Musculoskeletal diseases

Musculoskeletal system

Responsible for movement and shape in all animals

Bone fractures

Usually the result of trauma

Steps after bone fracture

-Stabilize patient vitals first

-Check for open wounds or bleeding

-Immobilize fracture

-Take radiographs

Open or compound fracture

The bone is broken and there is a break or wound in the skin in the same area

Closed or simple fracture

The bone is fractured, but there is no skin wound

Types of bone fractures

-Greenstick. The fracture is incomplete

-Comminuted. Many fragments

-Transverse. Across the bone

-Oblique. Fracture is diagonal

-Spiral. Caused by twisting the bone excessively

Healing process of bone fracture

1. Clot or hematoma forms

2. Granulation tissue and capillaries creep in

3. A callus forms then becomes mineralized

4. Soft woven bone is consolidated into stronger lamellar bone

5. Bone continues to remodel until it regains full strength

Fractures won’t heal properly with

-Lack of apposition of the fracture

-Too much movement

-Osteomyelitis (bone infection)

Fracture reduction

How a bone is fixed or set.

The ends of the fracture must be close to one another to heal.

Support is needed to prevent movement while healing.

Support can be internal or external

Internal fracture repairs

1. Intramedullary pinning or Kirschner wire (K-wire)

2. Cerclage wire

3. Bone plating

External fracture repairs

-Kirschner -Ehmer Apparatus (KE apparatus)

-Splinting/Casting/Bandaging

Casting. Bone fractures

-Plaster of Paris cast

-Fiberglass cast

-Robert Jones

-Modified Robert Jones

-Ehmer slings

-Velpeau sling

Home care. Bone fractures

-Activity Restrictions

-Pain control

-Cast and splint management

Cruciate Ligament Injury

Anterior and posterior cruciate ligaments are intraarticular structures that help stabilize the stifle joint.

Most commonly affect middle-aged to older dogs.

Clinical signs

Cruciate ligament injury

Non-weight bearing on a back leg

Swelling of the stifle joint

“Sit sign”

Medial buttress (if chronic)

Treatment

Cruciate ligament injury

-Surgical fixation is usually needed for a return to normal.

-Limping will improve with rest alone, but do not typically resolve

Post-op home care

Cruciate ligament injury

-Exercise restriction for 4-8 weeks then gradual return to activity

-Pain control

-Joint supplements

-Weight control

-Physical therapy

Medial Patella Luxation (MPL)

Common in small, toy breed dogs

Clinical signs

Medial Patella Luxation

Abnormal or intermittently abnormal gait, skipping or hopping in the back legs

Treatment

Medial Patella Luxation

Surgery for patients who are painful.

Hip Dysplasia

Genetic disease that primarily affects large breed dogs

Clinical signs

Hip Dysplasia

-Stiffness which may improve with movement

-Back leg lameness, limping, muscle atrophy

-Younger animals with severe hip dysplasia may not walk or stand

Treatment

Hip dysplasia

Non surgical:

-Exercise restriction

-Pain control

-Weight control

-Joint supplements

Surgical

Degenerative Joint disease (DJD)

Aka arthritis or osteoarthritis

Clinical signs

DJD

Limpin or stiffness

Sleeping more

Slower on walks or not wanting to walk

Not wanting to be touched/pet

Urinary or fecal accidents

Slow to rise or lay down

Difficulty jumping up

Change in posture or gait

Treatment

DJD

Weight control

Pain control

Joint supplements

Physical rehabilitation

Bone cancer

Most common bone tumor in dogs is an osteosarcoma.

Typically affects large breed, around 7 years of age.

The sites most affected can be remembered by this phrase “away from the elbow, toward the knee“

Clinical signs

Bone cancer

Lameness, pain and swelling

Weight loss

Treatment

Bone cancer

Amputation of affected limb

Chemotherapy

Radiation

Pain medications

Leg-calve-Perthes disease

A non-inflammatory necrosis of the femoral head and neck of the femur.

Affects young toy breeds and terriers

Treated with a FHO surgery

Osteochondrosis Dissecans

This is a lesion or wound of the cartilage.

Cartilage separates from bone.

