PRESENTED BY: DR.SINDU.P.GOWDAR

METABOLIC BONE DISORDERSPART II

OSTEOPOROSIS

DEFINITION:

Systemic skeletal disease characterized by low bone mass and micro architectural deterioration of bone tissue , with a consequent increase in bone fragility and susceptibility to bone fracture

OSTEOPOROSIS

• Osteoporosis is one of the most devastating disorders associated with aging.

• Osteoporosis-related fractures result in significant morbidity and mortality.

• Characterized by qualitatively normal but quantitatively deficient bone.

• Generalized decrease in bone mass is seen.• Bone is normal structurally as determined by histological

and chemical analysis• Radiographs in patients with osteoporosis reveal increased

radiolucency of bone (Osteopenia)• Osteopenia occurs when bone resorption exceeds bone

formation.

"Microarchitectural deterioration" refers to the thinning of the trabeculae and the loss of intertrabecular connections in bone

Major risk factors Minor risk factors-Age > 65 years-Systemic glucocorticoid therapy of >3 months duration-Mal-absorption syndrome-Primary hyper parathyroidism-Propensity to fall-Osteopenia apparent on X-ray film-Hypo-gonadism-Early menopause (before age 45)-Family history of osteoporotic fracture (especially maternal hip fracture)

- Rheumatoid arthritis- Past history of clinical hyperthyroidism- Chronic anticonvulsant therapy- Low dietary calcium intake- Smoker- Excessive alcohol intake- Excessive caffeine intake- Weight <57 kg- Weight loss >10% of weight at age 25- Chronic heparin therapy

PROXIMAL PORTION OF THE FEMUR:

Analysis of the trabecular pattern of the upper end of the femur has been used as an index of osteoporosis.

In this region, five anatomic groups of trabeculae can be identified. 1. Principal compressive group.

2. Secondary compressive group.

3. Greater trochanter group.

4. Principal tensile group.

5 .Secondary tensile group.

Patterns of trabecular loss may correlate with increasing severity of osteoporosis. This trabecular analysis is termed as SINGH INDEX.

ANATOMIC GROUPS OF TRABECULA

• Principle compressive group

• Principal tensile group

• Secondary compressive group

• Secondary tensile group

• Greater trochanter group

• Wards triangle

NORMAL TRABECULAR PATTERNS. Proximal Femur. A. Three major patterns exist: principal compressive group (1), secondary compressive group (2), and principal tensile group (3). The confluence of these trabeculae leaves an area relatively void of structure, Ward’s triangle (W). B. Specimen Radiograph- the arrangement of the trabecular bundles can be discerned, defining Ward’s triangle, which is relatively devoid of bony struts. C. Specimen Radiograph. The corresponding plain film confirms the trabecular orientation and arrangement within the proximal femur and Ward’s triangle.

SINGH INDEX

OSTEOPOROSIS IS CLASSIFIED AS:

1. Generalized

(involving the major portion of the skeleton, particularly its axial component)

2. Regional

(involving one segment of the skeleton)

3. Localized

(single multiple focal areas of osteoporosis)

1. Primary osteoporosis

• Involutional (most common) - osteoporosis in which no underlying cause can be identified. oType I (postmenopausal)oType II (aging related)

• Idiopathico JuvenileoAdult

2. Secondary osteoporosis - osteoporosis in which there is an underlying cause.

OSTEOPOROSIS CAN ALSO BE CLASSIFIED AS

PRIMARY OSTEOPOROSIS

• Postmenopausal osteoporosis occurs in women within 15-20 years after menopause.

• Age-related, or senile, osteoporosis describes the disease in the elderly.

• Juvenile osteoporosis affects prepubescent boys and girls.

• Idiopathic osteoporosis describes the condition in young adults when the cause is not related to another disease.

Note the diminished density of the vertebral bodies and the thinned but relatively prominent cortical endplates. No fracture deformities are seen.

INVOLUTIONAL OSTEOPOROSIS

Postmenopausal (Type I)

Senile (Type 2) Osteoporosis:• Most common cause of generalized

osteoporosis.

• Peak bone mass occurs in the second decade of life.

• Then gradual loss of skeletal mass occurs, beginning in the fifth or sixth decade of life in men fourth decade in women

Patients may be• entirely asymptomatic,• significant loss of bone mass accompanied by

various clinical signs– Bone pain, particularly in the back, – Loss of height owing to vertebral compression. – Increase thoracic kyphosis is apparent (dowagers hump). – Neurologic complications are unusual. – Fractures

• Laboratory analysis elevated urinary hydroxyproline levels.

Involutional Osteoporosis

Type I (PM) Type 2 (Senile)

Age 51-75 yrs > 70 yrs

Sex ratio (F:M) 6:1 2:1

Type of bone loss Mainly trabecular Cortical and trabecular

Fracture types Vertebral (crush), distal radius

Vertebral (multiple wedge), hip, proximal humerus and tibia

Rate of bone loss Accelerated Not accelerated

Parathyroid function Decreased Increased

Main causes Estrogen deficiency Aging, calcium deficiency

IDIOPATHIC JUVENILE OSTEOPOROSIS• uncommon, self-limited disease of childhood.• clinically evident disease present about 2 years before puberty with

• spinal symptoms.• extra spinal symptoms.

• On radiographic examination,• osteoporosis of the spine may be combined with vertebral collapse.• Kyphosis represents the characteristic spinal complication.• transverse and oblique fractures occur in the peripheral skeleton,• typical feature appears to be metaphyseal injury, especially about the knees and

ankles,• Metaphyseal lucent lesions may lead to complete fractures with subsequent

deformities

• D/D: Osteogenesis imperfecta

ADULT IDIOPATHIC OSTEOPOROSIS

• uncommon,

• affects

premenopausal women

middle aged or young men.

• Vertebral compression fractures are a prominent feature.

