Diagnostic imaging findings in lame Warmblood horses with bone injuries of the medial proximal phalanx glenoid cavity.

This retrospective study aims to describe baseline and follow-up imaging findings in subchondral and trabecular bone damage occurring outside of the sagittal groove in the proximal phalanx (P1) glenoid in a case series of lame Warmblood horses. Thirteen lame horses (16 forelimbs) with standing magnetic resonance imaging (sMRI) evidence of nonsagittal groove glenoid subchondral and trabecular bone injury of P1 as the main lesion were included. All injuries were located at the medial aspect of the P1 glenoid. At sMRI, changes included subchondral bone plate thickening and trabecular sclerosis, bone marrow edema-like signal, subchondral bone resorption (11/16), and new bone production (8/16). Subchondral bone resorption in the transverse plane was linear (8/11), round (2/11), or ill-defined (1/11). Sclerosis, bone resorption, and new bone production were seen radiographically in 10, 4, and 5 limbs, respectively. All limbs had concurrent metacarpal condyle sMRI imaging abnormalities, osteophytosis, and joint effusion. Follow-up sMRIs were obtained in 8 of 16 limbs, five of which showing progression of the resorptive lesion. One horse encountered a comminuted fracture of the affected P1 18 months after the follow-up sMRI examination. The imaging appearance of the medial glenoid bone injuries of P1 in this case series is consistent with chronic bone overload. The linear configuration of bone resorption seen in eight lesions suggests short, incomplete stress fractures, which is supported by the ultimate catastrophic fracture occurring in one case.

Injury to the palmar supporting structures of the fetlock alters limb stiffness and fetlock angle.

BACKGROUND: In vivo measurement of limb stiffness and conformation provides a non-invasive proxy assessment of superficial digital flexor tendon (SDFT) and suspensory ligament (SL) function. Here, we compared it in fore and hindlimbs and after injury. OBJECTIVES: To compare the limb stiffness and conformation in forelimbs and hindlimbs, changes with age, and following injury to the SDFT and SL. STUDY DESIGN: Retrospective cohort study. METHODS: Limb stiffness was calculated using floor scales and an electrogoniometer taped to the dorsal fetlock. The fetlock angle and weight were simultaneously recorded five times with the limb weight-bearing and when the opposite limb was picked up (increased load). Limb stiffness of both limbs was calculated from the gradient of the regression line of angle versus load. Fetlock angle when the weight was zero was extrapolated from the graph and used as a measure of conformation. Limb stiffness was measured in uninjured forelimbs (n = 42 limbs), hindlimbs (n = 19 limbs), forelimbs with SDFT injury (n = 18) and hindlimbs with SL injury (n = 5). RESULTS: Limb stiffness correlated with weight in forelimbs as shown previously (p < 0.001) but also in hindlimbs (p = 0.006). When normalised to the horse's weight (503 kg, IQR 471.5-560), forelimb stiffness was significantly higher (22.3 [±4.5] × 10-3 degree-1) than for the hindlimb (16.4 [±4.0] × 10-3 degree-1; p < 0.001). While there were no significant differences between forelimb and hindlimb conformation in unaffected or SDFT injury, both limb stiffness and conformation was significantly greater in limbs with SL injury (p = 0.009 and p = 0.002, respectively). MAIN LIMITATIONS: Small sample size, lack of clinical data including lameness and quantification of injuries. CONCLUSIONS: Injury to the forelimb SDFT does not alter limb stiffness or conformation in the long-term, while hindlimb SL injury simultaneously increases limb stiffness and fetlock angle, suggesting an increase in SL length following injury.

Comparison of radiography and computed tomography for identification of third metacarpal structural change and associated assessment of condylar stress fracture risk in Thoroughbred racehorses.

