Proximal Sesamoid Bones Research Articles

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

To describe the development and maturation of equine proximal sesamoid bones (PSBs) in fetuses and young horses using radiography, microcomputed (micro)-CT, and histology. 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. 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. 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. 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.

Concurrent radiological and ultrasonographical findings in the forelimb proximal sesamoid bones and adjacent suspensory ligament branches in yearling and 2-year-old Thoroughbred sales horses.

Changes in the proximal sesamoid bones (sesamoids) and the insertional region of the adjacent suspensory ligament branch (branch) are of particular importance in young Thoroughbreds sold at public auction. Little is known about the prevalence of concurrent ultrasonographical branch change, relative to the various grades of radiological sesamoid appearance. To examine the existence of concurrent radiological and ultrasonographical findings in individual sesamoid-branch units in sales horses; to determine whether there are any radiological findings that are consistently accompanied by a particular degree of insertional branch change, and to provide practical recommendations as to when suspensory branch ultrasonography may be warranted in a sales environment. Prospective cohort study using an enrolled sample. Horses were enrolled with consignor permission from a large Thoroughbred yearling sale and five 2-year-old Thoroughbred sales the following year. Data from the radiological evaluation of forelimb sesamoids and the ultrasonographical examination of the adjacent forelimb suspensory branches were described. A total of 2204 yearling forelimb sesamoid-branch units and 1336 2-year-old forelimb sesamoid-branch units were included, from 551 sales yearlings and 334 sales 2-year-olds. The proportion of yearling sesamoids with grade ≤1 vascular channels that had adjacent grade ≥2 fibrillar branch change was 1.2%. The same proportion for 2-year-olds was 3.8%, with medial forelimb sesamoids with grade 1 vascular channels overrepresented in 2-year-olds in this category. In yearlings, 31% of sesamoids with grade 2 vascular channels had adjacent grade ≥2 fibrillar branch change and 59% of sesamoids with grade 3 vascular channels had adjacent grade ≥2 fibrillar branch change. In 2-year-olds, 47% of sesamoids with grade 2 vascular channels had adjacent grade ≥2 fibrillar branch change and 67% of sesamoids with grade 3 vascular channels had the same. Only one yearling sesamoid and one 2-year-old sesamoid with radiological abaxial concavity had grade ≥2 fibrillar branch change. Hindlimbs were not included. Clinical examinations were not performed and the status of any past or present inflammatory process at the sesamoid-branch enthesis could not be inferred from radiographs and ultrasonographic images alone. The existence and prevalence of concurrent radiological and ultrasonographical findings in the proximal sesamoid bones and adjacent suspensory ligament branches in yearling and 2-year-old Thoroughbred sales horses has been established. General recommendations have been made for selective branch ultrasonography on the basis of radiological sesamoid appearance. The results support a separate aetiology for radiological sesamoid abaxial concavity that does not primarily involve the suspensory branch insertion.

Ultrasonography of the suspensory ligament branches in yearling and 2-year-old Thoroughbred sales horses: Prevalence, progression of findings and associations with racing performance.

Equine suspensory ligament branch (branch) ultrasonography is becoming increasingly commonplace presale. No ultrasonographical branch reference data exists for Thoroughbred sales horses. To define the prevalence of ultrasonographical findings in the forelimb suspensory branches of yearling and 2-year-old sales Thoroughbreds and to analyse associations with racing performance. To track changes in branch findings between 1 and 2 years of age in horses that present for sale at both ages. Prospective cohort study using an enrolled sample. Horses were enrolled from a 2016 yearling sale and five 2017 2-year-old sales with consignor permission. Ultrasonography was performed immediately prior to the sales. Ultrasonographical findings relating to branch size, fibrillar pattern, the presence of hyperechoic foci, periligamentar tissue thickness and the adjacent proximal sesamoid bone surface were examined. Associations with racing performance from 2 to 4 years of age were investigated using multivariate regression analyses. Clinical follow-up was sought to ascertain why horses that did not race never started. A total of 593 sales yearlings and 367 2-year-olds had forelimb branch ultrasonography performed. Grade ≥2 fibrillar branch change was present in 8.9% of yearlings and 14.4% of 2-year-olds. A 0.25 cm increase in branch width was associated with a 49-day delayed start to racing careers (P < 0.001, 95% confidence interval (95% CI): 21-77 days). The presence of grade 2 hyperechoic foci was associated with significantly lower total earnings (P = 0.01, 95% CI: $2000-$16 022) and lower earnings per start (P = 0.003, 95% CI: $349-$1718) in United States Dollars. Grade 3 fibrillar branch change had clinically important reductions in the probability of racing, the calibre of racing performance and earnings. Grade 1 fibrillar pattern was associated with significantly higher earnings per start (P = 0.004, 95% CI: $2641-$5759). The findings are applicable to horses prepared for public auction and deemed fit to be entered for sale. The results may underestimate the proportion of severe lesions in horses not entered for sale. Reference values specific to young Thoroughbreds have been established. Grade 1 fibrillar branch change should be regarded as an acceptable appearance in sales yearlings and 2-year-olds. Approximately one-third of grade 2 yearling branches progressed to a grade 3 lesion. Evidence of enlarged branch width and grade 2 hyperechoic foci at 2-year-old sales constitute a risk to racing performance.

