Is there an association between clinical features, response to diagnostic analgesia and radiological findings in horses with a magnetic resonance imaging diagnosis of navicular disease or other injuries of the podotrochlear apparatus?

A preliminary assessment of hoof morphometry in a population of lame and non-lame working donkeys in Pakistan

BACKGROUND

Hoof morphometry, conformation and shoeing practices have all been associated with lameness in horses. Hoof morphometry in working donkeys in Pakistan has not been objectively measured.

OBJECTIVES

To quantitatively assess hoof morphology in donkeys, to identify factors underlying hoof morphology, and interrelationships between conformation, lameness, and shoeing status.

STUDY DESIGN

Cross-sectional study.

METHODS

Donkeys were assessed in-harness using a modified five-point lameness scale by two veterinarians and digital photographs of front hooves taken alongside a grid. Factor analysis was used to examine the interrelationships among morphometric data. Associations between conformation, shoeing, age and lameness were assessed.

RESULTS

Sixty-one donkeys were examined; 28 were unshod. There were significant left-right hoof asymmetries between heel height (0.27 (Standard Deviation [SD]) 0.92 cm; p=0.02), toe-heel angle (2.97° SD 8.85°; p=0.03) and medio-lateral symmetry (0.5, SD 1.75 cm; p=0.05). Ten percent of donkeys (n=6) were sound and 64% donkeys (n=39) were consistently lame. Conformational defects were seen in 41% (n=25) of donkeys. Eleven factors were extracted, accounting for 83% of the variance encountered in the original variables. Shoeing, and asymmetry between or within feet were not associated with lameness in donkeys; older donkeys were more likely to be lame (P=0.02).

MAIN LIMITATIONS

As a convenience sample of draught donkeys, most of which were lame, the study may not reflect non-pathological hoof morphology in working donkeys. There are no validated objective lameness measures for donkeys and donkeys were in harness when assessed.

CONCLUSION

This study represents a snapshot of hoof morphology and lameness in a single population and under various limitations. Further work should use larger datasets and more homogenous samples to discriminate between 'normal' and 'abnormal' feet and how these might contribute to lameness. Factor analysis highlighted the clustering of hoof morphometric features in donkeys, suggesting the potential for targeted studies in the future. This article is protected by copyright. All rights reserved.

When radiography and ultrasonography are not enough: the use of computed tomography and magnetic resonance imaging for equine lameness cases

MRI and CT have enhanced our diagnostic abilities for equine lameness beyond what is available using radiography and ultrasonography. This has allowed veterinarians to better prognosticate and treat lameness conditions, improving patient outcomes. This article discusses the basic principles behind MRI and CT, their advantages and disadvantages, the different types of equipment available for clinical use in horses, the typical diagnostic workup prior to pursuing advanced imaging, and common regions where MRI and CT are used clinically. The companion Currents in One Health by Spriet, AJVR, July 2022, discusses even more advanced equine imaging in the form of positron emission tomography. Combined, these future directions of MRI, CT, and positron emission tomography may include improved ability to image standing horses or screen for injury prevention.

Modified Z-bar shoe eliminates occasional frog bruising accompanying Z-bar shoeing for navicular syndrome management in underrun-heeled horses

Two horses diagnosed with underrun heels leading to navicular syndrome were fitted with Z-bar shoes. They occasionally showed moderate lameness on the affected legs after the sixth and tenth consecutive farrier adjustments. The affected hooves were sensitive to compression of the frog and sole in their palmar regions. Modified Z-bar shoes were created and shod on the lame legs based on previous with regional anaesthesia and recent clinical examination. The lameness scores were slightly improved at the first shoeing with the modified Z-bar shoes but were markedly improved at four and eight weeks aftershoeing, without medication. The modified Z-bar shoes in this report could potentially protect the palmar structure damaged by usual Z-bar shoes and contribute to reducing pathogenic impacts deriving from underrun heels and navicular syndrome.

