Bone imaging Health Dictionary

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Bone Imaging: From 1 Different Sources

Techniques for providing pictures that show the structure or function of bones. X-ray images are the most commonly used technique for diagnosing fractures and injuries. More detailed information is provided by tomography, CT scanning, or MRI, which can show tumours

cavities; it may be red or yellow. Red bone marrow is present in all bones at birth and is the factory for most of the blood cells. During the teens, red bone marrow is gradually replaced in some bones by less active yellow marrow. In adults, red marrow is confined chiefly to the spine, sternum, (breastbone), ribs, pelvis (hip-bones), scapulae (shoulderblades), clavicles (collarbones), and bones of the skull.

Stem cells within the red marrow are stimulated to form blood cells by the hormone erythropoietin.

Yellow marrow is composed mainly of connective tissue and fat.

If the body needs to increase its rate of blood formation, some of the yellow marrow will be replaced by red.

Sometimes marrow fails to produce sufficient numbers of normal blood cells, as occurs in aplastic anaemia (see anaemia, aplastic) or when marrow has been displaced by tumour cells.

In other cases, marrow may overproduce certain blood cells, as occurs in polycythaemia and leukaemia.

Health Source: BMA Medical Dictionary
Author: The British Medical Association

Bone

The framework upon which the rest of the body is built up. The bones are generally called the skeleton, though this term also includes the cartilages which join the ribs to the breastbone, protect the larynx, etc.

Structure of bone Bone is composed partly of ?brous tissue, partly of bone matrix comprising phosphate and carbonate of lime, intimately mixed together. The bones of a child are about two-thirds ?brous tissue, whilst those of the aged contain one-third; the toughness of the former and the brittleness of the latter are therefore evident.

The shafts of the limb bones are composed of dense bone, the bone being a hard tube surrounded by a membrane (the periosteum) and enclosing a fatty substance (the BONE MARROW); and of cancellous bone, which forms the short bones and the ends of long bones, in which a ?ne lace-work of bone ?lls up the whole interior, enclosing marrow in its meshes. The marrow of the smaller bones is of great importance. It is red in colour, and in it red blood corpuscles are formed. Even the densest bone is tunnelled by ?ne canals (Haversian canals) in which run small blood vessels, nerves and lymphatics, for the maintenance and repair of the bone. Around these Haversian canals the bone is arranged in circular plates called lamellae, the lamellae being separated from one another by clefts, known as lacunae, in which single bone-cells are contained. Even the lamellae are pierced by ?ne tubes known as canaliculi lodging processes of these cells. Each lamella is composed of very ?ne interlacing ?bres.

GROWTH OF BONES Bones grow in thickness from the ?brous tissue and lime salts laid down by cells in their substance. The long bones grow in length from a plate of cartilage (epiphyseal cartilage) which runs across the bone about 1·5 cm or more from its ends, and which on one surface is also constantly forming bone until the bone ceases to lengthen at about the age of 16 or 18. Epiphyseal injury in children may lead to diminished growth of the limb.

REPAIR OF BONE is e?ected by cells of microscopic size, some called osteoblasts, elaborating the materials brought by the blood and laying down strands of ?brous tissue, between which bone earth is later deposited; while other cells, known as osteoclasts, dissolve and break up dead or damaged bone. When a fracture has occurred, and the broken ends have been brought into contact, these are surrounded by a mass of blood at ?rst; this is partly absorbed and partly organised by these cells, ?rst into ?brous tissue and later into bone. The mass surrounding the fractured ends is called the callus, and for some months it forms a distinct thickening which is gradually smoothed away, leaving the bone as before the fracture. If the ends have not been brought accurately into contact, a permanent thickening results.

VARIETIES OF BONES Apart from the structural varieties, bones fall into four classes: (a) long bones like those of the limbs; (b) short bones composed of cancellous tissue, like those of the wrist and the ankle; (c) ?at bones like those of the skull; (d) irregular bones like those of the face or the vertebrae of the spinal column (backbone).

The skeleton consists of more than 200 bones. It is divided into an axial part, comprising the skull, the vertebral column, the ribs with their cartilages, and the breastbone; and an appendicular portion comprising the four limbs. The hyoid bone in the neck, together with the cartilages protecting the larynx and windpipe, may be described as the visceral skeleton.

AXIAL SKELETON The skull consists of the cranium, which has eight bones, viz. occipital, two parietal, two temporal, one frontal, ethmoid, and sphenoid; and of the face, which has 14 bones, viz. two maxillae or upper jaw-bones, one mandible or lower jaw-bone, two malar or cheek bones, two nasal, two lacrimal, two turbinal, two palate bones, and one vomer bone. (For further details, see SKULL.) The vertebral column consists of seven vertebrae in the cervical or neck region, 12 dorsal vertebrae, ?ve vertebrae in the lumbar or loin region, the sacrum or sacral bone (a mass formed of ?ve vertebrae fused together and forming the back part of the pelvis, which is closed at the sides by the haunch-bones), and ?nally the coccyx (four small vertebrae representing the tail of lower animals). The vertebral column has four curves: the ?rst forwards in the neck, the second backwards in the dorsal region, the third forwards in the loins, and the lowest, involving the sacrum and coccyx, backwards. These are associated with the erect attitude, develop after a child learns to walk, and have the e?ect of diminishing jars and shocks before these reach internal organs. This is aided still further by discs of cartilage placed between each pair of vertebrae. Each vertebra has a solid part, the body in front, and behind this a ring of bone, the series of rings one above another forming a bony canal up which runs the spinal cord to pass through an opening in the skull at the upper end of the canal and there join the brain. (For further details, see SPINAL COLUMN.) The ribs – 12 in number, on each side – are attached behind to the 12 dorsal vertebrae, while in front they end a few inches away from the breastbone, but are continued forwards by cartilages. Of these the upper seven reach the breastbone, these ribs being called true ribs; the next three are joined each to the cartilage above it, while the last two have their ends free and are called ?oating ribs. The breastbone, or sternum, is shaped something like a short sword, about 15 cm (6 inches) long, and rather over 2·5 cm (1 inch) wide.

