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Background: Few studies have described incidences of proximal limb and pelvic fracture (PLPF) in Thoroughbred racehorses occurring on race day and during training. Information regarding clinical presentations and future racing careers in cases of PLPF is limited., Objectives: To describe the incidence, clinical presentation and outcome of PLPF sustained by horses in racing and training at the Hong Kong Jockey Club (HKJC) between 2003 and 2014., Study Design: Retrospective cohort study., Methods: Horses with PLPF confirmed by nuclear scintigraphy, ultrasonography, radiography or post-mortem examination were identified using veterinary clinical records. Training and racing data for case horses were described. Incidences of fractures were estimated per 1000 horses in training and per 1000 race starts for fractures sustained during racing. Descriptive statistics were used to describe the study population., Results: A total of 129 instances of PLPF were sustained by 108 racehorses. The most commonly fractured bone was the humerus (49.6%), followed by the tibia (29.4%). Nine horses sustained fatal fractures, eight of which occurred during racing. The incidence of fracture during racing was 0.30 per 1000 starts. Two-thirds of fractures occurred during training. The majority of horses presented with grade 3 lameness (n = 42 of 119 injury events, 35.3%). All horses presenting with grade 5 lameness sustained fatal injuries. Following noncatastrophic injury, all horses underwent box rest and 81 horses subsequently resumed racing; 45 of these won a race. Horses were retired at a median of 25 months (interquartile range: 15-36 months) after injury., Main Limitations: Protocols for resting non-training racehorses at the HKJC and for recording rehabilitation regimens post-injury prevented the calculation of horse days at risk., Conclusions: The incidence of PLPF at the HKJC is low. Non-fatal PLPF is not necessarily a career-ending injury and many horses resume racing successfully following conservative treatment., (© 2017 EVJ Ltd.)

Background: Thirty years have elapsed since the last published review of outcome following fracture of the proximal phalanx in Thoroughbred racehorses in the UK and contemporary results are needed to be able to advise of expected outcome., Objectives: Collect and analyse outcome data following repair of fractures of the proximal phalanx in Thoroughbred racehorses in the UK., Study Design: Retrospective case series., Methods: Case records of all Thoroughbred racehorses admitted to Newmarket Equine Hospital for evaluation of a parasagittal fracture of the proximal phalanx during a 5 years period were reviewed. Follow-up data regarding racing careers was collected for horses that underwent repair. Following exclusion of outliers, cases with incomplete data sets and comminuted fractures, mixed effect logistic regression was used to identify variables affecting returning to racing and odds ratios and confidence intervals calculated., Results: Of 113 repaired cases, fracture configurations included short incomplete parasagittal (n = 12), long incomplete parasagittal (n = 86), complete parasagittal (n = 12) and comminuted (n = 3). A total of 54 (48%) cases raced after surgery. Horses that fractured at 2 years of age had increased odds of racing following surgery than those older than 2 years of age (OR 1.34; 95% CI 1.13-1.59, P = 0.002). Horses sustaining short incomplete parasagittal fractures had increased odds of racing following surgery compared with those with complete parasagittal fractures (OR 2.62; 95% CI 1.36-5.07, P = 0.006). No horses with comminuted fractures returned to racing., Main Limitations: Data are relevant only to Thoroughbred racehorses in the UK., Conclusions: Approximately half of the cases in this series raced following surgical repair. More 2-year-old horses raced following surgery, but this likely reflects horses, specifically older horses, passing out of training from unrelated factors. Fracture configuration affects odds of racing, which is relevant to owners when deciding on treatment., (© 2017 EVJ Ltd.)

Palmar/plantar annular desmitis is a common disease that may be associated with adhesions and structures affecting the flexor tendons, which requires tenoscopy to diagnose. The purpose of this descriptive study was to develop a dynamic sonographic technique for evaluating the motion of normal equine flexor tendons in relation to the palmar/plantar annular ligament and to compare findings with horses previously diagnosed with palmar/plantar annular desmitis. Ten healthy adult horses were examined prospectively and the images of four horses diagnosed with palmar/plantar annular desmitis were retrospectively evaluated. Dynamic sonography was performed at the level of the metacarpo/metatarsophalangeal joint by maximally extending and flexing the interphalangeal joints. Palmar/plantar annular ligament thickness (mm), size of any gap between the flexor tendons, and subjectively increased angulation of the long linear echoes of the superficial digital flexor tendon were measured. The presence of gliding motion between the palmar/plantar annular ligament and superficial digital flexor tendon was determined by consensus. Twenty-eight healthy control limbs (16 hind/12 fore) and four with palmar/plantar annular desmitis (3 hind/1 fore) were evaluated. Controls had unrestricted gliding motion between the palmar/plantar annular ligament and flexor tendons and zero to 13° of angulation of the long linear echoes. The four affected horses had restricted gliding motion and between 20-35° angulation of the long linear echoes. Dynamic ultrasound is a feasible technique for detecting restricted flexor tendon and palmar/plantar annular ligament gliding motion, as well as subjectively increased angulation of the long linear echoes of the flexor tendon in affected horses compared with controls and warrants further investigation., (© 2016 American College of Veterinary Radiology.)

