Effect of video angle on detection of induced front limb lameness in horses.

BACKGROUND: Lameness examinations are commonly performed in equine medicine. Advancements in digital technology have increased the use of video recordings for lameness assessment, however, standardization of ideal video angle is not available yielding videos of poor diagnostic quality. The objective of this study was to evaluate the effect of video angle on the subjective assessment of front limb lameness. A randomized, blinded, crossover study was performed. Six horses with and without mechanically induced forelimb solar pain were recorded using 9 video angles including horses trotting directly away and towards the video camera, horses trotting away and towards a video camera placed to the left and right side of midline, and horses trotting in a circle with the video camera placed on the inside and outside of the circle. Videos were randomized and assessed by three expert equine veterinarians using a 0-5 point scoring system. Objective lameness parameters were collected using a body-mounted inertial sensor system (Lameness Locator®, Equinosis LLC). Interobserver agreement for subjective lameness scores and ease of grading scores were determined. RESULTS: Induction of lameness was successful in all horses. There was excellent agreement between objective lameness parameters and subjective lameness scores (AUC of the ROC = 0.87). For horses in the "lame" trials, interobserver agreement was moderate for video angle 2 when degree of lameness was considered and perfect for video angle 2 and 9 when lameness was considered as a binary outcome. All other angles had no to fair agreement. For horses in the "sound" trials, interobserver agreement was perfect for video angle 5. All other video angles had slight to moderate agreement. CONCLUSIONS: When video assessment of forelimb lameness is required, a video of the horse trotting directly towards the video camera at a minimum is recommended. Other video angles may provide supportive information regarding lameness characteristics.

Dorsal-to-palmar branch neuroanastomosis in horses undergoing palmar digital neurectomy does not reduce neuroma formation or improve outcome.

OBJECTIVE: Chronic foot pain, a common cause of forelimb lameness, can be treated by palmar digital neurectomy (PDN). Complications include neuroma formation and lameness recurrence. In humans, neuroanastomoses are performed to prevent neuroma formation. The aim of the study was to evaluate the outcome of horses undergoing dorsal-to-palmar branch neuroanastomosis following PDN. STUDY DESIGN: Retrospective case series. ANIMALS: Eighty-five horses with PDN and dorsal-to-palmar branch neuroanastomosis. METHODS: Medical records for horses undergoing this procedure at two hospitals between 2015 and 2020 were reviewed. Palmar and dorsal nerve branches of the PDN were transected and end-to-end neuroanastomosis was performed by apposition of the perineurium. Follow-up was obtained from medical records and telephone interviews. Success was defined as resolution of lameness for at least one year. RESULTS: Lameness resolved following surgery in 81/85 (95%) horses with 57/84 (68%) sound at one year. Postoperative complications occurred in 19/85 (22%) cases. The main limitations of the study were an incomplete data set, inaccurate owner recall, and variations in procedure. CONCLUSION: Compared to previous studies, this technique resulted in similar numbers of horses sound immediately after surgery, a comparable rate of postoperative neuroma formation but a higher recurrence of lameness rate at 1 year postoperatively. CLINICAL SIGNIFICANCE: End-to-end neuroanastomosis of the dorsal and palmar branches of the PDN does not reduce the rate of neuroma formation in horses. Long-term outcome was less favorable compared to previously reported PDN techniques.

Interobserver agreement of lateral and oblique radiography and standing cone beam CT of the caudal cervical articular process joints of horses.

Caudal cervical articular process joint osteoarthritis (CAPJ OA) leads to career-altering clinical signs in the horse. Oblique radiographs and standing cone beam computed tomography (CBCT) facilitate the assessment of this area, however, the variability of interpretation of these images is currently unknown. This retrospective, secondary analysis, methods comparison study investigated interobserver agreement between clinicians and modality in grades of CAPJ OA on lateral and oblique radiographs and CBCT. We hypothesized that agreement between clinicians' grades of CAPJ OA would be lowest for oblique radiographs and highest for CBCT, and agreement between grades of CAPJ OA would be low for all pairs of modalities. Horses underwent lateral and oblique radiography and CBCT of the CAPJs of C5-C6 and C6-C7. Radiographs and CBCT images were graded retrospectively by four blinded clinicians using 3-point scales. Cohen's kappa analysis was used to evaluate interobserver agreement between grades of CAPJ OA, and agreement between grades of CAPJ OA between different modalities was explored using kappa-weighted analysis. Agreement between clinicians' grades of CAPJ OA was moderate for lateral radiographs (0.49), and fair for oblique radiographs (0.23) and CBCT (0.36). For all modalities, agreement was slight to fair between clinicians for CAPJs with grade 1 (normal, 0.21-0.32) or 2 (mild, 0.13-0.36) CAPJ OA, and moderate to substantial for grade 3 (moderate to severe, 0.45-0.77) CAPJ OA. Agreement between grades of CAPJ OA was fair for all pairs of modalities. This study provides important information regarding the inconsistency of interpretation of mild CAPJ OA on radiographs and CBCT amongst clinicians.