APPENDICULAR SKELETON The upper limb consists of the shoulder region and three segments – the upper arm, the forearm, and the wrist with the hand, separated from each other by joints. In the shoulder lie the clavicle or collar-bone (which is immediately beneath the skin, and forms a prominent object on the front of the neck), and the scapula or shoulder-blade behind the chest. In the upper arm is a single bone, the humerus. In the forearm are two bones, the radius and ulna; the radius, in the movements of alternately turning the hand palm up and back up (called supination and pronation respectively), rotating around the ulna, which remains ?xed. In the carpus or wrist are eight small bones: the scaphoid, lunate, triquetral, pisiform, trapezium, trapezoid, capitate and hamate. In the hand proper are ?ve bones called metacarpals, upon which are set the four ?ngers, each containing the three bones known as phalanges, and the thumb with two phalanges.

The lower limb consists similarly of the region of the hip-bone and three segments – the thigh, the leg and the foot. The hip-bone is a large ?at bone made up of three – the ilium, the ischium and the pubis – fused together, and forms the side of the pelvis or basin which encloses some of the abdominal organs. The thigh contains the femur, and the leg contains two bones – the tibia and ?bula. In the tarsus are seven bones: the talus (which forms part of the ankle joint); the calcaneus or heel-bone; the navicular; the lateral, intermediate and medial cuneiforms; and the cuboid. These bones are so shaped as to form a distinct arch in the foot both from before back and from side to side. Finally, as in the hand, there are ?ve metatarsals and 14 phalanges, of which the great toe has two, the other toes three each.

Besides these named bones there are others sometimes found in sinews, called sesamoid bones, while the numbers of the regular bones may be increased by extra ribs or diminished by the fusion together of two or more bones.... bone

Bone Graft

See BONE TRANSPLANT.... bone graft

Brittle Bone Disease

Brittle Bone Disease is another name for OSTEOGENESIS IMPERFECTA.... brittle bone disease

Bone Marrow

Bone marrow is the soft substance occupying the interior of bones. It is the site of formation of ERYTHROCYTES, granular LEUCOCYTES and PLATELETS.... bone marrow

Bone Marrow Transplant

The procedure by which malignant or defective bone marrow in a patient is replaced with normal bone marrow. Sometimes the patient’s own marrow is used (when the disease is in remission); after storage using tissue-freezing technique (cryopreservation) it is reinfused into the patient once the diseased marrow has been treated (autologous transplant). More commonly, a transplant uses marrow from a donor whose tissue has been matched for compatibility. The recipient’s marrow is destroyed with CYTOTOXIC drugs before transfusion. The recipient is initially nursed in an isolated environment to reduce the risk of infection.

Disorders that can be helped or even cured include certain types of LEUKAEMIA and many inherited disorders of the immune system (see IMMUNITY).... bone marrow transplant

Bone, Disorders Of

Bone is not an inert sca?olding for the human body. It is a living, dynamic organ, being continuously remodelled in response to external mechanical and chemical in?uences and acting as a large reservoir for calcium and phosphate. It is as susceptible to disease as any other organ, but responds in a way rather di?erent from the rest of the body.

Bone fractures These occur when there is a break in the continuity of the bone. This happens either as a result of violence or because the bone is unhealthy and unable to withstand normal stresses.

SIMPLE FRACTURES Fractures where the skin remains intact or merely grazed. COMPOUND FRACTURES have at least one wound which is in communication with the fracture, meaning that bacteria can enter the fracture site and cause infection. A compound fracture is also more serious than a simple fracture because there is greater potential for blood loss. Compound fractures usually need hospital admission, antibiotics and careful reduction of the fracture. Debridement (cleaning and excising dead tissue) in a sterile theatre may also be necessary.

The type of fracture depends on the force which has caused it. Direct violence occurs when an object hits the bone, often causing a transverse break – which means the break runs horizontally across the bone. Indirect violence occurs when a twisting injury to the ankle, for example, breaks the calf-bone (the tibia) higher up. The break may be more oblique. A fall on the outstretched hand may cause a break at the wrist, in the humerus or at the collar-bone depending on the force of impact and age of the person. FATIGUE FRACTURES These occur after the bone has been under recurrent stress. A typical example is the march fracture of the second toe, from which army recruits suffer after long marches. PATHOLOGICAL FRACTURES These occur in bone which is already diseased – for example, by osteoporosis (see below) in post-menopausal women. Such fractures are typically crush fractures of the vertebrae, fractures of the neck of the femur, and COLLES’ FRACTURE (of the wrist). Pathological fractures also occur in bone which has secondary-tumour deposits. GREENSTICK FRACTURES These occur in young children whose bones are soft and bend, rather than break, in response to stress. The bone tends to buckle on the side opposite to the force. Greenstick fractures heal quickly but still need any deformity corrected and plaster of Paris to maintain the correction. COMPLICATED FRACTURES These involve damage to important soft tissue such as nerves, blood vessels or internal organs. In these cases the soft-tissue damage needs as much attention as the fracture site. COMMINUTED FRACTURES A fracture with more than two fragments. It usually means that the injury was more violent and that there is more risk of damage to vessels and nerves. These fractures are unstable and take longer to unite. Rehabilitation tends to be protracted. DEPRESSED FRACTURES Most commonly found in skull fractures. A fragment of bone is forced inwards so that it lies lower than the level of the bone surrounding it. It may damage the brain beneath it.

