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Musculoskeletal Disorders INAG 120 – Equine Health Management November 14, 2011.

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Presentation on theme: "Musculoskeletal Disorders INAG 120 – Equine Health Management November 14, 2011."— Presentation transcript:

1 Musculoskeletal Disorders INAG 120 – Equine Health Management November 14, 2011

2 Musculoskeletal Disorders Normal muscle physiology Muscle response to injury Muscle problems Tendon disorders Ligament problems

3 Normal Muscle Physiology Type 1 – Slow Twitch High oxidative capacity, lots of mitochondria Aerobic metabolism Low glycogen storage capacity Narrow muscle, slim

4 Normal Muscle Physiology Type 2a & 2b – Fast Twitch Well-developed glycolytic pathway, few mitochondria Anaerobic metabolism High glycogen storage capacity Quarter horses, big muscles

5 Muscle Tissue Response to Injury Muscle can repair well if the supporting structures remain intact Atrophy = decrease in volume due to a decrease in size of the individual muscle cells –Generalized = symmetrical; may be due to ↓ nutritional status, old age –Localized = due to paralysis, area of damage –Neurogenic = deprivation of nerve supply

6 Classification of Muscle Diseases in Horses 1.Muscle damage –Non-exertional Inflammatory, nutritional, toxic or metabolic –Exertional Sporadic or chronic 2.Muscle atrophy –Neurogenic EMND, EPM, focal nerve damage –Myogenic Immune-mediated, chronic disease, malnutrition, disuse, Cushing’s disease, PSSM

7 Classification of Muscle Diseases in Horses 3.Abnormal muscle twitching –Myogenic Myotonia, HYPP, electrolyte imbalance, botulism –Neurogenic Shivers, myoclonus, focal nerve damage, ear ticks 4.Muscle weakness and exercise intolerance –Metabolic disorders

8 Exertional Rhabdomyolysis Exercise-related myopathy Monday Morning Disease Exercise-induced myositis Tying-upAzoturia Most Affected Muscles

9 Tying Up Equine Exertional Rhabdomyolysis Clinical signs varied, depending on severity: –Mild – somewhat stiff after exercise –Severe – incapacitation; horse unable to stand or bear weight –Muscles of hindquarters most severely affected

10 Tying Up Pain persists for several hours Exhausted Horse Syndrome  common in endurance horses –Depression –Severe dehydration –Hyperthermia –“Thumps” (fluttering of the diaphragm) –Extensive muscle damage with or without cramping

11 Tying Up Severe cases  dark red-brown colored urine –Myoglobinuria Diagnosis = presence of creatine kinase (CK) and aspartate aminotransferase (AST) in the blood, muscle biopsy, genetic testing © IVIS Reviews in Veterinary Medicine © Knottenbelt DC, Pascoe RR, Diseases and Disorders of the Horse, Saunders, 2003

12 Tying Up – Causes Two broad categories: Sporadic exertional rhabdomyolysis –Horses which, on rare occasion, experience tying up Chronic exertional rhabdomyolysis –Horse experiences repeated episodes with the first usually occurring at a young age

13 Sporadic ER Exercise exceeds the horse’s fitness level –Horse competing after a lay-off and only minimal training before the event Electrolyte imbalance Deficiencies of vitamin E and/or selenium Horses with concurrent illness –Respiratory viral infections

14 Chronic ER Animals prone to relapse  limit athletic career! Many different breeds affected (Thoroughbreds, Arabians, Standardbreds, QH, drafts and warmbloods) Possible causes: –Hormonal imbalances (low thyroid) –Lactic acidosis within muscle –Diet High grain diet Vitamin E and/or selenium deficiency Electrolyte imbalances –Calcium? –Genetics

15 Chronic ER Study by Valberg et al. (1999) uncovered two specific causes of Chronic ER: –Polysaccharide storage myopathy (PSSM) –Recurrent Exertional Rhabdomyolysis (RER)

16 PSSM Polysaccharide Storage Myopathy –Storage of excess carbohydrate in the muscle Muscle glycogen concentrations are 1.5 – 4 times higher –Affects drafts, Quarter Horses, warmbloods and a few Thoroughbreds –Clinical signs often develop at a young age when horse begins training –Hereditary?

17 PSSM 40% of the type II muscle fibers have been found to have an acid mucopolysaccharide inclusion –Abnormal metabolism  increased uptake of glucose from the blood and quicker storage as glycogen CK and AST levels are elevated –CK may remain high weeks after event (esp. in QH) Seen in calm, sedate horses that are heavily muscled

18 Heredity of PSSM Genetic mutation occurred early on –Present in many different horse breeds –Accounts for over 90% of PSSM cases in some horse breeds –P = horse carries mutant gene –N = normal gene P/P = more severely affected, harder to manage (rare) P/N = affected with PSSM, clinical signs vary N/N = unaffected w/ PSSM type 1 Second mutation (MH) intensifies the clinical signs in Quarter Horses and related breeds

19 Treatment PSSM attack Treatment: –Oral or IV fluids to correct dehydration –Physical therapy 24 hours after episode = large box stall to move around Few minutes of hand-walking ok, but best to allow horse to move on its own Small paddock turnout with quiet horse Duration and frequency of walking bouts should be increased over a week –Massage therapy –Detailed diagnostic exam if chronic

20 RER Recurrent Exertional Rhabdomyolysis –Defect in the mechanism of muscle contraction Increased sensitivity to contraction when exposed to certain stimuli Abnormal location of nuclei in muscle biopsies Abnormal regulation of calcium movement within cells –Common in Thoroughbred, Arabian and Standardbred horses –May be hereditary in Thoroughbreds –Increased levels of CK after exercise

21 Predispositions for RER Age –2 year old >> 3 year old > 4 year old, etc. Gender –65% are fillies Temperament –Nearly half characterized as “nervous” Lameness –Lameness is more common in horses that tie up Diet –Fed >10lbs of grain/sweet feed per day Exercise intensity –Tie up more often when gallop training than breezing or racing –Three-day-event horses tie-up after the steeplechase, prior to cross-country phase –Racing Standardbreds tie-up after 15 minutes of jogging.