The equine navicular apparatus as a premier enthesis organ: Functional implications

Navicular syndrome has been traditionally characterized by progressive lameness with chronic degeneration of the navicular bone. Advances in imaging techniques have revealed that its associated soft tissue structures are also affected. This distribution of lesions is explained by conceptualizing the equine navicular apparatus as an enthesis organ that facilitates the dissemination of mechanical stress throughout the tissues of the foot. The navicular apparatus has the same structural adaptations to mechanical stress as the human Achilles tendon complex. These adaptations efficiently dissipate mechanical force away from the tendon's bony attachment site, thereby protecting it from failure. The comparison of these two anatomically distinct structural systems demonstrates their similar adaptations to mechanical forces, and illustrates that important functional insights can be gained from studying anatomic convergences and cross-species comparisons of function. Such a functional conceptualization of the equine navicular apparatus resolves confusion about the diagnosis of navicular syndrome and offers insights for the development of mechanically based therapies. Through comparison with the human Achilles complex, this review (1) re-conceptualizes the equine navicular apparatus as an enthesis organ in which mechanical forces are distributed throughout the structures of the organ; (2) describes the relationship between failure of the navicular enthesis organ and lesions of navicular syndrome; (3) considers the therapeutic implications of navicular enthesis organ degeneration as a form of chronic osteoarthritis; and based upon these implications (4) proposes a focus on whole body posture/motion for the development of prehabilitative and rehabilitative therapies similar to those that have already proven effective in humans.

Navicular Syndrome-related changes to collagen proportion of different cross-sections of the flexor tendons in equine distal forelimb

The aim of this study was to quantify the distribution of aligned and non-aligned collagen in cross-sections of the superficial digital flexor tendon (SDFT) and deep digital flexor tendon (DDFT) in different levels of the distal forelimb of equines diagnosed with NS (Navicular Syndrome). Sixty equine forelimbs were collected. Was compared two groups (NA, Not affected vs. NS-group) by t-Student. Diagnosis of NS was based on clinical and lameness examination, diagnostic analgesia and radiological findings. The proportion of aligned and non-aligned collagens at 2 levels for the SDFT and 3 levels for the DDFT were measured by histochemical stains. The amount of aligned and non-aligned collagen in tendons were calculated using Colour-Based Segmentation function. Regarding collagen, there were significant differences in the amount of aligned collagen (NA: 21.2 ± 1.31; NS-group: 12.2 ± 4.67; p = 0.0026) and non-aligned collagen (NA: 21.8 ± 2.22; NS: 25.1 ± 1.73; p = 0.0241) at the DDFT insertion in the distal phalanx. We concluded that the flexor tendons of the forelimb in equines with NS have different proportions of collagen than those that do not present the diagnosis, indicated by histologically visible increased proportions of non-aligned collagen and decreased of aligned collagen in the extracellular matrix.

Oral Supplementation with Ultramicronized Palmitoylethanolamide for Joint Disease and Lameness Management in Four Jumping Horses: A Case Report

Simple Summary

This paper reports the efficacy of Ultramicronized Palmitoylethanolamide (PEA-um) supplementation for four show-jumping horses with lameness and joint disease. Joint disease is often associated with inflammatory states and pain that lead to lameness or impairment in athletic performances. PEA-um is a nutraceutical compound that is well-known for its anti-inflammatory and analgesic proprieties, and is widely used in human medicine and small animal veterinary medicine. Although it includes a small number of cases, our study describes for the first time the efficacy of the use of PEA-um in horses. PEA-um was introduced to the normal diet of four horses with non-responsive lameness and significant impairment of athletic performance. After four months of PEA-um supplementation, all horses showed remissions of lameness that led to their reintroduction into showjumping competitions without disease recurrence. Therefore, despite the small number of cases included in this study, the observations suggest that PEA-um may be beneficial in the maintenance of joint disease in athletic horses.

Abstract

Background: Four show jumping horses were evaluated for non-responsive lameness, which caused their withdrawal from show jumping competitions. The clinical evaluation was performed by radiographic examination, flexion tests, diagnostic anesthesia and lameness evaluation using the American Association of Equine Practitioners (AAEP) scale. The diagnoses were a case of navicular syndrome, a complicated case of chronic navicular syndrome and arthrosis of the distal interphalangeal joint of the right anterior limb and two cases of distal intertarsal joint arthritis. Nutraceuticals are often an important management strategy or coadjutant of pharmacological therapies in joint disease. Ultramicronized Palmitoylethanolamide (PEA-um) is an endogenous fatty acid amide that is well-known for its anti-inflammatory and analgesic proprieties widely used in human medicine and small animal veterinary medicine. Although it includes a small number of cases, our study describes for the first time the efficacy of the use of PEA-um in horses. The four horses with non-responsive lameness and significant impairment in athletic performance were daily treated with PEA-um into their normal diet. After four months of PEA-um supplementation, all horses showed remissions of lameness that led to their reintroduction into showjumping competitions without disease recurrence. Therefore, despite the small number of cases included in this study, these observations suggest a good prospective for developing a controlled experiment to test PEA in a larger cohort of horses.