• The disorder is often severe, progressive, and refractory to standard treatment.

SECONDARY OSTEOPOROSISIs diagnosed when an identifiable cause other than age or menopause is present.

CAUSES• Genetic

• Endocrine

• Deficiency state

• Neoplastic

• Iatrogenic

• Drugs

• Miscellaneous

SECONDARY OSTEOPOROSIS CAUSES

Genetic Osteogenesis imperfecta, Gonadal dysgenesis, Turner syndrome, Klinefelter syndrome, Hypophosphatasia, Homocystinuria, Mucopolysaccharidosis, Gaucher disease, Sickle-cell anemia, Thalassemia, Hemophilia

Deficiency Scurvy, Malnutrition, Anorexia nervosa, Protein deficiency, Alcoholism, Vitamin D deficiency, Calcium deficiency

Medications Corticosteroids, Antiepileptics, Phenobarbital, phenytoin, Cytotoxics: methotrexate, cyclosporin A, Thyroid hormone, Lithium, Heparin, warfarin

Endocrine Hyperthyroidism, Hyperparathyroidism, Cushing syndrome, Acromegaly, Estrogen deficiency, Hypogonadism, Diabetes mellitus, Pregnancy

Neoplastic Myeloma, leukemia, lymphoma, metastatic disease

Iatrogenic Heparin induced, steroid induced, dilantin (phenytoin) induced

Miscellaneous Amyloidosis, ochronosis, immobility, weightlessness

EVALUATION OF SECONDARY OSTEOPOROSIS• Increased creatinine level : Renal disease

• Increased hepatic transaminase levels: Hepatic disease

• Increased calcium level :Primary hyperparathyroidism or malignancy

• Decreased calcium level: Malabsorption, vitamin D deficiency

• Decreased phosphorus level: Osteomalacia

• Increased alkaline phosphatase level: Liver disease, Paget's disease, fracture, other bone pathology

• Decreased albumin level :Malnutrition

• Decreased TSH level : Hyperthyroidism

• Increased ESR: Myeloma

• Anemia: Myeloma

• Decreased 24-hour calcium excretion level: Malabsorption, vitamin D deficiency

Radiographic Features:

• Generalized osteoporosis is most prominent in the axial skeleton, particularly the

• vertebral column,

• pelvis,

• ribs,

• sternum.

• less extensive changes may become evident in the tubular bones.

GENERALIZED OSTEOPOROSIS

General radiological features of osteoporosis:

• Increased radiolucency• Cortical thinning• Altered trabecular patterns• Fracture deformity

A. AP Shoulder. B. AP Knee. Observe the decreased density, trabecular enhancement, and thin cortices.

PELVIS AND FEMORA. AP Pelvis. Observe the thin cortices and relative accentuation of those remaining trabeculae. Within the femoral necks, the principal compressive trabeculae (arrows) are enhanced. Of incidental notation are calcified abdominal mesenteric lymph nodes (crossed arrows) and a supra-acetabular bone island (arrowhead).

Spinal Manifestations of Osteoporosis

DECREASED BONE DENSITY

TRABECULAR CHANGES

Accentuation of primary trabeculae (pseudo-hemangiomatous appearance)

Washed-out appearance

CORTICAL THINNING

CHANGES IN VERTEBRAL SHAPE

Vertebra plana (pancake vertebra or silver dollar vertebra)

Wedged vertebra

Biconcave deformities (fish vertebra)

Localized endplate deformities

Schmorl’s nodes

Spinal manifestations are distinctive and pronounced.

Curve changes:

Increased kyphosis is common due to

• compression fractures,

• anterior vertebral body remodeling

• loss of disc height

Decreased bone density: Especially density, of the vertebral body, diminishes in parallel with loss of bone mass.

DOWAGERS HUMPSEVERE SENILE KYPHOSIS.Lateral Thoracic Spine. The severe postural alteration, which is a complication owing to loss of disc height and anterior wedging of the vertebral bodies. This underlies the physical appearance of the buffalo or dowager’s hump deformity.

“EMPTY BOX” APPEARANCE

Trabecular changes:

“Empty box” appearance

Initially there is relative increase in the density of vertebral end plates due to resorption of spongy bone causing what is called as “empty box” appearance

TRABECULAR CHANGES:

• Within the vertebral bodies the vertical trabeculae appear to become increasingly accentuated. This is largely due to preferential resorption of the horizontal trabeculae, allowing easier delineation of those remaining.

• In certain individuals this may simulate the vertical radio dense striations of hemangioma (pseudohemangiomatous).

• Osteoporosis can be differentiated, since it involves a number of contiguous segments, while hemangioma is usually a solitary lesion. In some instances no internal trabeculae may be visible

• It is the vertical trabecular accentuation that produces the so-called pseudo-hemangiomatous appearance of moderately advanced osteoporosis.

A. Lateral Lumbar SpineThe vertical struts appear more prominent

B. Lateral Thoracic Spinevertical trabeculae distinctively conspicuous. A minimal wedged anterior compression deformity is also present

PSEUDO-HEMANGIOMATOUS APPEARANCE. A. Lateral Lumbar Spine Pseudo-Hemangioma. Observe the accentuated vertical trabecular patterns of multiple segments, producing a pseudo-hemangiomatous appearance. This is a manifestation of early to moderate osteoporosis, the appearance being lost in advanced cases. There is loss of the horizontal supports with thickening of the vertical struts. B. Lateral Thoracolumbar Spine Hemangioma. Note that this most common benign tumor of the spine presents with strikingly similar accentuated vertical trabecular markings (corduroy cloth appearance) but is localized to only one level (arrow)

Cortical ThinningThe cortical outlines of the vertebral body and neural arch are usually notably thinned. This is best depicted at the vertebral body end plates, which are normally relatively thick

Changes in shapes:

A number of altered vertebral configurations seen.

