Musculoskeletal System

KNH 413

Skeletal System

Cartilage, ligaments, tendons, bones

Metabolically active cells and tissue

Continual state of change

Skeletal System

Cartilage – flexible yet firm connective tissue consisting of cells and collagen fibersChondroblasts/chondrocytes – cellsCollagen – fibrous protein, most common protein in

the bodyChondroitin sulphate – most common polysaccharide

of cartilage

Skeletal System

Bone – osseous tissueOrganic – mineralized or calcified by inorganic

component; flexibility Inorganic - hydroxyapatite; stiffness, weight bearingReady source of calcium and phosphorus for

extracellular fluids Hydroxyapaptite (99%) Readily available pool (1%)

Skeletal System

BoneAbnormalities in serum calcium critical

Hypocalcemia – excessive excitability of the nervous system, tetany , respiratory arrest, convulsions

Hypercalcemia – fatigue, depression, metal confusion, anorexia, nausea, vomiting, constipation, hypercalciuria

Skeletal System

Cells of Osseous TissueOsteogenic cells – stem cells that differentiate into

osteoblastsOsteoblasts - bone-building cellsOsteocytes – mature osteoblasts, majority of cells in

boneOsteoclasts – bone-removing cells that secrete HCl;

bone resorption

Skeletal System

Skeletal growth and developmentContinual state of change; linear and circumferential

growth, and in response to changes in forces applied to them - remodeling

Osteoclasts remove bone from low-stress areas, osteoblasts lay down new bone in high-stress areas

Skeletal System

Cortical boneDense, outer surface of most bones, shafts of

long bones, and caps over end of long bones75% of skeletal weight

Trabecular boneLoosely organized with a sponge-like

appearance; lattice-like pattern“Ends” of long bones, primary bone of

vertebrae, pelvis, sternum, scapula25% of skeletal weight

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© 2007 Thomson - Wadsworth

© 2007 Thomson - Wadsworth

Skeletal System

Hormonal control of bone metabolismCalcium and phosphorus homeostasis

Cortisol, growth hormone, thyroid hormones Primary regulators: parathyroid hormone (PTH),

calcitonin, vitamin D

Skeletal System

PTH – increases blood calcium when low Increase in osteoclasts and bone resorption Inhibition of collagen synthesis and bone depositionCalcium resorption by kidneysFinal step in vitamin D synthesis, enabling intestinal

absorption of calcium

Skeletal System

Calcitonin – decreases blood calcium when high Inhibits activity of osteoclastsStimulates osteoblastsReduces renal reabsorption of calcium and

phosphate

Skeletal System

Vitamin D – increases blood concentrations of calcium and phosphorusPromotes their absorption in GIPromotes reabsorption by kidneysStimulates osteoclast formation and release of

calcium and phosphorus from bone

Skeletal System

Vitamin D –

Ergocalciferol - dietaryCholecalciferol – dietary,

exposure to sunlightBoth biologically inactive until

modified by liver and kidney to 1,25-dihydroxyvitamin D

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Osteoporosis

Decreased bone mineral and organic matrix which weakens bones, making them more susceptible to fracture and pain

Bone strength reflects:Bone densityBone quality

© 2007 Thomson - WadsworthHealthy (L) and osteoporotic (R) trabecular bone

OsteoporosisDiagnosis

Measures of bone mineral density (BMD)DXA – dual-energy x-ray absorptiometry “T-score” – comparing patient’s BMD to healthy young

reference populationBMD assessed at hip and lumbar spineSee WHO criteria

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DEXA scan of the left hip

Osteoporosis

Diagnosis

Others:Quantitative ultrasound of the heel used in

conjunction with risk assessment – useful for screening

Osteopenia – bone mineral density is low but not low enough to be classified as osteoporosis, although fracture risk is increased

Osteoporosis

BMD increases rapidly during growth spurt (ages 11-14 y)

