dogs with muscle slings appeared congested and swollen beneath and distal to the ostectomy site, with infarction involving 50 to 90% of the muscle mass. On days 30 and 60, the muscle slings were atrophic and fibrous, and by day 60 a synovial membrane covered the surfaces of all slings within the pseudarthrosis. Muscle fiber loss was attributed to infarction, necrosis, and disuse atrophy.     

Changes in the Proximal Femur and Coxofemoral Joint Following Intramedullary Pinning of Diaphyseal Fractures in Young Dogs

We report radiographic changes and clinical results seen in the proximal femur and coxofemoral joint of 7 young dogs following intramedullary pinning. Changes seen radiographically included coxa valga, a small malformed femoral head, a short thin femoral neck, and coxofemoral subluxation. Epiphyseal trauma, ischemia, and mechanical impairment of normal femoral neck growth due to presence of the intramedullary pin are discussed as possible etiologic factors.     

Evaluation of the Cortisol‐to‐ACTH Ratio in Dogs with Hypoadrenocorticism,Dogs with Diseases Mimicking Hypoadrenocorticism and in Healthy Dogs

Background

The adrenocorticotropic hormone (ACTH) stimulation test is the gold standard for diagnosing hypoadrenocorticism (HA) in dogs. However, problems with the availability of synthetic ACTH (tetracosactrin/cosyntropin) and increased costs have prompted the need for alternative methods.

Objectives

To prospectively evaluate the cortisol‐to‐ACTH ratio (CAR) as a screening test for diagnosing canine HA.

Animals

Twenty three dogs with newly diagnosed HA; 79 dogs with diseases mimicking HA; 30 healthy dogs.

Methods

Plasma ACTH and baseline cortisol concentrations were measured before IV administration of 5 μg/kg ACTH in all dogs. CAR was calculated and the diagnostic performance of ACTH, baseline cortisol, CAR and sodium‐to‐potassium ratios (SPRs) was assessed based on receiver operating characteristics (ROC) curves calculating the area under the ROC curve.

Results

The CAR was significantly lower in dogs with HA compared to that in healthy dogs and in those with diseases mimicking HA (P < .0001). There was an overlap between HA dogs and those with HA mimicking diseases, but CAR still was the best parameter for diagnosing HA (ROC AUC 0.998), followed by the ACTH concentration (ROC AUC 0.97), baseline cortisol concentration (ROC AUC 0.96), and SPR (ROC AUC 0.86). With a CAR of >0.01 the diagnostic sensitivity and specificity were 100% and 99%, respectively.

Conclusion and Clinical Importance

Calculation of the CAR is a useful screening test for diagnosing primary HA. As a consequence of the observed overlap between the groups, however, misdiagnosis cannot be completely excluded. Moreover, additional studies are needed to evaluate the diagnostic reliability of CAR in more dogs with secondary HA.     

Evaluation of the Cranial Rectus Abdominus Muscle Pedicle Flap as a Blood Supply for the Caudal Superficial Epigastric Skin Flap in Dogs

This study evaluates the cranial rectus abdominus muscle pedicle flap as the sole blood supply for the caudal superficial epigastric skin flap. This flap was composed of a cranially based rectus abdominus muscle pedicle flap that was attached to the caudal superficial epigastric island skin flap (including mammary glands 2 to 5) via the pudendoepigastric trunk. Selective angiography of the cranial epigastric artery in eight cadaver dogs proved that the arterial vasculature in the cranial rectus abdominus was contiguous with that in the caudal superficial epigastric skin flap. In the live dog study, three of six of the flaps failed because of venous insufficiency. Necrosis of mammary gland 2 occurred in two of six flaps. One of six flaps survived with the exception of the cranial most aspect of mammary gland 2. Angiography of the cranial epigastric artery proved that arterial blood supply to these flaps was intact. Histological evaluation of the failed flaps showed full-thickness necrosis of the skin and subcutaneous tissues, the presence of severe congestion, and venous thrombosis. Retrograde venous blood flow through the flap was inconsistent, and hence resulted in failure of this myocutaneous flap. Use of this flap for clinical wound reconstruction cannot be recommended.