These are

• rare in the cervical spine,

• less common in the upper thoracic spine,

• most common in the mid-thoracic & thoraco-lumbar regions

VERTEBRAL BODY CONFIGURATIONS: A. Normal. B. Normal with Pencil-Thin Cortices. C. Wedge Shape Owing to Anterior Loss of Height. D. Plana with Both Anterior and Posterior Collapse. E. Biconcave (Fish Vertebra) Owing to Gradual Endplate Depression. F. Angular Endplate Depression from Acute Fracture.

Vertebra plana (“Pancake” Vertebra): Pancake vertebra is a compression deformity of the vertebral body characterized by a loss in both the anterior and posterior vertical heights, often in multiple segments.

This is an unusual presentation for osteoporosis and, if seen, must arouse the suspicion for these other malignant bone diseases to be the underlying cause for these fractures.

When present, this configuration must be differentiated from a more serious cause, especially metastatic carcinoma and multiple myeloma, by pertinent laboratory investigations.

MRI does not reliably differentiate between pathologic and osteoporotic fractures.

VERTEBRAL BODY PATHOLOGIC FRACTURE (VERTEBRA PLANA)

Isolated compression fracture at the T8 segment noted (arrow).

The loss of the posterior and anterior height suggests an underlying pathologic condition for which the differential diagnosis includes • multiple myeloma, • metastatic carcinoma, • other malignancy, • osteoporosis.

The diagnosis in this case was osteoporosis.

Lateral lumbar spine radiograph shows severe crush fracture of L2

Wedged Vertebra:

• Compression deformities that demonstrate loss of the anterior vertebral body height with preservation of the posterior height are termed wedged vertebrae.

• The resultant trapezoidal configuration is diagnostic of this type of compression abnormality and may also be seen at multiple levels

• The same shape is also common in traumatic compression fractures of the spine, even those that exhibit normal mineralization.

• These are most common in the midthoracic and thoracolumbar regions.

Lateral thoracic spine radiograph:Wedge compression fracture seen in lateral thoracic vertebra

VERTEBRAL BODY SHAPE CHANGES:In Lateral Thoracic Spine.

Note that several changes in vertebral body shape can be observed: • wedge (W)• plana (P)• biconcave (B)

Also, the thoracic kyphosis has increased, which is a frequent sequela.

Biconcave Deformities (Fish, Codfish, Fish mouth or Hourglass Vertebrae): Due to Central depression of the vertebral body endplates seen at multiple contiguous levels, endplates show an exaggerated concavity(this simulates the vertebral body appearance found in a normal fish) This deformity is the direct mechanical sequelae of pressure on the weakened bone from the nucleus pulposus.Intervertebral disc spaces are usually of normal height.

The same endplate defects are frequently seen in diseases such as Osteomalacia, Paget’s disease, Hyperparathyroidism.

BICONCAVE ENDPLATES (FISH VERTEBRAE). A. Lateral Lumbar Spine. Note that the endplates are markedly concave in contour at multiple levels. Note the thin cortices and normal intervertebral disc spaces. This configuration does not occur unless there is loss of vertebral body strength and a normally hydrated nucleus pulposus to exert mechanical deformation of the endplate. B. Alaskan King Salmon Spine. Note the profile of the endplates can be seen to be deeply depressed centrally, creating an appearance of distinctly biconcave endplates (arrows). It is from this striking similarity to the endplate deformities of the osteoporotic vertebral body that the term fish vertebra has arisen.

Isolated Endplate Deformities:

Frequently, isolated endplate fractures occur peripherally or centrally. Central endplate fractures are most frequent at L1 and L4. These deformities are often depicted only on a single view, such as an oblique on which the endplate is projected into a slightly different plane.

Radiographic manifestations consist of an altered orientation of the endplate, sharp offset in continuity, and increased density adjacent to the fracture site.

A standard lateral standing radiograph of the lower lumbar spine: Disk space narrowing at the level L5/S1. Endplate irregularities of the fifth lumbar vertebra and the first sacral vertebra.

Schmorl’s Nodes:

Localized intrabody discal herniations are frequently superimposed on the osteoporotic spinal column.

Most commonly, these nuclear extrusions occur in the thoracic and upper lumbar spines.

RISK FACTORS FOR OSTEOPOROTIC FRACTURES

NOT MODIFIABLE

WhitesAdvanced ageFemaleDementiaPoor health FrailityH/o fracture in a first degree relativePersonal history of fracture as an adult

POTENTIALLY MODIFIABLE FACTORS• Current cigarette smoking• Low body weight [<58kg]• Estrogen deficiency• Lifelong low calcium intake• Alcoholism• Recurrent falls• Inadequate physical activity• Poor health / fraility• Impaired eyesight despite correction

SIGNS AND SYMPTOMS

• Symptoms of osteoporosis indicate advanced disease.

• Fractures of the hip, spine, and wrist are most common.

• Kyphosis (dowager's hump) results from collapse of several vertebral bodies.

• Skeletal back pain may also be a symptom.

COMPLICATIONS

• Vertebral fracture (morphometric fractures].

• Back pain and decreased mobility.

• Disfiguring kyphosis (dowager's hump)

• Height loss

• Decreased pulmonary capacity

• Abdominal protrusion

INSUFFICIENCY FRACTURES

• Insufficiency fractures occur when the elastic strength of the bone is not sufficient to withstand normal physiological stress.

• In osteoporosis, the most common locations for complication from insufficiency fractures are the spine, hip, and distal radius.

• When affecting the weight-bearing bones of the lower limb, these fractures are frequently bilateral. Such fractures characteristically affect the weight-bearing bones, including metatarsal necks, posterior calcaneum, distal and proximal tibia and fibula at their outer margins, medial neck of femur, and sacral ala.

• The fracture site may be marked by localized periosteal response and transverse opaque zones of callus.

