Effectiveness of a paraverterbral nerve block versus local portal blocks for laparoscopic closure of the nephrosplenic space: A pilot study.

OBJECTIVE: To compare the effectiveness of a paravertebral nerve block vs local portal blocks for laparoscopic closure of the nephrosplenic space in standing sedated research horses. STUDY DESIGN: Randomized clinical trial. ANIMALS: Twelve horses were randomly allocated to two groups (n = 6 per group), paravertebral block of nerves T18 , L1 , and L2 or local blocks of the three laparoscopic portals. METHODS: Horses were sedated with dexmedetomidine (4 µg/kg IV and constant rate infusion [CRI] of 2.5 µg/kg/h) and morphine (50 µg/kg IV and CRI of 30 µg/kg/h). According to group allocation, 20 mL of either lidocaine or saline was injected into each paravertebral nerve site or into each local portal site to facilitate laparoscopy for closure of the nephrosplenic space. The overall quality of sedation, analgesia, behavior exhibited during surgery, and ease to perform the surgery were blindly scored by using a visual analog scale (VAS). RESULTS: Time to complete local anesthesia was similar for both blocks, and there was no difference in VAS scores between groups. Total duration of surgery was also similar between the paravertebral (79 ± 16 min) and local portal blocks (85 ± 25 min) groups. CONCLUSION: The paravertebral nerve block and the local portal blocks provided similar conditions during surgery and can be used interchangeably for closure of the nephrosplenic space. CLINICAL SIGNIFICANCE: The paravertebral nerve block can be readily performed and may be useful in surgical procedures.

Comparison of 3 blind brachial plexus block techniques during maintenance of anesthesia and postoperative pain scores in dogs undergoing surgical procedures of the thoracic limb.

The degree of analgesia provided by blind techniques for brachial plexus blocks (BPBs) has not been compared in clinical cases undergoing surgery of the thoracic limb. The objective of this study was to evaluate the anesthetic conditions and postoperative analgesia resulting from 3 different BPB local anesthetic techniques in canine patients undergoing such surgery. Twenty-four client-owned dogs received a standardized premedication/induction protocol (hydromorphone and acepromazine/propofol), maintained with isoflurane in oxygen using mechanical ventilation, in a prospective, randomized, blinded clinical trial. Before surgery, dogs received 1 of 3 anatomical BPB techniques: traditional, perpendicular, or axillary, with 0.2 mL/kg body weight (BW) of bupivacaine 0.5%. Cardiorespiratory variables and isoflurane end-tidal concentrations were recorded throughout anesthesia. Scores for anesthetic maintenance (0-best to 4-responsive), recovery quality (0-not responsive to 3-responsive), and Glasgow pain scale were recorded for up to 24 h postoperatively. All dogs recovered uneventfully from anesthesia and no differences in the measured variables or scores were noted among groups, during and after anesthesia. When thoracic limb amputations in each of the 3 groups (n = 9; 4 in traditional, 3 in perpendicular, 2 in axillary) were compared to the other surgical procedures (n = 15); however, scores for anesthetic maintenance were higher [0 (0 to 1) versus 0 (0 to 0); median (interquartile range)], recovery [1 (0 to 2) versus 0 (0 to 0)], and pain [2.4 (2.4 to 3.0) versus 1.6 (1.4 to 2.2)] in the first 3 h post-extubation. Surgery times were also longer with amputations [115 min (100 to 138 min) versus 50 min (41 to 90 min)]. The 3 BPB techniques provided similar anesthesia and postoperative pain scores. Despite higher pain scores in thoracic limb amputations than in less invasive surgeries, the BPB appeared to provide significant comfort.