Equine Autologous Conditioned Serum and Autologous Protein Solution.

Orthobiologics are used with increasing frequency in equine musculoskeletal disease to improve the quality of the repair tissue and prevent reinjury. Autologous blood-based products, or hemoderivatives, are made by processing the patient's blood using different systems to produce a final therapeutic product. Autologous conditioned serum (ACS) and autologous protein solution (APS) are commonly used to treat joint disorders and can also be used treat tendon and ligament injuries. Hemoderivatives contain increased concentrations of anti-inflammatory and immunomodulatory cytokines, and growth factors that help direct tissue healing and repair. The specifics of ACS and APS for treatment of musculoskeletal injuries are discussed.

Computed tomographic assessment of fracture characteristics and subchondral bone injury in Thoroughbred racehorses with lateral condylar fractures and their relationship to outcome.

OBJECTIVE: To investigate the effects of fracture characteristics and concurrent subchondral bone pathology identified with computed tomography (CT) on the racing performance of Thoroughbred racehorses with fractures of the MC3/MT3 lateral condyle. STUDY DESIGN: Retrospective cohort study. SAMPLE POPULATION: Thoroughbred racehorses (n = 50) with a fracture of the MC3/MT3 lateral condyle, which had preoperative CT and internal fixation performed. METHODS: Medical records were reviewed for age, sex, limb, and surgical treatment. Computed tomography scans were evaluated to determine fracture characteristics including length, whether the fracture was incomplete or complete, and displacement. The presence of subchondral bone injury (SBI), sesamoid bone fracture, articular comminution, and fragmentation in the joint was noted. Racing data was obtained from an online database. Univariable and multivariable analyses determined associations between independent variables and outcomes. RESULTS: Thirty-three (66%) horses raced after surgery. Horses with sesamoid bone fractures (P = .021), MC3/MT3 comminution (P = .016) and intra-articular fragmentation (P = .015) were less likely to race postoperatively. Concurrent SBI did not affect outcome. In the final multivariable model, sex (P = .015) and whether a fracture was incomplete or complete (P = .007) were the most significant predictors of racing postoperatively with females and horses with complete fractures being less likely to race. CONCLUSION: The prognosis for racing after a lateral condylar fracture is favorable but is decreased in horses with complete fractures and certain concurrent joint pathology. CLINICAL SIGNIFICANCE: Horses presenting with lateral condylar fractures commonly have concurrent joint pathology. Computed tomography can aid in preoperative evaluation and prognostication by enabling more complete fracture assessment.

Treatment and outcome of eight horses with limb cellulitis and septic tendonitis or desmitis.

OBJECTIVE: To report the clinical features, treatment, and outcome in horses with cellulitis and concurrent septic tendonitis and/or desmitis. STUDY DESIGN: Short case series. METHODS: Medical records from 2000 to 2019 were reviewed, identifying horses with cellulitis and concurrent septic tendonitis and/or desmitis based on sonographic examination and positive bacterial culture. Signalment, ultrasonographic results, bacterial culture, treatment, duration of hospitalization, and complications were recorded. Long-term outcome data were obtained from follow-up examinations and/or telephone interviews. Successful outcome was defined as return to intended use. RESULTS: Eight horses met the inclusion criteria. All infections occurred in hindlimbs, with septic suspensory ligament in six of eight horses, and septic superficial digital flexor tendon in one of eight horses. Surgical debridement was performed in six of eight horses. All horses were treated with systemic and regional intravenous antimicrobials and were discharged from the hospital. Long-term follow-up was available in seven of eight horses. Of these, four horses returned to their intended athletic function, two horses returned to their intended function as a broodmare or pasture pet, and one horse is still rehabilitating. CONCLUSION: Septic tendonitis or desmitis is a rare but possible sequela of limb cellulitis. Based on the findings in this study, prognosis for return to athletic function is fair to good for horses diagnosed with cellulitis and concurrent septic tendonitis or desmitis.