Affects the shoulder, hock, stifle, and elbow joints

Affects rapidly growing, young, large breed dogs

Panosteitis

“Growing pains”. It affects bones of rapidly growing puppies.

May last up to one year.

Puppies might have a fever, poor appetite and weight loss

Coxofemoral Luxation

Joint Luxation most commonly occurs from trauma.

Tearing of the joint capsule also occurs

Fixed with a closed reduction (without surgery) or open reduction (surgical repair)

Ehmer sling for 7-10 days

FHO is also an option

Myopathies

Any disease affecting the muscle.

Myopathies can be immune mediated, infectious, or acquired

Muscle atrophy

When the muscle mass decreases in size. Caused bye prolonged inactivity.

Inflammation

Is a natural response of living tissue to cellular injury. The signs of inflammation are redness, heat, swelling, pain, and loss of function.

Phases of inflammation

-Early or vascular phase, inflammation, vasodilation and increased permeability of blood vessels result in increased local perfusion and the movement of blood substances and fluid from the plasma to the injured tissue.

-Delayed or cellular phase. Can last hours to days after the injury occurs. Accumulation of leukocytes in inflamed tissue, reduced blood flow due to congestion, and tissue damage may occur.

Chemicals that induce inflammation

Prostaglandins and leukotrienes

Neuromuscular junction

The point at which a motor nerve fiber connects to muscle

Acetylcholine (ACh)

Neurotransmitter that releases when an electrical impulse of sufficient strength travels from the spinal cord to the neuromuscular junction.

Acetylcholinesterase (AChE)

Enzyme that breaks down ACh and readies the muscle for the next nerve impulse.

Arachidonic acid

When an injury occurs, the phospholipids in cell membranes are broken down into arachidonic acid.

Arachidonic acid is broken down by two enzymes: COX-1 and COX-2

COX-1

Produces beneficial thromboxanes/prostaglandins:

-GI protectants

-Help with renal blood flow

-Prevalent platelet aggregation

COX-2

Produces prostaglandins that cause inflammation and pain

Drugs that affect skeletal muscle

-Anti-inflammatory

-Neuromuscular blockers

-Skeletal muscle spasmolytics

Endogenous corticosteroids

Hormones produced by the adrenal cortex, the outer part of the adrenal gland.

Types of corticosteroids

Glucocorticoids (cortisol is the main form in animals) and mineralcorticoids (aldosterone is the main form in animals).

Mineralocorticoids

Primarily help the body retain sodium and water, maintaining the fluid and electrolyte balance crucial for body functions.

Glucocorticoids

Affect many functions of the body, including carbohydrate, protein, and fat metabolism, and muscle and blood cell activity. Also have anti-inflammatory effects, because inhibit phospolipase.

Steroidal anti-inflammatory drugs

Glucocorticoids (aka steroids) reduce inflammation by blocking the action of phospholipase.

Low doses= anti-inflammatory

High doses= immuno-suppressive

Commonly used glucocorticoids

•Hydrocortisone

•Dexamethasone

•Prednisone

•Prednisolone

•Methylprednisolone

•Triamcinolone

Glucocorticoids uses

·Inflammatory conditions

·Neoplasia (cancer)

·Allergies

·Immune-mediated diseases

Pruritus (itching)

Glucocorticoids. Long term use side effects

•Polyuria/polydipsia/polyphagia

•Immunosuppression

•Delayed wound healing

•Diabetes mellitus

Topical glucocorticoids increased the risk of corneal ulceration if corneal damage already exists

Glucocorticoids facts

-Animals should be tapered off to prevent iatrogenic Addison’s disease

-Cats and animals with liver problems should be prescribed prednisolone instead of prednisone

Cushing’s disease

Condition usually caused by overproduction of endogenous glucorticoids due to an adrenal tumor or pituitary disease. Clinical signs are PU, PD, and lethargy; bilaterally symmetrical alopecia; and a pendulous abdomen

Occurs when an animal has been treated with glucorticoids for an extended period of time.

Addison’s disease

Condition caused by insufficient glucocorticoid in the animal’s system.