Reasons for Performing Study: Knowledge of the site distribution of ligamentous injuries facilitates clinical diagnosis of suspensory apparatus conditions., Objectives: To determine if lesions within the suspensory ligament (SL) and distal ligaments of the proximal sesamoid bones (DSLs) were associated with suspensory apparatus failure or metacarpal lateral condylar fracture in California Thoroughbred racehorses., Study Design: Cross-sectional study., Methods: Suspensory apparatus specimens from 327 deceased Thoroughbred racehorses were sectioned within the SL body and branches, and oblique and straight DSLs. Purple lesions ≥2 mm in width were categorised as moderate and paler or smaller lesions as mild. Associations between moderate lesions and age, sex, racetrack and cause of death were evaluated using multivariable logistic regression., Results: Moderate lesions were evident in 16% and milder lesions in 77% of racehorses. Moderate lesions occurred with similar frequency in SL branches and oblique DSLs. Moderate lesions were more likely to occur in horses that died as a result of suspensory apparatus failure (odds ratio [OR] = 4.60; 95% confidence interval [CI] 1.61-13.13; and P = 0.004) or metacarpal lateral condylar fracture (OR = 5.05; 95% CI 1.42-17.93; and P = 0.012) compared with horses that died from nonmusculoskeletal causes, and in horses aged ≥7 years horses compared with 2-year-old horses (OR = 5.33; 95% CI 1.44-19.75; and P = 0.012)., Conclusions: Moderate lesions are common in the SL branches and oblique DSLs of racehorses, and may be associated with risk for suspensory apparatus failure and metacarpal condylar fracture. Monitoring health of the suspensory apparatus ligamentous structures may be a simple means of assessing fatigue in, and preventing more extensive injuries to, the forelimb suspensory apparatus and metacarpal condyles., (© 2014 EVJ Ltd.)

Objective: To compare bony changes in the metacarpophalangeal joint (MCPJ) of racehorses with (cases) and without (controls) biaxial proximal sesamoid bone (PSB) fracture as determined by 2 grading scales applied to images of cadaveric forelimbs obtained by means of standing MRI (sMRI)., Design: Case-control study., Sample: Forelimbs from 74 Thoroughbred racehorses (21 cases and 53 controls) that were euthanized at a Florida racetrack., Procedures: Both forelimbs were harvested from cases and controls. Each forelimb underwent sMRI to obtain images of the MCPJ. Two grading scales were described and used for image evaluation; one assessed the density of the PSBs, and the other assessed the integrity of the subchondral bone (SCB) plate at the distopalmar aspect of the third metacarpal bone (MC3). Logistic regression was used to compare the grades between case and control limbs., Results: Biaxial PSB fracture was associated with a total PSB grade (sum of lateral and medial PSB grades) ≥ 5 for the fractured limb, total MC3 SCB grade (sum of lateral and medial MC3 SCB grades) ≥ 5 for the contralateral limb, and the presence of orthopedic disease in the contralateral MC3., Conclusions and Clinical Relevance: For cases with biaxial PSB fracture, the density of the PSBs in the affected limb was greater and the MC3 of the contralateral limb was more likely to have orthopedic disease, compared with those for controls. Further evaluation of sMRI as a screening tool for identification of racehorses at risk of biaxial PSB fracture is warranted.

The aim of this study was to determine whether horses with a proximal palmar/plantar first phalangeal osteochondral fragment (POF) had comparable racing careers (prior to and following surgery) to horses without this fracture. A retrospective cohort study included 174 Swedish Standardbred trotters with osteochondral fragmentation in the palmar/plantar fetlock joint and 613 radiographically negative control horses presented for prepurchase examinations. Medical records and radiographs were examined for each horse. Racing data were retrieved from online Swedish Standardbred harness racing records. The effect of having a POF on race speed compared to radiographically negative control horses was examined using generalised estimating equations. Multivariable regression was used to examine differences in money earned and career longevity. The horses raced a total of 16,448 races. Horses gained speed as a function of race number. There was no difference in racing speed between horses with POF fractures that raced before surgery and control horses. Horses did not slow before, nor speed up after, surgery. There was no difference in the number of days between the last race prior to, or the first race after, the hospital visit between POF and control horses. Career earnings and lifetime starts were not significantly different between groups. The results of this study suggest the need to reevaluate the previously reported benefits of surgical intervention for POF., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Objective: To determine intralimb orientation changes with an inertial measurement unit (IMU) in hooves of horses at a walk and trot after induction of weight-bearing single forelimb lameness and to determine whether hoof orientations are similar to baseline values following perineural anesthesia., Animals: 6 clinically normal horses., Procedures: 3-D hoof orientations were determined with an IMU mounted on the right forelimb hoof during baseline conditions, during 3 grades of lameness (induced by application of pressure to the sole), and after perineural anesthesia. Linear acceleration profiles were used to segment the stride into hoof breakover, stance, initial swing, terminal swing, and total swing phases. Intralimb data comparisons were made for each stride segment. A repeated-measures mixed-model ANOVA was used for data analysis., Results: Lameness resulted in significant changes in hoof orientation in all planes of rotation. A significant increase in external rotation and abduction and a significant decrease in sagittal plane rotation of the hoof were detected at hoof breakover during lameness conditions. For sagittal plane orientation data, the SDs determined following perineural anesthesia were higher than the SDs for baseline and lameness conditions., Conclusions and Clinical Relevance: Results of this study indicated the IMU could be used to detect 3-D hoof orientation changes following induction of mild lameness at a walk and trot. An increase in data variability for a sagittal orientation may be useful for assessment of local anesthesia for hooves. The IMU should be further evaluated for use in clinical evaluation of forelimb lameness in horses.

