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BACKGROUND: Lidocaine is a local anesthetic that is sometimes administered in combination with epinephrine. The addition of epinephrine increases the time lidocaine remains at the site of administration, thus prolonging the duration of effect. Due to their potential to prevent the visual detection of lameness, the administration of local anesthetics is strictly regulated in performance and racehorses. Recent reports of positive regulatory findings for lidocaine in racehorses suggests a better understanding of the behavior of this drug is warranted. The objective of the current study was to describe serum and urine concentrations and the pharmacokinetics of lidocaine and its primary metabolites following administration in combination with epinephrine, as a palmar digital nerve block in horses. Twelve horses received a single administration of 1 mL of 2% lidocaine HCl (20 mg/horse) with epinephrine 1:100,000, over the palmar digital nerve. Blood samples were collected up to 30 h and urine samples up to 48 h post administration. Lidocaine and metabolite concentrations were determined by liquid chromatography- mass spectrometry and pharmacokinetic (non-compartmental and compartmental) analysis was performed. RESULTS: Serum concentrations of lidocaine and 3-hydroxylidocaine were above the LOQ of the assay at 30 h post administration and monoethylglycinexylidide (MEGX) and glycinexylidide (GX) were below detectable levels by 24 and 48 h, respectively. In urine, lidocaine, MEGX and GX were all non-detectable by 48 h post administration while 3-hydroxylidocaine was above LOQ at 48 h post administration. The time of maximal concentration for lidocaine was 0.26 h (median) and the terminal half-life was 3.78 h (mean). The rate of absorption (Ka) was 1.92 1/h and the rate of elimination (Kel) was 2.21 1/h. CONCLUSIONS: Compared to previous reports, the terminal half-life and subsequent detection time observed following administration of lidocaine in combination with epinephrine is prolonged. This is likely due to a decrease in systemic uptake of lidocaine because of epinephrine induced vasoconstriction. Results of the current study suggest it is prudent to use an extended withdrawal time when administering local anesthetics in combination with epinephrine to performance horses.

ObjectivesThis study aimed to define the antimicrobial peptide (AMP) expression pattern of the equine ocular surface and amniotic membrane using a targeted qPCR approach and 3'Tag-sequencing. It will serve as a reference for future studies of ocular surface innate immunity and amniotic membrane therapies.ProceduresA targeted qPCR approach was used to investigate the presence of orthologs for three of the most highly expressed beta-defensins (DEFB1, DEFB4B, and DEFB103A) of the human ocular surface and amniotic membrane in equine corneal epithelium, conjunctiva, and amniotic membrane. 3'Tag-sequencing was performed on RNA from one sample of corneal epithelium, conjunctiva, and amniotic membrane to further characterize their AMP expression.ResultsEquine corneal epithelium, conjunctiva, and amniotic membrane expressed DEFB1, DEFB4B, and DEFB103A. DEFB103A was expressed at the highest amounts in corneal epithelium, while DEFB4B was most highly expressed in conjunctiva and amniotic membrane. 3'Tag-sequencing from all three tissues confirmed these findings and identified expression of five additional beta-defensins, 11 alpha-defensins and two cathelicidins, with the alpha-defensins showing higher normalized read counts than the beta-defensins.ConclusionsThis study identified AMP expression in the equine cornea and conjunctiva, suggesting that they play a key role in the protection of the equine eye, similar to the human ocular surface. We also determined that equine amniotic membrane expresses a substantial number of AMPs suggesting it could potentiate an antimicrobial effect as a corneal graft material. Future studies will focus on defining the antimicrobial activity of these AMPs and determining their role in microbial keratitis.

BackgroundEquine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM) is an inherited neurodegenerative disorder associated with a vitamin E deficiency within the first year of life. Vitamin E consists of 8 isoforms metabolized by the CYP4F2 enzyme. No antemortem diagnostic test currently exists for eNAD/EDM.Hypothesis/objectivesBased on the association of α-tocopherol deficiency with the development of eNAD/EDM, we hypothesized that the rate of α-tocopherol, but not γ-tocopherol or tocotrienol metabolism, would be increased in eNAD/EDM-affected horses.AnimalsVitamin E metabolism: Proof of concept (POC) study; eNAD/EDM-affected (n = 5) and control (n = 6) horses. Validation study: eNAD/EDM-affected Quarter Horses (QHs; n = 6), cervical vertebral compressive myelopathy affected (n = 6) horses and control (n = 29) horses. CYP4F2 expression and copy number: eNAD/EDM-affected (n = 12) and age- and sex-matched control (n = 11-12) horses.MethodsThe rates of α-tocopherol/tocotrienol and γ-tocopherol/tocotrienol metabolism were assessed in equine serum (POC and validation) and urine (POC only) using liquid chromatography tandem mass spectrometry (LC-MS/MS). Quantitative reverse-transcriptase PCR (qRT-PCR) and droplet digital (dd)-PCR were used to assay expression and genomic copy number of a CYP4F2 equine ortholog.ResultsMetabolic rate of α-tocopherol was increased in eNAD/EDM horses (POC,P

