Pilot evaluation of a novel unilateral onychectomy model and efficacy of an extended release buprenorphine product.

BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAIDs), transdermal fentanyl patches, and transmucosal buprenorphine are probably the most commonly used options for providing post-operative analgesia in the early at-home period. However, these require daily administration or are associated with abuse concerns. One of the significant unmet needs in veterinary surgery and pain management is for longer acting opioids for cats to effectively bridge the gap between the in-hospital and at-home recovery periods. A proof of concept study of an extended release formulation of buprenorphine HCL (ER-Bup) was conducted using objective kinetic measures and a unilateral onychectomy model. Using a blinded, randomized, two period crossover design, four cats were allocated to control (saline) or ER-Bup (0.6 mg/kg, subcutaneously [SC]) treatment groups. All animals underwent a unilateral forelimb onychectomy per period with a washout/recovery period in between. Observational pain scores and kinetic data (using a pressure sensitive walkway [PSW]) were collected prior to (baseline) and at intervals for 72 h following surgery. Symmetry indices were derived for kinetic variables (peak vertical force [PVF]; vertical impulse [VI]) of each forelimb for landing following a jump and for walking. A rescue analgesic protocol was in place. Effect of surgery and treatment were evaluated using a mixed model statistical approach. RESULTS: No cats required rescue analgesics based on subjective pain score. ER-Bup had a positive influence on subjective pain scores during the 72 h postsurgery (p = 0.0473). PVF and VI of the operated limb were significantly decreased for both landing (p < 0.0001 and p < 0.0001) and walking (p < 0.0001 and p < 0.0001 respectively) compared to control. ER-Bup resulted in significantly decreased asymmetry in limb use during landing (PVF, p < 0.0001; VI, p < 0.0001) and walking (PVF, p = 0.0002, VI, p < 0.0001). The novel use of data collected following a jump from an elevated platform appeared to provide all desired information and was easier to collect than walking data. CONCLUSION: This study demonstrates that SC administration of ER-Bup may be an effective analgesic for a 72 h period postoperatively. Furthermore, landing onto a PSW from an elevated perch may be a useful and efficient way to assess analgesics in cats using a unilateral model of limb pain.

Prevalence of radiographic appendicular osteoarthritis and associated clinical signs in young dogs.

This study aimed to determine the prevalence of osteoarthritis (OA) and associated clinical signs in young dogs. Owners of dogs aged 8 months-4 years from a single practice, were contacted in random order, to participate in a general health screen. Clinical and orthopedic examinations were performed. Each joint was scored for pain reactions (0-4). Orthogonal radiographs of all joints were made under sedation. Each joint was scored for radiographic OA (rOA) severity on an 11-point scale. Clinical OA (cOA) was defined as an overlap of rOA and joint pain in ≥ 1 joint. Owners completed OA questionnaires. The owners of 123 dogs agreed to participate. Overall, 39.8% (49/123) of dogs had rOA in ≥ 1 joint, and 16.3% (20/123) or 23.6% (29/123) dogs had cOA, depending on the cut-off value of joint pain; moderate (2), or mild (1), respectively. Owners of dogs with cOA observed signs of impairment in approximately 30% of cases. Only 2 dogs with cOA were receiving OA pain management. The most commonly affected joints in descending order of frequency were elbow, hip, tarsus, and stifle. Radiographically visible OA is common in young dogs, and 40-60% of dogs with rOA had cOA. However, OA-pain appears underdiagnosed and undertreated in young dogs.

A Pilot, Open-Label Study to Evaluate the Efficacy of Intra-Articular Administration of a Caninized TNF Receptor Fc Fusion Protein as a Treatment for Osteoarthritis-Associated Joint Pain.