Influence of osteochondrosis on the longevity and racing performance of standardbred trotters and pacers.

OBJECTIVE: To determine the influence of clinical osteochondrosis (OC) on the short-term (2, 3, and 4-year-old) and long-term racing performance and longevity of standardbred racehorses. STUDY DESIGN: Retrospective case-control study. SAMPLE POPULATION: Standardbred racehorses from a single breeding farm born between 2009 and 2017 that survived to racing age (n = 2711). Three hundred eighty-two (14%) horses were OC-affected (829 lesions confirmed arthroscopically during surgical treatment), and 2329 (86%) horses were nonaffected. METHODS: Racing performance data were obtained from an online database and evaluated with multiple linear regression models. RESULTS: Trotters were more likely than pacers to be affected by OC (odds ratio [OR] = 1.4, 95% CI = 1.1-1.9, P = .006). Compared with nonaffected horses, long-term OC-affected horses had 8.8 fewer starts (95% CI = -14.4 to -3.2, P = .002), 1.0 fewer wins (95% CI = -1.9 to -0.1, P = .030), and 3.8 fewer total number of first through third place finishes (95% CI = -6.2 to -1.4, P < .0001). Nonaffected horses had longer careers compared with OC-affected horses, racing 0.32 years longer (95% CI = -0.52 to -0.12, P = .002). Osteochondrosis had no impact on short-term racing performance. Horses with lesions at the distal intermediate ridge of the tibia or lateral trochlear ridge of the talus had decreased performance compared with horses without these lesions. CONCLUSION: Pacers were less likely than trotters to be affected by OC. Affected horses had fewer starts and shorter careers, despite early surgical intervention. CLINICAL SIGNIFICANCE: Osteochondrosis decreases long-term racing performance in racing standardbreds.

Progression of aural plaques to squamous cell carcinoma in a horse.

BACKGROUND: Aural plaques are associated with and thought to be caused by one or more Equus caballus papillomaviruses (EcPV). Aural plaques have not previously been reported to be associated with squamous cell carcinoma (SCC). HYPOTHESIS/OBJECTIVES: To describe a horse with aural plaques and squamous cell carcinoma (SCC) on the right pinna. ANIMALS: A 28-year-old thoroughbred gelding presented for multiple plaques and a mass on the right pinna. METHODS AND MATERIALS: Pinnal resection, histopathological investigation, multiple conventional PCRs for papillomavirus DNA and Sanger sequencing were performed. RESULTS: Multiple, raised, pale tan, fronded plaques covered 60% of the concave surface of the right pinna. Focally these plaques coalesced into an exophytic ulcerated mass near the base of the pinna. Multiple aural plaques and a SCC were diagnosed histopathologically. EcPV4 was detected via PCR in a sample of the SCC. CONCLUSIONS AND CLINICAL IMPORTANCE: This report demonstrates the possibility of malignant transformation from aural plaques to SCC on the pinna of a horse. To the best of the authors' knowledge, this is the first report of EcPV4 associated with SCC.

Transendoscopic correction of epiglottic entrapment with a silicone-covered laser guide and diode laser in 29 horses.

OBJECTIVE: To describe the use of a silicone-covered laser guide and diode laser for surgical correction of epiglottic entrapment and report postoperative outcomes in horses with epiglottic entrapment. STUDY DESIGN: Retrospective case series. ANIMALS: Thoroughbred and standardbred racehorses (n = 29) with epiglottic entrapment. METHODS: A silicone-covered laser guide was placed endoscopically to direct the diode laser cutting action during transection of the entrapping subepiglottic membrane and to act as a physical barrier between the membrane and the epiglottic cartilage. Postoperative complications and trainer satisfaction were recorded via use of a follow-up questionnaire. Race records were reviewed to determine return to racing and detect differences in the number of starts, wins, or earnings before and after surgery. RESULTS: The entrapping membrane was successfully released in all horses. Mild postoperative complications such as swelling of the surgical site (12 horses) and coughing or mild nasal discharge (5 horses) were recorded during the first few days after surgery. Ninety-six percent of trainers were satisfied with the outcome of the procedure; 93% of horses returned to racing. CONCLUSION: Laser guide-assisted transection of the subepiglottic membrane corrected epiglottic entrapment in standing horses. CLINICAL SIGNIFICANCE: Ease of surgical technique, mild postoperative complications, and a good prognosis to return to racing make this a suitable alternative to the traditional laser procedure.