ObjectiveTo determine period prevalences of postmortem diagnoses for spinal cord or vertebral column lesions as underlying causes of ataxia (spinal ataxia) in horses.Animals2,861 client-owned horses (316 with ataxia [ataxic group] and 2,545 without ataxia [control group]).ProceduresThe medical records database of the University of California-Davis Veterinary Medical Teaching Hospital was searched to identify horses necropsied between January 1, 2005, and December 31, 2017. Results were compared between the ataxic and control groups and between various groups of horses in the ataxic group. Period prevalences were determined for the most common causes of ataxia.Results2,861 horses underwent full necropsy, and the period prevalences for the most common definitive diagnoses for ataxia were 2.7% (77/2,861) for cervical vertebral compressive myelopathy (CVCM), 1.3% (38/2,861) for equine neuroaxonal dystrophy or equine degenerative myeloencephalopathy (eNAD-EDM), and 0.9% (25/2,861) for trauma; the period prevalence of ataxia of unknown origin was 2.0% (56/2,861). Horses in the ataxic group (vs the control group) were more likely to have been warmblood horses (OR, 2.70) and less likely to have been Arabian horses (OR, 0.53). In the ataxic group, horses < 5 (vs ≥ 5) years of age had greater odds of CVCM (OR, 2.82) or eNAD-EDM (OR, 6.17) versus trauma or ataxia of unknown origin. Horses in the ataxic group with CVCM were more likely Thoroughbreds (OR, 2.54), whereas horses with eNAD-EDM were more likely American Quarter Horses (OR, 2.95) and less likely Thoroughbreds (OR, 0.11).Conclusions and clinical relevanceResults indicated that breed distributions differed for horses with CVCM versus eNAD-EDM; therefore, breed should be considered in the clinical evaluation of spinal ataxia in horses.

Following the successful creation of a biobank from two adult Thoroughbred mares, this study aimed to recapitulate sample collection in two adult Thoroughbred stallions as part of the Functional Annotation of the Animal Genome (FAANG) initiative. Both stallions underwent thorough physical, lameness, neurologic, and ophthalmic (including electroretinography) examinations prior to humane euthanasia. Epididymal sperm was recovered from both stallions immediately postmortem and cryopreserved. Aseptically collected full thickness skin biopsies were used to isolate, culture and cryopreserve dermal fibroblasts. Serum, plasma, cerebrospinal fluid, urine, and gastrointestinal content from various locations were collected and cryopreserved. Under guidance of a board-certified veterinary anatomic pathologist, 102 representative tissue samples were collected from both horses. Whole tissue samples were flash-frozen and prioritized tissues had nuclei isolated and cryopreserved. Spatially contemporaneous samples of each tissue were submitted for histologic examination. Antemortem and gross pathologic examination revealed mild abnormalities in both stallions. One stallion (ECA_UCD_AH3) had unilateral thoracic limb lameness and bilateral chorioretinal scars. The second stallion (ECA_UCD_AH4) had subtle symmetrical pelvic limb ataxia, symmetrical prostatomegally, and moderate gastrointestinal nematodiasis. DNA from each was whole-genome sequenced and genotyped using the GGP Equine 70K SNP array. The genomic resources and banked biological samples from these animals augments the existing resource available to the equine genomics community. Importantly we may now improve the resolution of tissue-specific gene regulation as affected by sex, as well as add sex-specific tissues and gametes.