• Only occasionally a fracture line may be visible.

• These usually are metaphyseal in location.

INTERTROCHANTERIC FEMORAL FRACTURE. The fracture through the intertrochanteric region.

Fractures of the proximal femur are the most common severe presentation of osteoporosis. Such fractures can occur elsewhere within the proximal femur, including subcapital, midcervical, basocervical, and subtrochanteric locations.

SACRUM:• The most common cause of fracture of the sacrum is senile and

postmenopausal osteoporosis with a history of a recent fall onto the buttocks.

• It is precipitated by the high shear forces through the sacral ala during walking and may coincide with a recent increase in activity.

• Onset usually after age 65.

• F:M= 5:1

• Increased pelvic tilt is thought to be a predisposing factor.

• Pain severity is variable, from severely debilitating to relatively asymptomatic.

• Up to 75% of patients have a co-existing insufficiency fracture within the pelvic ring, most commonly of a pubic ramus.

The two symmetrically located insufficiency fractures in the lateral sacrum (arrows). Note the characteristic cortical offset at the anterior sacral margin (arrowhead)

The most sensitive method of detection is isotopic bone scan. Three patterns of sacral insufficiency fractures occur based on bone scan appearance:

• H pattern (butterfly or “Honda” sign). Bilateral vertical fractures through the sacral ala are connected by a transverse fracture through the S2, S3, or S4 bodies.

• I pattern. A single vertical fracture passes through the sacral ala. This is the most common form of sacral insufficiency fracture in at least 70% of cases.

• Arc pattern. A linear or curvilinear transverse fracture passes horizontally across the sacrum.

Frontal Technetium-99m Isotopic Bone Scan:The dense uptake of the isotope within the lateral sacrum as two vertical components corresponding to the sites of fracture (arrows). These two vertical fractures are joined centrally by a transverse fracture through the S2 body, signified by the transverse linear uptake zone (arrowhead). The combination of these three components produces an H-shaped lesion referred to as the Honda sign.

INSUFFICIENCY FRACTURE OF THE PUBIS: AP Pubes. Initial Radiograph. Note that no abnormality is identified, with the pubis bilaterally normal. Follow-up Radiograph. Note that a fracture line extends vertically through the body of the pubis immediately adjacent to the articular margin of the symphysis pubis (arrows)

REGIONALIZED OSTEOPOROSIS

REFLEX SYMPATHETIC DYSTROPHY SYNDROME:

• Reflex sympathetic dystrophy syndrome is a unique clinical and radiographic entity

• Also called post-traumatic osteoporosis, Sudeck’s atrophy, acute bone atrophy, and causalgia.

• Although the mechanism has not been delineated, the syndrome is characterized by an acute onset of a painful regional osteoporosis, usually following trivial antecedent trauma.

Bilateral PA Hands. Note the distinct loss of bone density in the affected hand (arrow), especially in the periarticular regions of all articulations. Compare this appearance with the normal other side. A minor trauma had been incurred at the wrist 8 weeks previously.

Clinical Features• > 50 years of age.• History of recent trauma that may have been trivial.• Progressive pain, swelling, and atrophy distal to the trauma

site.

Pathologic Features• Neurovascular imbalance, promoting osseous hyperemia.

Radiologic Features• Patchy, mottled osteoporosis.• Metaphyseal localization.• Later, more generalized osteoporosis.

Disuse and Immobilization Osteoporosis

• Traumatic injuries that are immobilized, motor paralysis, and inflammatory lesions of bones and joints constitute the most common causes.

• Changes appear on plain film after 7-10 days, becoming most extreme by 2-3 months.

• Four radiologic patterns of disuse atrophy: 

• Uniform- All bones involved exhibit a similar degree of bone loss. • Spotty- Localized circular lucencies predominate, especially within the

epiphyseal portions of the bones• Bands-  Linear transverse subchondral or metaphyseal lucent zones• Cortical lamination or scalloping- Lamination or scalloping loss of

definition in the outer and inner cortical margins.

A. Lateral Elbow. Note that the bones are demineralized in a uniform manner following immobilization owing to a cerebrovascular accident.

B. PA Wrist. Observe the spotty form of disuse osteoporosis of the wrist after immobilization for an elbow fracture.

C. PA Foot. A similar spotty type of deossification has occurred after immobilization for an ankle fracture.

TRANSIENT REGIONAL OSTEOPOROSIS

General Considerations: • No associated cause.• Sudden and reversible; affects periarticular bone.

TWO ENTITIES:

Transient Osteoporosis of the Hip:• 20-40 years; males predominant.• Associated with pregnancy in females, left hip exclusively.• Marked osteoporosis of the femoral head; less severe in femoral neck and

acetabulum.

Regional Migratory Osteoporosis:• Males most commonly affected.• Usually in lower extremities.• Localized, regressing, migratory osteoporosis.

DISUSE OSTEOPOROSIS: POLIO. AP Pelvis. Osteoporosis of hemi pelvis Decreased joint space hip & SI jointUnder development of femur, pubis & ischium

TRANSIENT OSTEOPOROSIS OF THE HIP Plain X-rays

Diffuse osteopenia of the right femoral neck and head

MRI study

Decreased marrow signal on T1 images of the right hip

TRANSIENT OSTEOPOROSIS OF THE HIP: A. T1-Weighted MRI, Coronal Hip. B. T1-Weighted MRI, Axial Hip.

Note the diffuse loss of signal intensity in the right femoral head and neck (arrows).

On T2-weighted images (not shown) this low signal intensity area became hyperintense, consistent with transient osteoporosis.

The clinical presentation is variable.MRI plays an important role in establishing the differential diagnosis and excluding other pathology such as osteonecrosis.

DIAGNOSTIC APPROACH

• Risk factors and Simple Calculated Osteoporosis Risk Estimation (SCORE)

• Clinical features

• Laboratory tests

• Radiologic techniques to assess bone

• Measurement of bone mineral density (BMD) by noninvasive techniques.

