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Objective—To describe in detail the radiographic appearance of ossified ungular cartilages in horses and to evaluate the usefulness of a flexed dorsolateral-palmaromedial oblique (flexed oblique) radiographic view in evaluating the ungular cartilages.
Design—Retrospective case series.
Sample—Radiographs of 1,255 front feet of horses.
Procedures—Ossification of the ungular cartilages was graded during evaluation of radiographs on a scale from 0 to 5; feet with cartilages with an ossification grade ≥ 2 were included (386 feet [271 horses]). The shape (straight, curved outward or inward, and dorsopalmar extension of ossification) was determined. The view on which abnormalities were best identified was documented. Abnormalities of the compact bone, radiopacity, trabecular architecture, compactospongious demarcation, and presence of radiolucent lines were recorded; grouped as modeling, adaptive changes, or both; compared with ossification grade, separate centers of ossification, mediolateral symmetry of ossification, shape, cartilage (medial or lateral), and foot (left or right); and tested for significant associations.
Results—Fractures (n = 35) were most common in feet with cartilages with an ossification grade of 4 (18) or 5 (17) and were best identified in flexed oblique images, compared with more commonly recommended images. Multivariable logistic regression showed a significant positive association of ossification grade with modeling or adaptive changes; feet with cartilages with an ossification grade of 4 (OR, 11.59; 95% CI, 6.52 to 20.60) or 5 (OR, 72.90; 95% CI, 25.32 to 209.90) were more likely than those with an ossification grade of 2 or 3 to have modeling or adaptive changes. Abnormally shaped cartilages were more likely to have modeling or adaptive changes, compared with normally shaped cartilages (OR, 4.90; 95% CI, 1.94 to 12.42).
Conclusions and Clinical Relevance—Extensive ossification and the presence of inward or outward curvature as well as palmar curvature or a bulbous shape were significant risk factors for modelling and adaptive changes. Flexed oblique images provided clinically useful information, including detection of abnormal shape and fractures, that may not be evident on other currently recommended images. Such images are recommended for complete radiographic appraisal of ossified ungular cartilages of the foot in horses. (J Am Vet Med Assoc 2015;247:801–811)
OBJECTIVE To use high-field and low-field MRI to describe the anatomy of the proximal portion of the tarsal region (proximal tarsal region) of nonlame horses.
SAMPLE 25 cadaveric equine tarsi.
PROCEDURES The proximal portion of 1 tarsus from each of 25 nonlame horses with no history of tarsal lameness underwent high-field (1.5-T) and low-field (0.27-T) MRI. Resulting images were used to subjectively describe the anatomy of that region and obtain measurements of the collateral ligaments of the tarsocrural joint.
RESULTS Long and short components of the lateral and medial collateral ligaments of the tarsocrural joint were identified. Various bundles of the short collateral ligaments were difficult to delineate on low-field images. Ligaments typically had low signal intensity in all sequences; however, multiple areas of increased signal intensity were identified at specific locations in most tarsi. This signal intensity was attributed to focal magic angle effect associated with orientation of collagen fibers within the ligaments at those locations. Subchondral bone of the distal aspect of the tibia was uniform in thickness, whereas that of the medial trochlear ridge of the talus was generally thicker than that of the lateral trochlear ridge. In most tarsi, subchondral bone of the talocalcaneal joint decreased in thickness from proximal to distal.
CONCLUSIONS AND CLINICAL RELEVANCE Results generated in this study can be used as a reference for interpretation of MRI images of the proximal tarsal region in horses.
Objective—To establish and validate an objective method of radiographic diagnosis of anatomic changes in laminitic forefeet of donkeys on the basis of data from a comprehensive series of radiographic measurements.
Animals—85 donkeys with and 85 without forelimb laminitis for baseline data determination; a cohort of 44 donkeys with and 18 without forelimb laminitis was used for validation analyses.
Procedures—For each donkey, lateromedial radiographic views of 1 weight-bearing forelimb were obtained; images from 11 laminitic and 2 nonlaminitic donkeys were excluded (motion artifact) from baseline data determination. Data from an a priori selection of 19 measurements of anatomic features of laminitic and nonlaminitic donkey feet were analyzed by use of a novel application of multivariate statistical techniques. The resultant diagnostic models were validated in a blinded manner with data from the separate cohort of laminitic and nonlaminitic donkeys.
Results—Data were modeled, and robust statistical rules were established for the diagnosis of anatomic changes within laminitic donkey forefeet. Component 1 scores ≤ −3.5 were indicative of extreme anatomic change, and scores from −2.0 to 0.0 denoted modest change. Nonlaminitic donkeys with a score from 0.5 to 1.0 should be considered as at risk for laminitis.
