DIAGNOSIS OF OSTEOPOROSIS

DR NITIN KAUSHIK

J.R. ORTHOPAEDICS

Definition

A systemic skeletal disease characterized by low bone mass and micro architectural deterioration of bone tissue leading to bone fragility and susceptibility to fracture

Who Gets Osteoporosis?

Immobilization Hypogonadal states Endocrine disorders Malnutrition, parenteral nutrition and

malabsorption rheumatologic disorders Renal insufficiency Hematologic disorders Several inherited disorders

Osteoporosis

Mechanisms causing osteoporosis Imbalance between rate of resorption and

formation Failure to complete stages of remodeling

Types of osteoporosis Type I Type II Secondary

Osteoporosis - Types

Postmenopausal osteoporosis (type I) Caused by lack of estrogen Causes PTH to overstimulate osteoclast

Age-associated osteoporosis (type II) Bone loss due to increased bone turnover Malabsorption Mineral and vitamin deficiency

Classification

Primary Postmenopausal

Bone loss – 2-3% per year of total bone mass Most common fx: vertebral, distal forearm

Age related – 3rd decade of life starts slow decline in bone mass at rate of 0.5-1% per year Most common types of fx: hip and radius F>M

Secondary

Secondary OsteoporosisDisease states

Acromegaly Addison’s disease Amyloidosis Anorexia COPD Hemochromatosis Hyperparathyroidis

m Lymphoma and

leukemia

Malabsorption states Multiple myeloma Multiple sclerosis Rheumatoid arthritis Sarcoidosis Severe liver dz, esp.

PBC Thalessemia Thyrotoxicosis

Secondary OsteoporosisDrugs

Aluminum Anticonvulsants Excessive thyroxine Depo Provera (decreased bone mass

reversible after stopping medication) Glucocorticoids GnRH agonists Heparin Lithium

Diagnosing Osteoporosis

Outcome of interest: Fracture Risk! Outcome measured (surrogate): BMD

Key: Older women at higher risk of fracture than younger women with SAME BMD!

Other factors: risk of falling, bone fragility not all related to BMD

Prevalence of osteoporosis

Osteopenia Osteoporosis

FemaleAge > 50 year

37-50% 13-18%

MaleAge > 50 year

28-47% 3-6%

Incidence of osteoporotic Fx

Incidence of osteoporotic Fx

Diagnosis of Osteoporosis

Physical examination Measurement of bone mineral content• Dual X-ray absorptiometry (DXA)• Ultrasonic measurement of bone• CT scan• Radiography

Physical examination

Osteoporosis Height loss Body weight Kyphosis Humped back Tooth loss Skinfold

thickness Grip strength

Vertebral fractureArm span-height differenceWall- occiput distanceRib-pelvis distance

Physical examination

No single maneuver is sufficient to rule in or rule out osteoporosis or vertebral fracture without further testing

Physical examination

Diagnosing Osteoporosis

Laboratory Data Limited value in diagnosis Markers of bone turnover (telopeptide) more

useful in monitoring effects of treatment than in diagnosis

Helpful to exclude secondary causes Hyperthyroidism Hyperparathyroidism Estrogen or testosterone deficiency Malignancy Multiple myeloma Calcium/Vitamin D deficiency

Work-up

Screen for secondary causes Serum calcium, phosphorus, alk phos PTH if calcium is high (hyperparathyroidism) 25-hydroxyvitamin D if low ca,

low phos and high alk. phos (osteomalacia) Thyroid function tests (thyrotoxicosis) SPEP, UPEP (multiple myeloma) 24-hour urinary calcium (hyper or hypo calciuria) Serum testosterone (hypogonadism)

Methods to evaluate for osteoporosis

Quantitative Ultrasonography Quantitative computed tomography Dual Energy X-ray Absorptiometry (DEXA)

?”gold standard” Measurements vary by site Heel and forearm: easy but less reliable (outcome

of interest is fracture of vertebra or hip!) Hip site: best correlation with future risk hip

fracture Vertebral spine: predict vertebral fractures; risk of

falsely HIGH scores if underlying OA/osteophytes

Dual X-ray absorptiometry

2-dimensional study BMD = Amount of mineral

AreaAccuracy at hip > 90%Low radiation exposureError in

OsteomalaciaOsteoarthritisPrevious fracture

How to interpret the BMD

T score: standard deviation of the BMD from the average sex matched 35-year-old

Z score: less used; standard deviation score compared to age matched control

For every 1 decrease in T score, double risk of fracture

1 SD decrease in BMD = 14 year increase in age for predicting hip fracture risk

Regardless of BMD, patients with prior osteoporotic fracture have up to 5 times risk of future fracture!