Reasons for Performing Study: Sesamoiditis is believed to be associated with injury to the suspensory branch attachment and is a common radiographic finding in yearling Thoroughbreds. No study has investigated relationships between yearling sesamoiditis and subsequent development of suspensory ligament branch injury (SLBI) in early racehorse training., Objectives: To establish the prevalence of SLBI within a population of juvenile training racehorses and retrospectively investigate relationships between clinical signs of SLBI and sesamoiditis to determine if sesamoiditis is a risk factor for clinical suspensory branch injury., Study Design: Retrospective case control study., Methods: Presale radiographs of 291 clinically normal yearling Thoroughbreds were reviewed for sesamoiditis and graded using 3 objective scales. Medical records encompassing the first year of race training were reviewed to identify cases of SLBI and the remaining unaffected controls from the cohort. Statistical analysis determined the relationship between sesamoiditis and the development of SLBI during training., Results: The prevalence of SLBI was 9.97%. Case and control horses demonstrated a similar prevalence of sesamoiditis overall but SLBI cases demonstrated increased severity of sesamoiditis on yearling radiographs compared with unaffected controls. This significant relationship between sesamoiditis and cases of SLBI was only observed using one of the 3 scales. Using that scale, sesamoids exhibiting more pronounced sesamoiditis on yearling radiographs were 5 times more likely to develop SLBI in the adjacent suspensory branch (OR 4.56, 95% CI 2.18-9.53, P = 0.0001)., Conclusions: This study reveals that the grading scale used is important when providing prognostic advice on the significance of radiographic signs of sesamoiditis. Evidence of significant sesamoiditis implies a 5 times greater risk of developing clinical SLBI with the onset of training. Clinicians should be aware that sesamoiditis may be an indicator of future SLBI in yearlings which are clinically normal at the time of sale., (© 2013 EVJ Ltd.)

Reasons for Performing Study: Fractures of the proximal phalanx are generally considered to result from monotonic supraphysiological loads, but radiological observations from clinical cases suggest there may be a stress-related aetiology., Objectives: To determine whether there are radiologically identifiable prodromal changes in Thoroughbred racehorses with confirmed parasagittal fractures of the proximal phalanx., Study Design: Retrospective cross-sectional study., Methods: Case records and radiographs of Thoroughbred racehorses with parasagittal fractures of the proximal phalanx were analysed. Thickness of the subchondral bone plate was measured in fractured and contralateral limbs, and additional radiological features consistent with prodromal fracture pathology documented., Results: The subchondral bone plate was significantly thicker in affected than in contralateral limbs. Evidence of additional prodromal fracture pathology was observed in 15/110 (14%) limbs with parasagittal fractures, and in 4% of contralateral limbs., Conclusions: The results of this study are not consistent with monotonic loading as a cause of fracture in at least a proportion of cases, but suggest a stress-related aetiology. Increased thickness of the subchondral bone plate may reflect (failed) adaptive changes that precede fracture., Potential Relevance: Better understanding of the aetiology of fractures of the proximal phalanx may help develop strategies to reduce the risk of fracture., (© 2013 EVJ Ltd.)

Reasons for Performing Study: Although fractures of the proximal phalanx are one of the most common long bone fractures of Thoroughbred horses in training, limited details on variations in morphology and radiological progression have been published., Objectives: To describe in detail the configuration of parasagittal fractures of the proximal phalanx in a group of Thoroughbred racehorses, to report fracture distribution within this group of horses and to document radiological progression of fracture healing in cases treated by internal fixation., Study Design: Restrospective case series., Methods: Case records and radiographs of Thoroughbred racehorses with parasagittal fractures of the proximal phalanx admitted to Newmarket Equine Hospital between 2007 and 2011 were analysed., Results: One hundred and twenty-one fractures were identified in 120 Thoroughbred racehorses. Fractures were frequently more complex than was appreciated immediately following injury; a feature that has not been reported previously. There was seasonality of fractures in 2- and 3-year-old horses, but not in older horses., Conclusions and Potential Relevance: Fractures of the proximal phalanx may be more complex than recognised previously, although often their complexity cannot be identified radiographically immediately following injury. The seasonality observed in 2- and 3-year-old horses is most likely to be a consequence of the timing of the turf-racing season in the UK. The Summary is available in Chinese - see Supporting information., (© 2013 EVJ Ltd.)

