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Topic:Musculoskeletal System
The musculoskeletal system in horses encompasses the bones, muscles, tendons, ligaments, and joints that facilitate movement and provide structural support. This system is essential for locomotion, athletic performance, and overall health in equine species. The equine skeleton consists of approximately 205 bones, which are connected by joints and supported by a network of muscles and connective tissues. Tendons connect muscles to bones, while ligaments link bones to other bones, contributing to joint stability. The musculoskeletal system is subject to various conditions, including injuries, degenerative diseases, and developmental disorders, which can impact a horse's mobility and performance. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, pathology, and treatment of musculoskeletal conditions in horses.
Pathological aspects of Australian Stringhalt. Nine horses with clinical signs of Australian Stringhalt were killed and tissues collected for a detailed pathological study. Lesions were limited to peripheral nerves and muscles. The most severely affected nerves were the superficial and deep peroneal, distal tibial, plantar digital, volar and recurrent laryngeal nerve with changes characterised by a selective loss of large diameter myelinated fibres with various degrees of demyelination, fibrosis, Schwann cell proliferation and onion-bulb formation. A routine evaluation of the brain and spinal cord by light microscopy failed to reveal any c...
Skeletal muscle fiber size in untrained and endurance-trained horses. The mean area and minimal diameter of 3 histochemically determined myofiber types (1, 2A, and 2B; myosin ATPase in acid buffer) were calculated in middle gluteal muscle biopsy specimens from 62 stallions, 47 Andalusians and 15 Arabians, ranging in age from 6 to 12 years. Fourteen Andalusians and 7 Arabians were untrained, and the remainder were actively endurance-trained. The 6-month training schedules involved walking, slow trotting, and cantering. Fourteen Andalusians were moderately endurance-trained, whereas the other 19 Andalusians and 8 Arabians were strongly endurance-trained. Significa...
Long-term effects of desmotomy of the accessory ligament of the deep digital flexor muscle in standardbreds: 23 cases (1979-1989). Desmotomy of the accessory ligament of the deep digital flexor muscle (inferior check desmotomy) permitted Standardbred foals affected with flexural deformities to reach their full athletic potential. Long-term effects of inferior check desmotomy were examined in 23 Standardbreds over a 10-year period. Six of 11 foals that were treated surgically either raced 6 times and obtained a race record or were training sound (if yearlings). All 12 horses with flexural deformity that did not receive an inferior check desmotomy had an unfavorable outcome (no race record). Foals that had surgery performed...
Ejaculation. Physiology and dysfunction. In summary, important events of ejaculation include emission of sperm and the accessory gland fluids into the urethra, simultaneous closure of the bladder neck, and forceful ejaculation of the combined semen through the urethra. Emission and bladder neck closure are primarily alpha-adrenergically mediated thoracolumbar sympathetic reflex events with supraspinal modulation. Ejaculation is a sacralspinal reflex mediated by the pudendal nerve. In stallions, the most common ejaculation disorders are emission and ejaculation failure, and urine contamination of semen. Rare disorders are azoospermia ...
Respiratory muscle perfusion in ponies during prolonged submaximal exercise in thermoneutral environment. Distribution of blood flow among various respiratory muscles was examined in 8 healthy ponies during submaximal exercise lasting 30 minutes, using radionuclide labeled 15-microns diameter microspheres injected into the left ventricle. From the resting values (40 +/- 2 beats/min; 37.3 +/- 0.2 C), heart rate and pulmonary arterial blood temperature increased significantly at 5 (152 +/- 8 beats/min; 38.6 +/- 0.2 C), 15 (169 +/- 6 beats/min; 39.8 +/- 0.2 C), and 26 (186 +/- 8 beats/min; 40.8 +/- 0.2 C) minutes of exertion, and the ponies sweated profusely. Mean aortic pressure also increased progr...