BACKGROUND: Catastrophic injury has a low incidence but leads to the death of many Thoroughbred racehorses. OBJECTIVES: To determine sensitivity, specificity, and reliability for third metacarpal condylar stress fracture risk assessment from digital radiographs (DR) and standing computed tomography (sCT). STUDY DESIGN: Controlled ex vivo experiment. METHODS: A blinded set of metacarpophalangeal joint DR and sCT images were prepared from 31 Thoroughbreds. Four observers evaluated the condyles and parasagittal grooves (PSG) of the third metacarpal bone for the extent of dense bone and lucency/fissure and assigned a risk assessment grade for condylar stress fracture based on imaging features. Sensitivity and specificity for detection of subchondral structural changes in the condyles and PSG, and for risk assessment for condylar stress fracture were determined by comparison with a reference assessment based on sCT and joint surface examination. Agreement between observers and the reference assessment and reliability between observers were determined. Intra-observer repeatability was also assessed. RESULTS: Sensitivity for detection of structural change was lower than specificity for both imaging methods and all observers. For agreement with the reference assessment of structural change, correlation coefficients were generally below 0.5 for DR and 0.49-0.82 for sCT. For horses categorised as normal risk on reference assessment, observer assessment often agreed with the reference. Sensitivity for risk assessment was lower than specificity for all observers. For horses with a reference assessment of high risk of injury, observers generally underestimated risk. Diagnostic sensitivity of risk assessment was improved with sCT imaging, particularly for horses categorised as having elevated risk of injury from the reference assessment. Assessment repeatability and reliability was better with sCT than DR. MAIN LIMITATIONS: The ex vivo study design influenced DR image sets. CONCLUSIONS: Risk assessment through screening with diagnostic imaging is a promising approach to improve injury prevention in racing Thoroughbreds. Knowledge of sensitivity and specificity of fetlock lesion detection provides the critical guidance needed to improve racehorse screening programs. We found improved detection of MC3 subchondral structural change and risk assessment for condylar stress fracture with sCT ex vivo.

Cone beam computed tomography and cross-sectional anatomy of the region of the fetlock in the horse (Equus caballus).

This study aimed to delineate the detailed anatomy of the metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints in healthy horses using cone beam computed tomography (CBCT). The fetlock region of 15 cadaveric forelimbs and 14 cadaveric hindlimbs from nine adult horses without orthopaedic disease underwent CBCT scanning. Additionally, arthrography CBCT scans were conducted following intra-articular injection of a radiopaque contrast medium containing blue epoxy resin dye. Subsequently, limbs were frozen and sectioned to visualize anatomical structures in sectional planes corresponding to selected CBCT images. CBCT proved suitable for detailed visualization of the bony components of the fetlock region. Furthermore, the common digital extensor tendon, superficial and deep digital flexor tendons, suspensory ligament, and straight and oblique sesamoidean ligaments were identifiable on CBCT images. However, certain ligaments, such as the collateral sesamoidean ligaments and intersesamoidean ligaments, were not clearly identified. The hyaline cartilage of the MCP and MTP joint facets was assessable on the post-contrast sequence. In cases where a radiographic or ultrasound examination cannot provide a definitive diagnosis and determine the extent of disease, CBCT can provide additional valuable data on the equine MCP and MTP joint. The images obtained in this study can serve as a reference for CBCT examination of the equine MCP and MTP joint.

Lesion Distribution in the Metacarpophalangeal and Metatarsophalangeal Region of 341 Horses Using Standing Magnetic Resonance Imaging.

Pain localised to the metacarpophalangeal (MCP) and metatarsophalangeal (MTP) region represents a frequent cause of lameness in sport horses, and standing magnetic resonance imaging (MRI) of these regions is increasingly being acquired. This multicentre retrospective study describes the ranges of abnormalities identified on standing MRI of the MCP/MTP region and compares patterns of abnormalities between forelimbs, hindlimbs and different sports disciplines. In total, 341 MRI reports were reviewed. Subchondral bone plate irregularities, condylar and proximal phalanx pathologies were frequently identified with subchondral bone defect, sclerosis and increased intensity on STIR images often described. Medial pathology was frequently identified in the forelimbs, and more lateral pathology was reported in the hindlimbs, which could potentially reflect differences in the loading patterns. Significant differences in MRI findings were found between different sports activities, with MCP/MTP bone pathology occurring more frequently in MRI reports from race and endurance horses and MCP/MTP soft tissue injuries being reported more frequently in dressage and show-jumping horses, particularly in the suspensory apparatus, including the distal sesamoidean ligaments. The findings of this study identify patterns of MCP/MTP abnormalities detected using standing MRI, with differences seen between forelimbs and hindlimbs and between different sports disciplines.

