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Topic:Anatomy
Anatomy in horses encompasses the study of the structural organization of the equine body, including the bones, muscles, organs, and systems that function together to sustain life and enable movement. Understanding equine anatomy is important for veterinarians, equine scientists, and horse owners, as it provides insights into how horses move, how they respond to external stimuli, and how various conditions can affect their health and performance. Key anatomical features in horses include the musculoskeletal system, which provides support and locomotion; the cardiovascular system, which circulates blood and nutrients; and the respiratory system, which facilitates gas exchange. This page compiles peer-reviewed research studies and scholarly articles that explore the detailed anatomy of horses, focusing on the structure and function of different body systems, their interrelationships, and their relevance to equine health, performance, and veterinary care.
Partial ostectomy of the dens to correct atlantoaxial subluxation in a pony. To report a surgical technique that allows decompression and anatomic re-alignment for management of subluxation of the atlantoaxial articulation. Methods: Clinical report. Methods: Four-year-old Welsh Section B pony gelding. Methods: Attempts at closed reduction of subluxation of the atlantoaxial articulation under general anesthesia were unsuccessful, so a ventral surgical approach allowing partial ostectomy of the dens of the axis was used to facilitate reduction. Results: Recovery from surgery was uneventful and the pony remained comfortable without neurologic deficits. Both neck stiffness...
Evaluation of a minimally invasive arthrodesis technique for the carpometacarpal joint in horses. To evaluate a minimally invasive technique for arthrodesis of the carpometacarpal (CMC) joint in horses. Methods: Experimental study. Methods: Healthy horses (n=6). Methods: A 5.5 mm, 3-drill tract arthrodesis technique was evaluated in 1 randomly selected CMC joint in each of 6 normal horses. Peak vertical ground reaction force (GRF) values were recorded before surgery and at 6, 8, and 12 months thereafter. Radiographic and clinical lameness scores were assigned at regular intervals until 12 months after surgery when the horses were euthanatized. Gross and histologic examinations were perfo...
Decreased expression of p63, a regulator of epidermal stem cells, in the chronic laminitic equine hoof. Abnormal epidermal stem cell regulation may contribute to the pathogenesis of equine chronic laminitis. Objective: To analyse the involvement of p63, a regulator of epidermal stem cell proliferative potential, in chronic laminitis. Methods: Epidermal tissues from skin, coronet and lamellae of the dorsal foot were harvested from 5 horses with chronic laminitis and 5 control horses. Tissues were analysed using histopathology, immunofluorescence microscopy and quantitative immunoblotting. Results: Hoof lamellae of laminitic horses had a lower frequency of p63 positive cells than control lamellae,...
The effect of hoof angle variations on dorsal lamellar load in the equine hoof. In the treatment of laminitis it is believed that reducing tension in the deep digital flexor tendon by raising the palmar angle of the hoof can reduce the load on the dorsal lamellae, allowing them to heal or prevent further damage. Objective: To determine the effect of alterations in hoof angle on the load in the dorsal laminar junction. Methods: Biomechanical finite element models of equine hooves were created with palmar angles of the distal phalanx varying from 0-15°. Tissue material relations accounting for anisotropy and the effect of moisture were used. Loading conditions simulating t...
Comparison of three methods of injecting the proximal interphalangeal joint in horses. The efficacy of three methods of injecting the equine proximal interphalangeal (pastern) joint was compared using cadaver limbs. Five veterinary students without prior experience attempted to inject an aqueous radiographic contrast medium into the joint using five limbs for each technique. The number of attempts was recorded and successful injection of the joint was confirmed by the presence of intra-articular contrast on radiographic examination. Levels of accuracy for the dorsal, dorsolateral and palmaroproximal approaches were 32, 48 and 36 per cent, respectively. There was inadvertent inje...