TECHNOLOGIES USED• Radiographs

• Dual X-ray absorptiometry (DXA)

• Dual-photon absorptiometry (DPA)

• Single X-ray absorptiometry (SXA)

• Single-photon absorptiometry (SPA)

• Quantitative computed tomography (QCT)

• Quantitative ultrasound (QUS).

• MRI

Changes in bone mass are detectable on X-ray only when 30-50% of bone has already been lost.

• Increased radiolucency of bones.• Decreased number and increased thickness of trabeculae.• Cortical thinning. • Juxta-articular osteopenia with trabecular prominence. • Bone bars (reinforcement lines). • Insufficiency fractures.

• Vertebral wedge fractures, fish vertebrae, Schmorl nodes and decreased heights of vertebrae and accentuation of the cortical outlines.

RADIOGRAPHY

ab +cd= combined cortical thicknessab +cd = INDEX OF BONE MASS

ad  ab+cd=ad/2(the sum of cortices approximates one half of the bone’s diameter) 

REINFORCEMENT LINE (BONE BARS):

In patients with chronic osteopenia, radiographs of the tubular bones commonly reveal strands of trabeculae of variable thickness, extending partially or completely across the marrow cavity. The precise pathogenesis of bone bars is not clear.

INTRODUCTION• Studies have shown large (5%-20%) annual losses in spinal

trabecular BMD in women undergoing surgical or natural menopause

• BMD assessment techniques have progressed from simple radiography to more sensitive methods,

• Uses • early detection of osteoporosis

• monitor response to therapy

• assess bone strength reliably

• predict fracture risk.

PATIENTS RECOMMENDED FOR BMD MEASUREMENTS

• Women over age 65 and women under 65 with risk factors

• Amenorrhea, early menopause

• Bilateral oophorectomy before normal menopause

• Women not receiving hormone replacement therapy for at least 5 years after menopause

• All men age 70 and older and Men with hypogonadism.

• Strong family history of osteoporosis.• Patients undergoing prolonged Rx with glucocorticosteroids.• Hyperparathyroidism• Post chemotherapy (esp. breast and hematologic CA).• Adults with a disease or condition associated with low bone

density

Basic Principles of BMD

• Bone attenuates or absorbs ionizing radiation. More bone present, the more radiation the bone absorbs.

• Unabsorbed radiation passes through the bone and is measured in a radiation detector.

• BMD refers to grams of bone mineral — specifically hydroxyapatite — per square centimeter of bone cross-section and is expressed in units of g/cm2.

Every Patient

• Spine• L1-L4

• Hip• Total Proximal Femur

• Femoral Neck

• Trochanter

Some Patients

• Forearm (33% Radius)• If hip or spine cannot be

measured

• Hyperparathyroidism

• Very obese

WHICH SKELETAL SITES SHOULD BE MEASURED?

RADIOGRAMETRY

Thickness of the cortices of bone is measured with a caliper on fine detail radiograph to provide an index for bone density and bone mass.

Usual site:

2nd, 3rd and 4th metacarpals, radius and clavicle.

Disadvantages:

positioning and measuring errors.

Advantages:

Inexpensive,

low dose of radiation,

readily available.

Single photon Absorptiometry This couples a monoenergetic photon source such as iodine-125 with a

sodium iodide scintillation counter A single-photon source emits a photon beam that is attenuated as it passes

through bone, usually the radius or calcaneus. The density of bone is calculated by the measured transmission count rate.

The calcaneus, distal radius and radial shaft all have about an equal degree of association with vertebral osteoporosis but have high false-negative rates, which makes the technique unreliable.

The radiation dose is 2-5 mrad.

DUAL PHOTON ABSORPTIOMETRY

• uses gadolinium-153• This allows scanning of the spine and femur, as it is independent

of variation in soft tissue thickness• the technique cannot measure absolute bone mineral content• Aside from bone density analysis, modern advances of this

technique that can deliver high-resolution images have made this modality a useful alternative for the clinical diagnosis and evaluation of vertebral fractures.

• The major advantage is the relatively low radiation dose. The radiation dose is 5-15 mrad.

• useful in quantitative mineral content changes

Single X-ray Absorptiometry• SXA has succeeded single-photon absorptiometry• Used for quantitative BMD assessment of the

peripheral skeleton • SXA has been used successfully in the diagnosis of

osteoporosis with reasonable precision and low radiation dose.

Dual X-ray Absorptiometry

Because single-energy measurements cannot be obtained at sites with variable soft-tissue thickness and composition (e.g., axial skeleton, hip), dual-energy techniques were introduced.

Two xray beams of different energy levels are aimed at the patient bones. When soft tissue absorption is subtracted out, BMD can be determined from the absorption of each beam by bone.

the most widely available BMD test Low radiation dose : 5 mradhigh degree of accuracybone tissue per unit area ( g/cm2 )

• Central BMD measures the axial and appendicular skeleton, which are the most commonly measured sites.

• Peripheral BMD measures the most peripheral areas of the appendicular skeleton — namely, the forearm, phalanges, and calcaneus.• This can - Predict fracture risk

• But cannot diagnose osteoporosis and monitor therapy

LIMITATIONS OF DXA:

• Presence of barium or recent administration of radionuclides (within 10 half-lives of the injected tracer) may yield inaccurate BMD measurements.

• Presence of radiopaque implants in the measurement area.

• Inability to straighten the lumbar spine or internally rotate the thigh.

• Marked obesity.

the anatomic sites where DXA is typically applied

T SCORE INTERPRETATION

BMD or bone mineral content (BMC) within 1 SD of the young-adult reference means

Normal

-1 to –2.5 SD Low bone mass (osteopenia)

Below –2.5 SD Osteoporosis

Below –2.5 SD +one or more fragility fractures

Severe (established) osteoporosis

WHY -2.5?

