musculoskeletal disorders 1

skeletal system

functions in support and protection of the body, composed of bone and cartilage embedded in nonliving ECM

bone

widely spread cells embedded in a solid matrix formed by collagen and crystallized mineral salts; forms solid support sturcture and acts as reservoir for calcium and phosphate

cartilage

widely spread cells embedded in a gelatinous matrix that are slightly flexible in structure; has roles in prenatal and childhood development of the skeleton and the surface of atricular ends of skeletal joints

ossification

bone formation; involves deposition of inorganic crystals in an organic matrix

osteoprogenitor cells

stem cells from bone cell lineage that differentiate into osteoblasts

osteoblasts

bone-building cells from bone cell lineage that secrete ECM and become osteocytes

osteocytes

mature bone cells from bone cell lineage that maintain bone metabolism

osteoclasts

cells from the WBC lineage that releases enzymes that break down bone ECM

bone resorption

process in which osteoclasts release enzymes and acids that digest organic protein matric and inorganic components of bone, forming a tunnel-like space in osteon

bone deposition

process in which osteoblasts synthesize and secrete collagen fibers to build successive lamellae on canal wall; calcium and other minerals are deposited and ECM hardens

RANKL

protein produced by osteoblsts; binds to RANK receptor on osteoclasts

RANK

receptor found on osteoclasts; directly activates the osteoclast when RANKL binds

osteoprotegerin (OPG)

acts as a decoy receptor for RANKL and produced by osteoblasts, inhibits osteoclasts by preventing RANKL from binding to RANK

wnt

plays key role in bone formation; activates osteoblasts and promotes bone formation

sclerostin

encoded by SOST gene and acts as a wnt inhibitor; inhibits bone formation by dec osteoblasts and OPG, and inc osteoclasts and RANKL

sclerostin inhibtor

inhibits sclerostin action and promotes bone formation

calcium and phosphate

nutritional factor needed for healthy bone; required for bone formation and growth

vitamin D

nutritional factor needed for healthy bone; increases calcium absorption from GI tract

vitamin C

nutritional factor needed for healthy bone; required for collagen synthesis

vitamin A

nutritional factor needed for healthy bone; stimulates osteoblast activity during bone remodeling

vitamin K and B12

nutritional factor needed for healthy bone; needed for synthesis or bone proteins

GH and insulin like growth factors

hormonal factors needed for healthy bone; promotes osteoblast activity and protein synthesis

thyroid hormones

hormonal factors needed for healthy bone; stimulate osteoblasts

sex hormones

hormonal factors needed for healthy bone; slows bone resorption by osteoclasts and promotes bone deposition by osteoblasts

calcitonin

hormonal factors needed for healthy bone; released when Ca levels are high; inhibits osteoclasts

parathyroid hormone

hormonal factors needed for healthy bone; promotes osteoclast activity; promotes formation of calcitriol in kidneys, and inc calcium reabsorption from urine

fracture

a break in the continuity of a bone; occurs when amount of stress is greater than the amount of force the bone can absorb

complete fracture

fracture occuring when parts of the bone are completely separated

partial fracture

fracture occuring when the break is incomplete; ex. greenstick fractures

open fracture

also compound; when broken ends of bone protrude through the skin

closed fracture

also simple; broken bones do not break through skin

comminuted fracture

when bone fractres into more than 2 pieces

compression fracture

when bone is crushed or sqeezed together

impacted fracture

when one end of fractured bone is forcefully drived into interior of the other end

stress fracture

failure of one external surface of the bone

avulsion fracture

separation of a small piece of bone at the site of a ligament or tendon

reduction

bone fracture treatment; align bone close to anatomical position

immobilization

bone fracture treatment; maintain proper alignment of fragments during healing using casts, splints, traction, etc.