Tumor necrosis factor-α (TNF-α) is a potential target for osteoarthritis (OA) treatment. In several recent clinical studies in human OA, anti-TNF-α therapy showed promising results; however, these were open-label and based on patient-reported outcome measures. In this study, we developed a caninized TNF-α receptor-Fc (caTNFR-Fc) fusion protein and conducted a non-randomized, open-label, pilot study in dogs with OA using objectively measured ground reaction forces and activity. The aims of the study were to assess the efficacy of the intra-articular (IA) injection of the caTNFR-Fc fusion protein as a treatment for OA pain, and additionally to evaluate TNF concentrations in synovial fluid (SF) between joints with/without OA in dogs. Dogs (n = 12) with single-limb lameness due to single joint appendicular OA were recruited. All dogs received caTNFR-Fc fusion protein injection into the affected joint under sedation. Objective kinetic gait analysis using force plate was performed prior to (baseline), and at 14- and 28-days following treatment. Additionally, SF samples were collected from OA joints (n = 69) and non-OA joints (n = 79) in a different cohort of dogs and TNF-α were measured using enzyme-linked immunosorbent assay. No significant treatment effects on the limb use, activity, and the questionnaire were found. The concentration of TNF-α was significantly higher in OA joints than in healthy joints (p = 0.0019), but TNF-α was detected in only 10/69 OA samples. The IA injection of caTNFR-Fc fusion protein provided no benefit in terms of objective limb use and activity data in dogs with OA in this pilot study. Although the SF concentration of TNF-α was significantly higher in OA joints, few OA joints had measurable TNF-α. Collectively, the data indicate TNF-α may not be a good therapeutic target in canine OA.

Refinement of the Feline Musculoskeletal Pain Index (FMPI) and development of the short-form FMPI.

OBJECTIVES: The aim of this study was to investigate the reliability and responsiveness of the Feline Musculoskeletal Pain Index (FMPI) using the collective results of multiple clinical studies and iteratively refine the FMPI for future use. METHODS: Data were compiled from previously conducted studies involving client-owned cats with degenerative joint disease (DJD) and which used the FMPI. The reliability of the FMPI was assessed using the data from the initial visits of those studies. For the assessment of responsiveness of the FMPI, only placebo-controlled studies that used analgesic treatments were included. Treatment groups from each study were combined and categorized as 'placebo' group and 'analgesic' group. Then, the mean change from baseline in score of each FMPI item and across all items within and between these groups were assessed. Based on the results of the reliability and responsiveness of the FMPI, stepwise elimination was used to remove the items that were least able to distinguish between the placebo and analgesic groups. Finally, after the stepwise elimination, a proposed new FMPI-short form (FMPI-sf) was constructed and its reliability was reassessed using the data sets described above. Individual and combined data sets of the studies were also used to compare the responsiveness of the original FMPI and the FMPI-sf. RESULTS: The data from 180 cats from four studies were included. The original FMPI had a reasonable reliability, but low/no responsiveness. The elimination process of FMPI items refined the responsiveness of the instrument while maintaining its reliability. When the responsiveness was compared between the original FMPI (17 items) and the FMPI-sf (nine items), the treatment effect between groups was always greater when the FMPI-sf was used. CONCLUSIONS AND RELEVANCE: The proposed FMPI-sf may be able to better distinguish between placebo and analgesic effects in cats with DJD.

Initial exploration of the discriminatory ability of the PetPace collar to detect differences in activity and physiological variables between healthy and osteoarthritic dogs.

Background: Accelerometry has been used to evaluate activity in dogs with osteoarthritis (OA) pain, especially in relation to effect of treatment; however no studies have compared accelerometry-measured activity in dogs with OA-pain and healthy dogs. The aims of this study were to (1) compare activity output from the PetPace collar with the validated Actical monitor and (2) determine if PetPace collar outputs (overall activity, activity levels, body position, and vital signs) differed between healthy dogs and dogs with OA-pain. Methods: This was an observational, non-interventional study in healthy dogs and dogs with OA-pain. All dogs were outfitted with the PetPace collar and the Actical monitor simultaneously for 14 days. Output from these devices was compared (correlations), and output from the PetPace device was used to explore differences between groups across the activity and vital sign outputs (including calculated heart rate variability indices). Results: There was moderate correlation between the PetPace collar and Actical monitor output (R 2 = 0.56, p < 0.001). Using data generated by the PetPace collar, OA-pain dogs had lower overall activity counts and spent less time standing than healthy dogs. Healthy dogs spent more time at higher activity levels than OA-pain dogs. Certain heart rate variability indices in OA-pain dogs were lower than in healthy dogs. Conclusions and clinical relevance: The results of this study suggest that the PetPace collar can detect differences between healthy dogs and those with OA-pain, and that OA-pain negatively impacts overall activity levels in dogs, and especially higher intensity activity.

Defining the rate of, and factors influencing, radiographic progression of osteoarthritis of the canine hip joint.