Clinical and Radiological Evaluation of Racehorses with Sesamoiditis: Case Series

Background: Sesamoiditis causes intermittent lameness in horses and is characterized by the enlargement of vascular channels, local osteolysis, osteophyte and enthesophyte formation on radiography. This study aimed to report the relationship between the clinical and radiological findings of racehorses diagnosed with sesamoiditis, the treatment applied and long-term results. Methods: The study included a total of 30 Arabian and Thoroughbred racehorses aged 2-7 years diagnosed with sesamoditis based on clinical and radiological examinations. These horses were treated and followed for nine months. Result: Radiographic examination revealed different numbers of enlarged vascular channels in the proximal sesamoid bones in all the cases and osteophytosis (n=3), enthesophytosis (n=9), osteolysis (n=3) and fractures (n=6) in some cases. In addition, low heels were important in 27 cases. The body conformation and low-heeled hoof structure play a role in the development of sesamoiditis in horses and should be considered. As a result, body structure and low heel structure play a role in the development of sesamoiditis in horses and should be considered. This situation should be tried to be corrected by farriers during the foaling period. Sesamoiditis can have a positive prognosis with appropriate treatment and adequate rest, for this reason, treatment should be started in the early period.

Morphological and radiographic studies on the Manus region in the Arabian one-humped camel (Camelus dromedaries).

The study aims to analyse the normal anatomical and radiographical features of the Manus of the southern Aswanian-adapted Arabian one-humped camel, providing crucial data for diagnosing and treating various ailments. Our study was applied to 10 cadaver forelimbs of adult male one-humped camels (4-5 years old) for an explanation of the gross anatomy of the bones of the Manus region from under the carpal bones by using traditional techniques, including the gross anatomical, radiographic and x-ray (at the dorsopalmar and lateral planes) of the preparation of Manus bones. Our results showed that the large fused (third and fourth) metacarpal bones, in which the fusion extended along the entire length of the bone except at the distal end, diverged to form separate articulations with cross-ponding digits. As described in all ruminant species, especially the camel, there were two digits, and each digit consisted of three phalanges and two proximal sesamoid bones. Our radiographic x-ray data revealed that the complete radiopaque septum that completely divided the medullary cavity into two separate parts was clear from the dorsopalmar view, while the lateral view showed the proximal sesamoid bones that were placed over each other and located palmar to the head of the large metacarpal bone. In conclusion, our study reveals the adaptations of the Arabian one-humped camel to Egyptian conditions, aiding in the early diagnosis of lameness and digit problems and enabling veterinarians and camel owners to better address these issues, thereby improving the overall health and well-being of these animals.