Dual X-ray absorptiometryBMD compare with young adult female

T score

Normal < 1 SD below >/= -1

Low bone mass ( Osteopenia ) 1-2.5 SD below < -1> -2.5

Osteoporosis >/= 2.5 SD below </= -2.5

Severe osteoporosis >/= 2.5 SD below PLUS Fracture

Dual X-ray absorptiometry

WHO criteria - Hip BMD Normal Low bone mass (Osteopenia)OsteoporosisSevere osteoporosis

Osteoporosis Can Be Assessed by DXA

Relative Risk of Fracture per SD Decrease in BMD

0

0.5

1

1.5

2

2.5

3

Rel

ativ

e R

isk

Forearm

Hip

Spine

DXA-assessed content is a proven effective method for assessing osteoporosis related fracture risk.Population surveys and research studies demonstrate a decrease in bone density measured by DXA predicts fracture at specific sites.

Ultrasonic measurement

Broad-band ultrasound attenuationNo radiation exposureCannot be used for diagnosisPreferred use in assessment of fracture risk

The calcaneus is the most common skeletal site for quantitative ultrasound assessment because

-It has a high percentage of trabecular bone that is replaced more often than cortical bone, providing early evidence of metabolic change.

-Also, the calcaneus is fairly flat and parallel, reducing repositioning errors.

The McCue CUBA: Ultrasonometry Technology That Can Assess Osteoporosis

Heel BUA is Significantly Lower in Subjects With Future Hip Fracture.

0

10

20

30

40

50

60

Fracture No Fracture

BU

A (d

B/s

q M

Hz)

Subjects who developed hip fracture showed significantly (p<0.001) lower heel BUA results.

CT scan

True volumetric studyQuantitative Computed Tomography (QCT) utilizes CT technology to detect low bone mass and monitors the effects of therapy in patients undergoing treatment. It is a fast, non-invasive exam that detects low bone mass earlier and more accurately than other bone density exams

QCT in a 62-year-old female patient

The trabecular BMD is indicated as the most important parameter, and interpreted using the Felsenberg classification, based on the following cut-off values:

Normal BMD > 120 mg/cc Osteopenia < 120 mg/cc Osteoporosis < 80 mg/cc Very high fracture risk < 50 mg/cc

Advantages over DXA:

Ability to separate cortical and trabecular bone

Provides true volumetric density in units of mg/cc

No errors due to spinal degenerative changes or aortic calcification

Clinicians and researchers favor DXA because

-scanners are readily available and relatively inexpensive.

-The radiation dose is negligible

-The T-score scale, defined by the WHO specifically for DXA, provides a standardized classification.

Plain radiography

Low sensitivityHigh availabilitySubclinical vertebral fracture is a strong risk factor for subsequent fractures at new vertebral site and other sites

The main radiographic features of generalized osteoporosis are cortical thinning and increased radiolucency

Singh Index

The Singh index describes the trabecular patterns in the bone at the top of the thighbone (femur).

X-rays are graded 1 through 6 according to the disappearance of the normal trabecular pattern.

Studies have shown a link between a Singh index of less than 3 and fractures of the hip, wrist, and spine.

ASSESSMENT OF FRACTURE RISK

Assessment of fracture risk DXA and quantitative ultrasound Clinical risk factors Markers of bone turnover

Bone formationBone resorption

Assessment of fracture risk DXA

Risk of fracture = 1.5-3.0 for each SD decrease in BMD

Low sensitivity ( comparable to BP in predicting stroke )

Screening is not recommended

Quantitative ultrasound Risk of fracture = 1.5-2.0 for

each SD decrease in BMD

Assessment of fracture risk

Markers of bone turnover

Bone resorption markersHydroxyprolinePyridinium crosslinks & associated peptides

Bone formation markersAlkaline phosphataseBone isoenzyme APOsteocalcinProcollagen propeptides of type I collagen

Assessment of fracture riskMarkers of bone turnover Associated with osteoporotic fracture

independent of bone density 2-Fold increase in fracture risk ? Combined approach with BMD to

increased sensitivity

Assessment of fracture risk

Clinical risk factors for fracture Low bone mass History or falls Impaired cognition ( plus medication adverse effect ) Low physical function Presence of environmental hazards Long hip axis length Chronic glucocorticoid use Existing fracture Chronic use of seizure medications Renal, hepatic, thyroid, parathyroid, malabsorptive disorder,

vitamin D deficiency, MM and local neoplasia to be ruled outNational Osteoporosis Foundation 1998

Assessment of fracture risk

Predictors of low bone mass Female Advanced age Gonadal hormone deficiency ( estrogen or testosterone ) White race Low body weight & BMI Family history of osteoporosis Low calcium intake Smoking / excessive alcohol intake Low level of physical acitivity Chronic glucocorticoid use History of fracture National Osteoporosis Foundation

1998

When to Measure BMD in Postmenopausal Women

All women 65 years and older Postmenopausal women <65 years of

age: If result might influence decisions about

intervention One or more risk factors History of fracture

When Measurement of BMD Is Not Appropriate

Healthy premenopausal women Healthy children and adolescents Women initiating ET/HT for menopausal

symptom relief (other osteoporosis therapies should not be initiated without BMD measurement)

THANK YOU