BACKGROUND: This study aimed to define the rate of progression of radiographic osteoarthritis (OA) of the canine hip joint and to describe factors affecting this progression. METHODS: Dogs that underwent unilateral total hip replacement (THR) were reviewed for the evaluation of radiographic appearance of the non-operated hip joint over time. Standard extended ventrodorsal hip radiographs were taken preoperatively and postoperatively. All images were anonymized, randomized and scored using three different methods. The mean daily change between evaluations was calculated in each individual dog, and the effect of sex, age, body weight, open/closed status of the proximal femoral physis, preoperative severity of OA, time after surgery and their interactions, were investigated as potential influencing factors. RESULTS: After reviewing the medical records, 163 dogs (468 images) met the inclusion criteria. Consistent across the three scoring systems, radiographic progression of OA was greater in younger (open physis) and spayed female dogs. A subset of seven patients (4.3%) had a faster progression of OA and was considered outliers. No dog was rated as outlier by all three scoring systems. CONCLUSION: The rate of progression of radiographically assessed coxofemoral OA varies greatly, but is faster in younger, spayed female dogs. Unusually fast progression occasionally occurs.

Biological resurfacing in a canine model of hip osteoarthritis.

Articular cartilage has unique load-bearing properties but has minimal capacity for intrinsic repair. Here, we used three-dimensional weaving, additive manufacturing, and autologous mesenchymal stem cells to create a tissue-engineered, bicomponent implant to restore hip function in a canine hip osteoarthritis model. This resorbable implant was specifically designed to function mechanically from the time of repair and to biologically integrate with native tissues for long-term restoration. A massive osteochondral lesion was created in the hip of skeletally mature hounds and repaired with the implant or left empty (control). Longitudinal outcome measures over 6 months demonstrated that the implant dogs returned to normal preoperative values of pain and function. Anatomical structure and functional biomechanical properties were also restored in the implanted dogs. Control animals never returned to normal and exhibited structurally deficient repair. This study provides clinically relevant evidence that the bicomponent implant may be a potential therapy for moderate hip osteoarthritis.

Development of a checklist for the detection of degenerative joint disease-associated pain in cats.

OBJECTIVES: The aim of this study was to develop an evidence-based, clinically expedient checklist to identify cats likely to have degenerative joint disease (DJD)-associated pain. METHODS: Data were compiled from previously conducted studies that employed a standardized subjective outcome measure consisting of a series of questions. These studies included a prevalence study (with DJD non-informed owners) and therapeutic trials (with DJD-informed owners). For each cat, and each question, response scores were converted to 'impaired' and 'unimpaired'. Cats were categorized as 'DJD pain' and 'non-DJD' based on orthopedic pain and radiographic DJD scores. These binary data were compared between cat phenotypes (non-DJD and DJD pain) for each question. Sensitivity and specificity of each question were calculated using the binary data; based on this, potential questions for the checklist were selected. Sensitivity and specificity across this group of questions were calculated, and questions sequentially removed to optimize length, sensitivity and specificity. Finally, the proposed checklist was applied to a novel data set to evaluate its ability to identify cats with DJD pain. RESULTS: In total, 249 DJD pain cats and 53 non-DJD cats from five studies were included. Nine questions with adequate sensitivity and specificity were initially identified. Following sequential removal of questions, a checklist with six binary questions was proposed. Based on the data from the cohorts of DJD-informed and DJD non-informed owners, the sensitivity and specificity of the proposed checklist were approximately 99% and 100%, and 55% and 97%, respectively. CONCLUSIONS AND RELEVANCE: The proposed checklist represents a data-driven approach to construct a screening checklist for DJD pain in cats. This checklist provides a clinically expedient tool likely to increase veterinarians' ability to screen for DJD pain in cats. The identified behaviors comprising the checklist may further provide a foundation for increasing awareness of DJD pain among cat owners.

Correlation of Artemin and GFRα3 With Osteoarthritis Pain: Early Evidence From Naturally Occurring Osteoarthritis-Associated Chronic Pain in Dogs.