Professor John Kanis says:

“Such a cutoff value identifies approximately 30% of postmenopausal women as having osteoporosis using measurements made at the spine, hip or forearm. This is approximately equivalent to the lifetime risk of fracture at these sites.”

Kanis JA et al. J Bone Miner Res. 1994;9:1137.

QUANTITATIVE COMPUTED TOMOGRAPHY

A software package allows the conversion of relative Hounsfield units,

determined in the center of a vertebral body,

to an absolute measurement of bone density of calcium in milligrams per cubic centimeter.

QUANTITATIVE CTFeatures• measures trabecular or cortical bone separately at any skeletal

site in three dimensions

Uses: • primarily to determine trabecular bone density in the vertebral

centrum.

• As trabecular bone is important for vertebral strength, it is used to

• assess vertebral fracture risk,

• measure age-related bone loss,

• follow up of osteoporosis and other metabolic bone diseases

Quantitative Computed Tomography

QCT determination of density in vertebrae is compared to known density readings of external phantoms

A computer program compares the density of the patient's spinal vertebrae (outlined in turquoise) with a special reference device placed under the patient during the exam.

PERIPHERAL QUANTITATIVE CT

• Peripheral quantitative CT is used to obtain BMD measurements in the peripheral skeleton (principally the distal radius).

• The measurement of multiple sections is potentially more representative of changes in the distal radius and therefore may reflect the bone status of an individual more accurately.

Declination of cortical and central trabecular bone in the forearm. (a) Peripheral cross-sectional quantitative CT scan obtained at the level that represents

4% of the ulnar length from the distal radial end plate shows the area of interest (box). (b) Magnified view of the area of interest shows the bone declination to greater

advantage.

QUANTITATIVE ULTRASOUNDPRINCIPLE

• The attenuation and velocity of a sound wave passing through bone are related to the biomechanical properties, geometry, density of the bone;

• The more complex the structure, the greater the attenuation and velocity.

QUANTITATIVE US

• Normal bone demonstrates higher attenuation and is associated with greater sound velocity than osteoporotic bone.

• Quantification of bone density and structure can be achieved by analyzing the attenuation or velocity of US in bone.

QUANTITATIVE US

USES

• portable,

• inexpensive,

• easy to use,

• No ionizing radiation.

• can be obtained at various easily accessible anatomic sites

DISADVANTAGES

• The data produced are machine specific and subject to the use of dissimilar databases by different manufacturers.

• Clinical features (eg, ankle edema) are potential causes of error.

• Choice of right or left heel for measurement can influence the result unduly.

MAGNETIC RESONANCE IMAGING

• Can provide more detailed images of the structure of osteoporotic bone than DXA and may be used to diagnose subtle osteoporotic fractures.

• MRI is based on the different magnetic properties of bone and bone marrow, which cause a distinct loss of signal that is proportional to the density and spatial architecture of each tissue.

• Major disadvantage of MRI is the high cost

T1-weighted fat-suppressed image obtained after administration of contrast agent shows enhancement in T12 and L1 vertebrae but no enhancement of L2 vertebra

T1-weighted image shows that acutely fractured T12 and L1 vertebrae have lower signal intensity than chronically fractured L2 vertebra.

Radionuclide bone scan of a patient with TOH of the right hip shows marked uptake in the right femoral head and neck.

T1-weighted coronal MR of hips of the same patient with TOH shows a diffuse zone of low signal intensity in e femoral head and neck consistent with marrow edema.

• In the past, the techniques used to assess BMD were imprecise and inaccurate.

• Today, the most widely used techniques-SXA, DXA, and quantitative CT have errors in precision of 0.5%-2%

• To achieve this degree of precision, strict quality control measures and careful technical monitoring are necessary

• Of the three techniques, DXA and SXA are the most precise, whereas quantitative CT is the most sensitive

QCT is the most accurate BMD test

Ultrasound is the least accurate of the tests

DEXA is the most widely available BMD test

GAUCHER DISEASE

Gaucher disease (GD) is the most common lysosomal storage disease in humans arising from a deficiency of gluco-cerebrosidase activity,

accumulation of a glycolipid (gluco-cerebroside) within the lysosomes of macrophages, particularity in the bone marrow.

Classification

• Type I (non-neuropathic form or adult form):

• commoner type

• progressive hepatosplenomegaly, anaemia and thrombocytopaenia, and marked skeletal involvement; lungs and kidneys may also be involved but the CNS is spared

• Type II (acute neuropathic form or infantile form): severe progressive neurological involvement with death by 1 to 2 years of age; hepatosplenomegaly is also present (usually evident by 6 months of age)

• Type III: type I with neurological involvement presenting in late adolescence or early childhood

• Bone crisis

• Osteonecrosis

• Osteopenia, osteoporosis

• Erlenmeyer flask deformity

• Short stature, growth arrest lines

• Cortical bone ‘infarct’

• Medullary bone ‘infarct’

• Deficient bone formation

• Deficient bone remodelling

• Failed linear bone growth

PATHOLOGICAL EVENT RESULTING SIGN OR SYMPTOM

Cortical ThinningThought to arise from marrowcanal expansion and impairedremodeling.

RADIOGRAPHIC FEATURES

Widening ofthe marrowcanal

Avascular Necrosisand Collapse of theLunate

DIFFUSE OSTEOPENIA

ErlenmeyerFlaskDeformity

Flared metaphyseal regions

Results from an impaired remodeling process

CT

• Higher marrow attenuation values owing to increased amounts of fibrotic and calcific replacement.

