What is the function of the musculoskeletal system?
supports the body, protects the organs, provides for movement, stores calcium, produces blood cells.
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.
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
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
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.
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).
bruise (ecchymosis) contusion- soft tissue injury that often accompanies skeletal trauma. results from direct trauma, overlying skin remains intact.
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.
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)
tear of muscle ligaments, structures surrounding joint from abnormal movement of joint, signs inflammatory response, pain, swelling subside more slowly than strain,
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
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)
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.
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.
fragments are wedged together. Usually in the humerus and is less serious and treated without surgery
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.
spiral, oblique and comminuted fractures
more unstable and likely to change position after reduction.
Manifestations of fractures
pain and tenderness, swelling, loss of function, deformity, abnormal mobility,angulation, shortening and rotation,
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.
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)
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.
bony callus (ossification) 3-4 weeks, mature bone replace fibrocartilaginous callus. Bone begins to calcify as the mineral salts and calcium is deposited.
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.
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.
individual factors that delay bone healing
age, medications, disease like (RA, diabetes, local stress, circulatory problems, nutrition.
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
failure of union to unite in the normal period eg. 20 weeks for fracture of tibia or femur in adult.
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