Assessment of body fat in the pony: part I. Relationships between the anatomical distribution of adipose tissue, body composition and body condition. Evaluation of equine body fat content is important for nutritional and clinical purposes. However, our understanding of total body fat and its regional distribution in the body is sparse. Currently, body fat evaluation relies on the subjective assessment of body condition score (BCS), which has never been validated against 'gold standard' chemical analysis or dissection measurements in ponies. Objective: To define the relationships between subjective (BCS), objective (morphometric) indices of body fat and 'gold standard' measurements of actual body composition. Objective: BCS and morphometry o...
Evaluation of a tenoscopic approach for desmotomy of the accessory ligament of the deep digital flexor tendon in horses. To develop a tenoscopic approach for desmotomy of the accessory ligament of the deep digital flexor tendon (AL-DDFT) in horses. Methods: Experimental. Methods: Cadaveric forelimbs (n=10) and 4 forelimbs from 2 horses anesthetized for terminal teaching procedures, and 12 forelimbs of 6 experimental horses. Methods: Saline distention of the carpal flexor sheath facilitated insertion of an arthroscope into the distal medial aspect of the sheath between the AL-DDFT and deep digital flexor tendon (DDFT). Location of an instrument portal on the lateral aspect of the metacarpus was identified with a ...
An in vitro biomechanical comparison of equine proximal interphalangeal joint arthrodesis techniques: two parallel transarticular headless tapered variable pitch screws versus two parallel transarticular AO cortical bone screws inserted in lag fashion. To compare the mean number of cycles to failure under axial compression of equine proximal interphalangeal (PIP) joint arthrodesis constructs created by 2 parallel transarticular Acutrak Plus screws (AP-TS) or 2 parallel transarticular 5.5 mm cortical screws inserted in lag fashion (AO-TLS). Methods: Paired in vitro biomechanical testing of 2 methods of stabilizing cadaveric adult equine forelimb PIP joints. Methods: Cadaveric adult equine forelimbs (n=5 pairs). Methods: For each forelimb pair, 1 PIP joint was stabilized with AP-TS and 1 with AP-TLS. The 5 construct pairs were tested for cycli...
Inertial properties of equine limb segments. Quantifying the dynamics of limb movements requires knowledge of the mass distribution between and within limb segments. We measured segment masses, positions of segmental center of mass and moments of inertia of the fore and hind limb segments for 38 horses of different breeds and sizes. After disarticulation by dissections, segments were weighed and the position of the center of mass was determined by suspension. Moment of inertia was measured using a trifilar pendulum. We found that mass distribution does not change with size for animals under 600 kg and report ratios of segmental masses to...
Statistical analysis of bone mineral density using voxel-based morphometry-an application on proximal sesamoid bones in racehorses. Voxel-based morphometry (VBM) is a computational technique that has been used to analyze statistical differences between groups of MR brain images. This study outlines a new VBM pipeline, designed for determining statistical variation in bone mineral density (BMD). CT images of proximal sesamoid bone (PSB) specimens from the right forelimb of six racehorses that had suffered PSB fractures were compared with six age-matched control specimens. Following segmentation, masked gray-scale images were co-aligned to a statistical template generated with all 12 CT datasets iteratively. Student t-tests ...
Identification and prevalence of errors affecting the quality of radiographs submitted to Australian thoroughbred yearling sale repositories. We aimed to identify common mistakes made when radiographing yearling sale horses. Radiographic examinations from repositories at eight yearling sales held in Australia in 2003 were assessed by one of four veterinary radiology specialists. Each radiographic examination consisted of a maximum of 34 radiographs. Each radiograph was assessed for errors associated with movement, exposure, positioning, labeling or marker placement, and processing, and categorized as either ideal, less than ideal or nondiagnostic. In addition, from the first 800 sets catalogued, 167 were selected randomly and read t...