HAIR-LINE FRACTURES These occur when the bone is broken but the force has not been severe enough to cause visible displacement. These fractures may be easily missed. Symptoms and signs The fracture site is usually painful, swollen and deformed. There is asymmetry of contour between limbs. The limb is held uselessly. If the fracture is in the upper

limb, the arm is usually supported by the patient; if it is in the lower limb then the patient is not able to bear weight on it. The limb may appear short because of muscle spasm.

Examination may reveal crepitus – a bony grating – at the fracture site. The diagnosis is con?rmed by radiography.

Treatment Healing of fractures (union) begins with the bruise around the fracture being resorbed and new bone-producing cells and blood vessels migrating into the area. Within a couple of days they form a bridge of primitive bone across the fracture. This is called callus.

The callus is replaced by woven bone which gradually matures as the new bone remodels itself. Treatment of fractures is designed to ensure that this process occurs with minimal residual deformity to the bone involved.

Treatment is initially to relieve pain and may involve temporary splinting of the fracture site. Reducing the fracture means restoring the bones to their normal position; this is particularly important at the site of joints where any small displacement may limit movement considerably.

with plaster of Paris. If closed traction does not work, then open reduction of the fracture may

be needed. This may involve ?xing the fracture with internal-?xation methods, using metal plates, wires or screws to hold the fracture site in a rigid position with the two ends closely opposed. This allows early mobilisation after fractures and speeds return to normal use.

External ?xators are usually metal devices applied to the outside of the limb to support the fracture site. They are useful in compound fractures where internal ?xators are at risk of becoming infected.

Consolidation of a fracture means that repair is complete. The time taken for this depends on the age of the patient, the bone and the type of fracture. A wrist fracture may take six weeks, a femoral fracture three to six months in an adult.

Complications of fractures are fairly common. In non-union, the fracture does not unite

– usually because there has been too much mobility around the fracture site. Treatment may involve internal ?xation (see above). Malunion means that the bone has healed with a persistent deformity and the adjacent joint may then develop early osteoarthritis.

Myositis ossi?cans may occur at the elbow after a fracture. A big mass of calci?ed material develops around the fracture site which restricts elbow movements. Late surgical removal (after 6–12 months) is recommended.

Fractured neck of FEMUR typically affects elderly women after a trivial injury. The bone is usually osteoporotic. The leg appears short and is rotated outwards. Usually the patient is unable to put any weight on the affected leg and is in extreme pain. The fractures are classi?ed according to where they occur:

subcapital where the neck joins the head of the femur.

intertrochanteric through the trochanter.

subtrochanteric transversely through the upper end of the femur (rare). Most of these fractures of the neck of femur

need ?xing by metal plates or hip replacements, as immobility in this age group has a mortality of nearly 100 per cent. Fractures of the femur shaft are usually the result of severe trauma such as a road accident. Treatment may be conservative or operative.

In fractures of the SPINAL COLUMN, mere damage to the bone – as in the case of the so-called compression fracture, in which there is no damage to the spinal cord – is not necessarily serious. If, however, the spinal cord is damaged, as in the so-called fracture dislocation, the accident may be a very serious one, the usual result being paralysis of the parts of the body below the level of the injury. Therefore the higher up the spine is fractured, the more serious the consequences. The injured person should not be moved until skilled assistance is at hand; or, if he or she must be removed, this should be done on a rigid shutter or door, not on a canvas stretcher or rug, and there should be no lifting which necessitates bending of the back. In such an injury an operation designed to remove a displaced piece of bone and free the spinal cord from pressure is often necessary and successful in relieving the paralysis. DISLOCATIONS or SUBLUXATION of the spine are not uncommon in certain sports, particularly rugby. Anyone who has had such an injury in the cervical spine (i.e. in the neck) should be strongly advised not to return to any form of body-contact or vehicular sport.

Simple ?ssured fractures and depressed fractures of the skull often follow blows or falls on the head, and may not be serious, though there is always a risk of damage which is potentially serious to the brain at the same time.

Compound fractures may result in infection within the skull, and if the skull is extensively broken and depressed, surgery is usually required to check any intercranial bleeding or to relieve pressure on the brain.

The lower jaw is often fractured by a blow on the face. There is generally bleeding from the mouth, the gum being torn. Also there are pain and grating sensations on chewing, and unevenness in the line of the teeth. The treatment is simple, the line of teeth in the upper jaw forming a splint against which the lower jaw is bound, with the mouth closed.

Congenital diseases These are rare but may produce certain types of dwar?sm or a susceptibility to fractures (osteogenesis imperfecta).

Infection of bone (osteomyelitis) may occur after an open fracture, or in newborn babies with SEPTICAEMIA. Once established it is very di?cult to eradicate. The bacteria appear capable of lying dormant in the bone and are not easily destroyed with antibiotics so that prolonged treatment is required, as might be surgical drainage, exploration or removal of dead bone. The infection may become chronic or recur.