Non-steroidal anti-inflammatory drugs

NSAIDS

This drugs are used to treat pain and inflammation.

Inhibit the COX enzymes in the arachidonic acid pathway

NSAID. Adverse effects

Some NSAIDs inhibit both COX enzymes and have a lot of GI side effects.

COX-2 may be less likely to cause GI side effects.

Acute kidney injury, especially in dehydrated or hypovolemic patients, and hepatotoxicity in some patients.

NSAIDs commonly used

•Carprofen (Rimadyl®)

•Deracoxib (Deramaxx®)

•Firocoxib (Previcox®)

•Robenacoxib (Onsior®)

Meloxicam (Metacam®)

NSAIDs new

Grapiprant (Galliprant). Prostaglandin receptor antagonist: Inhibits a specific prostaglandin receptor, further downstream and it’s safer for animals with GI, renal, or liver disease

Antipyretic

Fever reducing

Other anti-inflammatory drugs

Do not fall into either the steroidal or nonsteroidal categories.

-Dimethyl sulfoxide (DMSO)

Analgesic drugs

Relieve pain without causing loss of consciousness.

Narcotic (opioid) and nonnarcotic

Analgesics

-Acetaminophen

-Amantadine

-Ketamine

-Lidocaine

Considerations when selecting an analgesic

-Effectiveness of the agent

-Duration of action

-Duration of therapy

-Available routes of drug administration

Gabapentinoids

Gabapentin and pregabalin, were originally introduced as anticonvulsants.

Analgesic and anxiolytic effects.

Especially beneficial for neuropathic pain

N-methyl-D-aspartate (NMDA) Receptor Antagonist

-Ketamine

-Amantadine

Osteoarthritis treatments

Glycosaminoglycans or GAGs:

-Hyaluronic acid, also called hyaluronate

-Polysulfated glucosaminoglycans

-Glucosamine and chondroitin sulfate

Antihistamines

Drugs that counteract the effect of histamine competing for its receptor sites.

H1 blockers have a local anesthetic effect.

-Trimeprazine

Non-pharmacological treatments

-Cryotherapy

-Thermotherapy

-Acupuncture

-Physical rehabilitation

-Nutraceuticals (joint supplements)

Immunomodulators

Immunomodulation is the adjustment of the immune response to a desired level.

-Cyclosporine. One of the most effective immunosuppressant agents.

-Tacrolimus

-Oclacitinib

-Piroxicam

Spasmolytics

Treat acute episodes of muscle spasticity associated with neurological and musculoskeletal disorders.

Spasmolytics/ muscle relaxants

•Methocarbamol (Robaxin®). Is used as an adjunctive therapy for inflammatory and traumatic conditions of skeletal muscle.

•Guaifenesin. Muscle relaxant that blocks nerve impulses in the CNS and is used to relax both laryngeal and pharyngeal muscles

•Diazepam (Valium). Decreases the turnover of ACh in the brain.

Dantrolene. Inhibits calcium release from the muscle making it less responsive to nerve impulses.

Neuromuscular blocking agents

Called neuromuscular blockers, administered intravenously, paralyze muscles by disrupting the transmission of nerve impulses from motor nerves to skeletal muscle fibers.

Do not provide analgesia or sedation.

Sequence of muscle group paralysis with neuromuscular blocker

From first to last: Muscles of face, jaw, and tail; neck muscles and distal limbs; proximal limb muscles; muscles of the pharynx and larynx; abdominal muscles; intercostal muscles; and diaphragm.

Competitive nondepolarizers

Also called Curarizing agents are Neuromuscular blockers that compete with ACh for the same receptor sites, thus inhibiting the effects of ACh.

-Pancuronium

-Atracurium

-Rocuronium

-Vecuronium

Antidotes

Given to counteract the effects of another drug.

Antidotes to competitive nondepolarizers

-Neostigmine

-Pyridostigmine

-Edrophonium

Depolarizing drug

Also referred to as a non competitive neuromuscular blocker. It mimic the action of ACh in muscle fibers, and because the are not destroyed by AChE, their action is prolonged.

-Succinylcholine. It is used to reduce the muscle contraction associated with toxicities or pharmacologically induced convulsions.