Mineralization of equine proximal sesamoid bones precedes articular cartilage and fibrocartilaginous enthesis maturation in early postgestational development.

OBJECTIVE: To describe the development and maturation of equine proximal sesamoid bones (PSBs) in fetuses and young horses using radiography, microcomputed (micro)-CT, and histology. METHODS: A descriptive study. Forelimb PSBs from 12 equids ranging in age from 105 days of gestation to 540 days postgestation were evaluated. Radiography was used for preliminary assessment of metacarpophalangeal joint and PSB mineralization, and micro-CT imaging was performed to assess mineralized PSBs. Tissue volume, bone volume fraction, height, width, depth, trabecular thickness, and anisotropy were quantified from midplanar micro-CT sections in 3 dimensions. Midsagittal PSB histologic sections stained with H&E and Safranin O/Fast Green were used to determine the ratio of ossification center to cartilage template size and to describe the formation and development of the cartilage template, ossification center, spherical growth plate, articular cartilage, and entheses. RESULTS: Mineralization of equine PSBs is associated with cartilage canals and a spherical growth plate that undergoes endochondral ossification during the late gestation to early postgestational period. The apical, flexor, basilar, and articular ossification fronts demonstrate morphologic variability. Structural organization of the articular cartilage and entheses occurs concurrently with the development of an underlying plate of compact bone. At 540 days postgestation, the fibrocartilaginous entheses of the flexor cortex of the PSB had yet to mature. CONCLUSIONS: Equine PSBs mineralize predominantly by endochondral ossification during the late gestation to early postgestational period. Mineralization precedes maturation of the articular cartilage and fibrocartilaginous entheses. CLINICAL RELEVANCE: The postgestational maturation of the PSB and its surrounding tissues may predispose young horses to developing lesions at these sites, such as apical avulsion fractures, warranting further investigation.

Magnetic Resonance Imaging, Computed Tomographic and Radiographic Findings in the Metacarpophalangeal Joints of 31 Warmblood Showjumpers in Full Work and Competing Regularly.

There is a limited description of magnetic resonance imaging (MRI) and no information on computed tomographic (CT) findings in the fetlock of non-lame, non-racing sports horses. This study aimed to document comparative CT, MRI and radiographic findings in the metacarpophalangeal joints of showjumpers in full work. Clinical and gait assessments, low-field MRI, fan-beam CT and radiographic examinations of both metacarpophalangeal joints were performed on 31 showjumpers. Images were analysed descriptively. In most limbs (53/62, 85.5%), there were CT and MRI changes consistent with densification in the sagittal ridge and/or condyles of the third metacarpal bone (McIII). Hypoattenuation (subchondral bone resorption) was seen in CT reconstructions in the metacarpal condyle dorsoproximally (n = 2) and dorsodistally (n = 1), in the sagittal groove (n = 2) and medial fovea (n = 1) of the proximal phalanx. The McIII resorptive lesions were detected on MR images but not the proximal phalanx lesions. None were identified on radiographs. In conclusion, MRI and CT abnormalities previously associated with lameness were seen in the front fetlocks of showjumpers without relevant lameness. Densification in the sagittal ridge and the metacarpal condyles likely reflects an adaptive change to exercise. Subchondral bone resorption may indicate an early stage of disease; follow-up information is needed to establish its clinical significance.

Computed Tomographic Evaluation of the Sagittal Ridge of the Third Metacarpal Bone in Young Thoroughbred Racehorses: A Longitudinal Study.

Metacarpophalangeal joint region pain is a common cause of lameness in racehorses. Radiological abnormalities in the sagittal ridge (SR) of the third metacarpal bone have been associated with joint effusion, lameness and reduced sales prices. The aims were to describe computed tomographic (CT) appearance of the SR in racehorses, and to document the progression of these findings over three assessments. Forty yearlings were enrolled at the first examination (time 0). Re-examinations were performed twice, approximately six months apart on 31 (time 1) and 23 (time 2) horses, respectively. Computed tomographic examinations of both metacarpophalangeal regions were performed with the horses in a standing position. Computed tomographic reconstructions were analysed subjectively and objectively. The mean Hounsfield Unit values (Hus) of eight radial segments and location, size and shape of hypoattenuating lesions were recorded. Mean Hus at time 1 were higher than at time 0. There was no difference between mean HU at times 1 and 2. The mean HU values of the dorsal half were higher in the right forelimbs and in fillies. Hypoattenuation was identified in 33/80 (41.3%) limbs at time 0, in 22/62 (35.5%) limbs at time 1 and in 14/46 (30.4%) limbs at time 2. All hypoattenuations were located in the dorsodistal aspect of the SR. The most common shapes were hypoattenuating lesions elongated proximodistally and those extending towards trabecular bone. An increase in attenuation of the SR occurred in the first six months of training. Hypoattenuating lesions could decrease in size and could resolve during early training. In this population, these lesions were not associated with lameness.

