pathophysiology, musculoskeletal

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Moore

What is the function of the musculoskeletal system?

supports the body, protects the organs, provides for movement, stores calcium, produces blood cells.

what is the musculoskeletal system comprised of?

bone, muscle, tendons, ligaments, joints, bursa

What is cancellous bone

found in interior, lattice like pattern, trabeculae or spicules of bone, filled with red or yellow marrow. Cancellous bone is relatively light weight but its structure is such that it has tensile strength and weight bearing properties

what is cortical bone?

forms the outer shell, compact bone, densely packed, calcified, more rigid than cancellous. compact bone is the main component of tubular bones, and along stress lines.

Bone cell types, what are osteogenic cells?

undifferentiated cells, differentiate into osteoblasts, active in normal growth, participate in removal of worn out bone tissue.

Osteoblasts are

bone building cells

Osteocytes

mature bone cells, maintain the bone matrix, can release calcium into the blood.

osteoclasts

multinusleated, bone chewing cells, large phagocytic cells, function in breakdown of bone matrix, release calcium and phosphate from bones, remove mineral content and organic matrix, parathyroid hormone controls the numbers and resorptive function, calcitonin hormones reduce the number and resorptive function

Osteoclast slide

osteoclasts cells are carried via bloodstream to the bone where the firmly attach and release acids and enzymes that dissolve bone/ Osteoblast appear and produce collagen core and coat it with adhesive, calcium adheres to collagen forming new bone.

What covers the bone

periosteum, except at articular ends by this membrane, outer layer is fiberous. inner layer contains osteogenic cells, needed for bone growth and development. contain vessels that anchor vessels as they enter and leave the bone.

hormonal control ov bone formation

parathyroid hormone (PTH) is secreted by the p glands. PTH causes an increase in serum calcium and phosphate release from bone causing kidney to conserve calcium and excrete phosphate. activates vitamin d to enhance intestinal absorption of calcium, reduces serum phosphate level

calcitonin

secreted by thyroid gland, decreases serum calcium, inhibits the release of calcium from bone into the blood. inhibits osteoclast activity and sequesters calcium in the bone cells. decreases re absorption of calcium by kidneys.

Vitamin D

steroid hormone, found in fish, liver, and fortified milk, uv light also produces, Actions: increases intestinal absorption of calcium, promotes actions of PTH (resoprtion/breakdown and release of calcium from bone).

Traumatic injuries

bruise (ecchymosis) contusion- soft tissue injury that often accompanies skeletal trauma. results from direct trauma, overlying skin remains intact.

hematoma,

also soft tissue injury, large area of local hemorrhage, causes pain when blood accumulates and puts pressure on nerve endings. pain and swellin take longer to subside than with a contusion.

strain and sprain

both musculoskeletal injuries but differ in terms of tissue affected

strain

involve muscles, or the muscle tendon unit, caused by stretch/partial tear of muscle that is actively contracting. signs: inflammation response at site, fibrous tissue replacement of damaged muscle fibers (pain, swelling, redness, warmth)

sprain

tear of muscle ligaments, structures surrounding joint from abnormal movement of joint, signs inflammatory response, pain, swelling subside more slowly than strain,

dislocation

abnormal displacement of the joint surfaces so that they are not in contact. follow sever trauma that disrupts the holding ligaments. complete loss of articulation of bone that ends with separation of joint capsule, can be traumatic, congenital, or pathologic (from RA, paralysis) signs pain, deformity, limited movement

subluxation

partial dislocation, bone ends still in joint, fingers shoulders

Fracture

disruption in the continuity of bone, bone can withstand compression and shearing

fracture occurs

more stress than the bone can absorb

grouped according to cause, causes are:

fatigue stress fracture, pathologic stress fracture, and fracture from sudden injury

sudden injury most common

force is direct, sudden blow, fall, indirect such as trauma transmitted along bone or massive contracture.

fatigue stress fracture

imcomplete fractures, excess stress applied to normal bone, occur on any weight bearing bone but most common on metatarsal, neck of the femur, calcaneus, tibia, fibula and pelvis (unusual stress and pain)

pathologic fracture

normal stress applied to bones that have been weakened. spontaneous or with little or no stress, underlying disease state can be local as with infections, cysts or tumors, generalized as in osteoporosis, paget disease or disseminated tumors.