Maximum density reached in late 20s or 30s

Females lose BMD at faster rate than men

Rate of loss increases during menopause

Osteoporosis

FracturesMost common sites: hip, spine, wristKyphosis – unnatural curvature of back, and loss of

height d/t compression fractures of spineHip fractures have severe impact on morbidity and

mortality 20% die within first year, 20% end up in nursing homes

Osteoporosis

EtiologyPrimary – disease of elderly, cumulative impact of

bone mineral loss and deterioration of bone with age; “age-related,” “postmenopausal”

Secondary - disease and drug associated 2/3 of cases in men

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Osteoporosis

Risk factors

Genetic susceptibilityFamily hxFemale sexCaucasian racePremenopausal amenorrheaPhysical inactivityLow calcium and vitamin D intakes

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Osteoporosis

Prevention strategiesRisk reduction in adolescence and early adulthoodAdequate calcium and vitamin D intakeWeight-bearing exerciseFall preventionSmoking cessationAvoidance of excessive alcohol intake

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Osteoporosis

Calcium Maintenance of serum calcium levels to

combat bone resorptionAchieve peak bone mass and minimize bone

mineral lossLower intakes of animal protein, sodium,

caffeineIncreased consumption of fruits, vegetables,

legumes, whole grainsMore physical activitySun exposure

OsteoporosisCalcium

Consume calcium-rich foodsCalcium-fortified foodsCalcium supplements

Calcium carbonate – least expensive, taken with meals, not at the same time as iron

Calcium citrate – taken any time Calcium with vitamin D Avoid dolomite and bonemeal – lead contamination Divided doses to improve absorption

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OsteoporosisVitamin D

Overt deficiency – rickets in children, osteomalacia in adults

Insufficiency found in dark-skinned, older, in northern latitudes (above 40 degree N)

Supplementation with vitamin D and calciumFortified dairy products Exposure to adequate sunlight

OsteoporosisPhysical activity

BMD increases with weight-bearing or impact-type activity

Very high levels can be detrimental if oligomenorrhea or amenorrhea present

OsteoporosisCigarette smoking

Lower BMD, increased bone mineral loss, increased risk of fractures

Nicotine and cadmium toxic to osteoblastsReduced intestinal calcium absorptionLower intakes of vitamin D, and lower serum vitamin

D

OsteoporosisAlcohol

Decreased BMD, reduced bone formation, increased risk of fractures

Increased calcium and magnesium lossesAdversely impacts vitamin D and overall nutritional

status Increased risk of falls

OsteoporosisPhosphorus – essential for bone formation

Carbonated soft-drinks have negligible effect on calcium excretion

High protein or sodium - increase urinary calcium losses

Potassium, magnesium, fruits, vegetables associated with higher BMD

OsteoporosisMedical management

Risk factor modificationDietary treatmentDrug therapy

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OsteoporosisPharmacologic prevention and treatment

Estrogens/ hormone therapySelective estrogen receptor modulators (SERMs)BisphosphonatesTeriparatide (synthetic PTH)Drug-nutrient interactions

Paget Disease

Localized, progressive, crippling disorder of bone remodeling d/t overactive osteoclasts and bone resorption followed by rapid formation of new bone which is structurally inferior

Bowing, deformity, fracture, poor healing

Upper femur, pelvis, vertebral bodies, skull, tibia

Genetic and viral factors

Adequate intake of vitamin D and calcium important

Rickets Inadequate maturation and

mineralization of bone in children

d/t vitamin D deficiency

Risk factors – Table 27.10

Symptoms: lethargy, weakness, growth stunting, enlargement of ends of long bones and ribs, abnormally shaped thorax, bowing of legs

Rickets

PreventionExclusively breast fed infants should receive

supplement of 200 IU vitamin DFortified infant formulas

If receiving less than 500 mL/day, should be given multivitamin supplement

After 1 year – vitamin D-fortified cow’s milk

Rickets

TreatmentBalanced, age-appropriate dietAdequate vitamin D, calcium, phosphorus

Osteomalacia

Organic matrix of bones inadequately mineralized in adults

Muscular weakness, bone pain, deformities of ribs, pelvis, legs

d/t vitamin D deficiency, impaired D action, calcium deficiency, hypophosphatemia