This study reports the prevalence of and risk factors for incisional complications in equids after ventral midline celiotomy for enterolithiasis. This study covered the years 2008 to 2015 and included 72 equids. Enteroliths were removed from the ascending or descending colon through 1 or more enterotomies. Complications were defined as surgical site infection and/or incisional hernia formation. Follow-up by telephone questionnaire or medical records determined that 10/72 (13.9%) equids experienced complications, with 6/72 (8.3%) developing a surgical site infection and 5/72 (6.9%) a hernia. Seven of ten were presented for chronic abdominal discomfort (> 24 hours), and 8/10 had right dorsal colon and pelvic flexure enterotomies. All equids that developed an incisional hernia and 4 with surgical site infection had enteroliths > 15 cm diameter removed from the right dorsal colon. Antimicrobial powder applied to the ventral midline incision during closure significantly reduced incisional complications. Removal of > 15 cm diameter enteroliths from the right dorsal colon may predispose to postoperative incisional complications.

REASONS FOR PERFORMING STUDY:Although muscle mass strongly influences performance, there is currently no effective means to measure the 3-dimensional muscle mass of horses. We evaluated a 3-dimensional (3D) scanning methodology for its ability to quantify torso and hindquarter volumes as a proxy for regional muscle mass in horses. OBJECTIVES:Determine the repeatability of 3D scanning volume (V) measurements and their correlation to body weight, estimated body volume and muscle/fat ultrasound (US) depth. METHODS:Handheld 3D photonic scans were performed on 16 Quarter Horses of known body weight 56 days apart (n = 32 scans) with each scan performed in duplicate (n = 32 replicates). Tail head fat, gluteal and longissimus dorsi muscle depths were measured using US. Processed scans were cropped to isolate hindquarter (above hock, caudal to tuber coxae) and torso (hindquarter plus dorsal thoracolumbar region) segments and algorithms used to calculate V. Torso and hindquarter volume were correlated with body weight and US using Pearson's correlation and with estimated torso volume (50% body weight / body density) with Bland-Altman analysis. RESULTS:Scans took 2 min with < 3.5% error for duplicate scans. Torso volume (R = 0.90, P< 0.001) and hindquarter volume (R = 0.82, P< 0.001) strongly correlated with body weight and estimated BV (R = 0.91) with low bias. Torso volume moderately correlated to mean muscle US depth (R = 0.4, P< 0.05) and tail head fat (R = 0.42, P< 0.01). Mean muscle US depth moderately correlated to body weight (R = 0.50, P< 0.01). MAIN LIMITATIONS:3D Scans determine body volume not muscle volume. CONCLUSIONS:The hand-held 3D scan provided a rapid repeatable assessment of torso and hindquarter volume strongly correlated to body weight and estimated volume. Superimposition of regional scans and volume measures could provide a practical means to follow muscle development when tail head fat depth remain constant.

BackgroundA subset of horses deficient in alpha-tocopherol (α-TP) develop muscle atrophy and vitamin E-responsive myopathy (VEM) characterized by mitochondrial alterations in the sacrocaudalis dorsalis medialis muscle (SC).ObjectivesTo quantify muscle histopathologic abnormalities in subclinical α-TP deficient horses before and after α-TP supplementation and compare with retrospective (r)VEM cases.AnimalsProspective study; 16 healthy α-TP-deficient Quarter Horses. Retrospective study; 10 retrospective vitamin E-responsive myopathy (rVEM) cases .MethodsBlood, SC, and gluteus medius (GM) biopsy specimens were obtained before (day 0) and 56 days after 5000 IU/450 kg horse/day PO water dispersible liquid α-TP (n = 8) or control (n = 8). Muscle fiber morphology and mitochondrial alterations were compared in samples from days 0 and 56 and in rVEM cases.ResultsMitochondrial alterations more common than our reference range (

BackgroundEquine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM) is a neurodegenerative disorder affecting genetically predisposed foals maintained on an α-tocopherol (α-TOH) deficient diet. Currently no antemortem diagnostic test for eNAD/EDM is available.HypothesisBecause α-TOH deficiency is associated with increased lipid peroxidation, it was hypothesized that F2 -isoprostanes (F2 IsoP), F4 -neuroprostanes (F4 NP) and oxysterols derived from free radical oxidation would be increased in the cerebrospinal fluid (CSF) and neural tissue of eNAD/EDM affected horses and could serve as potential biomarkers for disease.AnimalsIsoprostane Study A: 14 Quarter horse foals (10 healthy foals and 4 eNAD/EDM affected foals) at 1 and 6 months of age. Isoprostane Study B: 17 eNAD/EDM affected and 10 unaffected horses ≥ 1-4 years of age. Oxysterol study: eNAD/EDM affected (n = 14, serum; n = 11, CSF; n = 10, spinal cord [SC]) and unaffected horses 1-4 years of age (n = 12, serum; n = 10, CSF; n = 7, SC).ProceduresCerebrospinal fluid [F2 IsoP] and [F4 NP] were assessed using gas chromatography-negative ion chemical ionization mass spectrometry. Serum, CSF, and cervical SC [oxysterols] were quantified using high performance liquid chromatography mass spectrometry. Results were compared with respective α-TOH concentrations.ResultsSpinal cord [7-ketocholesterol], [7-hydroxycholesterol], and [7-keto-27-hydrocholesterol] were higher in eNAD/EDM horses whereas [24-ketocholesterol] was lower. No significant difference was found in CSF [F2 IsoP] and [F4 NP], serum [oxysterols] and CSF [oxysterols] between eNAD/EDM affected and unaffected horses. No correlation was found between [F2 IsoP], [F4 NP], or [oxysterols] and respective [α-TOH].Conclusions and clinical importanceIn the SC, targeted markers of cholesterol oxidation were significantly increased in horses with eNAD/EDM.