Long-term outcome and effect of diagnostic analgesia in horses undergoing interspinous ligament desmotomy for overriding dorsal spinous processes.

OBJECTIVE: To report the long-term outcome of horses treated with interspinous ligament desmotomy (ISLD) for pain associated with overriding dorsal spinous processes (ORDSP) and determine the influence of preoperative diagnostic analgesia on long-term outcome. STUDY DESIGN: Retrospective study. ANIMALS: Eighteen horses. METHODS: Data were collected from horses presenting for ISLD to the University of Pennsylvania New Bolton Center between January 2013 and May 2018. Follow-up of ≥3 months postsurgically was obtained from the owner, trainer, or referring veterinarian. Long-term improvement was compared between horses that improved with diagnostic analgesia presurgically and horses that did not undergo diagnostic analgesia presurgically by using a χ2 test. Univariate logistic regression was used to test associations between long-term improvement and independent variables. RESULTS: Clinical signs had improved in 13 of 18 horses at long-term follow-up (median, 14.5 months; range, 3-57). Clinical signs improved in nine of 10 horses responding to diagnostic analgesia but only in four of eight horses that did not undergo diagnostic analgesia (χ2 [1], N = 18) = 3.55; P = .06). Although the likelihood of long-term improvement increased with prior diagnostic analgesia (odds ratio = 6.3; 95% confidence interval = 0.73, 55.0; P = .09), it did not reach statistical significance. CONCLUSION: A higher proportion of horses experienced long-term improvement in clinical signs after ISLD when horses responding to preoperative diagnostic analgesia were compared with horses that were not tested. CLINICAL SIGNIFICANCE: This study provides some evidence to support the use of diagnostic analgesia in conjunction with clinical examination for identification of clinically relevant ORDSP.

The effect of hypoxia on chondrogenesis of equine synovial membrane-derived and bone marrow-derived mesenchymal stem cells.

BACKGROUND: Joint injury is extremely common in equine athletes and post-traumatic osteoarthritis (PTOA), a progressive and debilitating disease, is estimated to affect 60% of horses in the USA. The limited potential for intrinsic healing of articular cartilage has prompted intense efforts to identify a cell-based repair strategy to prevent progression of PTOA. Mesenchymal stem cells (MSCs) have the potential to become an ideal source for cell-based treatment of cartilage lesions; however, full chondrogenic differentiation remains elusive. Due to the relatively low oxygen tension in articular cartilage, hypoxia has been proposed as a method of increasing MSC chondrogenesis. The objective of this study was to investigate the effect of hypoxic culture conditions on chondrogenesis in equine synovial membrane-derived MSCs (SM-MSCs) and bone marrow-derived MSCs (BM-MSCs). MSCs were isolated from synovial membrane and bone marrow collected from 5 horses. Flow cytometric analysis was used to assess cell surface marker expression including CD29, CD44, CD90, CD105, CD45, CD-79α, MHCI and MHCII. MSC pellets were cultured in normoxic (21% O2) or in hypoxic (5% O2) culture conditions for 28 days. Following the culture period, chondrogenesis was assessed by histology, biochemical analyses and gene expression of chondrogenic-related genes including ACAN, COL2b, SOX9, and COL10A1. RESULTS: Both cell types expressed markers consistent with stemness including CD29, CD44, CD90, CD105, and MHCI and were negative for exclusion markers (CD45, CD79α, and MHCII). Although the majority of outcome variables of chondrogenic differentiation were not significantly different between cell types or culture conditions, COL10A1 expression, a marker of chondrocyte hypertrophy, was lowest in hypoxic SM-MSCs and was significantly lower in hypoxic SM-MSCs compared to hypoxic BM-MSCs. CONCLUSIONS: Hypoxic culture conditions do not appear to increase chondrogenesis of equine SM-MSCs or BM-MSCs; however, hypoxia may downregulate the hypertrophic marker COL10A1 in SM-MSCs.