Comparison of standing cone‐beam computed tomography and low‐field magnetic resonance imaging findings in the equine metacarpo‐ or metatarsophalangeal region of standing sedated horses

SummaryBackgroundCone‐beam computed tomography (CBCT) and low‐field magnetic resonance imaging (MRI) are increasingly used in standing horses, so it is important to understand an efficient application of these imaging modalities.ObjectiveTo compare CBCT and MRI findings in the metacarpo (MCP)/metatarsophalangeal (MTP) region of clinical patients imaged for diagnostic purposes.Study designRetrospective study.MethodsThe CBCT and MRI images of the MCP/MTP region from equine clinical patients undergoing both standing MRI and CBCT imaging for lameness localised to the fetlock region (2021–2023) were retrospectively reviewed. Presence, location and imaging features of lesions were compared between modalities using descriptive analysis.ResultsImaging studies of 24 MCP/MTP regions from 22 horses were included. CBCT provided the assessment of subchondral bone integrity in palmar/plantar osteochondral disease, details of the length and associated attenuation changes of third metacarpal/tarsal parasagittal groove and proximal phalanx sagittal groove fissures, structural integrity and attenuation changes of subchondral and trabecular bone injuries, proximal phalanx dorsoproximal defects and anatomical and structural details of proximal sesamoid bone injuries. MRI provided the evaluation of short tau inversion recovery (STIR) hyperintensity associated with bone lesions and the extent of increased fluid accumulation in bone. CBCT revealed reduced joint space, indicating articular cartilage loss, while MRI showed joint distension and synovitis. MRI revealed generalised osseous STIR hyperintensity associated with septic arthritis. Soft tissue injuries were most identified by MRI except for heterotopic mineralisation most detected by CBCT.Main limitationsImaging findings not verified by a gold standard.ConclusionsCBCT and MRI contributed different diagnostic information so optimal information was obtained by using both modalities. Standing CBCT showed changes in bone structure and attenuation but was limited in detecting soft tissue injuries. Standing MRI showed increased fluid accumulation in bone and soft tissue injuries but was limited in assessing structural details of bone injuries.

CT based 3D reconstruction of the forefoot’s blood supply in a white rhinoceros

BackgroundThe white rhinoceros (Ceratotherium simum) is close to extinction, listed as “Near Threatened”, with a decreasing population on the Red List of Threatened Species of the International Union for Conservation of Nature. In at least 50% of the specimens in captivity, podiatric diseases, such as osteitis, osteomyelitis, chip fractures, enthesophytes, fractures and osteoarthritis were found during necropsy. These osteal deformations cause further pathogenic alterations in the soft tissues, particularly in the digital cushion. The literature provides good description of the skeleton of the rhino’s limbs, but similar for the vascular system is non-existent. In order to recognize the symptoms in an early state and for a successful surgical treatment, precise knowledge of the vascular anatomy is essential. The purpose of our study was to provide detailed anatomical description of the blood supply of the digits and that of the digital cushion.ResultsThe blood supply of the distal foot, digits and digital cushions were perfectly visible on the reconstructed and coloured 3D models. The deep palmar arch provided not only the blood supply to the digits but had a palmaro-distal running branch which developed a trifurcation proximal to the proximal sesamoid bones of the third digit. Two of its branches participated in the blood supply of the digits’ proximal palmar surface, while the major branch supplied the digital cushion from proximal direction.ConclusionsOur findings show a unique blood supply: the main vessels of the digital cushion stem both directly from the deep palmar arch and from the digits’ own arteries. The detailed description of vessels may be useful in planning surgery of the region and also in cases where the veins of the ear are not accessible.

Radiological findings in the proximal sesamoid bones of yearling and 2-year-old Thoroughbred sales horses: Prevalence, progression and associations with racing performance.