Osteoporosis has been associated with pulmonary silicosis in California horses exposed to soils rich in cytotoxic silica dioxide crystals, a syndrome termed silicate associated osteoporosis (SAO). The causal mechanism for the development of osteoporosis is unknown. Osteoporotic lesions are primarily located in bone marrow-rich sites such as ribs, scapula and pelvis. Gene transcription patterns within bone marrow and pulmonary lymph nodes of affected horses may offer clues to disease pathobiology. Bone marrow core and tracheobronchial lymph node tissue samples harvested postmortem from affected and unaffected horses were examined histologically and subjected to RNA sequencing (RNA-seq). Sequenced data were analyzed for differential gene expression and gene ontology. Metatranscriptomic and metagenomic assays evaluated samples for infectious agents. Thirteen of 17 differentially expressed transcripts in bone marrow were linked to bone and cartilage formation such as integrin binding bone sialoprotein (log2FC = 3.39, PFDR = 0.013) and chondroadherin (log2FC = 4.48, PFDR = 0.031). Equus caballus solute carrier family 9, subfamily A2 (log2FC = 3.77, PFDR = 0.0034) was one of the four differentially expressed transcripts linked to osteoclast activity. Osteoblasts were hyperplastic and hypertrophic in bone marrow from affected horses. Biological pathways associated with skeletal morphogenesis were significantly enriched in affected horses. The 30 differentially expressed genes in affected lymph nodes were associated with inflammatory responses. Evidence of infectious agents was not found. The SAO affected bone marrow molecular signature demonstrated increased transcription and heightened activation of osteoblasts. Increased osteoblastic activity could be part of the pathological mechanism for osteoporosis or a compensatory response to the accelerated osteolysis. Transcriptome data offer gene targets for inquiries into the role of osteocytes and osteoblasts in SAO pathogenesis. Viral or bacterial infectious etiology in SAO is less likely based on metatranscriptomic and metagenomic data but cannot be completely ruled out.

OBJECTIVE To establish the pharmacokinetics of the cyclin-dependent kinase-9 inhibitor flavopiridol in equine middle carpal joints, using an extended-release poly lactic-co-glycolic acid (PLGA) microparticle formulation. ANIMALS 4 healthy horses without evidence of forelimb lameness. METHODS A 6-week longitudinal pharmacokinetic study was conducted in 2 phases (6 weeks each) in 4 healthy horses. The PLGA microparticles containing 122 μg flavopiridol in 3 mL saline were administered by intra-articular injection into 1 middle carpal joint, with empty PLGA microparticles injected into the contralateral joint as a control. Synovial fluid and plasma were collected at time points out to 6 weeks, and drug concentrations in synovial fluid and plasma were determined using validated protocols. Synovial fluid total protein and total nucleated cell count and differential, CBC, serum biochemistry, and lameness exams were performed at each of the time points. RESULTS Synovial fluid flavopiridol averaged 19 nM at week 1, gradually reduced to 1.4 nM by 4 weeks, and was generally below the detection limit at 5 and 6 weeks. There was no detectable flavopiridol in the plasma samples, and no adverse effects were observed at any time point. CLINICAL RELEVANCE Intra-articular injection of PLGA microparticle-encapsulated flavopiridol was well tolerated in horses, with detectable levels of flavopiridol in the synovial fluid out to 4 weeks with negligible systemic exposure. Flavopiridol is a cyclin-dependent kinase-9 inhibitor with potent anti-inflammatory and analgesic activity. The extended-release microparticle formulation promotes intra-articular retention of the drug and it may be an alternative to other intraarticular medications for treatment of equine joint disease. [ABSTRACT FROM AUTHOR]