Osteomalacia

TreatmentAddress underlying causeMultivitamin supplementationCalcium supplementationPharmacological doses of vitamin D

Arthritic Conditions

Affect joints, tissues surrounding joints, and connective tissues

Osteoarthritis, rheumatoid arthritis, gout (affecting all ages)

Risk factors - modifiable:Overweight Joint injuries Infections

Arthritic Conditions

Risk factors - nonmodifiable:Female sex – 60% of casesAgeFamily hx

Osteoarthritis

Most common, leading cause of physical disability

Disease process involving all structures of the jointLoss of load-bearing articular cartilageInflammationJoint pain, stiffness, limited movement,

wasting of periarticular muscles, joint instability and deformity

Osteoarthritis

Major risk factorsAgeFemale sexFamily hxMajor trauma to joint or soft tissueRepetitive joint stress related to occupation Obesity

Osteoarthritis

TreatmentReduce joint inflammation & pain, maintain mobility,

minimize disability Improve body postureProper footwearWeight reductionPeriodic rest of affected jointHeatPhysical activity/ therapeutic exercise

Osteoarthritis

TreatmentDrug therapy – pain relief

NSAIDs Glucosamine and chondroitin

Rheumatoid Arthritis

Chronic inflammatory disease; synovial membrane becomes inflamed resulting in swelling, stiffness, pain, limited range of motion, joint deformity, disability

Characterized by periods of exacerbation and remission

Autoimmune response

Rheumatoid Arthritis

Inflammation of joints of hands, wrists, knees, & feet results in warmth, redness, swelling, stiffness, and pain

Inflammation results in thickening of synovial membrane known as pannus – see Fig. 27.10

Enzymes from pannus digest adjacent bone and cartilage

Rheumatoid Arthritis

TreatmentReduce pain and inflammation, protect joint,

maintain function, control systemic infectionsPharmacological agents: NSAIDs, glucocorticoids,

immunosuppressives, DMARDs

Rheumatoid Arthritis

Diet Increase consumption of fruits and vegetables/

antioxidants Include sources of EPA and DHA (fatty acids)Fish oil supplementationExclusion of red meats, dairy, cereals, wheat glutenEvaluate and test for food allergy

Gout

Inflammatory disease resulting in swelling, redness, heat, pain, and stiffness in affected joint

d/t elevated serum concentrations of uric acid, formation of uric acid crystalsEnd product of purine (adenine and guanine)

metabolism

Gout

Hyperuricemia results from overproduction of uric acid, inadequate elimination by the kidneys, or combination

Most painful arthritic condition

Risk factors: genetics, male sex, older age, overweight, excessive alcohol consumption, eating foods rich in purines, exposure to lead, certain drugs

GoutMost commonly affects great toe, instep, ankles,

heels, knees, wrists, elbows, fingers

Rapid occurrence

Sudden severe pain; swelling; shiny, red skin around joint; extreme tenderness

Typically resolves 5-10 days, may reoccur

GoutAcute attack may be precipitated by:

Excessive exerciseCertain medications: aspirin, diuretics, nicotinic acid,

cyclosporine, levodopaPurine-rich foods Excessive alcohol consumptionCrash dieting

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GoutTreatment:

NSAIDs, glucocorticoids, colchicineTreat uricemiaLifestyle modifications

FibromyalgiaChronic musculoskeletal disorder characterized by

widespread muscle pain, joint stiffness, disturbed sleep, fatigue, headache, cognitive and memory problems, paresthesias, & tender points

Not crippling, deforming, or disabling

Etiology unknown

FibromyalgiaDg by ruling out other potential causes of

symptomsHx of pain that is widespread for at least 3 monthsExcessive tenderness or pain with pressure to at least

11 of 18 tender points

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FibromyalgiaTreatment

Improve sleep, treat depression, anxiety and pain, improve ability to relax

Antidepressants, counselingRegular physical activityCognitive behavioral therapy Intensive patient education

FibromyalgiaDiet

Avoidance of certain foods has worked for someLow-sodium, uncooked vegan diet has shown promise ? MSG avoidanceLack of sound scientific evidence at this time