Which anatomical region determines a positive flexion test of the distal aspect of a forelimb in a nonlame horse?

REASONS FOR PERFORMING STUDY: The flexion test is used routinely as part of lameness and prepurchase examinations. However, little is known about the mechanisms that cause a positive response to a flexion test. OBJECTIVE: To determine which anatomical regions play a role in a positive outcome of a flexion test of the distal aspect of a forelimb in a nonlame horse. METHODS: Eight clinically sound Dutch Warmblood horses were subjected to a standardised flexion test (force 250 N, time 60 s) inducing a consistent lameness. To discriminate between different areas of the distal aspect of a forelimb, effects of various nerve blocks on the outcome of the flexion test were investigated. Low palmar digital, palmar at the abaxial aspects of the base of the proximal sesamoids, high palmar, ulnar and low 4-point nerve blocks were performed. Flexion test induced lameness was scored before and after each nerve block in separate sessions. RESULTS: The low palmar digital nerve blocks and nerve blocks of the palmar nerves at the abaxial aspect of the base of the proximal sesamoid bones had no significant effect on the flexion test induced lameness score. The ulnar, high palmar and, most dramatically, the low 4-point nerve blocks all caused a significant (P<0.05) reduction in the flexion test induced lameness score. CONCLUSIONS: Anatomical structures (soft tissue nor synovial structures) located distal to the metacarpophalangeal joint appear to contribute only minimally to the outcome of a positive flexion test of the distal aspect of a forelimb in a clinically nonlame horse. The structures in the region of, and including, the metacarpophalangeal joint appear to contribute most to a positive flexion test of the distal aspect of a forelimb in a nonlame horse. POTENTIAL RELEVANCE: The flexion test of the distal aspect of a forelimb may be sensitive for investigating the metacarpophalangeal joint region in horses free from lameness, but may be less relevant for structures distal to this region.

[Rectal tears in the horse: two case reports]. / Rectumbeschadigingen bij het paard: twee casus.

Rectal tears occur incidentally and often have a poor prognosis. Early recognition of the problem and adequate therapy determine the outcome. The history, clinical examination, therapy, and outcome of two horses with grade IIIb and grade IV rectal tears are discussed.

A study on the pathogenesis of equine sesamoiditis: the effects of experimental occlusion of the sesamoidean artery.

In this study the potential role of circulatory disturbances in the pathogenesis of sesamoiditis was investigated by studying the clinical and histological effects of experimental occlusion of the sesamoidean artery, which is the main nutrient artery of the proximal sesamoid bone (PSB). For this purpose, five adult Dutch Warmblood horses were used in which the sesamoidean artery was occluded with polyvinyl alcohol foam particles. Bone labelling was carried out with oxytetracycline and calcein. All animal were checked clinically three times a week and radiographically at days 14, 21, 28 and 35. At day 35 the animals were killed and the fetlock was dissected and macroscopically evaluated. The PSBs were isolated and radiographed and the soft tissues adjacent to the abaxial side of the PSBs were histologically examined [routine histology and for the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP)]. The PSBs were divided into bony slices which were radiographed and evaluated histologically (routine, SP, CGRP, fluorescence). All horses showed a slight lameness that gradually diminished. Radiographically enlarged vascular channels were seen in only one horse. Histological data showed that on average 60% (range 37-89%) of the total area had been deprived of vascularization. In two horses an increase in the extent of the arterial network from the basal side of the PSB was seen. Only in the horse with the greatest extent of occlusion were bone necrosis and a reactively increased uptake of fluorochromes adjacent to the occluded arteries found. Bone density did not change. The distribution of neuropeptides in the surrounding soft tissues was not affected by the occlusion. From this study, it can be concluded that a large part of the arterial supply to the PSB can be interrupted without provoking histological and/or radiographic changes that are consistent with clinical sesamoiditis. Therefore, it seems very improbable that circulatory disturbances are a primary aetiopathogenic factor in the disease.

Influence of exercise on bone mineral density of immature cortical and trabecular bone of the equine metacarpus and proximal sesamoid bone.