Objective: To compare the effect of extracorporeal shock wave therapy (ESWT) on expression of fibroblast growth factor-7 (FGF-7), transforming growth factor-β1 (TGF-β1), insulin-like growth factor-1 (IGF-1), platelet-derived growth factor-A (PDGF), and vascular endothelial growth factor-A (VEGF) in skin with surgically created skin wounds and intact skin in horses., Animals: 14 healthy horses., Procedure: 8 horses were treated with ESWT at 6 locations along the neck at 36, 24, 12, 6, 2, or 1 hour prior to collection of full-thickness biopsy specimens from each location; a control specimen was collected from a sham-treated location. In 6 horses, 5 full-thickness wounds were created in each forelimb. Wounds in 1 forelimb/horse received ESWT immediately after creation and subsequently on days 7, 14, and 21; wounds in the contralateral forelimb remained untreated. Biopsy specimens were collected from 1 wound on each forelimb on days 7, 14, 21, 28, and 35. Expression levels of FGF-7, TGF-β1, IGF-1, PDGF, and VEGF were assessed in tissue samples from the horses' necks and forelimbs., Results: In surgically created wounds, ESWT treatment was associated with reduced TGF-β1 expression, compared with expression in control wounds, during the entire study period. At 28 days following wound creation, IGF-1 expression was significantly increased for treated and untreated wounds, compared with findings on days 7, 14, 21, and 35. There was no significant effect of treatment on FGF-7, TGF-β1, IGF-1, PDGF, or VEGF expression in intact skin., Conclusions and Clinical Relevance: Intervention with ESWT to suppress TGF-β1 may decrease granulation tissue production, resulting in improved wound healing on the distal portion of horses' limbs.

Two hundred and thirty-two horses with lameness localized to the metacarpo(tarso)phalangeal (MCP/MTP) region without a radiographic diagnosis were evaluated. All horses had high-field magnetic resonance (MR) imaging of the MCP/MTP region performed for the lame limb and the contralateral limb for comparison. There were 46 horses that had bilateral abnormalities in the forelimbs; 27 of these horses were not lame in the contralateral limb at the time of examination. Bilateral hind limb abnormalities were observed in 37 horses; 22 horses were not lame in the contralateral limb. Soft tissue abnormalities alone were observed in 218 limbs (162 horses). Subchondral bone and articular cartilage abnormalities alone were observed in 43 limbs (34 horses). A combination of soft tissue, subchondral bone, and cartilage abnormalities were observed in 64 limbs (36 horses). The distribution of primary abnormalities was as follows; oblique distal sesamoidean ligament desmitis (73 limbs in 56 horses), straight distal sesamoidean ligament desmitis (44 limbs in 38 horses), chronic subchondral bone injuries (15 limbs in 12 horses), suspensory ligament branch desmitis (14 limbs in 12 horses), collateral ligament desmitis (12 limbs in 12 horses), tendonitis of the superficial and deep digital flexor tendons (10 limbs in 10 horses), osteochondral defects greater than 1 cm (nine limbs in six horses), osteochondral defects less than 1 cm (eight limbs in seven horses), bone marrow lesions (six limbs in five horses), intersesamoidean ligament desmitis (five limbs in four horses). MR imaging is useful in diagnosing bone and soft tissue injuries when radiographs and ultrasound fail to yield a diagnosis., (© 2012 Veterinary Radiology & Ultrasound.)

This study evaluated the therapeutic effects of a gelatin-β-TCP sponge (sponge) incorporating BMP-2 (BMP-2/sponge) on bone regeneration in equines. Six bone defects were created in third metacarpals of five thoroughbred horses, and a total of six treatments were applied in a randomized manner. The treatments were BMP-2/sponge, BMP-2/gelatin hydrogel sheet (sheet), free BMP-2, bFGF/sheet, plain sponge, and plain sheet. The defects were monitored for 16 weeks by radiography and then examined by histological analysis. Radiographic evaluation scores of bone regeneration revealed significantly greater bone regeneration of defects treated with BMP-2/sponge than defects treated with plain sponge or BMP-2 sheet (P<0.05). In histological analysis, compact bone was observed over a wide area in the BMP-2/sponge treatment. We concluded that the treatment with BMP-2/sponge accelerated bone regeneration in the equines of this study., (Published by Elsevier India Pvt Ltd.)