Osteomalacia (rickets) is the loss of mineralisation of the bone rather than simple loss of bone mass. It is caused by vitamin D de?ciency and is probably the most important bone disease in the developing world. In sunlight the skin can synthesise vitamin D (see APPENDIX 5: VITAMINS), but normally rickets is caused by a poor diet, or by a failure to absorb food normally (malabsorbtion). In rare cases vitamin D cannot be converted to its active state due to the congenital lack of the speci?c enzymes and the rickets will fail to respond to treatment with vitamin D. Malfunction of the parathyroid gland or of the kidneys can disturb the dynamic equilibrium of calcium and phosphate in the body and severely deplete the bone of its stores of both calcium and phosphate.

Osteoporosis A metabolic bone disease resulting from low bone mass (osteopenia) due to excessive bone resorption. Su?erers are prone to bone fractures from relatively minor trauma. With bone densitometry it is now possible to determine individuals’ risk of osteoporosis and monitor their response to treatment.

By the age of 90 one in two women and one in six men are likely to sustain an osteoporosis-related fracture. The incidence of fractures is increasing more than would be expected from the ageing of the population, which may re?ect changing patterns of exercise or diet.

Osteoporosis may be classi?ed as primary or secondary. Primary consists of type 1 osteoporosis, due to accelerated trabecular bone loss, probably as a result of OESTROGENS de?ciency. This typically leads to crush fractures of vertebral bodies and fractures of the distal forearm in women in their 60s and 70s. Type 2 osteoporosis, by contrast, results from the slower age-related cortical and travecular bone loss that occurs in both sexes. It typically leads to fractures of the proximal femur in elderly people.

Secondary osteoporosis accounts for about 20 per cent of cases in women and 40 per cent of cases in men. Subgroups include endocrine (thyrotoxicosis – see under THYROID GLAND, DISEASES OF, primary HYPERPARATHYROIDISM, CUSHING’S SYNDROME and HYPOGONADISM); gastrointestinal (malabsorption syndrome, e.g. COELIAC DISEASE, or liver disease, e.g. primary biliary CIRRHOSIS); rheumatological (RHEUMATOID ARTHRITIS or ANKYLOSING SPONDYLITIS); malignancy (multiple MYELOMA or metastatic CARCINOMA); and drugs (CORTICOSTEROIDS, HEPARIN). Additional risk factors for osteoporosis include smoking, high alcohol intake, physical inactivity, thin body-type and heredity.

Individuals at risk of osteopenia, or with an osteoporosis-related fracture, need investigation with spinal radiography and bone densitometry. A small fall in bone density results in a large increase in the risk of fracture, which has important implications for preventing and treating osteoporosis.

Treatment Antiresorptive drugs: hormone replacement therapy – also valuable in treating menopausal symptoms; treatment for at least ?ve years is necessary, and prolonged use may increase risk of breast cancer. Cyclical oral administration of disodium etidronate – one of the bisphosphonate group of drugs – with calcium carbonate is also used (poor absorption means the etidronate must be taken on an empty stomach). Calcitonin – currently available as a subcutaneous injection; a nasal preparation with better tolerance is being developed. Calcium (1,000 mg daily) seems useful in older patients, although probably ine?ective in perimenopausal women, and it is a safe preparation. Vitamin D and calcium – recent evidence suggests value for elderly patients. Anabolic steroids, though androgenic side-effects (masculinisation) make these unacceptable for most women.

With established osteoporosis, the aim of treatment is to relieve pain (with analgesics and physical measures, e.g. lumbar support) and reduce the risk of further fractures: improvement of bone mass, the prevention of falls, and general physiotherapy, encouraging a healthier lifestyle with more daily exercise.

Further information is available from the National Osteoporosis Society.

Paget’s disease (see also separate entry) is a common disease of bone in the elderly, caused by overactivity of the osteoclasts (cells concerned with removal of old bone, before new bone is laid down by osteoblasts). The bone affected thickens and bows and may become painful. Treatment with calcitonin and bisphosphonates may slow down the osteoclasts, and so hinder the course of the disease, but there is no cure.

If bone loses its blood supply (avascular necrosis) it eventually fractures or collapses. If the blood supply does not return, bone’s normal capacity for healing is severely impaired.

For the following diseases see separate articles: RICKETS; ACROMEGALY; OSTEOMALACIA; OSTEOGENESIS IMPERFECTA.

Tumours of bone These can be benign (non-cancerous) or malignant (cancerous). Primary bone tumours are rare, but secondaries from carcinoma of the breast, prostate and kidneys are relatively common. They may form cavities in a bone, weakening it until it breaks under normal load (a pathological fracture). The bone eroded away by the tumour may also cause problems by causing high levels of calcium in the plasma.

EWING’S TUMOUR is a malignant growth affecting long bones, particularly the tibia (calfbone). The presenting symptoms are a throbbing pain in the limb and a high temperature. Treatment is combined surgery, radiotherapy and chemotherapy.

MYELOMA is a generalised malignant disease of blood cells which produces tumours in bones which have red bone marrow, such as the skull and trunk bones. These tumours can cause pathological fractures.

OSTEOID OSTEOMA is a harmless small growth which can occur in any bone. Its pain is typically removed by aspirin.