Background: 18F‐sodium fluoride (18F‐NaF) positron emission tomography (PET) has been validated as a useful imaging technique in the racehorse fetlock. The use of 18F‐NaF PET in the nonracehorse fetlock has not been reported. Objectives: To describe 18F‐NaF PET findings in nonracehorse fetlocks, to compare with computed tomography (CT) findings and to compare PET findings between horses with and without fetlock pain. Study design: Retrospective observational study. Methods: All horses undergoing 18F‐NaF PET and CT imaging of the fetlock between October 2016 and March 2021 were included in the study. Medical records were reviewed for associated lameness information. Results: Thirty‐six fetlocks (33 front and 3 hind) from 25 horses were included. The interobserver agreement for PET [0.62 (95% confidence interval [CI] 0.59–0.65)] was higher than for CT [0.47 (95% CI 0.43–0.51)]. Increased 18F‐NaF uptake was most common in the medial subchondral bone of the proximal phalanx (23/36), the dorsomedial (20/36) and dorsosagittal (16/36) metacarpal/metatarsal distal subchondral bone, whereas sclerosis was identified on CT in these areas in 22 of 36 (p > 0.9), 33 of 36 (p = 0.001) and 23 of 36 (p = 0.15), respectively. Significant correlations were found between PET grades and both subchondral sclerosis and resorption CT grades (p < 0.001, Spearman r = 0.19 and 0.21, respectively). Abnormal 18F‐NaF uptake in the proximal sesamoid bones (PSBs) was identified in 12 of 36 of the fetlocks, which was more common than CT abnormalities (3/36, p = 0.02). Periarticular increased uptake was seen in 7 of 36 fetlocks, whereas osteophytosis was recognised on CT in 20 of 36 (p = 0.1). Maximal standardised uptake values (SUVmax) were significantly higher in painful than in nonpainful fetlocks (22.0 and 11.9, respectively, p = 0.038). Main limitations: Retrospective study and limited sample size. Conclusions: Overall PET and CT findings follow a similar distribution in their location. PET identified more abnormalities in the PSBs than CT. SUVmax is a pertinent factor to take into consideration for the assessment of the clinical significance of findings. [ABSTRACT FROM AUTHOR]

Copyright of Equine Veterinary Journal is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: Facilitated ankylosis using intra‐articular ethanol has been reported as a viable alternative to proximal interphalangeal (PIP) arthrodesis for owners with financial constraints or reservations regarding the invasiveness of surgical arthrodesis. An 18‐year‐old gelding presented for a left front leg lameness (Grade 4/5 on the AAEP scale) localised to the pastern region. Radiographs revealed severe osteoarthritis of the proximal interphalangeal joint (PIJ). Facilitated ankylosis of the PIJ with 95% alcohol was elected. The horse presented 6 weeks later with a significant worsening of the lameness, swelling of the pastern region and was noticed with the toe elevated off the ground when transiently weight bearing. Radiographs revealed a comminuted fracture of the middle phalanx. The horse was humanely euthanised. Necropsy revealed a severe chronic closed comminuted fracture of the middle phalanx with partially devitalised bone. Potential aetiologies are a decreased bone quality prior to alcohol injection, or that the desensitisation due to the alcohol injection could have resulted in an overuse by the horse or a traumatic accident. While previously unreported, veterinarians should educate owners that catastrophic fracture is an unlikely but possible complication following intra‐articular ethyl alcohol injection. [ABSTRACT FROM AUTHOR]

The combination of 18F‐Sodium Fluoride (18F‐NaF) and 18F‐FluoroDeoxyGlucose (18F‐FDG) for positron emission tomography (PET) imaging of the equine foot is appealing for detection of both osseous and soft tissue lesions in a single scan. As the combination of tracers could lead to a loss of information, a sequential approach, consisting in imaging with one tracer prior to injecting the second tracer, might be valuable. The goals of this prospective, methods comparison, exploratory study were to establish the order of tracer injection and timing for imaging. Six research horses were imaged under general anesthesia with 18F‐NaF PET, 18F‐FDG PET, dual 18F‐NaF/18F‐FDG PET, and CT. Proper uptake could be identified in tendon lesions as early as 10 min after 18F‐FDG injection. Bone uptake was limited when 18F‐NaF was injected under general anesthesia, even at 1 h after injection, when compared with 18F‐NaF injection prior to anesthesia. The sensitivity and specificity of the dual tracer scans were 0.77 (0.63 to 0.86) and 0.98 (0.96 to 0.99) respectively, to assess 18F‐NaF uptake and 0.5 (0.28 to 0.72) and 0.98 (0.95 to 0.99), respectively, for 18F‐FDG uptake. These results suggest that the sequential dual tracer approach is a pertinent technique to optimize the PET data gained from a single anesthetic episode. Based on dynamics of tracer uptake, the optimal protocol consists in injecting 18F‐NaF prior to anesthesia, acquire 18F‐NaF data then inject 18F‐FDG and start acquisition of dual tracer PET data 10 min later. This protocol should be further validated in a larger clinical study. [ABSTRACT FROM AUTHOR]