Radiography and computed tomography in the diagnosis of nonneoplastic equine mandibular disease. We compared the information gained from computed tomography (CT) vs. radiography in horses with nonneoplastic disease of the mandible. We hypothesized that CT would provide additional diagnostic information. Medical records, radiographs, and CT images of horses with nonneoplastic mandibular disease evaluated between 1994 and 2008 were reviewed. Nineteen horses were identified; 11 had a tooth root abscess and related disease, four had a fracture of the teeth and/or mandible, and four had a nonneoplastic mass. Both CT images and radiographs allowed identification of diseased teeth that appeared ...
The appearance of the equine metacarpophalangeal region on high-field vs. standing low-field magnetic resonance imaging. The appearance of the equine metacarpophalangeal (MCP) joint on high-field (1.5 T) vs. low-field standing (0.27 T) magnetic resonance (MR) images was evaluated. Objectives were (1) to describe the MR appearance of anatomic structures of clinical interest on images of the equine MCP joint obtained from 20 equine cadaver limbs from horses without lameness using high-field and low-field systems, (2) to categorize the clarity of appearance of anatomic structures on low-field MR images in comparison to high-field images as a gold standard. We found that larger anatomic structures were visible with ...
Ultrasonographic findings in horses with foot pain but without radiographically detectable osseous abnormalities. Foot pain is an important cause of lameness in horses. When horses with foot pain have no detectable radiographic abnormalities, soft-tissue assessment remains a diagnostic challenge without magnetic resonance (MR) imaging. Ultrasonography can provide an alternative to MR imaging when that modality is not available but the extent of changes that might be seen has not been characterized. We reviewed the ultrasonographic findings in 39 horses with lameness responding positively to anesthesia of the palmar digital nerves and without radiographically detectable osseous abnormalities. Thirty of the...
Analysis of osteon morphotype scoring schemes for interpreting load history: evaluation in the chimpanzee femur. Osteon morphotype scores (MTSs) allow for quantification of mechanically important collagen/lamellar variations between secondary osteons when viewed in circularly polarized ight (CPL). We recently modified the 6-point MTS method of Martin et al. (Martin RB, Gibson VA, Stover SM, Gibeling JC, Griffin LV (1996a) Osteonal structure in the equine third metacarpus. Bone 19, 165-71) and reported superiority of this modified method in correlating with 'tension' and 'compression' cortices of both chimpanzee proximal femoral diaphyses and diaphyses of other non-anthropoid bones that are loaded in habi...
Early lesions of articular osteochondrosis in the distal femur of foals. Failure of the cartilage canal blood supply to epiphyseal growth cartilage has been implicated in the pathogenesis of articular osteochondrosis in horses and other animal species. In a previous study of the developmental pattern of the blood supply in the tarsus of foals, early lesions of osteochondrosis were consistently found in regions where the cartilage canal vessels traversed the chondro-osseous junction. The developmental pattern of blood vessels has also been described in the distal femoral epiphysis; however, the group of foals examined in that study did not have lesions of osteochond...
In vitro effect of ventriculocordectomy before laryngoplasty on abduction of the equine arytenoid cartilage. To determine whether ventriculocordectomy (VCE) performed before prosthetic laryngoplasty (PL) results in increased rima glottidis size compared with PL alone. Methods: Experimental study. Methods: Equine cadaver larynges (n=13). Methods: Right arytenoid cartilages were maximally abducted using a standard PL technique. Standard PLs were then performed on the left side and the force required to maximally abduct the left arytenoid cartilage recorded (F(max) ). Photographs were taken of the rima glottidis at zero force and at five equal levels of force up to F(max) . The force applied was release...
Magnetic resonance anatomy of the carpus of the horse described from images acquired from low-field and high-field magnets. Cadaver carpi of 30 mature horses with no history of carpal or proximal metacarpal pain were examined using low-field (0.27 T) and high-field (1.5 T) magnetic resonance imaging (MRI). Normal MRI anatomy in transverse, sagittal, and dorsal plane images was determined by comparison with anatomical specimens and standard texts. Subchondral bone and cortical bone thickness measurements were obtained from standardised sites. There was variable subchondral bone thickness in the radius and carpal bones; subchondral bone thickness was consistently larger at dorsal compared with palmar sites in the...