OSTEOSARCOMA is a malignant tumour of bone with a peak incidence between the ages of ten and 20. It typically involves the knees, causing a warm tender swelling. Removal of the growth with bone conservation techniques can often replace amputation as the de?nitive treatment. Chemotherapy can improve long-term survival.... bone, disorders of

Collar-bone

See CLAVICLE.... collar-bone

Frontal Bone

The bone which forms the forehead and protects the frontal lobes of the brain. Before birth, the frontal bone consists of two halves, and this division may persist throughout life – a deep groove remaining down the centre of the forehead. Above each eye is a heavy ridge in the bone, most marked in men; behind this, in the substance of the bone, is a cavity on each side (the frontal sinus) which communicates with the nose. CATARRH in these cavities produces the frontal headache characteristic of a ‘cold in the head’, and sometimes infection develops known as SINUSITIS (see NOSE, DISORDERS OF).... frontal bone

Parietal Bone

Either one of a pair of bones that form the top and sides of the cranium of the SKULL.... parietal bone

Scaphoid Bone

The outside bone on the thumb side of the HAND in the row of carpal (wrist) bones nearest to the forearm. Fracture of the scaphoid is a common wrist injury that usually occurs when someone falls on to their outstretched hand. The fracture may not be diagnosed at ?rst (even an X-ray may not be abnormal). Pain in and permanent damage to the wrist can occur.... scaphoid bone

Magnetic Resonance Imaging

See MRI.... magnetic resonance imaging

Marble Bone Disease

See osteopetrosis.... marble bone disease

Bone Transplant

The insertion of a piece of bone from another site or from another person to ?ll a defect, provide supporting tissue, or encourage the growth of new bone.... bone transplant

Magnetic Resonance Imaging(mri)

See MRI.... magnetic resonance imaging(mri)

Paget’s Disease Of Bone

Also called osteitis deformans, this is a chronic disease in which the bones (see BONE) – especially those of the skull, limbs, and spine – gradually become thick and also soft, causing them to bend. It is said to be the most common form of bone disease in the world, and it is estimated that some 600,000 people in England may suffer from it. It seldom occurs under the age of 40. Pain is its most unpleasant manifestation. The cause is not known, and there is no known cure, but satisfactory results are being obtained from the use of CALCITONIN and a group of drugs known as BISPHOSPHONATES

(e.g. etidronate). Those with the disease can obtain help and advice from the National Association for the Relief of Paget’s Disease.... paget’s disease of bone

Bone Disorders

May be present at birth or due to infection (osteomyelitis, tuberculosis, etc), fractures from injury or accident, osteoporosis, Paget’s disease (deformity due to mineral deficiency), tumour or sarcoma, osteomalacia, rickets due to Vitamin D deficiency. Brittle-bone disease. Arthritis. See separate entries.

Comfrey decoction. 1 heaped teaspoon to cup water gently simmered 5 minutes; strain when cold; 1 cup – to which is added 20 drops Tincture Calendula (Marigold), thrice daily. Fenugreek seeds may be used as an alternative to Comfrey.

Alternative:– Mixture: equal parts liquid extracts: Comfrey, Marigold, St John’s Wort. One teaspoon in water or honey thrice daily.

Tablets/capsules. Fenugreek, St John’s Wort.

Topical. Comfrey, Fenugreek or Horsetail poultice.

Supplements. Vitamin A, C, E. Dolomite, Zinc.

Supportive. Exposure of site to sunlight.

Comfrey. The potential benefit of Comfrey root outweighs possible risk for bone disorders. ... bone disorders

Cancer – Bone

May be myeloma (tumour-like over-growth of bone marrow tissue, a giant cell sarcoma, a medullary tumour or secondary deposit from breast, lung, prostate cancer etc. Risk of fracture. Inflammation of the bone – Yarrow. Comfrey. See: MYELOMA, SARCOMA. ... cancer – bone

Bone Abscess

A localized collection of pus in a bone (see osteomyelitis).... bone abscess

Bone Age

A measure of skeletal maturity used to assess physical development in children. X-rays, which show how

much bones have grown in a particular body area, are used to determine bone age. (See also age.)... bone age

Bone Cyst

An abnormal cavity in a bone.

Bone cysts typically develop at one end of a long bone and maybe discovered only by chance after a bone fracture at the site of the cyst.

Minor surgery to scrape out the cyst and fill the the cavity with bone chips usually cures the condition, although many small cysts do not need treatment.... bone cyst

Bone Density

The compactness of bone tissue in relation to its volume. A decrease in bone density is a normal part of aging. However, in some people, excessive loss of density (see osteoporosis) can lead to fractures. Less commonly, an increase in bone density (see osteosclerosis) occurs in certain disorders (see osteopetrosis; Paget’s disease). Bone density can be measured by a technique known as densitometry, which uses low-dose X-rays.... bone density

Kidney Imaging

Techniques for visualizing the kidneys, usually performed for diagnosis. Ultrasound scanning can be used to identify kidney enlargement, a cyst or tumour, and the site of any blockage. Conventional X-rays show the outline of the kidneys and most kidney stones. Intravenous urography shows the internal anatomy of the kidney and ureters. Angiography is used to image blood circulation through the kidneys. CT scanning and MRI provide detailed cross-sectional images and can show abscesses or tumours. Two types of radionuclide scanning are used for the kidney: DMSA and DTPA scanning. DMSA is a substance given by intravenous injection that binds to cells in the kidney tubule, giving a single, static picture of the kidneys. DTPA, also given intravenously, is filtered in the kidneys and passes out in the urine. Pictures taken at intervals record its passage through the urinary tract and show kidney function. ... kidney imaging