Incidence of sarcocysts in skeletal muscles of horses. The incidence of sarcocysts was examined in postural, propulsive and respiratory muscles from 74 horses ranging in age from mid-gestation to 14 years post-natal. Cryostat sections were stained for myosin adenosine triphosphatase (ATPase) at pH 9.5 and the type of muscle fibre containing sarcocysts was identified. Sarcocysts were found in muscles from three animals, all aged 1 year or more. Counts showed that they displayed no preference for any particular muscle. However, fibres with a high activity for myosin ATPase were preferentially colonized. Transverse sectional profiles of sarcocysts sh...
The teniae of the equine intestinal tract. At several locations along the equine cecum and colon, the outer longitudinal portion of the tunica muscularis is gathered into discrete bands of smooth muscle and connective tissue called "teniae". In this study, the disposition of the teniae ceci and coli was traced along the equine intestinal tract. It was discovered that, in several instances, arrays of teniae converge toward the valves and sphincters which separate the various intestinal compartments. The teniae may also provide support for and directionality to, peristaltic contraction waves. The tissue proportions of the teniae vary in ...
[Hematologic values and serum enzymes in horses inoculated with snake venoms for the production of antivenins in Costa Rica]. Blood components were studied in six horses immunized with snake venoms for the production of polyvalent antivenom in Costa Rica. No significant changes in hemoglobin or hematocrit throughout the immunization period were observed, whereas a significant increment in total serum proteins occurred in the second half of the immunization process, probably due to an increased synthesis of immunoglobulins. There were no significant changes in creatine kinase, but a slight increment was detected in both transaminases, although they did not exceed normal limits. These findings suggest the absence of re...
Influence of age on fibre type characteristics in the middle gluteal muscle of Andalusian foals. 34 Andalusian foals of both sexes were divided into three age-groups (A = mean age 1 month, B = 7 months, C = 14 months). Samples of the right m. gluteus medius were stained for m-ATPase and NADH-TR in order to determine fibre type composition and size as well as the relative area occupied by each type. Results revealed no statistically significant variation in the proportion of type I fibre among the three age-groups. Significant differences were recorded, however, for type II fibres; an increase in the proportion of IIA fibres was accompanied by a decrease in IIB ones, the difference being m...
Tension-band wiring and lag screw fixation of a transverse, comminuted fracture of a patella in a horse. A transverse, comminuted fracture of the patella was treated surgically by combining tension-band wiring and lag-screw fixation in a horse. Partial patellectomy or smaller detached fragments of the patella was performed. Satisfactory healing of the fracture was evident 10 weeks after surgery, and there were no complications. Implants were not removed. The horse was sound at a trot 4 months after surgery and was used for pleasure riding 8 months later.
Suspensory apparatus prosthesis in the horse. Part 1: In vitro mechanical properties. Mechanical properties of equine suspensory apparatus preparations and three braided synthetic prostheses were evaluated in vitro. Force versus displacement plots and failure modes were recorded from single load-to-failure testing in 18 cadaver limbs before and after replacement of each suspensory apparatus with a prosthesis. Mean load at failure, energy to failure, and stiffness values of polytetrafluoroethylene (PTFE) prostheses were lower than those of the suspensory apparatus and aramid prosthesis. The PTFE prosthesis failed by elongation or rupture of the prosthesis. Mechanical properties ...
Ultrastructural changes in skeletal muscle after fatiguing exercise. Thoroughbred horses were exercised to fatigue at 40, 85, and 100% of their maximal oxygen consumption (VO2max) on a treadmill and completed a 1,600-m gallop on a track to identify the effect of exercise of various durations and intensities on the ultrastructure of mitochondria and sarcoplasmic reticulum (SR) from the middle gluteal muscle. The percentage of the total area occupied by mitochondria and SR increased in electron micrographs of muscle samples collected at the termination of exercise and at 30 and 60 min of recovery compared with those collected before exercise. Mitochondrial area i...
The response of equine cortical bone to loading at strain rates experienced in vivo by the galloping horse. The behaviour of cortical bone under load is strain rate-dependent, i.e. it is dependent on the rate at which the load is applied. This is particularly relevant in the galloping horse since the strain rates experienced by the bone are far in excess of those recorded for any other species. In this study the effect of strain rates between 0.0001 and 1 sec-1 on the mechanical properties of equine cortical bone were assessed. Initially, increasing strain rates resulted in increased mechanical properties. Beyond a critical value, however, further increases in strain rate resulted in lower strain to...