Influence of microarchitecture on stressed volume and mechanical fatigue behaviour of equine subchondral bone.

Fractures of the equine metacarpophalangeal (MCP) joint are among the most common and fatal injuries experienced by racehorses. These bone injuries are a direct result of repetitive, high intensity loading of the skeleton during racing and training and there is consensus that they represent a mechanical fatigue phenomenon. Existing work has found the fatigue life of bone to be strongly determined by bone microarchitecture and the resulting stressed volume (i.e., the volume of bone stressed above assumed yield). The purpose of this study was to quantify the influence of bone microarchitecture on the mechanical fatigue behaviour of equine subchondral bone from the MCP joint across a wide variety of sample types. Forty-eight subchondral bone samples were prepared from the third metacarpal (MC3) and proximal phalanx (P1) of 8 horses and subsequently imaged using high resolution micro-computed tomography (µCT) to quantify microarchitectural features of interest, including bone volume fraction, tissue mineral density, pore size, pore spacing, and pore number. Samples were cyclically loaded in compression to a stress of 70 MPa, and fatigue life was defined as the number of cycles until failure. Finite element models were created from the µCT images and used to quantify stressed volume. Based on the expected log point-wise predictive density, stressed volume was a strong predictor of fatigue life in both the MC3 and P1. A regional analysis indicated fatigue life was more strongly associated with bone volume fraction in the superficial (r2 = 0.32, p < 0.001) and middle (r2 = 0.70, p < 0.001) regions of the subchondral bone, indicating the prominent role that the cortical plate played in the fatigue resistance of equine subchondral bone. By improving our understanding of the variance in fatigue life measurements, this research helps clarify the underlying mechanisms of the mechanical fatigue process and provides a basic understanding of subchondral bone injuries in the equine fetlock joint.

Comparison of cone-beam and fan-beam computed tomography and low-field magnetic resonance imaging for detection of proximal phalanx dorsoproximal osteochondral defects.

BACKGROUND: Dorsoproximal osteochondral defects commonly affect the proximal phalanx, but information about diagnosis on computed tomography (CT) and magnetic resonance imaging (MRI) is limited. OBJECTIVES: To assess CT and MRI diagnoses of osteochondral defects, describe the lesions and compare sensitivity and specificity of the modalities using macroscopic pathology as gold standard. STUDY DESIGN: Cross-sectional study. METHODS: Thirty-five equine cadaver limbs underwent standing cone-beam CT (CBCT), fan-beam CT (FBCT), low-field MRI and pathological examination. CT and MR images were examined for proximal phalanx dorsomedial and dorsolateral eminence osteochondral defects. Defect dimensions were measured. Imaging diagnoses and measurements were compared with macroscopic examination. RESULTS: Fifty-six defects were seen over 70 potential locations. On CBCT and FBCT, osteochondral defects appeared as subchondral irregularity/saucer-shaped defects. On MRI, osteochondral defects were a combination of articular cartilage defect on dorsal images and subchondral flattening/irregularity on sagittal images. Subchondral thickening and osseous short tau inversion recovery hyperintensity were found concurrent with osteochondral defects. Compared with pathological examination, the sensitivity and specificity of diagnosis were 86% (95% confidence interval [95% CI] 75%-93%) and 64% (95% CI 38%-85%) for FBCT; 64% (95% CI 51%-76%) and 71% (95% CI 46%-90%) for CBCT; and 52% (95% CI 39%-65%) and 71% (95% CI 46%-90%) for MRI. Sensitivity of all modalities increased with defect size. Macroscopic defect dimensions were strongly correlated with CBCT (r = 0.76, p < 0.001) and moderately correlated with FBCT and MRI (r = 0.65, p < 0.001). Macroscopic measurements were significantly greater than all imaging modality dimensions (p < 0.001), potentially because macroscopy included articular cartilage pathology. MAIN LIMITATIONS: Influence of motion artefact could not be assessed. CONCLUSIONS: Osteochondral defects could be visualised using both CT and MRI with sensitivity increasing with defect size. Diagnostic performance was best using FBCT, followed by CBCT then MRI, but CBCT-measured defect size best correlated with macroscopic examination. MRI provided useful information on fluid signal associated with defects, which could represent active pathology.