Marrow, Bone

See bone marrow.... marrow, bone

Mastoid Bone

The lower part of the temporal bone in the skull. It has a projection, known as the mastoid process, which can be felt behind the ear. The mastoid bone is honeycombed with air cells. These are connected to a cavity called the mastoid antrum, which leads into the middle ear. Infections of the middle ear (see otitis media) occasionally spread through the mastoid bone to cause acute mastoiditis.... mastoid bone

Metacarpal Bone

One of 5 long, cylindrical bones within the hand. The bones run from the wrist to the base of each digit, with the heads of the bones forming the knuckles.... metacarpal bone

Metatarsal Bone

One of 5 long, cylindrical bones within the foot. The bones make up the central skeleton of the foot and are held in an arch by the surrounding ligaments.... metatarsal bone

Pubic Bone

The front part of the fused bones that form the pelvis.... pubic bone

Stomach Imaging

See barium X-ray examinations.... stomach imaging

Bone-anchored Hearing Aid

(BAHA) a specialized form of *hearing aid for patients with certain forms of conductive *deafness. A small titanium screw is surgically fixed into the bone of the skull behind the external ear using a process called *osseointegration. Sound energy is passed from a miniature microphone and amplifier to the screw, through the bone, to the *cochlea.... bone-anchored hearing aid

Bone Growth Factors

a group of *growth factors that promote new bone formation. Bone morphogenic protein (BMP), a naturally occurring substance that induces *osteoblast formation, has been genetically synthesized to form bone morphogenetic protein, which stimulates new bone formation and assists with fracture healing. Other bone growth factors include a type of transforming growth factor (TGF?) and insulin-like growth factor II (IGF-II), which encourage collagen formation.... bone growth factors

Bone Scan

an imaging investigation of a patient’s bone using radioactive *tracers. *Technetium-99m phosphate is injected intravenously and absorbed into the hydroxyapatite crystals of bone. It concentrates in areas of increased blood flow and metabolism, such as areas of infection, trauma, and *neoplasia, and gives off radiation that can be detected by a *gamma camera, thereby producing a map or scan of activity in the target area. A bone scan is particularly useful in the diagnosis of subtle fractures (including stress fractures), avascular necrosis (see osteonecrosis), osteomyelitis, tumour spread (metastasis), and loosening of orthopaedic implants.... bone scan

Capitate Bone

the largest bone of the wrist (see carpus). It articulates with the scaphoid and lunate bones behind, with the second, third, and fourth metacarpal bones in front, and with the trapezoid and hamate laterally.... capitate bone

Colour Flow Ultrasound Imaging

see Doppler ultrasound.... colour flow ultrasound imaging

Cross-sectional Imaging

any technique that produces an image in the form of a section through the body with the structures cut across. The main techniques are *ultrasonography, *computerized tomography, *magnetic resonance imaging, and some *nuclear medicine techniques (see positron emission tomography; SPECT scanning). If a series of thin-section images is stacked they can be ‘cut’ through to show other planes or allow reconstruction of three-dimensional images.... cross-sectional imaging

Cuboid Bone

the outer bone of the *tarsus, which articulates with the fourth and fifth metatarsal bones in front and with the calcaneus (heel bone) behind.... cuboid bone

Diffusion Tensor Imaging

a variant of *diffusion weighted imaging in which both the direction and the amount of diffusion of water molecules in a tissue are coded in the image. This MRI technique can be valuable in linear structures, such as nerves and muscle fibres. In the brain the major tracts and their communications can be studied with this technique (see tractography).... diffusion tensor imaging

Diffusion Weighted Imaging

a method of creating images by *magnetic resonance imaging that relies on the amount of available space that individual water molecules have to move in, which depends on the local microstructure. Pathological tissues generally are less organized, with more space for diffusion and a higher signal.... diffusion weighted imaging

Digital Spot Imaging

(DSI) the production of static images using an *image intensifier, usually during a fluoroscopic examination. The images can be stored digitally (see digitization) and either transferred to photographic film or viewed on a TV monitor.... digital spot imaging

Duplex Imaging

see Doppler ultrasound.... duplex imaging

Ethmoid Bone

a bone in the floor of the cranium that contributes to the nasal cavity and orbits. The part of the ethmoid forming the roof of the nasal cavity – the cribriform plate – is pierced with many small holes through which the olfactory nerves pass. See also nasal concha; skull.... ethmoid bone

Functional Magnetic Resonance Imaging

(fMRI) a type of *magnetic resonance imaging that measures the increased hemodynamic response seen with neural activity in the brain or spinal cord. fMRI has allowed major advances in brain mapping (i.e. matching sections of the brain with particular behaviours, thoughts, or emotions).... functional magnetic resonance imaging

Fusion Imaging

see co-registration.... fusion imaging

Hamate Bone

(unciform bone) a hook-shaped bone of the wrist (see carpus). It articulates with the capitate and triquetral bones at the sides, with the lunate bone behind, and with the fourth and fifth metacarpal bones in front.... hamate bone

Hip Bone

(innominate bone) a bone formed by the fusion of the ilium, ischium, and pubis. It articulates with the femur by the acetabulum of the ilium, a deep socket into which the head of the femur fits (see hip joint). Between the pubis and ischium, below and slightly in front of the acetabulum, is a large opening – the obturator foramen. The right and left hip bones form part of the *pelvis.... hip bone