Conclusions and Clinical Relevance—Results indicated that the radiographic procedures evaluated can be used for the identification, assessment, and monitoring of anatomic changes associated with laminitis. Screening assessments by use of this method may enable early detection of mild anatomic change and identification of at-risk donkeys.
Objective—To investigate effects of exercise on hyaline cartilage (HC), calcified cartilage (CC), and subchondral bone (SCB) thickness patterns of equine tarsi.
Sample Population—30 tarsi from cadavers of horses with known exercise history.
Procedures—Tarsi were assigned to 3 groups according to known exercise history as follows: pasture exercise only (PE tarsi), low-intensity general-purpose riding exercise (LE tarsi), and high-intensity elite competition riding exercise (EE tarsi). Osteochondral tissue from distal tarsal joints underwent histologic preparation. Hyaline cartilage, CC, and SCB thickness were measured at standard sites at medial, midline, and lateral locations across joints with a histomorphometric technique.
Results—HC, CC, and SCB thickness were significantly greater at all sites in EE tarsi, compared with PE tarsi; this was also true when LE tarsi were compared with PE tarsi. At specific sites, HC, CC, and SCB were significantly thicker in EE tarsi, compared with LE tarsi. Along the articular surface of the proximal aspect of the third metatarsal bone, SCB was thickest in EE tarsi and thinnest in LE tarsi; increases were greatest at sites previously reported to undergo peak strains and osteochondral damage.
Conclusions and Clinical Relevance—Increased exercise was associated with increased HC, CC, and SCB thickness in mature horses. At sites that undergo high compressive strains, with a reported predisposition to osteoarthritic change, there was increased CC and SCB thickness. These results may provide insight into the interaction between adaptive response to exercise and pathological change.
Objective—To determine whether histopathologic characteristics of the osteochondral units of equine distal tarsal joints were associated with exercise history in horses without lameness.
Sample Population—30 cadaver tarsi from horses without lameness and with known exercise history were separated into 3 groups: nonridden, pasture exercise (group P); low-intensity, ridden exercise (group L); and high-intensity, elite competition exercise (group E).
Procedures—Standardized sites from the centrodistal and tarsometatarsal joints under went histologic preparation. A grading system was adapted to describe location, depth, and shape of lesions; cellular arrangement; organization at cartilage and subchondral bone (SCB) junctions; and organization of SCB. A high score signified a more severe pathological change than a low score. Exercise groups were compared by calculation of Spearman rank correlations.
Results—In the centrodistal joint, lesions were present in groups L and E but only medially. Cellular arrangement scores were higher at the dorsomedial location in group P than in groups L and E. Groups L and E had higher scores than group P for the organization of the cartilage, SCB junctions, and SCB, with higher scores at the dorsomedial location. In the tarsometatarsal joint, lesions were evident across the whole joint surface, with more severe lesions located laterally in all 3 groups. Overall, group E had higher scores for cellular arrangement and SCB organization than groups P and L.
Conclusions and Clinical Relevance—Ridden exercise may increase the risk of osteochondral lesions at distal tarsal sites predisposed to osteoarthritis relative to the risk with nonridden exercise.
Objective—To investigate effects of age on thickness and morphologic characteristics of hyaline cartilage, calcified cartilage, total cartilage, and subchondral bone (SCB) in the equine tarsometatarsal joint.
Sample Population—23 tarsal joints from cadavers of 23 ponies (11 days to 25 years old); ponies were limited to pasture exercise and euthanatized for reasons not related to this study.
Procedures—Tarsi were allocated into several age groups (11 days old [n = 3], 6 to 9 months old , 2 to 3 years old , 6 to 8 years old , 11 to 17 years old , and 20 to 25 years old ). Histologic examination and histomorphometric measurement of hyaline cartilage, calcified cartilage, total cartilage, and SCB were performed at medial and lateral sites.
Results—A significant decrease was detected in thickness of hyaline cartilage and total cartilage with increasing age, but there was a significant increase in thickness of calcified cartilage and SCB with increasing age. Differences in chondrocyte and collagen fiber arrangement, tidemark, and osteochondral junction morphology were evident among age groups.
Conclusions and Clinical Relevance—These findings suggested that the various tissues of the osteochondral unit change in different ways with age. The response of each tissue may be related to relative response of the tissues to strains induced by pasture exercise but could have an influence on how the overall properties of the osteochondral unit change with age. The findings may also be suggestive of changes that develop prior to the onset of osteoarthritis.