Arthrodesis of the metacarpophalangeal and metatarsophalangeal joints to treat osteoarthritis in 17 horses.

OBJECTIVE: To describe arthrodesis of the metacarpophalangeal (MCP) or metatarsophalangeal (MTP) joint with a locking compression plate (LCP) and a metallic tension band and report the outcome of horses treated for osteoarthritis (OA) with this technique. STUDY DESIGN: Retrospective case series. ANIMALS: Seventeen horses with OA of the MCP or MTP joint treated with arthrodesis. METHODS: Medical records (2004-2017) of horses treated for OA with arthrodesis of the MCP or MTP joint with an LCP and metallic tension band were reviewed. Preoperative variables included age, sex, breed, affected limb, and lameness grade. Surgical variables included implants used, surgery time, postoperative angle of joint, intraoperative complications, and anesthetic recovery method. Outcome was obtained from medical records and phone interviews. RESULTS: Lameness was scored as 4 out of 5 (range, 2-4) in 13 of 17 horses. All horses survived to discharge and were alive >6 months postoperatively, without any report of long-term complications. All horses were allowed unrestricted turnout, and 1 horse was lightly ridden. No postoperative infections or implant failures were reported. The only complications consisted of cast sores (n = 4). CONCLUSION: Arthrodesis of the MCP/MTP joint was associated with acceptable morbidity and good long-term outcomes in these 17 horses with OA refractory to medical management. CLINICAL SIGNIFICANCE: The morbidity and prognosis after fetlock arthrodesis for OA seem more favorable than reported in horses treated with traumatic disruption of the suspensory apparatus.

Return to racing after surgical management of third carpal bone slab fractures in thoroughbred and standardbred racehorses.

OBJECTIVE: To determine the prognosis for racing of horses surgically treated for slab fractures of the third carpal bone (C3). STUDY DESIGN: Retrospective case study. ANIMALS: Horses (n = 125) surgically treated for C3 slab fractures. METHODS: Medical records of horses surgically treated for dorsal or sagittal C3 fractures were reviewed for age, sex, breed, limb, fracture type, degree of cartilage damage, and surgical treatment. Radiographs were evaluated to determine fracture depth, width, and displacement. Osteophytes, C3 lysis, and fragmentation were scored. Racing performance was obtained from online databases. Univariable and multivariable analyses were used to determine associations between independent variables and outcomes. RESULTS: Fifty-four (43%) horses raced postoperatively. Among thoroughbreds, 35% (30/86) with dorsal fractures and 63% (17/27) with sagittal fractures raced postoperatively. Among standardbreds, 77% (10/13) with dorsal fractures and 0% (0/2) with sagittal fractures raced postoperatively. Fracture displacement, C3 lysis, and cartilage damage affected the likelihood of racing postoperatively. Placement of 3.5-mm screws vs 4.5-mm screws and the placement of fewer screws were associated with improved likelihood of racing. CONCLUSION: The prognosis for postoperative racing of thoroughbreds with dorsal C3 fractures was less favorable than that previously reported. Concurrent joint pathology, such as cartilage damage at time of surgery, affected the ability of the horse to race postoperatively. CLINICAL SIGNIFICANCE: Although internal fixation of C3 slab fractures is required to restore joint congruity, return to racing should be expected in only 42% of thoroughbreds and 67% of standardbreds.

Regenerative Medicine and Rehabilitation for Tendinous and Ligamentous Injuries in Sport Horses.

Tendon and ligament injuries are a common source of lameness in the athletic horse. Although tendons and ligaments have the ability to spontaneously heal, lesions tend to fill with biomechanically inferior fibrous tissue such that the horse is prone to reinjury. Regenerative medicine is used to improve quality of repair tissue and prevent reinjury. Platelet-rich plasma, stem cells, and autologous conditioned serum are the most commonly used orthobiologics in the horse. A tailored rehabilitation program is key to returning horses to athleticism following injury. The specifics of regenerative medicine and rehabilitation for tendonitis and desmitis in the horse are discussed.

Surgical Management of Osteochondrosis in Foals.