MRI

• Reduced T1 and T2 signal intensity from involved bone marrow (due to infiltration with Gaucher cells)

• may give a "salt and pepper pattern" due to scattered involvement

• features of superimposed osteonecrosis

Coronal STIR MR image shows a geographic area of low signal in the left iliac bone, surrounded by a serpiginous high signal rim. This is a characteristic appearance of a bone infarct

• Osteonecrosis in Gaucher disease. (a) Plain radiograph of osteonecrosis affecting both femoral heads (particularly the right)

• (b) MR image of the same patient.

• (c) T1-weighted MR image showing early stage osteonecrosis of the left femoral head in another patient with Gaucher disease.

• MR images of bone marrow infiltration in Gaucher disease. (a) T1- and (b) T2-weighted images of the spinal column illustrating the reduced signal intensities; (c) T1-weighted image of the left and right femur illustrating a heterogenous pattern of marrow infiltration

TREATMENT

• Enzyme replacement with human placental, macrophage-targeted glucocerebrosidase was shown to be safe and effective in clinical trials and was introduced as a definitive therapy.

MUCOPOLYSACCHARIDOSES

• MPS are a group of inherited metabolic disorders that result in widespread skeletal, visceral, and mental abnormalities.

• A defect in metabolic degradation leads to storage of mucopolysaccharide macromolecules in the nervous system and other body tissues.

• MPS re classified in to various types

• MPS-I HURLER’S SYNDROME

• MPS-II HUNTER’S SYNDROME

• MPS-III SANFLIPPO’S SYNDROME

• MPS-IV MORQUIO’S SYNDROME

• MPS-VI MAROTEAUX-LAMY SYNDROME

• MPS-VII SLY’S SYNDROME

• Out of these hurler’s and morquios’s are commonly encountered where as, others are very rare in incidence.

It carries an autosomal recessive inheritance manifesting in first year of life.

It is clinically characterised by

• mental retardation,

• corneal clouding,

• deafness,

• cardiac disease,

• with death resulting in first decade often from cardiac disease.

Epidemiology

The estimated incidence is at ~ 1: 100,000

HURLER SYNDROME

RADIOGRAPHIC FEATURESSkeletal features include

• concave articular surface of mandibular condyle

• macrocephaly

• J-shaped sella

• C1-C2 subluxation : atlanto-axial subluxation

• shortening and widening of long bones

• pointing of proximal metacarpals

• widening of anterior ribs (oar shaped / paddle ribs)

• hypoplastic vertebra at thoracolumbar junction

• inferior beaking of anterior vertebral margins 

• thoracolumbar kyphosis

Widening of anterior ribs (oar shaped / paddle ribs)

Lateral radiograph of the skull (magnified) showing ‘J’-shaped sella turcica (arrow)

Radiograph of both feet (AP view) showing

• short metatarsals (black arrows),

• bullet-shaped phalanges (white arrows),

• overlapping of the 3rd toe over the 2nd.

Radiograph of the pelvis (AP View) showing

• shallow acetabulums,

• coxa valga (white arrows), and

• flaring of the iliac wings (black arrows)

Lateral radiograph of the dorsolumbar spine showing pronounced inferior beaks in the lumbar vertebral bodies (arrows)

Radiograph of the chest and upper limbs showing

• increase in the cardio–thoracic ratio,

• oar-shaped ribs (white arrows),

• short and deformed clavicles (black arrows),

• shallow glenoid cavities, and

• irregular upper humeral metaphyses, bilaterally

• The disease is progressive. Patients with Hurler's syndrome appear normal at birth.

• They have accelerated growth during the first year of life, which is followed by slowing of both mental and physical growth.

• The developmental delay appears between 12 and 28 months. The radiological images are very characteristics of Hurler's disease.

TREATMENT

ENZYME REPLACEMENT THERAPIES ARE CURRENTLY IN USE

• It is an autosomal recessive condition with an estimated incidence of ~ 1:40000

Pathology• It results from an excess of Keratan sulphate from a deficit in its

degradation pathway .

• Keratan sulphate accumlates in various tissues inclusive of cartilage, the nucleus pulposus of the intervertabral disc and cornea.

MORQUIO SYNDROME

CLINICAL PRESENTATION• Many cases present at ~ 2 years of age and have normal intelligence

Features include

• severe dwarfism (< 4 ft)

• joint laxity

• corneal opacification / cloulding

• lymphadenopathy

• progressive deafness

• spinal kyphoscoliosis

• prominent mandible and lower face

• short neck

• deafness

RADIOGRAPHIC FEATURESPlain film / CT

• Spinal

• Platyspondyly (refers to flattened vertebral bodies throughout the axial skeleton)

• hypoplasia of odontoid peg

• atlanto axial subluxation

• os odontoideum (an uncommon craniovertebral junction (CVJ) abnormality characterized by a separate ossicle superior to the dens).

• anterior central vertebral body beaking

• round vertebral bodies

• Calvarial

• hypertelorism

• dolichocephaly

X-ray of skull; AP and lateral view (1A and 1B) and cervical spine in flexion and extension position (1C and 1D) showing a J-shaped sella and multi-level vertebra plana (flattened vertebrae).

Lateral view of the cervical spine obtained in flexion (right) demonstrates a 9 mm gap at the atlanto-axial articulation (arrows, right), which is reduced in extension (arrows, left). Atlanto-axial subluxation is called if the distance between the dens and the anterior arch of C1 exceeds 2.5 mm in adults or 4.5 mm in children.

X-ray of dorso-lumbar spine in AP and lateral view (2A and 2B) showing• kyphosis with multi-level vertebra plana • Ribs show broadening of the anterior portion (tongue shape).

Limbs

• metaphyseal flaring in long bones

• multiple epiphyseal centres

• wide metacarpals with proximal pointing, irregular carpal bones 

• short and wide tubular bones

• flattened femoral epiphyses ; risk of lateral subluxation and dislocation

Pelvis

• coxa valga

• goblet shaped flared iliac wings, increased acetabular angles and constricted iliac bone base

Sternum and chest

• anterior sternal bowing, increased AP chest diameter, wide ribs

X-ray of the pelvis and both femurs in AP view shows flared iliac bones laterally with inferior constriction (wine-glass shape). Enlargement of both acetabular cavities is seen with rough margins, and poorly formed femoral epiphyses and widened femoral necks with coxa valga.