Radiological findings in the proximal sesamoid bones (sesamoids) are a persistent source of controversy at Thoroughbred sales, due to inconsistent classification and conflicting assignment of potential clinical importance. To define the prevalence of sesamoid findings on sales repository radiographs in yearling and 2-year-old Thoroughbreds and to analyse associations with racing performance. To track the changes in sesamoid findings between 1 and 2 years of age in horses that present for sale at both ages. Prospective cohort study using an enrolled sample. Horses were enrolled from a 2016 yearling sale and five 2017 2-year-old sales with consignor permission. Radiological findings relating to sesamoid vascular channel appearance, abaxial contour changes and sesamoid fragments were examined. Associations between sesamoid findings and racing performance from 2 to 4 years of age were examined using multivariate regression analyses. Clinical follow-up was sought to ascertain why horses that did not race never started. A total of 2508 yearlings and 436 2-year-olds were included for evaluation. Interobserver agreement using the new grading system was substantial. Yearling findings associated with a significantly reduced probability of starting a race were: Grade 3 vascular channels in forelimb sesamoids (0.52, P < 0.001, 95% confidence interval (CI): 0.37-0.67), abaxial new bone in forelimb sesamoids (0.62, P = 0.01, 95% CI: 0.49-0.73), apical or abaxial fragments in forelimb sesamoids (0.55, P = 0.005, 95% CI: 0.37-0.72). For affected horses that did race, Grade 3 vascular channels in forelimb sesamoids were associated with fewer race starts (9.9 starts, P = 0.03, 95% CI: 8.0-12.2) and Grade 3 vascular channels in hindlimb sesamoids were associated with a delayed start to racing careers (54 days, P = 0.01, 95% CI: 20-89). Abaxial new bone in forelimb sesamoids was associated with a 54% reduction in total earnings (P = 0.003, 95% CI: 24-72) and a 46% reduction in earnings per start (P = 0.002, 95% CI: 21-64). Abaxial concavity occurred predominantly in yearling medial forelimb sesamoids, had no impact on racing performance and mostly resolved by 2-year-old sale. These findings are applicable to horses presented for sale at public auction and may underestimate the prevalence of severe lesions in non-sales horses. Grade 3 vascular channels, forelimb sesamoid abaxial new bone and forelimb sesamoid fragments are important findings in sales repository radiology. The new grading scale assigns a numerical grade for vascular channel appearance that matches the number of enlarged vascular channels evident in a given sesamoid. Abaxial contour changes, when present in sesamoids that are Grade 0 for enlarged vascular channels, are noted separately as either abaxial new bone or abaxial concavity. Fragments are also noted and interpreted separately.

Ultrasonography, computed tomography and magnetic resonance imaging of the dromedary camel distal limbs

BackgroundLameness associated with the distal limb region in dromedary camels is quiet prevalent. The diagnosis of lameness relies on a comprehensive orthopedic examination conjugated with an appropriate imaging modality to achieve a decisive diagnosis. Using of modern imaging tools provoked a significant breakthrough in the diagnosis of lameness. Ultrasonography (US) is widely established in dromedaries, whereas computed tomography (CT) and magnetic resonance imaging (MRI) are gaining popularity. CT provides a considerably higher bone detail than any other imaging modality. US and MRI continue to be the best options for soft tissue imaging. A truthful assessment of the clinical US, CT and MRI images dictates a comprehensive familiarity with the standard US, CT and MRI tissue deviations. Accordingly, our purposes were to present a full MRI protocol for investigating the dromedary camel distal limbs as well as comparing and illustrating the merits of using MRI, CT and US for evaluation of the front and hind distal limbs in 10 healthy lameness free dromedary camel cadavers. The limbs were scanned via a high-field 1.5 Tesla MRI magnet and a multi-detector CT scanner then subjected to a systematic US examination in both longitudinal and transverse planes. The obtained MRI, CT and US images were evaluated, correlated and compared.ResultsCT and MRI eliminated the structural superimposition in the dromedary camel distal limbs and afforded assessment of minute ligamentous and tendentious structures that were inaccessible by US including the axial collateral ligaments, ligaments supporting the proximal sesamoid bones and the palmar/plantar aspects of the inter-phalangeal joints. US and MRI were appreciated for the assessment of the articular cartilage that was not visible on the plain CT images.ConclusionsCT and MRI accurately identified and characterized bones and soft tissues constituting the dromedary camel distal limbs. US was appreciated for assessment of soft tissues, articular cartilage and bone contours. CT and MRI may be considered when US results are inconclusive or to evaluate the unreachable parts of the camel distal limbs. Images presented in this study could be used as a reference standard for evaluating dromedary camel distal limb diseases.

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 18F-sodium fluoride positron emission tomography and computed tomography for imaging of the fetlock in 25 nonracehorses.

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

Dose effect and duration of action of liposomal bupivacaine administered as a perineural analgesic in a reversible and adjustable frog-pressure model of equine lameness.

