Clinical presentation, diagnosis, and prognosis of chronic laminitis

Radiographic and Venographic Appearance of Healthy and Laminitic Feet in Amiata Donkeys

Introduction: Laminitis is a debilitating disorder resulting in irreversible anatomical changes in the feet of equids. Assessing specific anatomical features through radiography and venography provides diagnostic and prognostic information. The reference ranges are well-established in horses, but not in donkeys. It is also uncertain as to whether these ranges can be applied to every donkey breed. The present study characterizes the radiological and venographic hoof anatomy of healthy feet of Amiata donkeys and defines the changes associated with severe and mild laminitis. Materials and Methods: A total of 16 forefeet were evaluated in 8 Amiata jennies. The animals underwent musculoskeletal examination, Obel grading assessment and radiological evaluation. Based on clinical examination and radiographic findings, the forefeet were grouped as healthy, mild or severe laminitic feet, thus the digital venograms were performed according to the group definition. Results: Radiology revealed 7/16 healthy, 4/16 mild laminitic, and 5/16 severe laminitic forefeet. Statistical analysis showed differences between the healthy and laminitic forefeet for the dorsal angle (p < 0.0001) and angle of solar aspect (p < 0.0001) of the distal phalanx, for deviation between dorsal aspect of distal phalanx and the hoof wall (p < 0.0001) and phalangeal rotation angle (p = 0.0032). Venography was abnormal in mild and severe laminitic forefeet. In particular, the vascularization was reduced or absent at the lamellar-circumflex junction dorsally, at the sub-lamellar vascular bed and at the circumflex veins. Coronary plexus vascularization was absent in severe laminitic forefeet. Discussion and Conclusions: This study provides the radiological parameters for the assessment of healthy and laminitic forefeet of Amiata donkeys. The mild laminitic foot venogram showed decreased vascularization mainly on lamellar-circumflex junction and sub-lamellar vascular bed, in latero-medial views. The severe laminitic foot showed very poor or absent vascularization in multiple areas. The technique is easily applicable and provides diagnostic support in laminitis.

Hoof kinetic patterns differ between sound and laminitic horses

BACKGROUND

No kinetic data on hoof loading in laminitic horses are available, despite their importance for optimising supportive shoeing therapies.

OBJECTIVES

To quantify the load distribution pattern in laminitic and sound horses.

STUDY DESIGN

Controlled observational study.

METHODS

Fifty-four sound and laminitic horses were assigned to three groups: control group (sound horses), group 1 (G1) horses with acute laminitis, evaluated immediately after acute clinical signs subsided, and group 2 (G2) horses that had been free of acute laminitis signs for 6-12 weeks. Measurements on both forelimbs in barefoot condition were performed during walk using the Hoof^™ System. Kinetic parameters were recorded and compared between hoof regions and groups using covariance analyses and t tests (P < .05).

RESULTS

Peak loading in the toe region occurred during midstance phase in control group, but during break-over in laminitic horses. This is reflected by the time to peak vertical force in the toe, which was significantly shorter in the control group compared to laminitic horses (G1 and G2) (76% ± 6% vs 89% ± 9 [P = .002], 86% ± 7 [P = .001] of stance duration respectively). The relative vertical force in the toe in the control group (46% ± 7%) was significantly higher compared to laminitic horses (G1: 29% ± 9% [P = .001]; G2: 32% ± 10% [P = .003]). The main shift of the load occurred between toe and middle hoof regions in laminitic horses as compared with the control group. No significant differences were found between G1 and G2.

MAIN LIMITATIONS

Measurements were not obtained in horses with acute laminitis on admission, to avoid risk of further damage to the lamellae.

CONCLUSIONS

Supportive therapy in laminitis should focus on supporting both caudal and middle hoof areas to decrease the peak pressure in these regions, and ease break-over during which the maximal loading of the toe occurs.