22 Management of horses with RER Keep horse in quiet area of the barn Train first rather than last Turn-out Avoid training regimes like holding back at a gallop or intervals that excite the horse Tranquilize before exercise to prevent excitement Attention to and treatment of lameness Avoid stall rest or lay-up Use medications that affect intracellular calcium regulation –dantrolene 4mg/kg orally 1 hour before exercise

23 Tying Up – Prevention of attacks Feeding: –Fat supplemented diets Diets high in carbohydrates can cause excitement (RER) In horses with PSSM, problem is one of excess carbohydrate storage in muscle, so elimination of grain is a must 20-25% of calorie requirements from fat! –Balanced electrolytes, water and Ca:P ratio, Vitamin E and Selenium –High quality forage (alfalfa or grass)

24 Muscle Cramping Due to overactivity –Endurance horses –Exertional rhabdomyolysis –Hypocalcemia (not enough Ca) Stiffness, pain, periodic spasms Increase in muscle enzymes

25 Endurance Horse Muscle Cramping Clinical Signs –Elevated temperature, pulse, respiration –May be seen with “Thumps” –Stiffness, pain, periodic spasms –NO increase in muscle enzymes Treatment –Rest –Rehydration with appropriate electrolytes

26 Thumps Synchronous Diaphragmatic Flutter –Diaphragm contracts synchronously with the heart –Seen as a flank twitch coincident with heart rate Causes –Endurance exercise during hot weather –Hypocalcemia, digestive disturbances, some medications

27 Post-anesthetic Related Myopathies Localized –Found in individual muscle groups which are in contact with hard surface for prolonged periods –Musculature starved of blood Generalized –Involves multiple muscle groups, increased heart & respiratory rate, sweating and myoglobinuria –Reaction to anesthetic used

28 Equine Sports Massage Therapy Equine Sports Massage Therapy differs from other forms of massage: –Focuses on the cause of the muscle injury –Relieves pain –PREVENTION of future injuries to those muscles Involves a full body massage at every session

29 When and Why to Massage Pre-Event: Pre-Event: –Supple muscles –Enhance range of motion –Positive effect on the contraction and release process of the muscles Post-Event: Post-Event: –Reduce post- performance anxiety and stress –Prevents soreness –Release tension so the horse's muscles can relax

30 When and Why to Massage Post-Injury: Post-Injury: –Reduce inflammation and swelling in joints Stall Bound: Stall Bound: –Stimulate circulation of blood and lymph throughout the body –Increase production of vital fluids in joints Maintenance: Maintenance: –Maintain fitness by enhancing the muscle tone

31 Benefits of Massage 1.Increased blood flow to tissues More nutrients to cells  quicker removal of waste products More nutrients to cells  quicker removal of waste products 2.Increased lymphatic flow Reduction in swelling and removal of waste products Reduction in swelling and removal of waste products 3.Relief from muscle spasms Stretching and warming of muscle tissues allows for relaxation Stretching and warming of muscle tissues allows for relaxation 4.Fibrosis and scar tissue inhibited 5.Pain relief through release of endorphins

32 Tendon Properties Tendons connect muscle to bone Tough, inelastic band of fibers Shock absorbers in locomotion Change with age: become more prone to damage Poor at functional adaptation Original tendon strength after damage is not as high

33 Tendon Injury Catastrophic failure –Massive overload  exceeds strength of tendon (VERY unusual) Apparent catastrophic failure –Weakening of structure due to accumulated micro- damage Partial failure –Micro-damage limited to portion of tendon (tendonitis) (most common)

34 Tendon Injuries Treatment –Ice/cold therapy 20 minutes every hour for 1 st 24 hours –NSAIDs High doses; watch for ulcers, toxicosis –Wrap legs No heating agents or liniments; keep well-wrapped for first few months –PSGAG’s (e.g., Adequan) Controversial; may be injected into lesion Equine Emergency!

35 Tendon injuries… Controlled exercise program/ rehabilitation Therapeutic ultrasound? Stem Cell Therapy? Treatments losing favor: –Tendon splitting –Blistering/pin-firing –BAPN – “bapten” – plant derived substance that is injected into lesion to prevent formation of collagen during healing

36 Tendon Lacerations Tendon Lacerations Require IMMEDIATE specialist attention May prove fatal (may involve damage and subsequent infection of joint capsule) Septic tenosynovitis –Difficult to treat if left for more than a few hours Equine Emergency!

37 Ligament Properties Connect bone to bone Prevent displacement of tendons and joints Ligament that has been damaged loses elasticity and can obstruct movement

38 Annular Ligament Constriction Clinical signs –Non-specific lameness –Possible history of trauma to fetlock –Lameness worsens with exercise/ doesn’t improve with rest Treatment: –Surgical resection –Good prognosis if only ligament involved –If damage to tendon  guarded

39 Suspensory Ligament Rupture Complete rupture Partial rupture POOR PROGNOSIS Racing injury May occur with fractures of sesamoids Treatment = humane euthanasia May immobilize joint for breeding stock

40 Suspensory Desmitis Inflammation of suspensory ligament –Runs along the back of the cannon bone –Splits to become a medial and lateral branch –Attach to the proximal sesamoid bones and the proximal phalanx Similar to tendonitis – less well diagnosed Severe damage usually means the sesamoid bone has been cracked Treatment = same as for tendonitis

41 Sususpensory Ligament Desmitis


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