Osteoporosis

Stephanie Wetmore, PT

PED 596: Adv. Cardiac Rehab

Wayne State College

Osteoporosis

A disease characterized by irregularities in the quantity and architectural arrangement of bone tissue that lead to decreased skeletal strength and increased vulnerability to fractures.

Normal Physiology

FunctionsProvides support to body

Protects vital organs

Assists in movement via leverage

Hematopoiesis (blood cell production)

Storage area for Ca++

Cell TypesOsteoblasts

Synthesize boneRemodeling and repair

OsteoclastsResponsible for bone resorptionRemodeling and repair

OsteocytesPrimary cells of mature boneOsteoblasts surrounded by matrix during bone formationMaintenance and resorption

Bone Formation & Growth

Intermembranous ossificationBone forms directly in the embryonic connective tissue

Endochondral ossificationA “scale model” of hyaline cartilage is replaced by bone

Process of formation for most bones

A Closer Look at Endochondral Ossification and Growth

1. Formation of cartilage skeleton in embryo (6-12 wks gestation)

2. Ossification and growth occur in subsequent months

3. When ossification completed, growth in length occurs at epiphyseal plates

4. Widen by multiplication of cartilage cells and cancellous bone replaces the dying cartilage5. Growth in width occurs by depositing of compact bone beneath the periosteum (outer surface) and enlargement of the marrow cavity by bone resorption6. Growth ceases when epiphyseal plate is replaced by bone.

Endochondral Ossification & Growth

Homeostasis

Balance between bone formation & resorptionRemodeling process

Old bone destroyed by osteoclastsNew bone constructed by osteoblasts

Dependent upon Ca++, P, and vitamins (esp. vit. D)Controlled by hormones

Regulation of Bone Formation & Growth

Vitamin DIncreases rate of Ca++ absorption from intestine

Growth HormoneNeeded to stimulate proliferation of cartilage cells at growth plate

Vitamin CImportant in synthesis of collagen

ThyroxinIncreases rate of replacement of bone at growth plate and needed for synthesis of GH

Vitamin AStimulates resorption of bone

Estrogens & androgensPromote ossification and maintenance of matrix

Parathyroid hormone & CalcitoninRegulate release of Ca++ from bone

Parathyroid hormone & calcitonin

When blood Ca++ levels are low, PTH is released.Release of PTH increases rate of bone resorption, which increases the concentration of Ca++ in the blood.When blood Ca++ levels are high, calcitonin is released, which inhibits resorption.

Pathophysiology

Osteoporosis can be either hormonally induced or mechanically induced.

MechanicalElectrical changes created with weight bearing stimulate activity of osteoblasts, which lead to a build up of Ca++.

This does not occur without weight bearing (when someone is on bed rest)

As we age normally

Birth to age 20-30GH influences deposition of bone, which exceeds resorption rate

Age ~50 to age 80Resorption exceeds deposition due to decreased osteoblast activity and changes in Ca++ metabolism

Rates of Bone Loss with Normal Aging

Female >30-35Lose .5-1% of bone mass/year

Postmenopausal FemalesLose 2-3% bone mass/year until ~age 70

Women will lose ~45-50% in lifetime

Men will lose ~20-30% in lifetime

Normal Bone vs. Osteoporosis

Normal vs. Ostoeporosis

Classification System

Epidemiology of Primary Involutional Osteoporosis

Most common fracture sitesWrist, vertebrae and hip

Risk of Fracture

Caucasian WomenVertebral 15.6%

Hip 17.5%

Wrist 16%

Overall 39.7%

Caucasian MenVertebral 5%

Hip 6%

Wrist 2.5%

Overall 13.1%

Fracture Risk (cont.)

Wrist & hip fractures are most commonly the result of a combination of bone loss and moderate trauma such as a fall

Of all NH admissions, 21% are made following a hip fracture.

Vertebral compression fractures can occur simply by coughing, bending forward or hugging.

Risk Factors

Advancing age – 1.4 to 1.8 fold increase with each decade

Gender – women > men

Family or personal hx of fx as an adult

Repeated fx’s, severe stooped posture

Risk factors (cont.)

Race – Caucasian & Asian > African American or Hispanic

Bone Structure and Body Weight – small-boned and thin women (<127#) are at greater risk

Menopause/Menstrual historyNormal, premature (<45 y/o) or surgical

Late onset menarche (>15 y/o) or prolonged amenorrhea – anorexia nervosa, bulimia, excessively low body fat

Risk Factors (cont.)

Lifestyle/NutritionCigarette smoking – inhibits estrogen

Alcoholism

Inadequate intake of Ca++

Sedentary lifestyle

High caffeine consumption and phosphoric acid intake (cola drinks)

Eating disorders

Are you getting enough Calcium?

What is adequate Ca++ intake?