Objective: To examine the effect of endotoxins on metabolism and histopathologic changes of isolated perfused equine forelimbs., Sample: Forelimbs (comprising the metacarpus and digit) were collected from cadavers of 12 healthy adult horses after slaughter at an abattoir (14 limbs; 1 forelimb of 10 horses and both forelimbs of 2 horses)., Procedures: Forelimbs were perfused for 10 hours with autologous blood, with and without the addition of endotoxin (80 ng of lipopolysaccharide [LPS]/L). Two limbs of the endotoxin exposure group and 2 nonperfused limbs were loaded to failure of the suspensory apparatus of the pedal bone to evaluate the effect of body weight. Metabolic and histologic variables were evaluated., Results: Blood pressure increased during the first hour and did not differ between groups. Lactate dehydrogenase activity was similar in both groups and increased significantly during the 10-hour period; glucose consumption at 5 hours and lactate concentration at 8 hours were significantly higher in limbs exposed to endotoxin. The width of secondary epidermal lamellae was greater in LPS limbs. In the primary dermal lamellae of LPS limbs, there were significantly more vessels with an open lumen and aggregates of intravascular neutrophils., Conclusions and Clinical Relevance: In the blood-perfused isolated forelimbs of equine cadavers, exposure to LPS led to significant changes in the laminar tissue as well as to metabolic changes. Therefore, endotoxin should be considered as a causative factor for laminitis and not merely as a risk factor.

This article describes the ultrasonographic (US) appearance of bony abnormalities on the dorsal aspect of the third metacarpal/metatarsal bone of the equine fetlock in cadavers with radiographic signs of osteoarthrosis. After US, computed tomography was undertaken to better characterise the lesions. Twelve fetlock joints were collected and all had more than one bone abnormality on US. Normal subchondral bone appeared on US as a well-defined and regular hyperechoic line with distal acoustic shadowing. Bone abnormalities detected on US included (1) gaps in the proximal subchondral bone filled with material of heterogeneous echogenicity, (2) bone fragments represented as small straight smoothly delineated hyperechoic lines with distal shadowing located superficial to the surface of the adjacent bone, (3) proximal new bone formation visible as mild to severe cortical protrusions, (4) marginal osteophytoses seen as an elevation of the hyperechoic surface of the subchondral bone at the edges of the joint surfaces, (5) indentations in subchondral bone seen as a concave deviation of the hyperechoic line without interruption, (6) focal or diffuse irregularities of the subchondral bone seen as disruptions of the normal smooth bony contours, and (7) focal hyperechoic spikes originating from the subchondral plate and invading the articular cartilage. These findings are discussed., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Reasons for Performing Study: To enhance understanding of the nature and pathogenesis of scapular fractures in racehorses., Hypothesis: Scapular fractures in racehorses have a consistent configuration related to sites of pre-existing stress modelling and remodelling., Methods: Fractured and intact scapulae collected post mortem were examined visually and with computed tomography (CT). Scapular fracture configuration, bone modelling changes and standardised CT morphometry and density measurements were recorded. Statistical comparisons were made between fractured, nonfractured contralateral and control scapulae., Results: Thirty-nine scapulae from 10 Thoroughbred (TB) and 10 Quarter Horse (QH) racehorses were obtained. All 14 fractured scapulae (from 12 horses) had a consistent comminuted fracture configuration. A complete fracture coursed transversely through the neck of the scapula at the level of the distal aspect of the spine (8.9 ± 0.9 cm proximal to the lateral articular margin of the glenoid cavity). The distal fragment of 13 fractured scapulae was split into 2 major fragments by a fracture in the frontal plane that entered the glenoid cavity (2.8 ± 0.4 cm caudal to the cranial articular margin). Focal areas of periosteal proliferation and/or radiolucency were present in the distal aspect of the scapular spine of all fractured and intact contralateral scapulae, but less commonly (P<0.01) in intact scapula from horses without a scapular fracture. Fractured scapulae had 7-10% lower mean density and 46-104% greater density heterogeneity in the spine adjacent to the transverse fracture compared to control scapulae (P<0.03)., Conclusions and Clinical Relevance: Thoroughbred and QH racehorses have a characteristic scapular fracture configuration that is associated with pre-existing pathology of the distal aspect of the spine. This location is consistent with scapular stress fractures diagnosed in lame TB racehorses. Catastrophic fracture is the acute manifestation of a more chronic process. Consequently, there are opportunities for early detection and prevention of fatalities., (© 2010 EVJ Ltd.)