Le degré d'analgésie fournie par les blocs à l'aveugle du plexus brachial (BPBs) n'a pas été comparé lors de cas cliniques soumis à une chirurgie du membre thoracique. La présente étude visait à évaluer les conditions anesthésiques et l'analgésie post-opératoire résultant de trois techniques différentes d'anesthésie locale par BPB chez des patients canins soumis à une chirurgie. Vingt-quatre chiens appartenant à des propriétaires ont reçu une prémédication/induction standardisée (hydromorphone et acépromazine/propofol), avec maintien à l'isoflurane dans de l'oxygène en utilisant une ventilation mécanique, dans une étude clinique prospective, randomisée, et à l'aveugle. Avant la chirurgie, les chiens ont reçu un BPB par une des trois techniques anatomiques : traditionnelle, perpendiculaire, ou axillaire, avec 0,2 mL/kg de poids corporel de bupivacaïne 0,5 %. Les variables cardiorespiratoires et les concentrations d'isoflurane en fin d'expiration furent enregistrées tout au long de l'anesthésie. Les pointages pour le maintien de l'anesthésie (0-meilleur à 4-réactif), la qualité du rétablissement (0-non réactif à 3-réactif), et l'échelle de la douleur de Glasgow ont été notés jusqu'à 24 h post-opération. Tous les chiens ont récupéré sans problème de l'anesthésie et aucune différence mesurable dans les variables mesurées ou les pointages ne fut notée parmi les groupes, durant ou après l'anesthésie. Toutefois, lorsque les amputations du membre thoracique dans chacun des trois groupes (n = 9; 4 dans la traditionnelle, 3 dans la perpendiculaire, 2 dans l'axillaire) furent comparées aux autres procédures chirurgicales (n = 15), les pointages pour le maintien de l'anesthésie étaient plus élevés [0 (0 à 1) versus 0 (0 à 0); médiane (écart interquartile)], rétablissement [1 (0 à 2) versus 0 (0 à 0)], et douleur [2,4 (2,4 à 3,0) versus 1,6 (1,4 à 2,2)] dans les 3 h suivant l'extubation. La durée des chirurgies étaient également plus longues lors des amputations [115 min (100 à 138 min) versus 50 min (41 à 90 min)]. Les trois techniques de BPB produisaient des pointages similaires d'anesthésie et de douleur postopératoire. Malgré des pointages de douleur plus élevés lors d'amputations du membre thoracique que lors de chirurgies moins invasives, les BPB semblent fournir un confort significatif.(Traduit par Docteur Serge Messier).

Anatomical characterization of the brachial plexus in dog cadavers and comparison of three blind techniques for blockade.

OBJECTIVES: To describe the ventral spinal nerve rami contribution to the formation of the brachial plexus (BP), and to compare ease of performing and nerve staining between three blind techniques for BP blockade in dogs. STUDY DESIGN: Prospective, randomized, blind study. ANIMALS: A total of 18 dog cadavers weighing 28.2 ± 9.7 kg (mean ± standard deviation). METHODS: Dogs were randomly assigned to two of three BP treatments: traditional approach (TA), perpendicular approach (PA), and axillary approach (AA). Dye (0.2 mL kg-1) was injected in the left BP using a spinal needle; another BP treatment was used in the right BP. Landmarks (L) included: L1, midpoint between point of the shoulder and sixth cervical (C6) transverse process; L2, scapulohumeral joint; and L3, first rib. For TA, the needle was introduced craniocaudally through L1, medial to the limb and cranial to L3. For PA, the needle was directed perpendicular and caudal to L2, aligned with L1, until cranial to L3. For AA, the needle was directed ventrodorsally, parallel and cranial to L3 until at L1. All BPs were scored for dyeing quality [0 (poor) to 5 (excellent)]. The left BP was dissected for nerve origins. Durbin test was used to compare scores (p < 0.05). RESULTS: In all dogs, the musculocutaneous nerve originated from C7 and C8; the radial nerve from C8, the first thoracic vertebra (T1) (16/18 dogs) and C7 (2/18); and the median and ulnar nerves from C8, T1 (17/18) and C7 (1/18). Respective raw scores and adjusted scores for the incomplete block design were not significantly different (p = 0.72; ranks TA 16.5, PA 19.0, AA 18.5). CONCLUSIONS AND CLINICAL RELEVANCE: The musculocutaneous, median, ulnar and radial nerves originate from C7, C8 and T1. Regardless of the technique, knowledge of anatomy and precise landmarks are relevant for correct dye dispersion.

The magnitude of muscular activation of four canine forelimb muscles in dogs performing two agility-specific tasks.

BACKGROUND: The purpose of this study was to measure the muscular activation in four forelimb muscles while dogs performed agility tasks (i.e., jumping and A-frame) and to provide insight into potential relationships between level of muscular activation and risk of injury. Muscle activation in eight healthy, client-owned agility dogs was measured using ultrasound-guided fine-wire electromyography of four specific forelimb muscles: Biceps Brachii, Supraspinatus, Infraspinatus, and Triceps Brachii - Long Head, while dogs performed a two jump sequence and while dogs ascended and descended an A-frame obstacle at two different competition heights. RESULTS: The peak muscle activations during these agility tasks were between 1.7 and 10.6 fold greater than walking. Jumping required higher levels of muscle activation compared to ascending and descending an A-frame, for all muscles of interest. There was no significant difference in muscle activation between the two A-frame heights. CONCLUSIONS: Compared to walking, all of the muscles were activated at high levels during the agility tasks and our findings indicate that jumping is an especially demanding activity for dogs in agility. This information is broadly relevant to understanding the pathophysiology of forelimb injuries related to canine athletic activity.