Case-control study of risk factors for pasture-and endocrinopathy-associated laminitis in North American horses

OBJECTIVE To investigate risk factors for the development of pasture- and endocrinopathy-associated laminitis (PEAL) in horses and ponies in North America. DESIGN Case-control study. ANIMALS 199 horses with incident cases of PEAL and 351 horses from 2 control populations (healthy horses [n = 198] and horses with lameness not caused by laminitis [153]) that were evaluated in North America between January 2012 and December 2015 by veterinarian members of the American Association of Equine Practitioners. PROCEDURES North American members of the American Association of Equine Practitioners were contacted to participate in the study, and participating veterinarians provided historical data on incident cases of PEAL, each matched with a healthy control and a lameness control. Conditional logistic regression analysis was used to compare data on PEAL-affected horses with data on horses from each set of controls. RESULTS Horses with an obese body condition (ie, body condition score ≥ 7), generalized or regional adiposity (alone or in combination), preexisting endocrinopathy, or recent (within 30 days) glucocorticoid administration had increased odds of developing PEAL, compared with horses that did not have these findings. CONCLUSIONS AND CLINICAL RELEVANCE The present study identified several risk factors for PEAL that may assist not only in managing and preventing this form of laminitis, but also in guiding future research into its pathogenesis.

Decision-tree analysis of clinical data to aid diagnostic reasoning for equine laminitis: a cross-sectional study

The objective of this cross-sectional study was to compare the prevalence of selected clinical signs in laminitis cases and non-laminitic but lame controls to evaluate their capability to discriminate laminitis from other causes of lameness. Participating veterinary practitioners completed a checklist of laminitis-associated clinical signs identified by literature review. Cases were defined as horses/ponies with veterinary-diagnosed, clinically apparent laminitis; controls were horses/ponies with any lameness other than laminitis. Associations were tested by logistic regression with adjusted odds ratios (ORs) and 95% confidence intervals, with veterinary practice as an a priori fixed effect. Multivariable analysis using graphical classification tree-based statistical models linked laminitis prevalence with specific combinations of clinical signs. Data were collected for 588 cases and 201 controls. Five clinical signs had a difference in prevalence of greater than +50 per cent: 'reluctance to walk' (OR 4.4), 'short, stilted gait at walk' (OR 9.4), 'difficulty turning' (OR 16.9), 'shifting weight' (OR 17.7) and 'increased digital pulse' (OR 13.2) (all P<0.001). 'Bilateral forelimb lameness' was the best discriminator; 92 per cent of animals with this clinical sign had laminitis (OR 40.5, P<0.001). If, in addition, horses/ponies had an 'increased digital pulse', 99 per cent were identified as laminitis. 'Presence of a flat/convex sole' also significantly enhanced clinical diagnosis discrimination (OR 15.5, P<0.001). This is the first epidemiological laminitis study to use decision-tree analysis, providing the first evidence base for evaluating clinical signs to differentially diagnose laminitis from other causes of lameness. Improved evaluation of the clinical signs displayed by laminitic animals examined by first-opinion practitioners will lead to equine welfare improvements.

Treating laminitis: beyond the mechanics of trimming and shoeing

Laminitis is typically classified into developmental or prodromal, acute, subacute, and chronic phases. Scientific evidence regarding the pathophysiology of laminitis does exist, but it is often conflicting and dependent on the clinician's interpretation/understanding of the study or the model used for inducing laminitis. The diagnosis of laminitis consists of obtaining an accurate history, performing a thorough physical examination, and taking good-quality radiographs. The use of radiographs for diagnosis and interpretation of laminitis is an absolute necessity for the clinician. Laminitis is one disease that requires the assembly of a team consisting of the veterinarian, the farrier, and the owner to be successfully treated.

Risk factors for equine laminitis: a systematic review with quality appraisal of published evidence