Objective: To evaluate the diagnostic features, results of free-choice exercise treatment, prognosis, and postinjury racing performance of Thoroughbred racehorses with cumulative stress-induced bone injury (CSBI) of the distal portion of the third metacarpal and third metatarsal bones (MC3/MT3)., Design: Retrospective case series., Animals: 55 Thoroughbred racehorses with CSBI of the distal portion of MC3/MT3., Procedures: Data on signalment, history, and radiographic, scintigraphic, and lameness examination findings were reviewed. Horses with lameness localized to the distal portion of MC3/MT3, and that did not have concurrent lameness but did have radiographic and nuclear scintigraphic changes consistent with CSBI, were included in the study. Information on pre-and postinjury racing performance was acquired from race records., Results: Mean age was 3.2 years (median, 3 years [range, 2 to 6 years]). Ninety-five percent (52/55) of horses with CSBI raced after injury. Males were more commonly affected (75% [41/55]) than were females (25% [14/55]; odds ratio, 3.99 [95% confidence interval, 2.17 to 7.34]). There was no significant difference in postinjury total earnings, compared with total earnings before injury; horses had significantly more starts and less earnings per start after injury. Median time to first start after injury was 194 days. Of 45 horses that raced before and after injury, 31 % (14/45) had an increase in racing class, 31 % (14/45) had no change in class, and 38% (17/45) had a decrease in class., Conclusions and Clinical Relevance: Thoroughbred racehorses with CSBI of the distal portion of MC3/MT3 treated with free-choice exercise had a favorable prognosis with no appreciable decrease in class or performance.

Six cadaver forelimbs were imaged in two high-field magnetic resonance (MR) systems and one low-field MR system following the creation of osteochondral defects on the palmar distal aspect of the third metacarpal bone. The following sequences were performed using all three systems: proton density (PD) turbo spin echo, T2* gradient echo (GRE), T2-weighted fast spin echo, and short tau inversion recovery. In addition, 3D T1 GRE sagittal standard and motion insensitive sequences were obtained using the low-field system. PD fat saturated and 3D T1-weighted spoiled GRE images with and without fat suppression were acquired with the high-field systems. Lesions were measured and assigned a confidence score. The images obtained using high-field systems (1.0 and 1.5 T) more accurately represented the osteochondral defects when compared with low-field system (0.27 T) images. The largest difference was observed when evaluating articular cartilage defects, which were not identified on the low-field images. Sequence selection affected the appearance of the lesions. On all systems the turbo and fast spin echo sequences more accurately represented the lesion size and shape when compared with the GRE sequences. The T1 GRE sequence is the only sequence that appears to allow visualization of the articular cartilage on the low-field images, but is limited in providing adequate cartilage visualization. Confidence scores were greater on the high-field systems when compared with the low-field system., (© 2010 Veterinary Radiology & Ultrasound.)

This prospective study describes a series of 18 olecranon fractures in 16 horses that were treated with locking compression plates (LCP). Twelve of the 18 fractures were simple (type 2), whereas six were comminuted (type 4). Six fractures were open and 12 were closed. Each horse underwent LCP osteosynthesis consisting of open reduction and application of one or two LCP. Complete fracture healing was achieved in 13 horses. Three horses had to be euthanatized: two because of severe infection and one because of a comminuted radial fracture 11 days after fixation of the olecranon fracture. Complications encountered after discharge of the horses from the Equine Hospital at the Vetsuisse Faculty (University of Zurich) included implant infection (n=2) and lameness (n=3), which were successfully treated with implant removal. Despite being easier to use, LCP osteosynthesis resulted in a clinical outcome similar to DCP osteosynthesis.

Tendon injury is one of the most common causes of wastage in the performance horse; the majority of tendon injuries occur to the superficial digital flexor tendon (SDFT) whereas few occur to the common digital extensor tendon. This review outlines the epidemiology and aetiology of equine tendon injury, reviews the different functions of the tendons in the equine forelimb and suggests possible reasons for the high rate of failure of the SDFT. An understanding of the mechanisms leading to matrix degeneration and subsequent tendon gross failure is the key to developing appropriate treatment and preventative measures.

Neurectomy of the deep branch of the right lateral plantar nerve was performed on a single healthy mature horse. Six weeks after surgery, the horse was subjected to euthanasia and both hind suspensory ligaments harvested. The cross sectional area of the muscular part of the proximal part of the suspensory ligament was measured and assessed for morphological abnormalities in a blinded fashion. There was a clear difference in cross sectional area of the muscular part between treated and control ligament and there was profound neurogenic atrophy of the muscular fibres in the treated ligament.