Magnetic Resonance Imaging, Computed Tomographic and Radiographic Findings in the Metacarpophalangeal Joints of 40 Non-Lame Thoroughbred Yearlings.

Most catastrophic injuries in Thoroughbred racehorses involve the fetlock. There is no description of comparative imaging in Thoroughbreds entering racehorse training. The aim was to describe MRI, CT and radiographic findings in the metacarpophalangeal joint of non-lame Thoroughbred yearlings. Forty Thoroughbreds underwent low-field MRI, fan-beam CT and radiographic examinations of both metacarpophalangeal joints. Images were assessed subjectively. A hypoattenuating lesion of the sagittal ridge of the third metacarpal bone (McIII) was identified in 33/80 limbs in CT reconstructions. Cone-shaped mineralisation in the sagittal ridge was detected in MR images (n = 17) and in CT images (n = 5). Mild hyperattenuation was common in trabecular bone in the dorsomedial (36/80) and palmarolateral (25/80) metacarpal condyles in CT reconstructions. A focal lesion in the subchondral bone was seen in the proximal phalanx (n = 19) and in McIII (n = 11). Enlarged vascular channels were detected in the metacarpal condyles in 57/80 limbs and in the proximal sesamoid bones in all limbs. Signs of bone modelling are seen in yearling Thoroughbred fetlocks. Sagittal ridge lesions were common and are likely associated with osteochondrosis or other developmental osteochondral defects. Focal lesions in the subchondral bone of McIII and proximal phalanx can indicate developmental abnormalities or subtle subchondral bone injuries.

Comparison of cone-beam and fan-beam computed tomography and low-field magnetic resonance imaging for detection of palmar/plantar osteochondral disease in Thoroughbred horses.

BACKGROUND: Palmar/plantar osteochondral disease (POD) of the metacarpal/tarsal condyles is a common pathological finding in racehorses. OBJECTIVE: To compare diagnoses, imaging details, and measurements of POD lesions between cone-beam computed tomography CT (CBCT), fan-beam CT (FBCT), and low-field magnetic resonance imaging (MRI) using macroscopic pathology as a gold standard. STUDY DESIGN: Cross-sectional study. METHODS: Thirty-five cadaver limbs from 10 horses underwent CBCT, FBCT, MRI, and macroscopic examination. CT and MR images were examined for presence of POD, imaging details of POD, and measurements of POD dimensions and areas. Imaging diagnoses, details, and measurements were compared with macroscopic examination and between modalities. RESULTS: Forty-eight POD lesions were seen over 70 condyles. Compared with macroscopic examination the sensitivity and specificity of diagnosis were 95.8% (CI95 = 88%-99%) and 63.6% (CI95 = 43%-81%) for FBCT, 85.4% (CI95 = 74%-94%) and 81.8% (CI95 = 63%-94%) for CBCT, and 69.0% (CI95 = 54%-82%) and 71.4% (CI95 = 46%-90%) for MRI. Inter-modality agreement on diagnosis was moderate between CBCT and FBCT (κ = 0.56, p < 0.001). POD was identified on CT as hypoattenuating lesions with surrounding hyperattenuation and on MRI as either T1W, T2*W, T2W, and STIR hyperintense lesions or T1W and T2*W heterogeneous hypointense lesions with surrounding hypointensity. Agreement on imaging details between CBCT and FBCT was substantial for subchondral irregularity (κ = 0.61, p < 0.001). Macroscopic POD width strongly correlated with MRI (r = 0.81, p < 0.001) and CBCT (r = 0.79, p < 0.001) and moderately correlated with FBCT (r = 0.69, p < 0.001). Macroscopic POD width was greater than all imaging modality (p < 0.001). MAIN LIMITATIONS: Effect of motion artefact in live horse imaging could not be assessed. CONCLUSIONS: All imaging modalities were able to detect POD lesions, but underestimated lesion size. The CT systems were more sensitive, but the differing patterns of signal intensity may suggest that MRI can detect changes associated with POD pathological status or severity. The image features observed by CBCT and FBCT were similar.