Nonsurgical treatment of cubital subchondral cyst-like lesions in horses: seven cases (1983-1987). Subchondral cyst-like lesions of the cubital joint were diagnosed in 7 horses at the teaching hospital between 1983 and 1987. Diagnosis of the lesions was made by administration of intra-articular local anesthesia and/or radiographically. Initial treatment for all horses consisted of stall rest for 60 to 90 days. In addition, 2 horses were administered sodium hyaluronate intra-articularly, 1 horse was given injections of polysulfated glycosaminoglycans IM, and 1 horse was given phenylbutazone orally. Follow-up information was compiled 6 weeks to 4 years after initial examination. At the time o...
Follow-up of 28 horses with third metacarpal unicortical stress fractures following treatment with osteostixis. The results of 31 intracortical dorsal metacarpal stress fractures in 28 horses following unicortical osteostixis were reviewed. The incidence was predominately in the middle third of the lateral aspect of the left metacarpus, and males were affected more commonly. Approximately half of the surgical procedures were performed with the horse in the standing position. The mean times to return to training and racing were 4.25 and 6.9 months respectively. There was no correlation between time taken to return to racing and position of surgery. Complications experienced included lack of suture remova...
Total carnitine content of the middle gluteal muscle of thoroughbred horses: normal values, variability and effect of acute exercise. There was no detectable loss of total carnitine associated with intense exercise from the middle gluteal muscle of Thoroughbred horses. Measurements made on a single biopsy obtained during the course of a normal training and exercise programme may, therefore, be considered representative of the normal content at rest. The variability in total carnitine content within the normal muscle biopsy area amounted to 13.2 per cent of the normal mean content. Approximately 50 per cent of this variability could be attributed to covariation with citrate synthase, to which it was highly significantly corre...
Attempted reinnervation of the equine larynx using a muscle pedicle graft. Laryngeal hemiplegia was induced in 4 ponies via a left recurrent laryngeal neurectomy. Reinnervation of the denervated left cricoarytenoideus dorsalis muscle was then attempted using a muscle pedicle graft from the right cricoarytenoideus dorsalis muscle. In 3 ponies there was no return of abductor function and failure of graft survival. In the fourth pony there was return of abductor function along with survival of the muscle bridge, however, there was evidence of reinnervation across the neurectomy site. Muscle-to-muscle neurotization of the paralyzed equine larynx, utilizing the cricoaryte...
Inheritance of myotonic discharges in American quarter horses and the relationship to hyperkalemic periodic paralysis. Electromyography (EMG) was used to detect myotonic discharges in Quarter Horse breeding stock and to follow the results of mating horses with hyperkalemic periodic paralysis (HPP). The studies were performed on two brood mare farms. A total of six breeding stock showed myotonic discharges and 15 were nonmyotonic. Myotonic discharges were seen in five of six horses belonging to the blood line previously implicated as being predisposed to HPP. Two of these horses had shown clinical signs of HPP. Only one of 15 breeding horses unrelated to the HPP predisposed blood line showed myotonic discharges...
[The appearance of stress on the movement apparatus in dressage, jumping and versatility horses]. Jumping and military (three days events) horses are exposed, during sports activities, to a particularly high stress especially in the region of the extremities (limbs). The genesis of tendon, joint and bone diseases are traced in accordance to the centers of the load during movement sequence. A special statistics on injuries concerning the German competition horses does not exist yet. Out of the available statistics about the German competition horses it is not obvious that as a result of its use as sports horses a particular high loss occur among these horses.
[Physical performance–a comparison between horses and men]. During heavy exercise horses can increase oxygen uptake compared to resting conditions considerably more than man. Processes involved like respiration, heart size, cardiac output, oxygen transport capacity of the blood and oxygen release in the capillaries are discussed. Besides these advantages in the aerobic metabolism conditions for the anaerobic metabolism are also more advantageous in horses than in man. The portion of fast contracting muscle fibers with little fatigue-resistance and also some of the enzymes required for the anaerobic metabolism are higher in horses.