To determine the dose effect of peri-neural liposomal bupivacaine (LB) in an induced forelimb lameness model. 12 clinically normal adult horses. A randomized cross-over design was performed with 1 limb receiving saline and the other LB: low dose (6), high dose (6). Lameness was induced in 1 forelimb using a frog-pressure model. In the lame limb, peri-neural injection of the palmar nerves at the proximal sesamoid bones was performed using saline, low dose LB (0.25 mg/kg) (LDLB), or high dose LB (0.5mg/kg) (HDLB) in random order with a 1-week washout period between treatments. Distal limb swelling, mechanical nociceptive thresholds (MNT), and objective lameness data were collected before and up to 72 hours after peri-neural anesthesia. Data analysis was performed with mixed model ANOVA, equality of medians test, and Kaplan Meier survival analysis. Compared with baseline, horses treated with LDLB and HDLB had improvements in MNT and lameness (P < .001). In the LDLB group, the median duration of analgesia was 4.5 hours (range = 3-6 hours) and the median return to lameness was 7 hours (range = 4-24 hours). In the HDLB group, the median duration of analgesia was 12 hours (range = 4-48 hours) and the median return to lameness was 9 hours (range = 3-48 hours). Mild to moderate swelling was identified in 11/12 (92%) LB limbs. Both LDLB and HDLB resulted in loss of skin sensation and improvement of lameness. There was high variability among horses in duration of action for both doses.

Racing performance of Thoroughbred racehorses with suspensory ligament branch desmitis treated with mesenchymal stem cells (2010-2019).

Suspensory ligament branch desmitis (SLBD) is a common injury in Thoroughbred racehorses. Orthobiologic treatment of these injuries is a relatively new approach, and there is limited information available on post injury racing performance in racehorses treated with mesenchymal stem cells (MSCs). To assess racing performance post injury in Thoroughbred racehorses with SLBD treated with MSCs. Retrospective case series. Medical records of racehorses with SLBD treated with MSCs from 2010 to 2019 were reviewed. All horses were treated with allogeneic stem cells injected locally at the time of diagnosis and subsequently received 3-4 treatments with autologous bone-marrow derived MSCs. Ultrasonographic and radiographic images were evaluated to determine the degree of suspensory branch injury and sesamoiditis of the associated proximal sesamoid bone. Race performance was assessed by career length, class of races, number of starts and earnings post injury. Race performance of horses that raced pre and post injury were compared. Of 69 treated horses, 71% (49/69) [95% CI: 59%-81%] raced post injury. Horses that had raced pre injury were more likely to race post injury (90% [18/20]) than horses that did not race pre injury (63% [31/49]; p = 0.03). Females were less likely to race post injury than males (52% [11/21] vs. 79% [38/49], respectively; p = 0.02). In the 18 horses that raced pre and post injury, the number of races, earnings and earnings per start were not significantly different pre and post injury. The average career length of all horses that raced post injury was 29.5 months. Retrospective study design and lack of controls. Treatment with MSCs resulted in a majority of Thoroughbred racehorses with SLBD racing post treatment. Racing pre injury and being male was positively associated with racing post injury.

Radiographic Appearance of the Fore Digit and Carpal Joint in the Mule Foal from Birth to 3 Months of Age.

Few studies have established the normal radiographic anatomical development of the donkey foal and, to date, no data are available for mules. Our aim was thus to evaluate the radiographic development of the fore digit and carpal joint in the mule foal from 0 to 3 months of age. Ten forelimbs of five healthy full-term mule foals were included. Radiographs of the fore digit lateromedial and dorsopalmar and the carpus dorsopalmar were performed weekly for the first month of age, and bi-monthly during the following two months. Fore digit growth plate closure times, morphological, angular, and linear radiographic parameters, and also carpal cuboidal bone mineralization were evaluated. Growth plates were graded as open, closing, and closed. Carpal bone appearance was graded as mature, slightly immature, or immature. Growth plate closure times showed the following: middle phalangeal distal physis (DP) closed at birth, and proximal physis (PP) started to close at around two months; first phalanx DP closed at seven days, and PP started to close at three months; and third metacarpal bone DP started to close at two months. Carpal bones were immature at birth. Distal phalanx (PD) was triangular at birth, palmar processes had developed by one month, and proximal sesamoid bones were trapezoidal by three months. The hoof wall, PD dorsal wall, and palmar angles values changed in parallel, and hoof capsule thickness increased. No PD remodeling evidence within the hoof capsule or variations in the hoof axis with growth were found. We identified a baseline for the interpretation of forelimb radiological features in mule foals. The specific features found were intermediate between those found in horses and donkeys.