Cone-beam computed tomography produces images of numerically comparable diagnostic quality for bone and inferior quality for soft tissues compared with fan-beam computed tomography in cadaveric equine metacarpophalangeal joints.

Cone-beam computed tomography (CBCT) is an emerging modality for imaging of the equine patient. The objective of this prospective, descriptive, exploratory study was to assess visualization tasks using CBCT compared with conventional fan-beam CT (FBCT) for imaging of the metacarpophalangeal joint in equine cadavers. Satisfaction scores were numerically excellent with both CBCT and FBCT for bone evaluation, and FBCT was numerically superior for soft tissue evaluation. Preference tests indicated FBCT was numerically superior for soft tissue evaluation, while preference test scoring for bone was observer-dependent. Findings from this study can be used as background for future studies evaluating CBCT image quality in live horses.

Visualization of anatomical structures in the fetlock region of the horse using cone beam computed tomography in comparison with conventional multidetector computed tomography.

Introduction: Cone-beam computed tomography (CBCT) is regarded as a convenient and suitable alternative to conventional computed tomography. However, in the horse, the quality of obtained data sets needs to be evaluated. Therefore, the aim of this study was to compare the visibility and accessibility of clinically relevant anatomical structures displayed in CBCT and conventional multidetector computed tomography (MDCT). Materials and methods: Twenty-nine limbs from horses euthanized for reasons unrelated to this study were used. Native and intraarticular contrast scans of the fetlock (CBCT vs. MDCT) were performed. The visibility and accessibility of selected anatomical structures were blindly scored by three independent experienced observers using a scoring system previously reported and adapted to the fetlock joint. Results: Only minor differences between CBCT and MDCT were identified concerning the diagnostic quality of images for osseous structures. Soft tissue structures were better evaluated on MDCT images. In CBCT as well as in MDCT articular cartilage could only be visualized after intraarticular injection of contrast medium. Discussion/conclusion: Cone beam computed tomography of the fetlock is a useful and reliable diagnostic tool when evaluating osseous structures and delineating articular cartilage with contrast medium. However, this modality is limited for assessing soft tissues structures.

Radiomics Modeling of Catastrophic Proximal Sesamoid Bone Fractures in Thoroughbred Racehorses Using µCT.

Proximal sesamoid bone (PSB) fractures are the most common musculoskeletal injury in race-horses. X-ray CT imaging can detect expressed radiological features in horses that experienced catastrophic fractures. Our objective was to assess whether expressed radiomic features in the PSBs of 50 horses can be used to develop machine learning models for predicting PSB fractures. The µCTs of intact contralateral PSBs from 50 horses, 30 of which suffered catastrophic fractures, and 20 controls were studied. From the 129 intact µCT images of PSBs, 102 radiomic features were computed using a variety of voxel resampling dimensions. Decision Trees and Wrapper methods were used to identify the 20 top expressed features, and six machine learning algorithms were developed to model the risk of fracture. The accuracy of all machine learning models ranged from 0.643 to 0.903 with an average of 0.754. On average, Support Vector Machine, Random Forest (RUS Boost), and Log-regression models had higher performance than K-means Nearest Neighbor, Neural Network, and Random Forest (Bagged Trees) models. Model accuracy peaked at 0.5 mm and decreased substantially when the resampling resolution was greater than or equal to 1 mm. We find that, for this in vitro dataset, it is possible to differentiate between unfractured PSBs from case and control horses using µCT images. It may be possible to extend these findings to the assessment of fracture risk in standing horses.

Ultrasonography of the Metacarpal/Tarsal-Phalangeal Joints in Healthy Racehorses: Normal Appearance, Breed-Related and Age-Related Features.