Reason for Performing Study: The injury-prone, energy-storing equine superficial digital flexor tendon (SDFT) of the mature performance horse has a limited ability to respond to exercise in contrast with the noninjury-prone, anatomically opposing common digital extensor tendon (CDET). Previous studies have indicated low levels of cellular activity in the mature SDFT, but in foal tendons the tenocytes may still have the ability to adapt positively to increased exercise., Objectives: To measure tenocyte densities and types in histological sections from the SDFT and CDET of horses from controlled long-term, short-term and foal exercise studies., Methods: Specimens were collected from mid-metacarpal segments of the CDET and SDFT for each horse and processed for histology; central and peripheral regions of the SDFT cross-section were analysed separately (SDFTc, SDFTp). Tenocyte nuclei were counted in a total area of 1.59 mm(2) for each tendon region in each horse. Each nucleus was classified as type 1 (elongate and thin), type 2 (ovoid and plump) or type 3 (chondrocyte-like); type 1 cells are proposed to be less synthetically active than type 2 cells., Results: No significant differences were noted between exercise and control groups in any of the studies, with the exception of an exercise-related reduction in the proportion of type 1 tenocytes for all tendons combined in the long-term study. There were tendon- and site-specific differences in tenocyte densities and proportions of type 1 and 2 cells in all 3 studies., Conclusions and Potential Relevance: There was no indication that exercise increased tenocyte density or proportions of the (theoretically) more active type 2 cells in immature horses (short-term and foal studies), perhaps because the training regimens did not achieve certain threshold strain levels. In the foal study these findings can still be interpreted positively as evidence that the training regimen did not induce subclinical damage.

Biomechanical models that compute the lengths and forces of muscle-tendon units are broadly applicable to the study of factors that promote injury and the planning and effects of orthopedic surgical procedures in equine athletes. A three-dimensional (3D) generic musculoskeletal model of the equine forelimb comprised of bony segment, muscle-tendon, and ligament information, was developed based on high-resolution computed tomographic (CT) and T1-weighted magnetic resonance (MR) images from an isolated forelimb of a Thoroughbred racehorse. Image fusion was achieved through coregistration of CT and MR images with an image analysis program (Analyze) by adjustment of the relative position and orientation of fiducial markers visible in both modalities until the mutual information between the images was maximized. 3D surfaces of the bones and origin/insertion sites, centroid paths and volumes of the muscle-tendon and ligamentous structures were obtained from the multimodal (CT/MR) images using semiautomated and manual segmentation combined with sagittal and transverse color-cryosection anatomic images obtained from three other cadaveric equine forelimbs. Once bony and soft-tissue structures were reconstructed in the same coordinate system, data were imported to a software package for interactive musculoskeletal modeling (SIMM). The combination of integrated CT and MR acquisitions and anatomical images provided an accurate and efficient means of generating a 3D model of the musculoskeletal structures of an average-sized equine adult horse.

We describe the clinical, imaging, and necropsy findings of two horses with severe injury of the collateral ligaments of the distal interphalangeal (DIP) joint diagnosed using magnetic resonance (MR) imaging. In MR images it was possible to examine the collateral ligaments of the DIP joint from the origin at the middle phalanx to the insertion on the distal phalanx. Both horses in this report had abnormal high signal intensity within the collateral ligaments of the DIP joint, and one horse had abnormal high signal intensity within the bone of the distal phalanx on short tau inversion recovery (STIR) and T2-weighted imaging sequences. High signal intensity on STIR and T2-weighted images represents abnormal fluid accumulation indicative of inflammation, within ligament, tendon, or bone on these imaging sequences. Abnormalities were confirmed on necropsy in both horses. Injury of the collateral ligaments of the DIP joint should be considered as a source of pain in horses with lameness localized to the foot.

Magnetic resonance imaging (MRI) was tested for evaluation of the soft tissue structures of the equine digit in 16 limbs, derived from three adult warmblood horses and two newborn warmblood foals. The following measuring sequences were used in sagittal, transversal and coronal planes: spin echo, gradient echo, inversion recovery. The images were made with a 1.5 Tesla Siemens scanner in a CP-Helmholtz circular coil. To compare the visualization of the same tissue structures in adult and in newborn cases the limbs were imaged with the routinely used MRI sequences that are used for mature tissues. In newborn foals the bursa podotrochlearis could not be determined with the used sequences. For both the adult and newborn limbs the most visualization of the same tissue structures including the fluid spaces and growth plates were taken by the inversion recovery sequence. T2 sequence was very informative in adult cases but moderately in newborn foals.

Injury of the distal aspect of the deep digital flexor tendon (DDFT) is a recognized cause of lameness, but diagnosis is difficult. This study aimed to improve understanding of DDFT morphology and pathology using retrospective evaluation of magnetic resonance (MR) images. We hypothesized that: (1) The distal aspect of the DDFT in normal horses would have a repeatable proximal/distal pattern and symmetry between limbs and between lobes; (2) DDFT dimensions would be related to bodyweight, navicular bone dimensions and hoof size; (3) this symmetry and pattern would be lost in DDFT injury; and (4) DDFT size would increase with injury. MR images of 64 live horse limbs, 26 with no identified DDFT lesion and 38 with identified DDFT abnormalities, and 19 normal cadaver limbs were analyzed. Using standardized transverse images, measurements of DDFT cross-sectional area, medial-lateral (ML) width and dorsal-palmar depth were obtained at six preselected sites. A uniform distal to proximal shape pattern was identified in all horses. The flattened crescent shape at the insertion changed to a deeper bilobed shape more proximally, with the mid-navicular area having the greatest cross-sectional area. Strong ML (P < 0.0006) and left/right symmetry (P < 0.02) were observed. In addition, there was a strong association between DDFT cross-sectional area and horse weight (P = 0.005) and between DDFT and navicular bone ML width (P = 0.004). Symmetry between sides or between lobes was lost at sites with a unilateral lesion and correlation between horse weight and DDFT cross-sectional area was lost in the presence of lesions. DDFTs with core lesions had a consistent increase in cross-sectional area overall, but other lesion types had no significant increase in size. The shape and symmetry seen in normal tendons could be related to the mechanical demands placed upon individual lobes. The limited increase in cross-sectional area with injury may be explained by the restrictive structures of the hoof, possibly explaining the ongoing pain seen in such lesions.