Osteochondrosis is common in young, athletic horses. Some lesions respond to conservative therapy. Surgical management is the mainstay of treatment. Arthroscopic debridement is useful in the femoropatellar joint, tarsocrural joint, fetlock joint, and shoulder joint. Debridement is associated with good outcomes, except in the shoulder joint. Osteochondrosis lesions in the elbow may be difficult to access arthroscopically, thereby transosseous debridement. Surgical management of subchondral cystic lesions of the medial femoral condyle consists of debridement, debridement with grafting, transcondylar screws, and intralesional corticosteroid injection. Surgical management is indicated with lameness and persistent effusion, and in many horses intended for athletic use.

Implantation of rAAV5-IGF-I transduced autologous chondrocytes improves cartilage repair in full-thickness defects in the equine model.

Cartilage injury often precipitates osteoarthritis which has driven research to bolster repair in cartilage impact damage. Autologous chondrocytes transduced with rAAV5-IGF-I were evaluated in chondral defects in a well-established large animal model. Cartilage was harvested from the talus of 24 horses; chondrocytes were isolated and stored frozen. Twenty million cells were cultured and transduced with 10(5) AAV vg/cell prior to implantation. Chondrocytes from eight horses were transduced with rAAV5-IGF-I, chondrocytes from eight horses with rAAV5-GFP, and chondrocytes from eight horses were not transduced. A 15 mm full-thickness chondral defect was created arthroscopically in the lateral trochlear ridge of the femur in both femoropatellar joints. Treated defects were filled with naive or gene-enhanced chondrocytes, in fibrin vehicle. Control defects in the opposite limb received fibrin alone. rAAV5-IGF-I transduced chondrocytes resulted in significantly better healing at 8 week arthroscopy and 8 month necropsy examination when compared to controls. At 8 months, defects implanted with cells expressing IGF-I had better histological scores compared to control defects and defects repaired with naive chondrocytes. This included increased chondrocyte predominance and collagen type II, both features of hyaline-like repair tissue. The equine model closely approximates human cartilage healing, indicating AAV-mediated genetic modification of chondrocytes may be clinically beneficial to humans.

Laparoscopic-guided compared to skilled instructor support for student rectal examination training using live horses in the veterinary curriculum.

OBJECTIVES: To evaluate the veterinary student learning outcome of 2 methods of equine rectal examination training. STUDY DESIGN: Randomized prospective study. SAMPLE POPULATION: Veterinary students (3rd and 4th year; n = 40) and practicing equine veterinarians (n = 10). METHODS: Year 1: Group 1 (n = 11) and Group 2 students (n = 10) received skilled instructor (SI) and laparoscopic-guidance (LG), respectively, during rectal exam instruction. All students were tested on rectal identification of 4 abdominal organs. Year 2: One group of students (n = 19) was trained and subsequently tested using each technique, first SI, followed by LG. Subjective evaluation of laparoscopy as a teaching tool was achieved with veterinary students and equine practitioners. RESULTS: A significantly greater percentage of students having LG compared to SI were able to correctly identify the left kidney (Year 1) and the spleen, cecum, and right ovary (Year 2). A significantly greater proportion of LG trained students in years 1 and 2 (100% and 95%, respectively) were also able to identify 75% of organs compared with SI (27% and 21%, respectively). Both students and veterinarians uniformly provided favorable feedback for LG in teaching rectal palpation skills. CONCLUSION: The LG method of equine rectal examination instruction resulted in improved learning for identification of several key abdominal organs compared with SI.

Surgical treatment of 4 horses for cryptorchidism caused by failure of regression of the cranial suspensory ligament of the testis.

OBJECTIVE: To report surgical management of 4 horses with cryptorchidism caused by failure of regression of the cranial suspensory ligament (CSL). STUDY DESIGN: Retrospective case series. ANIMALS: Cryptorchid horses (n = 4). METHODS: Horses with unilateral or bilateral cryptorchidism caused by failure of regression of the CSL were treated by removing the retained testes through a standing laparoscopic approach (2), flank laparotomy (1), or paramedian celiotomy (1). After identification of the retained testis attached to the caudal pole of the kidney by the CSL, the vascular pedicle and ductus deferens were ligated and removed. RESULTS: Two horses had bilateral cryptorchidism and 2 horses had unilateral cryptorchidism. Standing laparoscopic cryptorchidectomy was performed successfully in 2 horses and in 2, the retained testes were removed using a flank or paramedian celiotomy. All testes were located in the dorsal aspect of the abdomen just caudal to the kidney and had a well-developed CSL. All horses recovered successfully from surgery. CONCLUSIONS: Failure of regression of the CSL is an uncommon cause of cryptorchidism in horses; however, affected horses can be treated using surgical approaches that facilitate exploration of the dorsocaudal aspect of the abdomen.