Arthritis, including osteoarthritis (OA) and other musculoskeletal-associated pain, is a worldwide problem, however, effective drug options are limited. Several receptors, neurotransmitters, and endogenous mediators have been identified in rodent models, but the relevance of these molecules in disease-associated pain is not always clear. Artemin, a neurotrophic factor, and its receptor, glial-derived neurotrophic factor (GDNF) family receptor alpha-3 (GFRα3), have been identified as involved in pain in rodents. Their role in OA-associated pain is unknown. To explore a possible association, we analyzed tissue from naturally occurring OA in dogs to characterize the correlation with chronic pain. We used behavioral assessment, objective measures of limb use, and molecular tools to identify whether artemin and GFRα3 might be associated with OA pain. Our results using banked tissue from well-phenotyped dogs indicates that artemin/GFRα3 may play an important, and hitherto unrecognized, role in chronic OA-associated pain. Elevated serum levels of artemin from osteoarthritic humans compared to healthy individuals suggest translational relevance. Our data provide compelling evidence that the artemin/GFRα3 signaling pathway may be important in OA pain in both non-humans and humans and may ultimately lead to novel therapeutics.

Correlation of activity data in normal dogs to distance traveled.

The objective of this study was to explore the mathematical relationships between independent variables (patient morphometrics and treadmill speed) and dependent variables (accelerometer or pedometer output) when evaluating data from accelerometers and pedometers in dogs. Twenty dogs took part in 3 randomized activities, consisting of exercise on a treadmill at 1.0, 1.5, and 2.0 m/s for a total distance of 1 km at each speed. Dogs simultaneously wore both an accelerometer and a pedometer. Statistical analysis used multiple regression models to discover the relationships between independent and dependent variables. A formula was developed to predict the distance traveled by a dog based on its morphometrics and activity monitor output. Shoulder height had stronger correlations to accelerometer and pedometer outputs than other morphometric variables. As shoulder height increased, all accelerometer and pedometer outputs decreased. As treadmill speed increased, both accelerometer and pedometer step counts decreased, while accelerometer activity counts increased. According to a formula derived to predict the total distance traveled using patient shoulder height and accelerometer or pedometer output, pedometer steps were the most accurate predictor of distance traveled. Accelerometer steps were less accurate when using the same model. Accelerometer activity counts did not reveal a meaningful predictive formula. The results of this study indicate that patient morphometrics and treadmill speed (as a measure of intensity) influenced accelerometer and pedometer data. The pedometer data more precisely and accurately estimated the distance traveled based on step counts and patient shoulder height. In normal dogs, accelerometer and pedometer steps may reasonably estimate distance traveled.

L'objectif de la présente étude était d'explorer les relations mathématiques entre des variables indépendantes (données morphométriques du patient et vitesse du tapis d'exercice) et des variables dépendantes (accéléromètre ou données du podomètre) lors de l'évaluation des données provenant d'accéléromètres et de podomètres chez des chiens. Vingt chiens ont pris part à trois activités randomisées, consistant en des exercices sur un tapis roulant à 1,0, 1,5, et 2,0 m/s pour une distance totale de 1 km à chaque vitesse. Les chiens portaient simultanément un accéléromètre et un podomètre. Les analyses statistiques utilisèrent des modèles de régression multiple afin de découvrir les relations entre les variables indépendantes et dépendantes. Une formule fut développée afin de prédire la distance parcourue par un chien sur la base de sa morphométrie et les données des moniteurs d'activité. La hauteur à l'épaule avait la plus forte corrélation aux données de l'accéléromètre et du podomètre comparativement aux autres variables morphométriques. À mesure que la hauteur à l'épaule augmentait, toutes les données de l'accéléromètre et du podomètre diminuaient. Avec l'augmentation de la vitesse du tapis d'exercice, il y eu une diminution du nombre de pas mesuré par l'accéléromètre et le podomètre, alors qu'il y avait une augmentation du compte d'activité de l'accéléromètre. Selon la formule dérivée pour prédire la distance totale parcourue en utilisant la hauteur à l'épaule du patient et les données de l'accéléromètre ou du podomètre, le nombre de pas du podomètre était le prédicteur le plus précis de la distance parcourue. Le nombre de pas avec l'accéléromètre était moins précis en utilisant le même modèle. Le dénombrement des activités par l'accéléromètre n'ont pas permis de déterminer une formule prédictive significative. Les résultats de cette étude indiquent que les données morphométriques des patients et la vitesse du tapis d'exercice (comme mesure d'intensité) influencent les résultats de l'accéléromètre et du podomètre. Les données du podomètre ont estimé avec plus de justesse et de précision la distance parcourue en se basant sur le nombre de pas et la hauteur à l'épaule du patient. Chez les chiens normaux, le nombre de pas mesuré par un accéléromètre et un podomètre peut raisonnablement estimer la distance parcourue.(Traduit par Docteur Serge Messier).