Is the T-ligament a ligament? A histological study in equine cadaver forelimbs

Foot pain is a frequent cause of lameness in horses and can involve multiple structures within the hoof. The T-ligament (an anatomical structure connecting the synovium of the distal interphalangeal joint, the digital flexor tendon sheath and the navicular bursa) is poorly described. Five pairs of equine cadaver distal forelimbs were collected from a slaughterhouse. Sagittal sections (medial, middle and lateral) were obtained and processed with Haematoxylin Eosin Safran, Unna's Orcein, and Picrosirius red stains. Histological assessment revealed that the T-ligament was covered by the surrounding synovia of the distal interphalangeal joint, the digital flexor tendon sheath and the navicular bursa. Its collagen content was lower (30.01%±10.15) than that of the collateral sesamoidean ligament (89.48%±5.8; P = .0008) and the middle phalanx (85.72%±3.67; P = .0008). Under polarized light microscopy, it showed a slight heterogeneous pattern of birefringence, with angle-related changes. Elastic fibres were more numerous (21.76%±8.72) than in the collateral sesamoidean ligament (0.28%±0.45), or deep digital flexor tendon (0.04%±0.02); and were more densely packed. Mean cell count was higher for the T-ligament than for other tissues (P = .0007). Blood vessels were identified in the T-ligament and were penetrating the deep digital flexor tendon (8/10 limbs, 5/5 horses). In conclusion, the T-ligament looked like a vinculum for the deep digital flexor tendon, with a central elastic core, surrounding loose connective tissue and blood vessels. It is not a ligament. Its clinical relevance still needs to be determined.

Standing MRI lesions of the distal interphalangeal joint and podotrochlear apparatus occur with a high frequency in warmblood horses

Foot pain is a common presenting complaint in Warmblood horses. The aim of this retrospective, cross-sectional study was to determine the spectrum of foot lesions detected by magnetic resonance imaging (MRI) in Warmblood horses used for dressage, jumping, and eventing. The medical records of 550 Warmblood horses with foot pain that were scanned using standing MRI were reviewed and the following data were recorded: signalment, occupation, lameness, diagnostic analgesia, imaging results, treatments, and follow-up assessments. Associations between standing MRI lesions and chronic lameness following treatment were tested. Abnormalities of the navicular bone (409 horses, 74%), distal interphalangeal joint (362 horses, 65%), and deep digital flexor (DDF) tendon (260 horses, 47%) occurred with the highest frequency. The following abnormalities were significantly associated (P < .05) with chronic lameness following conservative therapy: moderate to severe MRI lesions in the trabecular bone of the navicular bone, mild or severe erosions of the flexor surface of the navicular bone, moderate sagittal/parasagittal DDF tendinopathies, and moderate collateral sesamoidean desmopathies. Also, identification of concurrent lesions of the DDF tendon, navicular bone, navicular bursa, and distal sesamoidean impar ligament was associated with chronic lameness after conservative therapy. Development of effective treatment options for foot lesions that respond poorly to conservative therapy is necessary.

Factors associated with euthanasia in horses and ponies enrolled in a laminitis cohort study in Great Britain