Bone mineral density (BMD) and cross-sectional area (CSA), measured using peripheral quantitative computed tomography, were determined in the left third metacarpal bone (MCIII) and left medial proximal sesamoid bone (psb) in 3 differently exercised groups of foals. Group(box) (n = 14) was confined to a box stall from birth to age 5 months, Group(training) (n = 14) was kept in similar box stalls but additionally given a daily exercise programme consisting of an increasing number of gallop sprints and Group(pasture) (n = 15) remained at pasture. At 5 months of age, 8 foals from each group were randomly selected and subjected to euthanasia, the remaining 19 foals were given an identical light exercise regimen for an additional 6 months and were killed at age 11 months. In MCIII CSA increased with age and was also significantly (P<0.05) larger in Group(pasture) compared to Group(box) at age 5 months. At 11 months this difference had disappeared. In the dorsal cortex, BMD was significantly (P<0.05) higher in Group(box) than in both other groups. At age 11 months all significant differences had disappeared. In the psb, CSA increased with age, but there were no differences between the exercise groups. At the apical level, trabecular BMD was higher in Group(training) than in Group(box) and Group(pasture) (P<0.001 and P<0.01, respectively). At 11 months, trabecular BMD in the foals that had belonged to Group(training) was less than in the foals that had belonged to Group(box) (P<0.05). It is concluded that box-rest during the first months of life results in a retardation of normal development which is compensated for when the restriction on exercise is lifted. Exercise during the first months of life induces an increase in CSA in the third metacarpal bone. In the psb exercise increases BMD, principally in trabecular bone. There is an indication that the specific training regimen used in this study led to an overstimulation of the bone resulting in less active mineral deposition in the longer term.

Innervation of the equine mature and immature proximal sesamoid bone by calcitonin gene-related peptide and substance P-containing nerves.

OBJECTIVE: To localize and determine relative frequency of occurrence of calcitonin gene-related peptide (CGRP) and substance P (SP) fibers in the proximal sesamoid bones (PSB) and adjacent structures in sound horses. SAMPLE POPULATION: 4 foals and 3 adult horses. PROCEDURE: Medial PSB and adjacent ligaments of both forelimbs were collected, flushed, and fixed in buffered 4% formalin. The left PSB were cut into 5 longitudinal, sagittally oriented slabs, and the right PSB were cut into 5 transverse slabs. After decalcification in EDTA, slices were transferred to a 30% sucrose solution, deep frozen, sectioned (80 microm), and stored in Tris-buffered saline solution for free-floating immunocytochemical processing, staining of which was performed by use of the peroxidase-antiperoxidase method with polyclonal rabbit antibodies against CGRP and SP. Sections were examined by light microscopy. RESULTS: Calcitonin gene-related peptide and SP fibers were present throughout the PSB; in ligaments, they were concentrated at the attachment sites. Presentation of the fibers, the innervation pattern, and intensity in the bones of horses differed from that in foals, in which the fibers were more delicate and frequency of occurrence was lower. In horses, innervation with CGRP and SP fibers was more dense in the periphery of the bone, whereas in foals, local difference in innervation of the bone was not evident. With the exception of the intersesamoidean ligament, ligaments were more richly innervated than was bone. CONCLUSION: Presence of the nociceptive peptides CGRP and SP indicated that the PSB and, more practically, the adjacent ligaments are sensitive structures.

Experimental model of synovitis/capsulitis in the equine metacarpophalangeal joint.

OBJECTIVE: To develop and define a model of acute synovitis/capsulitis in the equine metacarpophalangeal joint (fetlock) to study clinical effects of diagnostic or therapeutic procedures. ANIMALS: 5 adult Standardbreds. PROCEDURE: Polyvinyl alcohol foam particles were injected into the left front fetlock of horses; the right front fetlock was used as a control. Horses were examined clinically and for lameness on a regular basis. Blood samples were taken to measure routine variables. Synovial fluid samples were collected from both fetlocks, and macroscopic, microscopic, and biochemical variables were measured. The effects of local diagnostic nerve blocks and intra-articular anesthesia of the fetlock on ensuing lameness were determined on days 2 and 3. After macroscopic evaluation at necropsy, histologic examination was performed on the fetlock cartilage and capsule. RESULTS: Changes in synovial fluid variables included increased TNF-alpha and matrix metalloproteinases values and in other indicators of acute inflammation. With respect to application of local nerve blocks, lameness decreased most after a combination of metacarpal and palmar nerve blocks, whereas lameness could only partially be blocked by intra-articular anesthesia. At necropsy, mild chronic inflammation of the synovium and deeper layers of the joint capsule was found; polyvinyl alcohol particles had been incorporated into the joint capsule. There was no evidence of articular cartilage damage. CONCLUSIONS: Injection of polyvinyl alcohol foam particles induces transient synovitis/capsulitis in the fetlock, mimicking clinical joint disorders. The model does not seriously affect the horse's long-term wellbeing. Such model serves well for studying the effect of diagnostic or therapeutic procedures.

[The proximal sesamoid bone of the horse; vascular and neurologic characteristics]. / Het proximale sesambeen bij het paard; vasculaire en neurologische kenmerken.