X-ray of both knees in AP view (5A) and leg with foot in AP (5B) and lateral view (5C) showing genu valgus, metaphyseal expansion of long bones, and tapering of the proximal phalanges respectively.

• Complications develop later and include breathing problems, cardiac problems, spinal cord damage leading to possible paralysis, vision problems, walking problems related to abnormal curvature of the spine, and other bony problems.

• Treatment is currently only palliative.

• Possible future treatments include enzyme replacement, gene therapy and allogenic bone marrow transplantation.

LANGERHANS CELL HISTIOCYTOSIS

• Langerhans cell histiocytosis (LCH) is a rare multi system disease with a wide and heterogeneous clinical spectrum and variable extent of involvement. 

Epidemiology

• The disease is more common in the paediatric population, with a peak incidence between 1 and 3 years of age . There is also a male predilection (M:F  1.2-2.1 : 1)  

Three clinical forms:

Acute disseminated langerhans cell histiocytosis (Letterer-Siwe disease)

• Occurs most frequently in infants 2 years of age or younger (and occasionally adults) Presents with multi system organ involvement.

• Infiltration of bone marrow and other organs lead to concurrent hepatosplenomegaly, lymphadenopathy, pulmonary lesions, anemia, thrombocytopenia, recurrent infections (otitis media)

• Eventually, there are destructive osteolytic bone lesions.If untreated, this disease is rapidly fatal

• With chemotherapy, 5 year survival rate is approximately 50 percent.

Unifocal langerhans cell histiocytosis (Eosinophilic granuloma or granulomatosis)

• Usually only affects the skeletal system of young adults.

• Typically presents as an osteolytic lesion involving the Calvaria,Vertebra,Rib,Mandible,Femur,Ilium,Scapula,

• Bony lesions are usually asymptomatic In some cases, can cause pain and even pathologic fractures.

• Skull (50%) Diploic space of parietal bone most often Round or ovoid punched out lesions with beveled edge Sclerotic margin during healing phase Beveled edge=hole-within-a-hole

• Button sequestrum- bony sequestrum within lytic lesion Axial skeleton (25%)

• "Vertebra plana"-"coin-on-edge"(Calve disease)=collapse of vertebral body, mostly thoracic.Most common cause of vertebra plana in children.

• Skull Lesions• Oval-shaped and well defined• Look like punched out lytic

lesions• Lytic lesions may contain a

fragment of intact bone referred to as a button sequestrum

• Skull may take on “geographic” appearance

• NO periosteal reaction or reactive sclerosis

• Spinal Lesions• Predilection for thoracic spine• May lead to near collapse with

“vertebra plana” appearance

Lateral collimated radiograph of thoracolumbar spine shows multiple vertebra plana deformities.

Anteroposterior radiograph shows an intramedullary osteolytic lesion of the tibial diaphysis accompanied by a subtle lamellar periosteal reaction (arrowhead).

b, c MR imaging reveals an oval lesion (arrowheads) within the bone marrow of the tibia with hypointense signal on b sagittal T1-weighted SE image and hyperintense signal on c sagittal STIR image, surrounded by a zone of extensive edema.

d Axial fat-suppressed T2-weighted FSE MR image reveals circular periosteal and parosteal edema, but absence of a soft tissue mass.

e Photomicrograph of histologic section (hematoxylin and eosin stain) shows histocyte-like cells (Langerhans' cells) and dense infiltrates of eosinophils

LCH of the left femur in a 6-year oldboy with a 3-month history of left knee pain and leg weakness. (a) AP radiograph of the left femur shows a well-defined area of lysis in the middle of the femoral diaphysis associated with thickly lamellatedpeniosteal reaction bridging the margins of uninvolvedbone. (b) Whole-body scintigram showsmarked radiotracer uptake in the middle of the left femoral diaphysis.

Multifocal langerhans cell histiocytosis (Hand-Schuller-Christian disease)

Triad of Diabetes insipidus, Exophthalmos, Holes in the bone

Bone-Lytic skull lesions with overlying soft tissue nodules. Large geographic skull lesions "Floating teeth" with mandibular involvement.

Diabetes insipidus is secondary to infiltration of the posterior pituitary stalk by the Langerhans cell.

CTSimilar to plain film findings with better demonstration of cortical erosion and soft tissue involvement. Excellent for biopsy and surgical planning.

MRISignal characteristics include T1 : typically low signal T2 : isointense to hyperintense C+ (Gd) : often shows contrast enhancement

Treatment and prognosisThe prognosis is excellent when disease is confined to the skeleton, especially if it is a solitary lesion,  with the majority of such lesions spontaneously resolving by fibrosis within 1-2 years.

However, where symptoms persist, other treatment options may be considered.

• excision and curettage 

• steroid therapy• chemotherapy• radiofrequency ablation 

REFERENCES• Bone and joint imaging – Donald Resnick• Greenspan textbook of Radiology• Osteoporosis: what a clinician expects to learn from a patient’s

bone density examination Radiology 2003; 228: 620.• Quantitative US of the Calcaneus: Cutoff Levels for the

Distinction of Healthy and Osteoporotic Individuals Radiology 2001; 220: 400.

• Percutaneous Vertebroplasty: Indications, Technique, and Results RadioGraphics 2003 23: 10e; published online as 10.1148/rg.e10

• Garnero P, Delmas PD. New developments in biochemical markers for osteoporosis. Calcif Tissue Int. 1996;59(Suppl 1): S2-S9.

• Levis S, Altman R. Bone densitometry: clinical considerations. Arthritis Rheum. 1998;41:577-587.

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