fractures are classified

location, type and direction, pattern of the fracture line.

how are fractures of the long bones described?

proximal, midshaft, distal. other descriptions are used when the fracture affects the head or neck of a bone, involves a joint or is near a prominence such as a condyle or malleolus.

the type of fracture is determined by:

its communication with the external environment, the degree of break in continuity of the bone, and the characteristic of the fracture pieces.

fracture can be classified

as open or closed. open or compound when bone is sticking out. closed the skin is not communication with outside.

greenstick

half broke half bent.

comminuted fracture

more than two pieces

compression,

squeezed, occurs in the vertebral body

impacted fracture

fragments are wedged together. Usually in the humerus and is less serious and treated without surgery

Reduction

is the restoration of a fractured bone to its normal anatomic position. the pattern of the fracture provides information about the easiest method for reduction.

Transverse fracture

simple angulatory forces, not likely to lose its place after reduction

spiral fracture

twisting motion or torque, unstable and may change position after reduction

spiral, oblique and comminuted fractures

more unstable and likely to change position after reduction.

oblique fracture

runs oblique to the bone, 45 degree angle

Manifestations of fractures

pain and tenderness, swelling, loss of function, deformity, abnormal mobility,angulation, shortening and rotation,

crepitus

grating sound, may be heard as the bone fragments rub against each other.

open fracture

bleeding from the wound where the bone protrudes. can cause hypovolemic shock (pelvic or multiple long bone)

four stages of bone healing: occurs in a manner similar to soft tissue healing but is more complex and takes longer

hematoma formation, fibrocartilaginous callus, bony callus, remodeling.

stage one

hematoma formation, 1-2 days, vessels damaged, clot forms around fragments, new blood vessels form, initiates cellular events (clotting factors, platelets, inflammatory cells held in area)

stage two

fibrocartilaginous callous- soft tissue callus, osteoblasts and fibroblasts migrate to the site, fibroblasts produce collagen that spans the break and connects the broken ends. Osteoblasts deposit bone into matrix. after a wed days fibrocartilage collar becomes evident around the fracture. eventually collar edges unite to form a bridge which connects the bone fragments.

stage three

bony callus (ossification) 3-4 weeks, mature bone replace fibrocartilaginous callus. Bone begins to calcify as the mineral salts and calcium is deposited.

stage four

Remodeling - excess bone callus removed by osteoclastic activity. as callus matures the portions not stressed by weight bearing activity are reabsorbed, callus reduced in size, shape and outline of bone is reestablished.

bone healing

children 4-6, adolescent 6-8, adult 10-18. children heal faster b/c more cellularity and vascularity of the childs periosteum. Periosteum in the membrane that lines all bones.

Delays to healing

in general, fractures of long bones, displaced fractures, and fractures with less surface area heal more slowly.

Functional return

within 6 months after union is complete. complete function may take longer.

individual factors that delay bone healing

age, medications, disease like (RA, diabetes, local stress, circulatory problems, nutrition.

fracture union

healing correctly, safe to remove support

malunion

healing with deformity, angulation, or rotation that is visible on the x ray. cause of malunion is improper of delay of treatment. early and aggressive treatment and reduction can prevent malunion. important in hand

delayed union

failure of union to unite in the normal period eg. 20 weeks for fracture of tibia or femur in adult.

non union

failure to produce a union and cessation of the process to repair. what bone most common? tibia most often open or crushing fractures, characterized by mobility of the fracture site and pain on weight, wobble.

complications of fractures

compartment syndrome, exists in the legs and forearms. the compartment is comprised of bone, muscle and nerve encapsulated in a inelastic fashia and skin. this closed space is created. fracture causes pressure to build in the compartment due to bleeding and swelling. eventually pressure on nerves and vessels.

compartment syndrome damage

nerve damage in 30 minutes, necrosis in 2-4 hours, irreversible function loss if persists greater than 12 hours. Mostly in forearm and tibia called Volkmanns ischemia. Paresthesias, severe pain, swelling, paralysis, foot drop, gangrene

Fat Emboli

Risk with long bone fracture and pelvic fracture, fat globules released from bone marrow into circulation. lodge in the brain and lungs causing PE, CVA. signs are from a few hours to 3-4 days after injury, not beyond one week. Respiratory distress, chest pain confusion.

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