Finite-Element Analysis of Bone Stresses on Primary Impact in a Large-Animal Model: The Distal End of the Equine Third Metacarpal.

OBJECTIVE: To assess whether the transient stresses of foot impact with the ground are similar to those found during midstance loading and if the location of high stress correlate with the sites most commonly associated with mechanically induced osteoarthritis (OA). We compared impact stresses in subchondral bone between two subject-specific, three-dimensional, finite-element models of the equine metacarpophalangeal (MCP) joint-one with advanced OA and one healthy, and with similar published data on the stresses that occur at midstance. METHODS: Two right MCP joints (third metacarpal and proximal phalanx) were scanned using micro-computed tomography (µCT). Images were segmented, and meshed using modified 10-node quadratic tetrahedral elements. Bone material properties were assigned based on the bone density. An impact velocity of 3.55 m/s was applied to each model and contact pressures and stress distribution were calculated for each. In a separate iteration, the third metacarpal was loaded statically. A sampling grid of 160 equidistant points was superimposed over selected slices, and average peak stresses were calculated for 6 anatomical regions. Within-region maximal peak and average von Mises stresses were compared between healthy and OA bones in both midstance and impact loading. RESULTS: Average impact stresses across all regions, in both locations (palmar and dorsal) were greater in the OA model. Highest impact stresses were located in the dorsal medial condyle in the healthy (12.8 MPa) and OA (14.1MPa) models, and were lowest in the palmar medial and lateral parasagittal grooves in the healthy (5.94 MPa) and OA (7.07 MPa) models. The healthy static model had higher peak (up to 49.7% greater) and average (up to 38.6% greater) stresses in both locations and across all regions compared to the OA static model. CONCLUSIONS: Under simulated footfall a trot, loading on the dorsal aspect of the third metacarpal at impact created stresses similar to those found during midstance. The high accelerations that occur under impact loading are likely responsible for creating the high stresses, as opposed to midstance loading where the high stresses are the result of high mass loading. Although the stress magnitudes were found to be similar among the two loading conditions, the location of the high stress loading occurred in sites that are not typically associated with osteoarthritic changes.

Internet-based survey of the nature and perceived causes of injury to dogs participating in agility training and competition events.

OBJECTIVE: To characterize injuries (on the basis of type and severity of injury and affected region of the body) among dogs participating in agility training and competition events and examine associations between injury characteristics and perceived causes of injury. DESIGN: Internet-based, retrospective, cross-sectional survey. ANIMALS: 3,801 privately owned dogs participating in agility training or trials. PROCEDURES: A retrospective electronic survey was developed to investigate demographic factors for dogs and handlers, frequency of participation in agility training and competition, and perceived causes and characteristics of injuries acquired by dogs during agility-related activities. Respondents were handlers recruited through member lists of large canine agility associations in Canada and the United Kingdom and through promotion on an agility blog site. Associations between cause and anatomic site or type of injury and between injury severity (mild vs severe) and setting (competition vs practice) were investigated. RESULTS: Surveys were received from 1,669 handlers of 3,801 agility dogs internationally. Handler-reported data indicated 1,209 of 3,801 (32%) dogs had ≥ 1 injury; of 1,523 analyzed injuries, the shoulder (349 injuries), back (282), and neck (189) regions and phalanges (202) were predominantly affected. Soft tissue injuries (eg, strain [muscle or tendon injury; 807], sprain [ligament injury; 312], and contusion [200]) were common. Injuries were most commonly incurred during interactions with bar jumps, A-frames, and dog walk obstacles (260, 235, and 177 of 1,602 injuries, respectively). Anatomic site and type of injury were significantly associated with perceived cause of injury. CONCLUSIONS AND CLINICAL RELEVANCE: These findings provided a basis for further experimental studies to identify specific mechanisms of various types of injury in dogs that participate in agility activities.

Survey-based analysis of risk factors for injury among dogs participating in agility training and competition events.