Euthanasia is a complex topic, with animal owners using multiple factors to shape their decision-making process. Previous epidemiological studies have described causes of equine mortality in specific populations, but there is limited evidence regarding factors contributing specifically to equine euthanasia in Great Britain (GB). This observational study used a prospective cohort design: the objectives were to describe owner-reported reasons for euthanasia, estimate the rate of euthanasia and identify associated factors in horses/ponies enrolled in a web-based epidemiological study of laminitis in GB. Self-selected horse/pony owners submitted regular management and health data over 29 months and reported dates and reasons for euthanasia during this period. The overall incidence of euthanasia was estimated and associated factors were identified using multivariable Cox regression modelling, adjusted for age, with variables retained in the final model if P ≤ 0.05. Data were available for 1070 horses/ponies contributing 1093 horse-years at risk (HYAR), with 80 owner-reported euthanasias. The incidence of euthanasia was 7.3 euthanasias per 100 HYAR (95 % confidence interval [CI] 5.9, 9.1). The most frequently reported health reasons contributing to euthanasia were laminitis-related consequences (25.0 % ; CI 16.8, 35.5 %), colic (21.3 % ; CI 13.7, 31.4 %), non-laminitic lameness (20.0 % ; CI 12.7, 30.1 %) and age-related deterioration, including owner-perceived compromised quality of life (20.0 % ; CI 12.7, 30.1 %). Health-related factors associated with significantly higher rates of euthanasia were colic (hazard ratio [HR] 26.4; CI 12.5, 55.8), pituitary pars intermedia dysfunction (HR 3.0; CI 1.7, 5.4) and lameness due to navicular syndrome (HR 5.9; CI 1.8, 20.0), soft tissue injury (HR 6.5; CI 2.7, 15.6) or laminitis (HR 2.7; CI 1.3, 5.7). Further factors included being pure bred (HR 1.7; CI 1.0, 2.8), female (HR 1.7; CI 1.0, 2.9), having poor owner-perceived hoof quality (HR 2.4; CI 1.1, 5.2), being entirely stabled (HR 5.0; HR 2.1, 12.0), being on loan or under temporary care of the study participant (HR 2.3; CI 1.2, 4.4) and participating in affiliated or professional competitions (HR 5.9; CI 2.4, 14.8). Euthanasia rates were significantly higher in the first two study years compared to the third (P < 0.001). Animals whose owners used the study's custom-designed weight tracker tool had significantly lower rates of euthanasia (HR 0.6; CI 0.3, 0.95). This study has identified a number of, arguably preventable, health-related factors associated with higher rates of euthanasia. Data on owners' decision-making process regarding euthanasia, including emotive and financial impacts, were not recorded but are important contributors to euthanasia that require better understanding.

Clinical efficacy of clodronic acid in horses diagnosed with navicular syndrome: A field study using objective and subjective lameness evaluation

Navicular syndrome, a common cause of equine forelimb lameness, is associated with pathological changes in the navicular bone. Consequently, administration of bisphosphonates (BPs) has been advocated in order to modify the rate of bone turnover. The present study aimed to assess the clinical efficacy of intramuscularly administered clodronic acid for the treatment of 11 horses with clinical and radiographic findings compatible with navicular syndrome. Magnetic resonance imaging was performed in 5 of the 11 horses. The animals were treated with an intramuscular dose of clodronic acid of 765 mg/horse, administered over three separate injection sites. Before and at 7, 30 and 90 days after treatment, horses were subjected to lameness and accelerometric evaluations. A clinical improvement was observed in 6 of the 11 horses. These 6 horses showed a mean reduction of two degrees in lameness score. Accelerometry in these horses revealed increased velocity, stride length, stride regularity and dorsoventral displacement of the gravity of centre together with a reduction in stride frequency, suggesting a gait improvement. This study demonstrates that intramuscular clodronic acid can be useful for lameness reduction in some horses with navicular syndrome.

Response of three digital anesthetic technics in horses with forelimb hoof lameness

ABSTRACT The presented study aimed to assess objectively the response of distal interphalangeal joint (DIJ), navicular bursa (NB) and deep digital flexor tendon sheath (DDFTS) anesthesia in horses with forelimb hoof lameness; and evaluate if the presence of radiographic abnormalities on navicular bone could interfere on blocks’ results. Fifteen horses with lameness improvement above 70% after palmar digital nerve (PDN) block were selected for this study. Blocks were assessed separately on five consecutive trials at seven different time-points. The fifth trial was performed to evaluate the influence of exercise on preexisting lameness. Most of horses (73.33%) presented pain related to the podotrochlear apparatus based on clinical and lameness exam and blocks’ responses. NB and DIJ anesthesia differed on the frequency of horses with lameness improvement above 70% only at 10min (p=0.03), and both differed from DDFTS block until 30’(p<0.05). The blocks’ response was variable along the time and the highest means for NB, DIJ and DDFTS were observed at 5-10 minutes (’), 15-20’ and 10-15’ respectively.Exercise had low interference on lameness intensity since no improvement above 50% was observed and an increase on lameness intensity over time was identified in seven horses. Variable grades of navicular bone radiographic lesions were observed in 14 horses, although these lesions had no interference on blocks’ response (p>0.05). The NB and DIJ blocks had similar responses and both were superior to DDFTS anesthesia, coincident with a major prevalence of podotroclear apparatus abnormalities in this equine population.