Fetal ultrasonography of the distal limb: a new tool to assess equine fetal age and bone development

In Quarter Horses (QH), fetal age can be predicted within 2 weeks prior to 200 days of gestation via ultrasonography, but as pregnancy advances, accuracy decreases (Renaudin.et.al. Reprod Dom Anim. 2022;57: 743-753). Recently, fetal ultrasonographic measurement of the first phalanx (P1) length was introduced as a novel biometric parameter during late gestation, and the time of apparition and closure of P1’s epiphyses were found to be potential markers of bone maturation in utero (Renaudin.et.al. AAEP.2021;67:264-265). The aim of this study was to determine if bone characteristics of the second phalanx (P2), distal metacarpal 3 (MC3), proximal and distal sesamoid can predict fetal age. Ten healthy pregnant mares (9 QH and 1 Thoroughbred carrying a QH fetus) with known ovulation dates were used. Fetuses were examined by transrectal ultrasound every 2 weeks from 9 months of gestation until parturition. At each examination, the length of the ossified portion of P2’s diaphysis was measured, the presence or absence of P2’s and distal MC3’s epiphyses and the time of appearance of the proximal and distal sesamoid bones were documented. P2 length correlated strongly with days of gestation (P < 0.0001; r 2 = 0.75) and a correlation equation was established: y = 0.1413x -24.89 (y = predicted value of P2 length; x = fetal age). The P2 proximal epiphysis and MC3 distal epiphysis appeared on ultrasound between 285 and 306 days of gestation (mean: 294 days),and 260 and 294 days of gestation (mean: 268 days) respectively and did not close before parturition. P2 distal epiphysis was never imaged. Proximal and distal sesamoids were first observed between 286 and 306 days of gestation (mean: 295 days) and 300 and 329 days of gestation (mean: 317 days) respectively except for the smallest foal where they appeared at 331 and 335 days respectively. In conclusion, P2 length can be used in addition to P1 length as a biometric parameter in late gestation. Distal MC3’s, P1’s and P2’s epiphyses, and sesamoid bones diaphyses appear in a chronological order with MC3 distal epiphysis appearing first, P1’s second, P2’s third, proximal sesamoids fourth and distal sesamoid last. Distal limb ossification can be considered complete in QHs when the MC3 distal epiphysis, P1 and P2 proximal epiphysis and all sesamoid bones are present. Clinically, fetal ultrasonography of the distal limb may be used to assess fetal age and in the decision-making process of not inducing parturition if in utero bone development is not complete. This project was supported by the Center for Equine Health with funds provided by the State of California satellite wagering fund and contributions by private donors.

Osteítis séptica secundaria a una herida accidental en plantar de nudo del miembro posterior en un equino Reporte de caso

The objective of this study was to report a clinical case and its subsequent evolution of a mare with septic osteitis in the proximal sesamoid bones in a hind limb due to a traumatic injury. The patient, an 8-year-old Thoroughbred race mare, from a sporting activity; who was admitted to the Veterinary Hospital Center of the Veterinary School in 2020, presenting a plantar wound of the phalangeal metatarsal joint of the right hind limb, product of a trauma when performing swimming exercises in a stream. In the clinical evaluation, a wound with a section of the superficial and deep digital flexor tendon was determined, evolving to tendosynovitis and septic arthritis with subsequent septic osteitis of the proximal sesamoid bones as a complication. The treatment consisted of a multimodal approach, with the purpose of controlling the infection and contamination of the wound, its repair and analgesia. Due to the aggressive treatment established after diagnosing septic osteitis, the patient evolves favorably, decreasing the degree of pain and lameness observing in subsequent radiographic examens, controlled bone infection and in the process of bone remodeling with ankylosis of the metatarsal phalangeal joint; which was beneficial in this case due to the disruption of the fetlock suspensory apparatus.