The study hypothesis was that navicular disease is a process analogous to degenerative joint disease, which leads to changes in navicular fibrocartilage and in deep digital flexor tendon (DDFT) matrix composition and that the process extends to the adjacent distal interphalangeal joint. The objectives were to compare the biochemical composition of the navicular articular and palmar cartilages from 18 horses with navicular disease with 49 horses with no history of front limb lameness, and to compare navicular fibrocartilage with medial meniscus of the stifle and collateral cartilage of the hoof. Cartilage oligomeric matrix protein (COMP), deoxyribonucleic acid (DNA), total glycosaminoglycan (GAG), metalloproteinases MMP-2 and MMP-9 and water content in tissues were measured. Hyaline cartilage had the highest content of COMP and COMP content in hyaline cartilage and tendon was higher in lame horses than in sound horses (p<0.05). The concentration of MMP-2 amount in hyaline cartilage was higher in lame horses than in sound horses. The MMP-2 amounts were significantly higher in tendons compared to other tissue types. Overall, 79% of the lame horses with lesions had MMP-9 in their tendons and the amount was higher than in sound horses (p<0.05). In horses with navicular disease there were matrix changes in navicular hyaline and fibrocartilage as well as the DDFT with potential implications for the pathogenesis and management of the condition.

Objective: To determine significant molecular and cellular factors responsible for differences in second-intention healing in thoracic and metacarpal wounds of horses., Animals: 6 adult mixed-breed horses., Procedure: A full-thickness skin wound on the metacarpus and another such wound on the pectoral region were created, photographed, and measured, and tissue was harvested from these sites weekly for 4 weeks. Gene expression of type-I collagen, transforming growth factor (TGF)-beta1, matrix metalloproteinase (MMP)-1, and tissue inhibitor of metalloproteinase (TIMP)-1 were determined by quantitative in situ hybridization. Myofibroblasts were detected by immunohistochemical labeling with alpha-smooth muscle actin (alpha-SMA). Collagen accumulation was detected by use of picrosirius red staining. Tissue morphology was examined by use of H&E staining., Results: Unlike thoracic wounds, forelimb wounds enlarged during the first 2 weeks. Myofibroblasts, detected by week 1, remained abundant with superior organization in thoracic wounds. Type-I collagen mRNA accumulated progressively in both wounds. More type-I collagen and TGF-beta1 mRNA were seen in forelimb wounds. Volume of MMP-1 mRNA decreased from day 0 in both wounds. By week 3, TIMP-1 mRNA concentration was greater in thoracic wounds., Conclusions and Clinical Relevance: Greater collagen synthesis in metacarpal than thoracic wounds was documented by increased concentrations of myofibroblasts, type-I collagen mRNA,TGF-beta1 mRNA, and decreased collagen degradation (ie, MMP-1). Imbalanced collagen synthesis and degradation likely correlate with development of exuberant granulation tissue, delaying healing in wounds of the distal portions of the limbs. Factors that inhibit collagen synthesis or stimulate collagenase may provide treatment options for horses with exuberant granulation tissue.

The suspensory apparatus of one forelimb was surgically disrupted in six adult horses by transecting the distal sesamoidean ligaments. A double-braided prosthetic ligament made of aramid yarn was installed to support the flexor surface of the metacarpophalangeal joint. The prosthesis was routed through tunnels in the third metacarpal bone and proximal phalanx, and secured to bone with screws. Evaluation by radiography, synovial fluid analysis, cinematography, and dynamography was performed before surgery and at weeks 16 and 30. Supracondylar cortical lysis and periosteal proliferation were observed on postoperative radiographs. Synovitis and fragmentation of the prosthesis were apparent from synovial fluid evaluation. Weight bearing and metacarpophalangeal joint motion were decreased and loading was transferred in part to the opposite forelimb. Clinical lameness improved and weight bearing increased during the second half of the 30-week period. At necropsy, there was abrasion of the prosthesis and the articular surfaces in contact with the prosthesis. Diffuse granulomatous synovitis developed in response to aramid fiber fragments within the synovium.