In adult horses, specific ultrasound (US) features and reference values have been reported for the appearance of the joint cartilage and thickness according to the type of joint, such as femoropatellar and tarsocrural. The US appearance of the fetlock has been described in several diseases. The present research evaluates the US features of the metacarpal/tarsal-phalangeal joints in healthy racehorses according to age and breed, since no information is available in the literature. Seventy-one fetlocks in 28 healthy horses (15/28 thoroughbreds and 13/28 standardbreds) were assessed. The horses were grouped as follows: group A < 5 years old vs. group B ≥ 5. A portable ultrasound machine and a linear transducer (5−7.5 MHz) were used. Dorsal metacarpal/tarsal-phalangeal joints were scanned. The US images were reviewed offline in terms of articular cartilage appearance, thickness, and subchondral bone appearance by an experienced observer. Data were reported as the median, minimum, and maximum for cartilage thickness values, and differences between groups were evaluated. Cartilage thickness values were statistically lower in group A than B in the standardbreds, except for the lateral thickness in longitudinal view. No differences were detected in the thoroughbreds within age groups. All of the young standardbreds showed a normal cartilage and subchondral appearance. No statistical differences were found between breeds. Our results highlight the characteristics of the US appearance of metacarpal/tarsal-phalangeal joints specifically in racehorses, with some variations according to age. Since the cartilage can change according to joint growth, age and training activity, the present findings suggest the use of specific references for US features, which are key to correctly evaluating the health of the fetlock.

Fetlock Joint Angle Pattern and Range of Motion Quantification Using Two Synchronized Wearable Inertial Sensors per Limb in Sound Horses and Horses with Single Limb Naturally Occurring Lameness.

Fetlock joint angle (FJA) pattern is a sensitive indicator of lameness. The first aim of this study is to describe a network of inertial measurement units system (IMUs) for quantifying FJA simultaneously in all limbs. The second aim is to evaluate the accuracy of IMUs for quantifying the sagittal plane FJA overground in comparison to bi-dimensional (2-D) optical motion capture (OMC). 14 horses (7 free from lameness and 7 lame) were enrolled and analyzed with both systems at walk and trot on a firm surface. All enrolled horses were instrumented with 8 IMUs (a pair for each limb) positioned at the dorsal aspect of the metacarpal/metatarsal bone and pastern and acquiring data at 200 Hz. Passive markers were glued on the center of rotation of carpus/tarsus, fetlock, and distal interphalangeal joint, and video footages were captured at 60 Hz and digitalized for OMC acquisition. The IMU system accuracy was reported as Root Mean Square Error (RMSE) and Pearson Correlation Coefficient (PCC). The Granger Causality Test (GCT) and the Bland−Altman analysis were computed between the IMUs and OMC patterns to determine the agreement between the two systems. The proposed IMU system was able to provide FJAs in all limbs using a patented method for sensor calibration and related algorithms. Fetlock joint range of motion (FJROM) variability of three consecutive strides was analyzed in the population through 3-way ANOVA. FJA patterns quantified by IMUs demonstrated high accuracy at the walk (RMSE 8.23° ± 3.74°; PCC 0.95 ± 0.03) and trot (RMSE 9.44° ± 3.96°; PCC 0.96 ± 0.02) on both sound (RMSE 7.91° ± 3.19°; PCC 0.97 ± 0.03) and lame horses (RMSE 9.78° ± 4.33°; PCC 0.95 ± 0.03). The two systems' measurements agreed (mean bias around 0) and produced patterns that were in temporal agreement in 97.33% of the cases (p < 0.01). The main source of variability between left and right FJROM in the population was the presence of lameness (p < 0.0001) and accounted for 28.46% of this total variation. IMUs system accurately quantified sagittal plane FJA at walk and trot in both sound and lame horses.

2D-SWE of the Metacarpophalangeal Joint Capsule in Horses.