Metacarpophalangeal Joint Pathology and Bone Mineral Density Increase with Exercise but Not with Incidence of Proximal Sesamoid Bone Fracture in Thoroughbred Racehorses

Proximal sesamoid bone (PSB) fracture is the leading cause of fatal musculoskeletal injury in Thoroughbred racehorses in Hong Kong and the US. Efforts are underway to investigate diagnostic modalities that could help identify racehorses at increased risk of fracture; however, features associated with PSB fracture risk are still poorly understood. The objectives of this study were to (1) investigate third metacarpal (MC3) and PSB density and mineral content using dual-energy X-ray absorptiometry (DXA), computed tomography (CT), Raman spectroscopy, and ash fraction measurements, and (2) investigate PSB quality and metacarpophalangeal joint (MCPJ) pathology using Raman spectroscopy and CT. Forelimbs were collected from 29 Thoroughbred racehorse cadavers (n = 14 PSB fracture, n = 15 control) for DXA and CT imaging, and PSBs were sectioned for Raman spectroscopy and ash fraction measurements. Bone mineral density (BMD) was greater in MC3 condyles and PSBs of horses with more high-speed furlongs. MCPJ pathology, including palmar osteochondral disease (POD), MC3 condylar sclerosis, and MC3 subchondral lysis were greater in horses with more high-speed furlongs. There were no differences in BMD or Raman parameters between fracture and control groups; however, Raman spectroscopy and ash fraction measurements revealed regional differences in PSB BMD and tissue composition. Many parameters, including MC3 and PSB bone mineral density, were strongly correlated with total high-speed furlongs.

Identification of Heterotopic Mineralization and Adjacent Pathology in the Equine Fetlock Region by Low-Field Magnetic Resonance Imaging, Cone-Beam and Fan-Beam Computed Tomography

Heterotopic mineralization in equine distal limbs has been considered an incidental finding and little is known about its imaging features. The study aimed to identify heterotopic mineralization and adjacent pathology in the fetlock region with cone-beam (CB) computed tomography (CT), fan-beam (FB) CT, and low-field magnetic resonance imaging (MRI). Images from 12 equine cadaver limbs were examined for heterotopic mineralization and adjacent pathology and verified by macro-examination. Retrospective review of the CBCT/MR images from 2 standing horses was also included. CBCT and FBCT identified twelve mineralization's with homogeneous hyperattenuation: oblique-sesamoidean-ligament (5) without macroscopic abnormality; deep-digital-flexor-tendon (1) and suspensory-branch (6) with macroscopic abnormalities. MRI failed to identify all mineralization's, but detected suspensory branch splitting, and T2 and STIR hyperintensity in 4 suspensory-branches and 3 oblique-sesamoidean-ligaments. Macro-examination found corresponding disruption/splitting and discoloration. All modalities identified 7 ossified fragments showing cortical/trabecular pattern: capsular (1), palmar sagittal ridge (1), proximal phalanx (2) without macroscopic abnormality, and proximal sesamoid bones (3). On MRI, fragments were most identifiable on T1 images. All abaxial avulsions had suspensory-branch splitting on T1 images with T2 and STIR hyperintensity. Macro-examination showed ligament disruption/splitting and discoloration. Suspensory-branch/intersesamoidean ligament mineralization's were identified by CBCT in standing cases; 1 had associated T2 hyperintensity. Both CT systems were generally superior in identifying heterotopic mineralization's than MRI, while MRI provided information on soft tissue pathology related to the lesions, which may be important for management.

Training drives turnover rates in racehorse proximal sesamoid bones

Focal bone lesions are often found prior to clinically relevant stress-fractures. Lesions are characterized by low bone volume fraction, low mineral density, and high levels of microdamage and are hypothesized to develop when bone tissue cannot sufficiently respond to damaging loading. It is difficult to determine how exercise drives the formation of these lesions because bone responds to mechanical loading and repairs damage. In this study, we derive steady-state rate constants for a compartment model of bone turnover using morphometric data from fractured and non-fractured racehorse proximal sesamoid bones (PSBs) and relate rate constants to racing-speed exercise data. Fractured PSBs had a subchondral focus of bone turnover and microdamage typical of lesions that develop prior to fracture. We determined steady-state model rate constants at the lesion site and an internal region without microdamage using bone volume fraction, tissue mineral density, and microdamage area fraction measurements. The derived undamaged bone resorption rate, damage formation rate, and osteoid formation rate had significant robust regression relationships to exercise intensity (rate) variables, layup (time out of exercise), and exercise 2–10 months before death. However, the direction of these relationships varied between the damaged (lesion) and non-damaged regions, reflecting that the biological response to damaging-loading differs from the response to non-damaging loading.

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.