Optic axis determination by fibre-based polarization-sensitive swept-source optical coherence tomography. We describe a fibre-based variable-incidence angle (VIA) polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) system to determine the 3D optical axis of birefringent biological tissues. Single-plane VIA-PS-OCT is also explored which requires measurement of the absolute fast-axis orientation. A state-of-the-art PS-SS-OCT system with some improvements both in hardware and software was used to determine the apparent optical birefringence of equine tendon for a number of different illumination directions. Polar and azimuthal angles of cut equine tendon were produced by the ...
The timeline of lamellar basement membrane changes during equine laminitis development. The timing of lamellar basement membrane (BM) changes occurring during laminitis development is incompletely understood. Objective: To determine the temporal progression of lamellar BM changes and whether laminin-332 (Ln-332) γ2 cleavage products are generated during laminitis development. Methods: Eight clinically normal Standardbred horses were allocated into treatment (n = 5) or sham (n = 3) groups. The treatment group received, via nasogastric intubation, an oligofructose (OF) bolus (10 g/kg bwt) while the sham group was given water. Laminitis induction proceeded for 48 h followed by euth...
Evaluation of ethyl alcohol for use in a minimally invasive technique for equine proximal interphalangeal joint arthrodesis. To determine whether intra-articular 70% ethyl alcohol alone (IAEA) or in combination with 2 percutaneously placed transarticular lag screws (EA-TLS) would result in arthrodesis of the equine proximal interphalangeal (PIP) joint. Methods: Experimental. Methods: Healthy horses (n=6), aged 1.5-3 years, free of lameness, diagonally paired front and hind PIP joints. Methods: Six milliliters 70% ethyl alcohol was injected into randomly selected diagonally paired front and hind PIP joints. Thirty days later, 2 parallel 5.5 mm cortical screws were inserted in lag fashion across the hind PIP joints an...
Arthrodesis of the equine proximal interphalangeal joint: a biomechanical comparison of 3-hole 4.5 mm locking compression plate and 3-hole 4.5 mm narrow dynamic compression plate, with two transarticular 5.5 mm cortex screws. To compare the biomechanical characteristics of 2 arthrodesis techniques for the equine proximal interphalangeal joint (PIP) using either a 3-hole 4.5 mm locking compression plate (LCP) or 3-hole 4.5 mm narrow dynamic compression plate (DCP), both with 2 transarticular 5.5 mm cortex screws. Methods: Experimental. Methods: Cadaveric adult equine forelimbs (*n=6 pairs). Methods: For each forelimb pair, 1 limb was randomly assigned to 1 of 2 treatment groups and the contralateral limb by default to the other treatment group. Construct stiffness, gap formation across the PIP joint, and rotation ab...
Immunohistochemical distribution of laminin-332 and collagen type IV in the basement membrane of normal horses and horses with induced laminitis. The basement membrane (BM) is a thin layer of extracellular matrix that regulates cell functions as well as providing support to tissues of the body. Primary components of the BM of epithelial tissues are laminin-332 (Ln-332) and collagen type IV. Equine laminitis is a disease characterized by destruction and dislocation of the hoof lamellar BM. Immunohistochemistry was used to characterize the distribution of Ln-332 and collagen type IV in the organs of normal horses and these proteins were found to be widespread. Analysis of a panel of tissue samples from horses with experimentally-induced l...
Glomus tumours in the skin and subcutis of three horses. Three horses presented with variably painful, nonulcerated masses of the head or neck that were diagnosed as glomus tumours. Grossly, they were fleshy, pink to tan masses ranging from 0.4 to 9 cm in diameter, involving either the deep dermis and subcutis or the subcutis and underlying skeletal muscle. Microscopically, neoplastic epithelioid cells were arranged in sheets, cords and packets within lobules. The neoplastic cells frequently abutted and formed nodular bulges into large endothelium-lined vascular spaces, especially around the tumour periphery. Large nerve branches were associated wit...