Pet Dogs with Subclinical Acute Radiodermatitis Experience Widespread Somatosensory Sensitization.

Radiation-induced dermatitis (RID) is a common and painful complication of radiotherapy. When severe, radiation-associated pain (RAP) can reduce the efficacy of radiotherapy by limiting the radiation dose given, and/or necessitating breaks in treatment. Current RAP mitigation strategies are of limited efficacy. Our long-term goal is to develop a comparative oncology model, in which novel analgesic interventions for RAP can be evaluated. The aim of this study was to validate quantitative end points indicative of RAP in pet dogs with subclinical and low-grade RID. Extremity soft tissue sarcomas were treated with post-operative irradiation (54 Gy in 18 fractions). Visual toxicity scores, questionnaire-based pain instruments and objective algometry [mechanical quantitative sensory testing (mQST)], were evaluated regularly. Breed-matched control populations were also evaluated to address the effect of potential confounders. Skin biopsies from within the irradiated field were collected at baseline and after 24 Gy irradiation, for analysis of pain-related genes using the nanoString nCounter platform. Relative to control populations, mechanical thresholds decreased in irradiated test subjects as the total radiation dose increased, with the most pronounced effect at the irradiated site. This was accompanied by increased mRNA expression of GFRα3, TNFα, TRPV2 and TRPV4. In a separate set of dogs with moderate-to-severe RID, serum concentrations of artemin (the ligand for GFRα3) were elevated relative to controls (P = 0.015). Progressive reduction in mechanical thresholds, both locally and remotely, indicates widespread somatosensory sensitization during radiation treatment. mQST in pet dogs undergoing radiation treatment represents an innovative tool for preclinical evaluation of novel analgesics.

Anti-nerve growth factor monoclonal antibodies for the control of pain in dogs and cats.

Nerve growth factor (NGF) is essential for the survival of sensory and sympathetic neurons during development. However, in the adult, NGF and its interaction with tropomyosin receptor kinase A receptor (TrkA) has been found to play a critical role in nociception and nervous system plasticity in pain conditions. Thus, various monoclonal antibody (mAb) therapies targeting this pathway have been investigated in the development of new pharmacotherapies for chronic pain. Although none of the mAbs against NGF are yet approved for use in humans, they look very promising for the effective control of pain. Recently, species-specific anti-NGF mAbs for the management of osteoarthritis (OA)-associated pain in dogs and cats has been developed, and early clinical trials have been conducted. Anti-NGF therapy looks to be both very effective and very promising as a novel therapy against chronic pain in dogs and cats. This review outlines the mechanism of action of NGF, the role of NGF in osteoarthritis, research in rodent OA models and the current status of the development of anti-NGF mAbs in humans. Furthermore, we describe and discuss the recent development of species-specific anti-NGF mAbs for the treatment of OA-associated pain in veterinary medicine.

Electrophysiological characterisation of central sensitisation in canine spontaneous osteoarthritis.

In man, central sensitisation (CS) contributes to the pain of osteoarthritis (OA). Dogs with spontaneous OA may also exhibit CS. Electrophysiological reflex measurements are more objective than behavioural assessments and can be used to evaluate CS in preclinical and clinical studies. It was hypothesised that dogs suffering from OA would exhibit electrophysiological characteristics indicative of CS, associated with reduced diffuse noxious inhibitory controls (DNICs). One hundred and seventeen client-owned dogs were recruited to the study. Hind limb nociceptive withdrawal reflex thresholds, stimulus response, and temporal summation characteristics were recorded, during alfaxalone anaesthesia, from 46 OA dogs, 29 OA dogs receiving nonsteroidal anti-inflammatory drugs (OANSAIDs), and 27 breed- and weight-matched control dogs. Efficacy of DNIC was evaluated in 12 control and 11 of the OA dogs, by application of a mechanical conditioning stimulus to the contralateral forelimb. Nociceptive withdrawal reflex thresholds were higher in OA compared with control dogs (P = 0.02). Stimulus response characteristics demonstrated an augmented response in OANSAID dogs compared with OA (P < 0.001) and control (P < 0.001) dogs. Temporal summation demonstrated exaggerated C-fibre-mediated responses in both OA (P < 0.001) and OANSAID (P = 0.005) groups, compared with control animals. Conditioning stimulus application resulted in inhibition of test reflex responses in both OA and control animals (P < 0.001); control animals demonstrated greater inhibition compared with OA (P = 0.0499). These data provide evidence of neurophysiological changes consistent with CS in dogs with spontaneous OA and demonstrate that canine OA is associated with reduced DNIC.