(1) Two-dimensional shear wave elastography (2D-SWE) employs an ultrasound impulse to produce transversely oriented shear waves, which travel through the surrounding tissue according to the stiffness of the tissue itself. The study aimed to assess the reliability of 2D-SWE for evaluating the elastosonographic appearance of the distal attachment of the fetlock joint capsule (DJC) in sound horses and in horses with osteoarthritis (OA) (2). According to a thorough evaluation of metacarpophalangeal joint (MCPJ), adult horses were divided in a sound Group (H) and in OA Group (P). Thereafter, a 2D-SWE of MCPJs was performed. Shear wave velocity (m/sec) and Young's modulus (kPa) were calculated independently by two operators at each selected ROI. Statistical analysis was performed with R software. (3) Results: 2D-SWE had good-excellent inter-CC and intra-CC in both groups. Differences in m/s and kPa between Groups H and P were found in transverse scans with lower values in Group P. No correlation with age or DJC thickness was found. (4) Conclusions: 2D-SWE was repeatable and reproducible. In Group H, DJC was statistically stiffer than in Group P only in transverse scan. The technique showed poor sensitivity and specificity in differentiating fetlocks affected by OA.

First phalanx exostosis in traditional equestrian horses in Western Libya.

Background: Orthopedic diseases involving the forelimb fetlock joint of horses other than those used in professional racing have not been widely reported in the literature. One of these problems is the exostosis on the proximal forelimb phalanx (P1), which has not been reported previously in Western Libya. Aim: The study aimed to investigate the prevalence of P1 exostosis in traditional equestrian horses (known locally as Sarj horses) of different breeds in Libya that participated in a special social event and described its clinical findings radiographic appearance. Methods: The current study involved 60 horses admitted to private veterinary clinics with varied fetlock orthopedic problems. The studied horses were aged between 6 and 11 years old and galloped on hard grounds. Clinical and radiographic examinations were carried out on all horses. Lateromedial radiographs for one or both forelimb fetlock joints were acquired for each horse. Results: Clinical examination revealed that 21 horses (35%) had hard non-painful swelling on the dorsal aspect of fetlock with joint stiffness during flexion. In 19 of them, the swelling was bilateral. No forelimb lameness was noticed. Radiographically, hard swelling was diagnosed as bone exostosis, with various sizes, on the proximo-dorsal aspect of P1. There was also a new bone formation on the disto-dorsal part of third metacarpal bone in two cases. Conclusion: This study has documented the first report on bone exostosis on the proximo-dorsal aspect of the forelimb proximal phalanx as a common problem in Sarj horses that galloped on hard grounds in Western Libya. Although this bone lesion did not cause lameness in all reported cases, further investigations are warranted to identify its histopathological nature, potential etiology, and proper treatment.

Stress fracture of the palmar, distal cortex of the third metacarpal bone: A diagnostic challenge with a good prognosis.

BACKGROUND: Transverse stress fracture of the palmar cortex of the distal aspect of the third metacarpal bone (TSF PCD McIII) is poorly documented. OBJECTIVES: To describe the typical signalment of this injury, the common clinical and radiological signs and prognosis. STUDY DESIGN: A retrospective hospital-based case series with follow-up of racing records. METHODS: All cases of TSF PCD McIII diagnosed among racehorses in training at the Hong Kong Jockey Club between 2011 and 2019 were identified. Clinical records were reviewed and documented signs were recorded for each case. Findings from a predefined list of radiological features were listed. Descriptive statistics were used to describe the age and training profile of horses, the clinical and radiological findings and time to return to ridden exercise. RESULTS: Twenty-three cases (n = 23) were identified. The majority (57%) had recently started or returned to training from a break and 35% (n = 8) of cases had not yet undertaken timed gallops at the time of injury. Most cases (20/23; 87%) were lame; in nine (39%), lameness was severe. Localised swelling of superficial soft tissues was reported in 15/23 (65%) cases. Pain on palpation of the distal McIII was present in 15/23 (65%) cases and in response to fetlock flexion in 12/23 (52%). Diffuse, localised increase in radiopacity, disruption to the outline of the bone periosteal surface and outward displacement of the button of the splint bone were common radiological features in early cases (70%, 67% and 67% of all cases). Sixty-one per cent of cases (14/23) were initially misdiagnosed. Most horses (n = 18/23) resumed training and racing after a median of 83 and 246 days. MAIN LIMITATIONS: Clinical notes were not consistent between cases. Radiographs were taken at different times. CONCLUSIONS: Horses commencing training are at risk of TSF PCD McIII, which presents with confusing clinical signs and subtle radiological findings. The long-term outlook is favourable.