closed manipulation

bone fracture treatment; for closed fractures → no surgery; skin is not open and bones are manipulated back into place

open manipulation

bone fracture treatment; for open fractures → surgical realignment of bone using screws, plates, nails, wires, etc

hematoma formation, fibrocartilage formation, bony callus formation, remodelling

4 steps of bone repair

hematoma formation

bone repair; blood vessels tear and bleed into and around bone, forming blood clot in next 4-6 hrs; facilitates formation of fibrin meshwork to seal off fracture site and provide framework for influx of inflammatory cells

fibrocartilaginous callus formation

bone repair; formation of granulation tissue or procallus; fibroblasts proliferate and create fibrocatilaginous bridge to connect bone fragments; procallus grows for 2-3 weeks but not strong enough for weight bearing

bony callus formation

bone repair; conversion of soft cartilage to bony callus → ossification; ospeoprogenitors develop into osteoblasts which produce spongy bone; bony callus gradually calcifies and is replaced by mature bone over next few weeks

bone remodelling

bone repair; dead portions of bone are removed by osteoclasts; compact bone replaces spingy bone at periphery; final stucture resembles original bone, but thickened area may remain on bone surface

delayed healing

healing complication; includes delayed union, malunion, or nonunion; anything that delays healing of the bone

delayed union

healing complication; failure of fracture to heal within predicted time, may be due to infection, smoking, malnutrition, corticosteroid use, dec vascularization of area, all due to supressed immune function

malunion

healing complication; bones do not come together in normal anatomical position and are not aligned properly, causing deformity at fracture site

nonunion

healing complication; failure of the bone to heal

osteonecrosis

healing complication; ischemia due to damaged or blocked vessels, causing death of bone tissue

compartment syndrome

healing complication; increased pressure in muscle compartment (may be due to hematoma, inflammation, etc.) which causes pressure on blood vessels and nerves leading to more damage

fat embolism

healing complication; since bone marrow is fatty → glob of fat may break away during fracture and travel through blood vessels

osteoarthritis

healing complication; bones do not come together exactly as they did before → causes more pressure over time

dislocation

temporary displacement of 2 bones where there is complete loss of contact between articular cartilage

sublaxation

occurs when contact between joint surfaces is only partially lost

osteomyelitis

a group of bone disorders involving poygenic inflammation of the bone and bone marrow due to infection

osteomyelitis SS

acute and chronic inflammation, fever, pain, necrotic bone; occurs mostly in metaphyses of long bones, vertebrae

skeletal TB

extrapulmonary form of TB → pathogen spreads from lungs to bone via blood or lymph, commonly in weight bearing joints or vertebrae

Pott’s disease

specific form of skeletal TB where it affects the spine → vertebral body necrosis → vertbral collapse → kyphosis and scoliosis → damage to motor and sensory function

osteoid ostoma

small benign tumour of osteoblasts, usually located on surface of long bones, flat bones, and skull; common in young adults and is 10-13% of all primary bone tumours

osteoblastoma

a larger, more lytic version of osteoid ostoma

giant cell tumour

benign but locally aggressive tumour of multinucleated giant osteoclasts usually located at the junction of metaphysis and epiphysis of long bones; common in 20-40 yrs females and is 10% of all primary bone tumours

osteosarcoma

highly malignant tumour of osteoblasts usually occuring around the knee; mainly affects 10-25 years and >60 years; is the most common primary malignant bone tumour

chrondrosarcoma

malignant tumour of boen cartilage usually around shoulder, pelvis and ribs; mainly affects males age 40-70 yrs; is the second most common primary malignant bone tumour

ewing sarcoma

highly malignant tumour of undifferentiated bone cells usually in the long bones and pelvis; mainly affects children and young adults undeer 20 yrs; is rare

fibrosarcoma

malignant tumour of fibroblasts usually in metaphysis of femur or tibia; commonly metastasizes to the lungs

secondary bone tumours

metastatic and often multifocal tumours that arise from other areas of the body and metastasizes to the bone via blood or lymph; most common form of bone cancer