Elbow extensor muscles of the horse: postural and dynamic implications. Based on histochemical and immunohistochemical evidence, horse elbow extensor muscles are composed of two morphologically distinct muscle groups. The long and lateral heads of the triceps brachii are large, predominantly type II (presumed fast) muscles. The long and lateral heads of the triceps together account for 96% of the weight of the elbow extensors (long head of triceps is 81%). The long and lateral heads contain three histochemical fiber types: types I, IIa and IIb. Type I muscle fibers account for approximately 18 and 27% of the fibers in the long and lateral heads of the triceps, res...
Preliminary studies on the vascular anatomy of the equine superficial digital flexor tendon. The vascular and microvascular anatomy of normal equine superficial digital flexor tendons was studied by dissection of vinyl-perfused specimens and by microangiography on high detail film. The presence of an extensive intratendinous vascular latticework was confirmed, and a 'nutrient artery' described closely associated with the accessory ligament of the superficial digital flexor tendon (proximal check ligament). Circumferential stripping of the paratenon from the tendon to eliminate afferent vessels was performed bilaterally in three horses and unilaterally in a fourth, followed by a treadm...
Effects of treadmill exercise on cortical bone in the third metacarpus of young horses. The effects of exercise and relative inactivity on cortical bone were compared in young horses. Two groups were used; one was given a 14-week programme of exercise (n = 6) and the other kept as unexercised controls (n = 6). The first nine weeks of exercise involved trotting and cantering (2 to 4 km d-1 at speeds up to 12 m s-1) on a treadmill set at an incline of 3 degrees. Over the next five weeks the horses were trained at near maximal speeds (that is, up to 14.5 m s-1) with no incline of the treadmill. At the end of the programme marked differences in cortical porosity and distribution of s...
Muscarinic receptor subtypes in equine tracheal smooth muscle. Selective muscarinic receptor antagonists were used to identify muscarinic receptor subtypes in equine trachealis strips. The M1 receptor antagonist pirenzepine (10(-7) mol/L to 3 x 10(-5) mol/L) and the M3 receptor antagonist 4-diphenylacetoxy-N-methylpiperidine (4-DAMP, 10(-9) mol/L to 3 x 10(-7) mol/L3) dose dependently inhibited the contractile responses to electrical field stimulation (EFS) and exogenous acetylcholine (ACh). Schild plots yielded a pA2 value for pirenzepine vs ACh of 6.75 +/- 0.09, which is consistent with the affinity for M2 or M3 receptors, and a pA2 value for 4-DAMP vs ...
Capillary supply and fibre area in locomotor muscles of horse and steer–a comparison between histochemistry and electron microscopy. In order to investigate possible differences in variables defining capillary supply of skeletal muscle derived from two methods, the electron-microscopical and the amylase-PAS histochemical methods were applied in a study of horse and steer muscles. Samples from several locomoter muscles were taken at slaughter from one horse and one steer, divided into two and prepared separately for the two techniques. It was found that there was no difference between the two methods in the values for the capillary-to-fibre ratio. Values for mean fibre area, on the other hand, were significantly higher in th...
Bee venom melittin is a potent toxin for reducing the threshold for calcium-induced calcium release in human and equine skeletal muscle. The modulation of Ca2+ release by synthetic bee venom melittin was examined in equine and human terminal cisternae-containing fractions. Melittin (0.1 microM) decreased the threshold of Ca(2+)-induced Ca2+ release by 20% in equine muscle and by 36% in human muscle. If terminal cisternae fractions were first preloaded with Ca2+ to greater than about 75% of the threshold of Ca(2+)-induced Ca2+ release and then melittin added, an immediate and sustained release of Ca2+ occurred in preparations from both species. Addition of melittin after a Ca2+ preload of < 50% of the threshold of Ca(2+)-induced...