Epidemiological studies into the risk factors for naturally-occurring equine laminitis are limited. There are a small number of such studies, although the results are inconsistent and remain disputed. The reasons for the conflicting results remain unclear. The aim of this review was to critically evaluate previous research in order to identify publications which provide the best evidence of risk factors for naturally-occurring equine laminitis. A systematic review of English language publications was conducted using MEDLINE (1950-2010), CAB Direct (1910-2010) and IVIS (1997-2010). Additional publications were included by searching bibliographies. Search terms included laminitis, equine, risk factors and epidemiology. Publications which compared a case population to a control population and made inferences about parameters as risk factors for naturally-occurring equine laminitis were included. Information was extracted using predefined data fields, including 18 study quality indicators. In total, 17 publications were fully appraised. Six were considered to provide the most reliable information about risk factors for naturally-occurring laminitis. Information on signalment was well researched and there was good evidence for an association with chronic laminitis and increasing age. There remain inconsistent results for many other horse-level risk factors including gender, breed and bodyweight. Previous publications estimating risk factors for equine laminitis were of reasonable quality, although they were limited in the number and scope of the risk factors studied. High-quality, evidence-based studies are needed to identify further risk factors and to establish consensus over previously identified risk factors for different equine populations.

Neuropathic changes in equine laminitis pain

Laminitis is a common debilitating disease in horses that involves painful disruption of the lamellar dermo-epidermal junction within the hoof. This condition is often refractory to conventional anti-inflammatory analgesia and results in unremitting pain, which in severe cases requires euthanasia. The mechanisms underlying pain in laminitis were investigated using quantification of behavioural pain indicators in conjunction with histological studies of peripheral nerves innervating the hoof. Laminitic horses displayed consistently altered or abnormal behaviours such as increased forelimb lifting and an increased proportion of time spent at the back of the box compared to normal horses. Electron micrographic analysis of the digital nerve of laminitic horses showed peripheral nerve morphology to be abnormal, as well as having reduced numbers of unmyelinated (43.2%) and myelinated fibers (34.6%) compared to normal horses. Sensory nerve cell bodies innervating the hoof, in cervical, C8 dorsal root ganglia (DRG), showed an upregulated expression of the neuronal injury marker, activating transcription factor-3 (ATF3) in both large NF-200-immunopositive neurons and small neurons that were either peripherin- or IB4-positive. A significantly increased expression of neuropeptide Y (NPY) was also observed in myelinated afferent neurons. These changes are similar to those reported in other neuropathic pain states and were not observed in the C4 DRG of laminitic horses, which is not associated with innervation of the forelimb. This study provides novel evidence for a neuropathic component to the chronic pain state associated with equine laminitis, indicating that anti-neuropathic analgesic treatment may well have a role in the management of this condition.

Evaluation Using Hoof Wall Strain Gauges of a Therapeutic Shoe and a Hoof Cast with a Heel Wedge as Potential Supportive Therapy for Horses with Laminitis

OBJECTIVE

To evaluate using strain gauges, a hoof cast with heel wedge, and a therapeutic shoe with unsupported toe for their effectiveness in redistribution of load from the dorsal hoof wall.

STUDY DESIGN

In vitro biomechanical study.

SAMPLE POPULATION

Twenty forelimb specimens.

METHODS

Rosette strain gauges were placed on the dorsal and lateral hoof wall of 20 normal shaped hooves. Limbs were loaded vertically using a tensile testing machine with a 1 Hz sinusoidally cycling load up to 3000 N during 15 seconds. Mean values of principal strain and direction at 2500 N load were calculated for 3 experimental conditions (unshod, therapeutic shoe with unsupported toe, and hoof cast with heel elevation) and tested by ANOVA (P<.05).

RESULTS

Vertical limb loading in an unshod hoof leads to a biaxial compression of the dorsal wall with high longitudinal compression (epsilon2 = -1515 microm/m). Principal strain at the dorsal wall (epsilon2) was decreased by 23% with the therapeutic shoe and by 59% with the hoof cast. On the lateral hoof wall principal strain was unchanged with the shoe, but increased by 34% with the cast.

CONCLUSIONS

Strain measurements indicate unloading of the dorsal hoof wall by both methods with the cast being more effective than the shoe.

CLINICAL RELEVANCE

The hoof cast with wedge offers substantial unloading of the dorsal wall, but increases load on the quarter. Therefore a hoof cast would likely be most helpful in acute laminitis when palmar structures can still bear load. The therapeutic shoe offers rehabilitation and regrowth of the dorsal wall without increased load on the quarter wall.