OBJECTIVE: To identify potential risk factors for agility-related injuries among dogs. DESIGN: Internet-based, retrospective, cross-sectional survey. ANIMALS: 3,801 privately owned dogs participating in agility training or trials. PROCEDURES: A retrospective electronic survey was used to investigate potential risk factors for injury among dogs participating in agility-related activities. Respondents were handlers recruited through member lists of large canine agility associations in Canada and the United Kingdom and through promotion on an agility blog site. Variables evaluated included demographic information for handlers and dogs, exposure variables (eg, frequency of agility practice and competition in the past year), and use of preventive measures intended to keep dogs fit for agility (warmup, cooldown, or conditioning exercises; alternative therapeutic treatments [eg, acupuncture, massage, or chiropractic care]; or dietary supplement products). RESULTS: Data were collected from 1,669 handlers of 3,801 agility dogs internationally; 1,209 (32%) dogs incurred ≥ 1 injury. Previous injury (OR, 100.5), ≤ 4 years of agility experience for dogs (OR, 1.5), use of alternative therapeutic treatments (OR, 1.5), and Border Collie breed (OR, 1.7) were associated with increased odds of injury. Handlers having 5 to 10 or > 10 years of experience (OR, 0.8 and 0.6, respectively) and dogs having > 4 years of experience in the sport (OR, 0.6) were associated with decreased odds of injury. CONCLUSIONS AND CLINICAL RELEVANCE: Specific factors were associated with agility-related injuries in dogs. Educational prevention strategies should target at-risk populations in an effort to reduce potential injuries. Future research should focus on the biomechanical factors associated with agility-related injuries.

Changes in growth of the hoof wall and hoof morphology in response to regular periods of trotting exercise in Standardbreds.

OBJECTIVE: To quantitate changes in hoof wall growth and hoof morphology induced by mild exercise in Standardbreds. ANIMALS: 18 Standardbreds. PROCEDURES: Horses were exercised at approximately 6 m/s (4,200 to 5,600 m/d) on 4 d/wk for 17 weeks. Both exercise (n = 9) and nonexercise (control group; 9) groups were housed in a large paddock throughout the study. At the beginning and end of the study, right forelimb feet of all horses were digitally photographed and underwent magnetic resonance imaging. Hoof wall measurements were obtained from the images to evaluate hoof wall growth and morphometric variables. Data were compared between the groups and within each group via a quadratic model. Changes in each variable and pairwise correlations between variables were evaluated. RESULTS: Morphometric variables did not significantly differ between the control and exercise groups. However, differences within each group between the start and the end of the study were significant for several variables; overall, values for hoof wall variables increased and those for solar variables decreased. Between the beginning and the end of the study, the amount of variation in values of hoof capsule variables in the exercise group decreased to a greater extent, compared with control group findings. Patterns of pairwise correlations for variables differed between the groups. CONCLUSIONS AND CLINICAL RELEVANCE: In Standardbreds, mild exercise for 17 weeks caused no significant changes in hoof wall growth or morphometric variables. Subtle changes may develop in equine hooves in response to loading, and mild exercise may not be a strong adaptive stimulus.

Cranial dimensions and forces of biting in the domestic dog.

The purpose of this paper is to analyse the effects of cranial size and shape in domestic dogs (Canis familiaris) on predicted forces of biting. In addition to continuous size-shape analysis, nine size-shape groups were developed based on three skull shape categories and three skull size categories. Bite forces were predicted from measurements made on dried skulls using two lever models of the skull, as well as simple models derived by regression analysis. Observed bite force values were not available for the database used in this study, so only comparisons between categories and models were undertaken. The effects of shape and size on scaled predicted bite forces were evaluated. Results show that bite force increases as size increases, and this effect was highly significant (P < 0.0001). The effect of skull shape on bite force was significant in medium and large dogs (P < 0.05). Significant differences were not evident in small dogs. Size x shape interactions were also significant (P < 0.05). Bite force predictions by the two lever models were relatively close to each other, whereas the regression models diverged slightly with some negative numbers for very small dogs. The lever models may thus be more robust across a wider range of skull size-shapes. Results obtained here would be useful to the pet food industry for food product development, as well as to paleontologists interested in methods of estimating bite force from dry skulls.

Calibration of estimated biting forces in domestic canids: comparison of post-mortem and in vivo measurements.