Age 1-3 years 500 mg/day

Age 4-8 years 800 mg/day

Age 9-18 years 1300 mg/day

Age 19-50 years 1000 mg/day

Age >50 years 1200 mg/day

Risk Factors…Medications

GlucocorticoidsCorticosteroidsExcessive thyroid hormonesAnticonvulsantsGonadotropin releasing hormonesMethotrexateCyclophosamideDexamethasoneLithium

Cyclosporine AHeparin or CoumadinCholestyramineNo ERT or HRTLow testosterone levelsChemotherapeuticsAntacidsIsoniazidImmunosuppressantsDiuretics

Risk Factors…Chronic DiseasesArthritisGlycocorticoid excessLung disease (COPD)Organ transplantsSCIHyperthyroidismHyperparathyroidismChronic kidney/liver diseaseRARSDMalabsorption problems

Turner syndromeCVAMSLupusIDDMChronic inflammationChron’s diseaseCABurnsAsthmaMental illness (depression)

Bone Mineral Density Testing

Painless, non-invasive test, which identifies osteoporosis, determines fx risk and monitors response to treatment.

WHO Definitions

Normal+/- 1 SD of the young adult mean

Low Bone Mass (osteopenia)-1 to –2.5 SD of the young adult mean

Osteoporosis>-2.5 SD of the young adult mean

Severe (established) osteoporosis>-2.5 SD of the young adult mean & one or more osteoporotic fractures

DEXA Images & Reports

Pharmacology

Estrogen Replacement Therapy/Hormone Replacement Therapy

Reduces bone loss, increases bone density, reduces risk of fx in postmenopausal women

Increase risk of uterine and breast CA, increased risk of thromboembolism

Biphosphonates

Alendronate Sodium (Fosamax)Reduces bone loss, increases bone density, reduces risk of spine and hip fracturesSide effects include bone, muscle and/or joint pain and headache

Risedronate Sodium (Actonel)Slows bone loss, increases bone density and decreases spine and hip fracturesAlso approved for men & women to prevent and/or treat steroid-induced osteoporosis

SERMs family

Selective estrogen receptor modulators

Raloxifene (Evista)Prevent bone loss, increase bone mass and decrease risk of vertebrae fracture

Side effects: DVT, leg cramps, syncope, arthralgia, tendon disorder and vertigo – chest pain, myalgia and arthritis possibly (<placebo).

Calcitonin (Miacalcin)

Naturally occurring hormone involved in Ca++ regulation and bone metabolism

Slows bone loss, increases bone density and relieves pain associated with vertebral fractures

Exercise Testing Modification/Exercise Limitations/Capacity

Weight-bearing exercise and resistance training recommended with precautions

Weight-bearing Exercise

Brisk walking is idealAlternatives: hiking, stair climbing, dancing and racquet sportsContraindicated = stair steppers, bicycling (including stationary), rowing machines, running and high-impact aerobics

Stair steppers – combination of unilateral WB and force to depress stepBicycle – increased flexionRowing machines – deep forward bending (flexion)

Testing Contraindications

Sub maximal cycle ergometer

Step-tests

Resistance Training

Light weights recommended

Major muscle groups emphasized

Slow progression over several monthsFatigue after 10-15 reps

Increases do not exceed 10% per week

Proper technique

Every third day

If joint swelling, limping or pain after, decrease weight by 25-50%.

Resistance TrainingContraindications

Weight carrying tests

Repetitive lifting tests

Flexibility Exercises

Flexion exercises contraindicated if vertebral bone density decreased or risk of compression fx

Avoid knee to chestForward bendingTouching the toesPartial sit-up

Okay if thoracic spine stabilized and do not lift head and chest above T-6 level.

Flexibility ExercisesContraindications

Sit-and-reach test

Curl-up muscular endurance test

Other exercise

HR, BP, ECG, ventilation frequency, tidal volume, oxygen saturation and expired oxygen and carbon dioxide should not be affected by osteoporosis medications.

Increasing kyphosis of the thoracic spine will make it more difficult to expand the lungs fully during inspiration

Sample Exercise PrescriptionBrisk walking 15-20 minutes 3-4x/wk

Begin with 5-minute walks and increase by one minute every other session

Flexibility program – body extender, shoulder pinches, chin tucks, elbow backs, arm reaches and back arches dailySinaki & Mikkelsen study

Flexion programs – 86% fx rateExtension programs – 16% fx rateControl group – 67% fx rateFlex/Ext programs – 57% fx rate

Sample Exercise (cont.)

Resistance TrainingEvery third dayMajor muscle groups especially those integral to fall prevention

Hip extensors, flexors, adductors, abductors, quadriceps, ankle dorsiflexors & plantar flexors and trunk extensors & stabilizers

One set 10-15 repsIncrease no greater than 10% per week for amount of weight

Resources

National Osteoporosis Foundationhttp://www.nof.org

American Academy of Orthopedic Surgeons http://www.aaos.org

Lewis, C.B. (1990), Aging: The Healthcare Challenge (2nd ed.)

Sinaki & Mikkelsen (1988)

Katz & Sherman (1998)