Short-term effect of therapeutic shoeing on severity of lameness in horses with chronic laminitis

OBJECTIVE

To evaluate the short-term effects of 4 therapeutic shoeing systems on lameness and voluntary limb-load distribution in horses with chronic laminitis.

ANIMALS

10 horses with chronic laminitis.

PROCEDURES

A clinical trial was conducted that used a concurrent control, crossover design to evaluate the relative effectiveness of a standard flat shoe, fullered egg-bar shoe, heart-bar shoe, and modified equine digital support system to alleviate chronic lameness in horses. Therapeutic success was assessed during a 7-day period by use of subjective (Obel grade and clinical score) and objective (force-plate data) evaluations.

RESULTS

Comparison of pretreatment and intertreatment control data indicated that disease status of the horses did not change during the course of the study. None of the therapeutic shoeing treatments used resulted in a significant change in severity of lameness.

CONCLUSIONS AND CLINICAL RELEVANCE

Results were interpreted to imply that substantial clinical improvement should not be expected during the first 7 days after therapeutic shoeing for the specific shoes tested in this study. On the basis of our results, we hypothesize that when used as the lone indicator of therapeutic success, severity of lameness may not be a valid indicator.

Laminitis in the geriatric horse

There are few diseases that instill a comparable sense of doom in the mind of a treating veterinarian as laminitis. There is a feeling of cautious optimism when a horse with laminitis responds favorably to treatment. Although this optimism all too often proves false when treating laminitic patients, management of the patient afflicted with chronic laminitis can be rewarding. Through diligent and careful client communication and instruction, many geriatric patients with chronic laminitis can be maintained for years as comfortable companions, for light riding use, or as productive breeding animals.

A gross and histopathological study of an ectopic white line development in equine laminitis

In horses with chronic laminitis, an abnormal horny structure called lamellar wedge, is generated between the hoof wall and the laminar epidermis. To be able to manage horses with chronic laminitis correctly, more information about the pathological state of this abnormal horn is required. The aim of this study was to collect and analyze objective morphological data about the abnormal horn in order to understand its morphology and development. In the study, the abnormal horn was grossly visible on the sagittal hoof section from approximately 20 days after the onset of disease. In the histological observations, the structural characteristics of this abnormal horn were similar to the white line tissue, suggesting it is an ectopic white line. Mean value of the cross-sectional area of the abnormal horn against the distal phalanx section area (A/D) was 0.29 cm(2) SD +/- 0.14 and it finally showed an eight-fold increase over the mean value of normal white line section area against the distal phalanx section area. In conclusion, a large amount of the ectopic white line is thought to be finally able to inhibit normal hoof wall growth, so that it should be resected at the optimum time when would be after one month from the onset of the disease.

Voluntary limb-load distribution in horses with acute and chronic laminitis

OBJECTIVES

To compare limb-load distribution between horses with and without acute or chronic laminitis.

ANIMALS

10 horses with carbohydrate-induced acute laminitis, 20 horses with naturally occurring chronic laminitis, and 20 horses without foot abnormalities (controls).

PROCEDURES

Limb-load distribution was determined, using a custom-designed system that allowed simultaneous quantification of the mean percentage of body weight voluntarily placed on each limb (ie, mean limb load) and the SD of the mean load over a 5-minute period (ie, load distribution profile [LDP]). Load distribution profile was used as an index of frequency of load redistribution.

RESULTS

Mean loads on fore- and hind limbs in control horses were 58 and 42%, respectively, and loads were equally and normally distributed between left and right limbs. In addition, forelimb LDP was greater, compared with hind limbs, and was affected by head and neck movement. In comparison, limb-load distribution in horses with chronic laminitis was characterized by an increase in the preferential loading of a forelimb, a decrease in total forelimb load, and an increase in LDP that was correlated with severity of lameness. In horses with carbohydrate-induced acute laminitis, mean limb loads after onset of lameness were not different from those prior to lameness; however, LDP was significantly decreased after onset of lameness.

CONCLUSION AND CLINICAL RELEVANCE

Quantification of limb-load distribution may be an applicable screening method for detecting acute laminitis, grading severity of lameness, and monitoring rehabilitation of horses with chronic laminitis.