Estimates of biting forces are widely used in paleontological and comparative studies of feeding mechanics and performance, and are usually derived from lever models based on measurements made on the skull that are relevant to the mechanics of the masticatory system. Owing to assumptions and unmeasurable errors in their estimation, such values are used comparatively rather than as absolute estimates. The purpose of this paper was to provide calibration of post-mortem calculated bite force estimates by comparing them to in vivo forces derived from a sample of 20 domestic dogs (Canis familiaris) during muscle stimulation under general anaesthesia. Two lever models previously described in the literature were used to estimate post-mortem values, and regression analysis was also performed to derive best-fit equations against a number of morphometric measurements on the skull. The ranges of observed forces in vivo were 147-946 N at the canine, and 524-3417 N at the second molar. The lever models substantially underestimated these forces, giving mean values between 39% and 61% of the observed means. Predictability was considerably improved by removing the linear bias and deviation of the regression slope from unity with an adjustment equation. Best-fit statistical models developed on these animals performed considerably better (calculated means within 0.54% of observed means) and included easily measureable variables such as bodyweight, dimensions of the temporalis fossa and out-lever from the jaw joint to the biting tooth. These data should lead to more accurate absolute, rather than relative, estimates of biting forces for other extant and fossil canids, and other carnivorans by extrapolation.

Biomechanical and mechanical investigations of the hoof-track interface in racing horses.

The aim of this article is to review current knowledge of kinetic variables of the hoof-track interaction and track properties relevant to the objective of minimizing injuries to horses at racing tracks. In each phase of the stance--primary impact, secondary impact, support, and breakover, the hoof experiences different combinations of force and acceleration. The role of each combination, and of measured track properties, in causing catastrophic and chronic injuries to the limbs of racing horses is unknown. Limited data of this type have been provided in previous epidemiologic studies of risk factors for breakdown. Future epidemiological studies should include characterization of the track surfaces and a more complete description of the kinematics of the hoof and surface. Consideration of an appropriate range of physical properties is necessary in track design, testing, and maintenance.

Bite club: comparative bite force in big biting mammals and the prediction of predatory behaviour in fossil taxa.

We provide the first predictions of bite force (BS) in a wide sample of living and fossil mammalian predators. To compare between taxa, we calculated an estimated bite force quotient (BFQ) as the residual of BS regressed on body mass. Estimated BS adjusted for body mass was higher for marsupials than placentals and the Tasmanian devil (Sarcophilus harrisii) had the highest relative BS among extant taxa. The highest overall BS was in two extinct marsupial lions. BFQ in hyaenas were similar to those of related, non-osteophagous taxa challenging the common assumption that osteophagy necessitates extreme jaw muscle forces. High BFQ in living carnivores was associated with greater maximal prey size and hypercarnivory. For fossil taxa anatomically similar to living relatives, BFQ can be directly compared, and high values in the dire wolf (Canis dirus) and thylacine (Thylacinus cynocephalus) suggest that they took relatively large prey. Direct inference may not be appropriate where morphologies depart widely from biomechanical models evident in living predators and must be considered together with evidence from other morphological indicators. Relatively low BFQ values in two extinct carnivores with morphologies not represented among extant species, the sabrecat, Smilodon fatalis, and marsupial sabretooth, Thylacosmilus atrox, support arguments that their killing techniques also differed from extant species and are consistent with 'canine-shear bite' and 'stabbing' models, respectively. Extremely high BFQ in the marsupial lion, Thylacoleo carnifex, indicates that it filled a large-prey hunting niche.

Mechanical behavior and quantitative morphology of the equine laminar junction.

The horse's hoof is structurally modified for its mechanical functions, but studying the functional design of internal structures is hampered by the external keratinous capsule. Finite-element analysis offers one method for evaluating mechanical function of components within the capsule, such as the laminar junction. This is the epidermodermal connection that binds the hoof wall strongly to the distal phalanx. Primary epidermal laminae (PEL), projecting inward from the wall, vary in morphology and are remodeled despite being keratinous. The aim of this study is to investigate the suggestion that remodeling of PEL is influenced by mechanical stress. Circumferential and proximodistal stress distribution and relative displacement in the laminar junction are assessed by finite-element analysis (FEA) of nine hoof models. Spacing, orientation, and curvature of PEL are assessed from sections through 47 other hooves and compared with the stress and displacement data. Significant correlations are found between laminar spacing and seven displacement and stress variables, supporting the link between stresses and remodeling. Differences in external hoof shape cause regional variation in stress magnitudes around the laminar junction. This finding is in accord with previous observations that laminar morphology is individually regionally variable. This work provides the first concrete link between mechanical behavior and laminar morphology.