Hyoid Bone

a small isolated U-shaped bone in the neck, below and supporting the tongue. It is held in position by muscles and ligaments between it and the styloid process of the temporal bone.... hyoid bone

Imaging

n. (in radiology) the production of images of organs or tissues by a range of techniques. These images are used by physicians in diagnosis and in monitoring the effects of treatment. They can also be used to guide *interventional radiology techniques. See also computerized tomography; magnetic resonance imaging; ultrasonography.... imaging

Innominate Bone

see hip bone.... innominate bone

Interparietal Bone

(inca bone, incarial bone) the bone lying between the *parietal bones, at the back of the skull.... interparietal bone

Lacrimal Bone

the smallest bone of the face: either of a pair of rectangular bones that contribute to the orbits. See skull.... lacrimal bone

Lamellar Bone

mature *bone, in which the collagen fibres are arranged parallel to each other to form multiple layers (*lamellae) with the osteocytes lying between the lamellae. It exists in two structurally different forms: cortical (compact) and cancellous (spongy) bone. See also woven bone.... lamellar bone

Lunate Bone

a bone of the wrist (see carpus). It articulates with the capitate and hamate bones in front, with the radius behind, and with the triquetral and scaphoid at the sides.... lunate bone

Malar Bone

see zygomatic bone.... malar bone

Membrane Bone

a bone that develops in connective tissue by direct *ossification, without cartilage being formed first. The bones of the face and skull are membrane bones.... membrane bone

Molecular Imaging

an emerging area of imaging that exploits recent developments of molecular and cell biology to create new markers. Most molecular imaging uses versions of these markers labelled with radioactive isotopes, which – after administration – are localized in the body and can be detected using such techniques as *positron emission tomography, *SPECT scanning, *magnetic resonance imaging, and optical imaging.... molecular imaging

Nasal Bone

either of a pair of narrow oblong bones that together form the bridge and root of the nose. See skull.... nasal bone

Navicular Bone

a boat-shaped bone of the ankle (see tarsus) that articulates with the three cuneiform bones in front and with the talus behind.... navicular bone

Occipital Bone

a saucer-shaped bone of the *skull that forms the back and part of the base of the cranium. At the base of the occipital are two occipital condyles: rounded surfaces that articulate with the first (atlas) vertebra of the backbone. Between the condyles is the foramen magnum, the cavity through which the spinal cord passes.... occipital bone

Bone Cancer

Malignant growth in bone, which may originate in the bone itself (primary bone cancer) or, more commonly, occur as a result of cancer spreading from elsewhere in the body (secondary, or metatastic, bone cancer). Primary bone cancers are rare. The type that occurs most often is osteosarcoma. Other types include chondrosarcoma and fibrosarcoma. Bone cancer can also start in the bone marrow (see multiple myeloma and leukaemia). The treatment of primary bone cancer depends on the extent to which the disease has spread. If it remains confined to bone, amputation may be recommended; but it may be possible to remove the cancer and fill the defect with a bone graft. Radiotherapy or chemotherapy, or both, may also be needed

The cancers that spread readily to form secondary bone cancer are those of the breast, lung, prostate, thyroid, and kidney.

These bone metastases occur commonly in the spine, pelvis, ribs, and skull.

Pain is usually the main symptom.

Affected bones are abnormally fragile and may easily fracture.

Bone cancer that affects the spine may cause collapse or crushing of vertebrae, damaging the spinal cord and causing weakness or paralysis of one or more limbs.

Secondary bone cancers from the breast and prostate often respond to treatment with hormone antagonists.... bone cancer

Bone Marrow Biopsy

A procedure to obtain a sample of cells from the bone marrow (aspiration biopsy) or a small core of bone with marrow inside (trephine biopsy). The sample is usually taken, under local anaesthesia, from the sternum (breastbone) or iliac crests (upper part of the hip-bones). Microscopic examination gives information on the development of the blood components

surrounding tissues. Radionuclide scanning detects areas throughout the skeleton in which there is high bone-cell activity. This type of scanning and on the presence of cells foreign to the marrow.

It is useful in the diagnosis of many blood disorders, including leukaemia and anaemia.

It can also show whether bone marrow has been invaded by lymphoma or cells from other tumours.... bone marrow biopsy

Bone Tumour

A bone swelling that may be cancerous (see bone cancer) or noncancerous.

The most common type of noncancerous bone tumour is an osteochondroma.

Other types are osteoma and chondroma (see chondromatosis).

Treatment is only necessary if the tumour becomes very large or causes symptoms by pressing on other structures.

In such cases, the tumour can be removed by surgery.

Osteoclastoma (also called a giant cell tumour), which usually occurs in the arm or leg of a young adult, is tender and painful and has to be removed.... bone tumour

Brain Imaging

Techniques that provide pictures of the brain; they are used to detect injury or disease and include X-rays, angiography, CT scanning, MRI, PET (positron emission tomography) scanning, and SPECT (single photon emission ). X-ray films can show changes in the skull caused by a fracture or, rarely, by a brain tumour or aneurysm. Angiography shows up the blood vessels in the brain, and is used to investigate subarachnoid haemorrhage, aneurysms, abnormalities of the blood vessels, and other circulatory disorders.

scanning gives images of the brain substance; it gives clear pictures of the ventricles (fluid-filled cavities) and can reveal tumours, blood clots, strokes, aneurysms, and abscesses. is especially helpful in showing tumours of the posterior fossa (back of the skull). and scanning are specialized forms of radionuclide scanning that use small amounts of radioactive material to give information about brain function as well as structure. They enable

blood flow and metabolic activity in the brain to be measured.