Sesamoiditis is characterized clinically by repeated lameness and radiologically by changes in the proximal sesamoid bones. This thesis, which was defended in June 1997, investigated two characteristics of sesamoiditis, namely the arterial blood supply and the innervation of the proximal sesamoid bones, in order to gain more insight into the etiopathogenesis of sesamoiditis. Experiments with patient material showed that the proximal sesamoid bones have an enormous arterial reserve, due in part to the formation of an arterial shift. Moreover, the sesamoid bones have their own sensory innervation, provided by a branch of the medial and lateral palmar nerve. This branch is called the sesamoid nerve in this article. A special technique was developed to anaesthetize this nerve and can be used for further differentiation of pastern lameness. That the sesamoid bones are sensitive to pain was demonstrated by detection of the so-called nociceptive neuropeptides, substance P and calcitonin gene-related peptide, which are specifically involved in pain sensation. However, the adjacent ligament appear to be even more sensitive. The etiopathogenesis of sesamoiditis is discussed, as are a number of clinical implications of pain in the sesamoid bones. A number of potential future developments are mentioned.

The diagnostic nerve block of the sesamoidean nerve: desensitized structures and possible clinical applications.

The sesamoidean nerve branches from the palmar nerve and runs towards the proximal sesamoid bone. To study the structures innervated by this nerve, a technique for blocking it was developed. The effect of this nerve block was determined in ponies with an induced lameness located in the lateral proximal sesamoid bone (5 ponies) or in the distal part of the lateral branch of the suspensory ligament (5 ponies), and in 10 horses with clinical sesamoidosis. A lameness provoked by the implantation of an expansion plug in the proximal sesamoid bone could, to a large extent, be anaesthetized by a sesamoidean nerve block. However, lameness due to a local tendonitis in the lateral branch of the suspensory ligament, was only partially eliminated by a sesamoidean nerve block. In horses with sesamoidosis the lameness improved, on average, by about 30%. It is concluded that the sesamoidean nerve contains sensory fibres that innervate the proximal sesamoid bone. The sesamoidean nerve block is highly specific for pain originating from the proximal sesamoid bone including the adjacent distal part of the extensor branch of the suspensory ligament. In horses suffering from sesamoidosis the main source of pain appears not to be located in the proximal sesamoid bone. The specificity of the sesamoidean nerve block makes it a useful technique for differentiating the site of a lameness located in the fetlock area.

The arterial shift features in the equine proximal sesamoid bone.

Sesamoidosis in horses is characterised by lameness and radiographic changes in the proximal sesamoid bones and the aetiology is attributed to either mechanical factors or circulatory disturbances. In this study arteriograms of proximal sesamoid bones were investigated in 17 lame patients suffering from sesamoidosis, 6 sound horses and 4 yearlings. The arterial patterns of the proximal sesamoid bones from the patients, showed a shift from an abaxial to a basal arterial blood supply. This shift was only found in radiographically changed bones. Histological evaluation showed a significantly higher percentage of arteries with a large diameter in sections from the base of proximal sesamoid bones that showed an arterial shift. The presence of the shift appeared to be related to a change in shape of the bone, in particular to new bone formation along the abaxial border. The results of this study suggest that in horses suffering from sesamoidosis changes in the arterial pattern arise which might be a compensatory mechanism in respons to a vascular iischaemic challenge. Further investigations are needed to characterise the initial stimulus that induces this compensation and to determine if the compensation is sufficient to maintain a continuous and adequate blood supply.

Nerve supply of the proximal sesamoid bone in the horse.

In chronical proximal sesamoid bone lameness it is difficult to localise the exact site of pain. A specific diagnostic analgesia is not available because of a deficiency of detailed information about the nerve supply to the proximal sesamoid bones and surrounding area. A macroscopic study of the nerve distribution to the proximal sesamoid bones of 10 foals and 5 adult horses revealed that these bones are innervated by two branches, in this study called the medial and lateral sesamoidean nerve, respectively, originating from the medial and lateral palmar nerve. Histology of the left forelimbs of two fetuses and one foal confirmed the macroscopic findings. Additionally, histology of ten proximal sesamoid bones of adult horses showed that myelinated nerve fibres are present in the nutrient foramina and in the trabecular bone, accompanying the larger arteries. This study provides possibilities for future diagnostics of proximal sesamoid bone lameness by specific local perineural analgesia.

[Pseudotuberculosis in goats also in the Netherlands. A literature review]. / Pseudotuberculose bij de geit, ook in Nederland. Een literatuuroverzicht.

Pseudotuberculosis or caseous lymphadenitis in goats is marked by superficial abscesses and was recently observed in the Netherlands. The literature on this disease is reviewed, concerning the incidence, aetiology, pathogenesis, symptoms, diagnosis, therapy and preventive measures. The damage which the disease could cause to goat husbandry in the Netherlands, is discussed. Although the losses from death and diminished production will probably be small, treatment is time-consuming and requires much labour. The greatest damage will possibly consist in the fact that breeders will not be able to sell their animals when caseous lymphadenitis occurs in their herd. Particularly, the export of breeding stock could be menaced by this disease.