Use of quantitative mass spectrometry-based proteomics and ELISA to compare the alpha 2 macroglobulin concentration in equine blood-based products processed by three different orthobiologic devices.

Introduction: Alpha 2 macroglobulin (A2M), a multi-functional protein in the plasma protease inhibitor class, regulates proinflammatory cytokines and the clearance of chondrodestructive enzymes in cases of joint injury and osteoarthritis (OA). The purpose of this study was to compare A2M concentrations in equine plasma samples processed by three commercial devices developed for stall-side regenerative joint therapy. Methods: Plasma samples were obtained from healthy adult horses (N = 13). Mass spectrometry analysis was used to determine the concentration of protein analytes in each sample. Selected reaction monitoring measured a specific A2M peptide as a surrogate of the whole A2M protein. A2M concentrations produced by each test device were compared for two sample types: a pre-concentrate or platelet-poor (PP) component and a final component for use in the horse. Results: There was no significant difference (p > 0.05) in the geometric mean (GM) concentration of A2M in the final concentration samples produced by the Alpha2EQ® device (N horses = 13) and the single-centrifugation PP samples produced by the Pro-Stride® APS (autologous protein solution) device (N = 13) and the Restigen® PRP (platelet-rich plasma) device (N = 11). When A2M content in final concentration samples produced by each device was compared, the Pro-Stride APS and Restigen PRP samples had significantly greater GM A2M content (p < 0.0001) compared to the Alpha2EQ samples, and the Pro-Stride APS final concentration samples had significantly greater GM A2M concentration (p < 0.0001) versus that for the Restigen PRP final samples. Discussion: This comparison demonstrated that the volume and A2M concentration of an Alpha2EQ final concentrate are no different than the volume and concentration of A2M in the PP from Pro-Stride or Restigen devices.

Prospective, longitudinal assessment of subchondral bone morphology and pathology using standing, cone-beam computed tomography in fetlock joints of 2-year-old Thoroughbred racehorses in their first year of training.

BACKGROUND: Catastrophic injuries of the fetlock joints occur in Thoroughbred racehorses and are preceded by stress-induced bone injury. Early detection of subchondral bone injury is essential to prevent irreversible damage or bone failure. OBJECTIVES: To investigate the use of standing, robotic cone-beam computed tomography (CBCT) for assessing longitudinal changes in subchondral bone morphology and pathology of the fetlock joints associated with race training in young Thoroughbreds. STUDY DESIGN: Observational cohort study. METHODS: Forty-one 2-year-old Thoroughbred racehorses were recruited prior to the start of race training. Standing CBCT and radiographs of all 4 metacarpo-/metatarsophalangeal (MCP/MTP) joints were obtained at 0, 6 and 12 months. Hyperdensity, as an estimate of subchondral bone sclerosis, was measured in the distal third metacarpal (MC3)/metatarsal (MT3) bone and proximal phalanx (P1) at each time point on computed tomography. CBCTs were examined for subchondral bone pathology consisting of areas of hypodensity within regions of hyperdensity. RESULTS: Subchondral bone sclerosis increased significantly over time in the medial and lateral MC3/MT3 condyles and in the medial and lateral parasagittal grooves of MC3/MT3. The presence of subchondral bone pathology increased significantly over time in the medial and lateral palmar condyles of MC3/MT3, the lateral parasagittal groove, the medial dorsal condyle and the medial and lateral ridges of P1. MAIN LIMITATIONS: There was attrition of horses due to relocation, change in ownership, and retirement from racing. Husbandry, training regimens and racing schedules were not controlled for in the study. CONCLUSIONS: Standing CBCT is an efficient and effective screening tool for assessing subchondral bone morphology and identifying pathology of the fetlock joint in young Thoroughbred racehorses. CBCT may facilitate early detection of bone pathology allowing for timely intervention and prevention of more serious injuries.