Ultrasound scanning is used only in premature or very young babies since ultrasound waves cannot penetrate the bones of a mature skull.... brain imaging

Funny-bone

A popular term for the small area at the back of the elbow where the ulnar nerve passes over a prominence of the humerus (upper-arm bone). A blow to the nerve causes acute pain, numbness, and a tingling sensation in the forearm and hand.... funny-bone

Heart Imaging

Techniques that provide images of heart structure. Imaging is used to detect disease or abnormalities. A chest X-ray, the simplest and most widely used method of heart imaging, shows heart size and shape, and the presence of abnormal calcification. Pulmonary oedema and engorgement of the vessels connecting the heart and lungs are also usually detectable.

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Echocardiography is useful for investigating congenital heart defects and abnormalities of the valves or heart wall. An ultrasound technique using the Doppler effect allows measurement of blood flow through valves. Radionuclide scanning and CT scanning provide information about the efficiency of heart function. Angiography may be used to show the heart chambers and to assess the condition of the coronary arteries and valves. High-quality images of the heart can be obtained by MRI.... heart imaging

Intestinal Imaging

See barium X-ray examinations.... intestinal imaging

Liver Imaging

Techniques that produce images of the liver, gallbladder, bile ducts, and blood vessels supplying the liver, to aid the detection of disease.

Ultrasound scanning, CT scanning, and MRI are commonly used.

Radionuclide scanning may reveal cysts and tumours and show bile excretion.

X–ray techniques include cholangiography, cholecystography, and ERCP (endoscopic retrograde cholangiopancreatography).

In these procedures, a contrast medium, which is opaque to X-rays, is introduced to show abnormalities in the biliary system.

Angiography reveals the blood vessels in the liver.... liver imaging

Lung Imaging

Techniques that provide images of the lungs to aid in the diagnosis of disease.

Most lung disorders can be detected by chest X-ray.

CT scanning and MRI play an important role in detecting the presence and spread of lung tumours.

Ultrasound scanning is sometimes used to reveal pleural effusion.

Radioisotope scanning is used to detect evidence of pulmonary embolism.... lung imaging

Palatine Bone

either of a pair of approximately L-shaped bones of the face that contribute to the hard *palate, the nasal cavity, and the orbits. See skull.... palatine bone

Petrous Bone

see temporal bone.... petrous bone

Pisiform Bone

the smallest bone of the wrist (*carpus): a pea-shaped bone that articulates with the triquetral bone and, indirectly by cartilage, with the ulna.... pisiform bone

Real-time Imaging

the rapid acquisition and manipulation of ultrasound information from a scanning probe by electronic circuits to enable images to be produced on TV screens almost instantaneously. The operator can place the scanning probe accurately on the region of interest in order to observe its structure and appreciate moving structures within it (see Doppler ultrasound). Using similar techniques, the instantaneous display of other imaging modalities, such as *computerized tomography scanning and *magnetic resonance imaging, can now be achieved. Real-time imaging is useful in guiding *interventional radiology procedures, for example, allowing a needle to be guided accurately as it is passed into the body. It is also useful for observing dynamic physiological activity.... real-time imaging

Replacement Bone

a bone that is formed by replacing cartilage with bony material.... replacement bone

Sesamoid Bone

an oval nodule of bone that lies within a tendon and slides over another bony surface. The patella (kneecap) and certain bones in the hand and foot are sesamoid bones.... sesamoid bone

Sphenoid Bone

a bone forming the base of the cranium behind the eyes. It consists of a body, containing air spaces continuous with the nasal cavity (see paranasal sinuses); two wings that form part of the orbits; and two pterygoid processes projecting down from the point where the two wings join the body. See skull.... sphenoid bone

Squamous Bone

see temporal bone.... squamous bone

Temporal Bone

either of a pair of bones of the cranium. The squamous portion forms part of the side of the cranium. The petrous part contributes to the base of the skull and contains the middle and inner ears. Below it are the *mastoid process, *styloid process, and zygomatic process (see zygomatic arch). See also skull.... temporal bone

Thallium-technetium Isotope Subtraction Imaging

a technique to image the parathyroid glands. Technetium is taken up only by the thyroid gland, but thallium is taken up by both the thyroid and parathyroid glands. *Digital subtraction of the two isotopes leaves an image of the parathyroid glands alone. It is an accurate technique (90%) for the identification of adenomas of the parathyroid glands secreting excess hormone.... thallium-technetium isotope subtraction imaging

Trapezoid Bone

a bone of the wrist (see carpus). It articulates with the second metatarsal bone in front, with the scaphoid bone behind, and with the trapezium and capitate bones on either side.... trapezoid bone

Turbinate Bone

see nasal concha.... turbinate bone

Unciform Bone

see hamate bone.... unciform bone

Wormian Bone

one of a number of small bones that occur in the cranial sutures.... wormian bone

Woven Bone

immature bone, in which the collagen fibres are arranged haphazardly and the cells have no specific orientation. It is typically found in the early stages of fracture healing, eventually being replaced by mature *lamellar bone.... woven bone

Zygomatic Bone

(zygoma, malar bone) either of a pair of bones that form the prominent part of the cheeks and contribute to the orbits. See skull.... zygomatic bone

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