Defining local nerve blocks for feline distal pelvic limb surgery: a cadaveric study.

Objectives Anatomical and methodological detail is lacking regarding local anesthetic peripheral nerve block techniques for distal pelvic limb surgery in cats. The aim of this study was to develop, describe and test nerve block methods based on cadaveric dissections and dye injections. Methods Ten pairs of feline pelvic limbs (n = 20) were dissected and the tibial nerve (T n.), common fibular (peroneal) nerve (CF n., and its two branches, the superficial fibular [peroneal] nerve [SpF n.] and the deep fibular [peroneal] nerve [DpF n.]) and the saphenous nerve (Sa n.) were identified. Based on these dissections, a 'distal crus block' (selective blockade of the CF n., T n. and Sa n.) and a 'distal pes block' (selective blockade of the SpF n., DpF n., T n. and Sa n.) were developed for surgical procedures in two different regions of the distal pelvic limb. Techniques were tested using new methylene blue (NMB) dye injections in feline pelvic limbs (n = 12). Using a 25 G × 5/8 inch needle and 1 ml syringe, 0.1 ml/kg of NMB dye solution was injected at the site of the CF n., and 0.05 ml/kg was injected at the sites of the SpF n., DpF n., Sa n. and T n. The length and circumference (fully or partially stained) of each stained nerve were measured. Results Positive staining of nerves was observed in 12/12 limbs. The lengths stained for the CF n., DpF n., SpF n., Sa n. and T n. were 27.19 ± 7.13, 20.39 ± 5.57, 22.82 ± 7.13, 30.89 ± 6.99 and 25.16 ± 8.09 mm, respectively. The nerves were fully stained in 12, 12, 10, 11 and 11 out of 12 limbs, respectively. Conclusions and relevance These two, three-point injection methods may be an effective perioperative analgesia technique for feline distal pelvic limb procedures.

Defining the local nerve blocks for feline distal thoracic limb surgery: a cadaveric study.

OBJECTIVES: Though controversial, onychectomy remains a commonly performed distal thoracic limb surgical procedure in cats. Peripheral nerve block techniques have been proposed in cats undergoing onychectomy but evidence of efficacy is lacking. Preliminary tests of the described technique using cadavers resulted in incomplete staining of nerves. The aim of this study was to develop nerve block methods based on cadaveric dissections and test these methods with cadaveric dye injections. METHODS: Ten pairs of feline thoracic limbs (n = 20) were dissected and superficial branches of the radial nerve (RSbr nn.), median nerve (M n.), dorsal branch of ulnar nerve (UDbr n.), superficial branch of palmar branch of ulnar nerve (UPbrS n.) and deep branch of palmar branch of ulnar nerve (UPbrDp n.) were identified. Based on these dissections, a four-point block was developed and tested using dye injections in another six pairs of feline thoracic limbs (n = 12). Using a 25 G × 5/8 inch needle and 1 ml syringe, 0.07 ml/kg methylene blue was injected at the site of the RSbr nn., 0.04 ml/kg at the injection site of the UDbr n., 0.08 ml/kg at the injection site of the M n. and UPbrS n., and 0.01 ml/kg at the injection site of the UPbrDp n. The length and circumference of each nerve that was stained was measured. RESULTS: Positive staining of all nerves was observed in 12/12 limbs. The lengths stained for RSbr nn., M n., UDbr n., UPbrS n. and UPbrDp n. were 34.9 ± 5.3, 26.4 ± 4.8, 29.2 ± 4.0, 39.1 ± 4.3 and 17.5 ± 3.3 mm, respectively. The nerve circumferences stained were 93.8 ± 15.5, 95.8 ± 9.7, 100 ± 0.0, 100 ± 0.0 and 93.8 ± 15.5%, respectively. CONCLUSIONS AND RELEVANCE: This described four-point injection method may be an effective perioperative analgesia technique for feline distal thoracic limb procedures.