Lesions of the deep digital flexor tendon (DDFT) are a cause for foot lameness in horses. Positron emission tomography (PET) could provide valuable information regarding the metabolic activity of these lesions. The aims of this exploratory, prospective, methods comparison study were to assess the ability of 18fluorine‐fluorodeoxyglucose (18F‐FDG) PET to detect DDFT lesions and to compare the PET findings with CT and MRI findings. Eight horses with lameness due to pain localized to the front feet were included. Both front limbs of all horses were imaged with 18F‐FDG PET, noncontrast CT, and arterial contrast‐enhanced CT; 11 limbs were also assessed using MRI. Two observers graded independently 18F‐FDG PET, noncontrast CT, arterial contrast CT, T1‐weighted (T1‐w) MRI, and T2‐weighted (T2‐w)/STIR MRI. Maximal standardized uptake values were measured. Lesions were found in seven of 16 DDFT on PET, 12 of 16 DDFT on noncontrast CT, six of 15 DDFT on arterial contrast CT, eight of 11 DDFT on T1‐w MRI, and six of 11 DDFT on T2‐w/STIR MRI. Positron emission tomography was in better agreement with arterial contrast CT (Kappa‐weighted 0.40) and T2‐w/STIR MRI (0.35) than with noncontrast CT (0.28) and T1‐w MRI (0.20). Maximal standardized uptake values of lesions ranged from 1.9 to 4.6 with a median of 3.1. Chronic lesions with scar tissues identified on noncontrast CT or T1‐w MRI did not have increased 18F‐FDG uptake. These results demonstrated that 18F‐FDG PET agreed more closely with modalities previously used to detect active tendon lesions, i.e. arterial contrast CT and T2‐w/STIR MRI. 18Fluorine‐fluorodeoxyglucose PET can be used to identify metabolically active DDFT lesions in horses. [ABSTRACT FROM AUTHOR]

Background: Increased 18F‐Sodium Fluoride (18F‐NaF) uptake at the chondrosesamoidean ligament (ChSL) attachment on the distal phalanx was identified in an exploratory positron emission tomography (PET) study. The prevalence and significance of this lesion has not been previously investigated. Objectives: The goal of this study was to assess the prevalence of this lesion, its association with other imaging findings and with clinical signs. Study design: Retrospective cross‐sectional analytical study. Methods: All horses with 18F‐NaF PET and computed tomography (CT) imaging of the feet performed between October 2016 and December 2017 were included in the study. All PET scans were independently assessed by two radiologists for increased uptake at the ChSL attachment site and concurrent imaging was reviewed. Clinical findings, treatment and outcome were retrieved from the medical records. Results: Fourteen of 30 horses (20/56 feet) had increased 18F‐NaF uptake in the region of interest. ChSL enthesopathy was the primary lesion in three horses. Other PET abnormalities included navicular bone uptake (13 feet) and ipsilateral palmar process uptake (9 feet). There was no significant association between ChSL enthesopathy and other lesions. ChSL enthesopathy was significantly associated with foot lameness. CT abnormalities at the ChSL attachment were initially identified in one foot, and retrospectively noted in another five following the results of PET imaging. Main limitations: The study is retrospective and there was a limited sample size. Conclusions: PET led to identification of ChSL enthesopathy in a large proportion of horses with foot pain. This finding is most commonly associated with other lesions but may also represent the main abnormality. The axial border of the palmar processes of the distal phalanx should be carefully assessed on cross sectional imaging to identify this lesion. ChSL enthesopathy may be an important but previously not recognised component of foot pathology in horses. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Veterinary Journal / Revue Vétérinaire Canadienne is the property of Canadian Veterinary Medical Association and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)