Bma Illustrated Medical Dictionary

disorders (see osteopetrosis; Paget’s dis-
ease). Bone density can be measured by
a technique known as densitometry,
which uses low-dose X-rays.
bone, disorders of Any of the group
of disorders that affects the bones,
including fractures; bone infections such
as osteomyelitis or a bone abscess;
inherited conditions such as achondro-
plasia and osteogenesis imperfecta; and
metabolic disorders such as osteomal-
acia, osteoporosis, andrickets. Tumours
and cysts (see bone cancerand bone
tumour) are another, uncommon, group
of bone disorders.
bone graftAn operation in which sev-
eral small pieces of bone are taken from
one part of the body and used to repair
or replace abnormal or missing bone
elsewhere. The bone graft eventually
dies, but it acts as a scaffold upon
which strong new bone grows.
Bone is most commonly taken from
the iliac crests (upper part of the hip-
bones), which contain a large amount
of the inner, spongy bone that is espe-
cially useful for getting grafts to “take”.
Other sources are the ribs (for curved
bone), and the ulna (in the forearm).
bone imagingTechniques for provid-
ing 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
and infections and
the effect of dis-
eased bone on the
surrounding tissues.
Radionuclide scan-
ning detects areas
throughout the skel-
eton in which there
is high bone-cell
activity. This type of
scanning is used
mainly to determine
whether or not can-
cer has spread to
the bones.
bone marrowThe
soft fatty tissue that
is found in bone

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 (shoulder-

blades), clavicles (collarbones), and

bones of the skull.

Stem cellswithin the red marrow are

stimulated to form blood cells by the

hormone erythropoietin. Yellow marrow

is composed mainly of connective tis-

sue 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 over-

produce certain blood cells, as occurs

in polycythaemiaand leukaemia.

bone marrow biopsyA 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 ster-

num (breastbone) or iliac crests (upper

part of the hip-bones). Microscopic

examination gives information on the

development of the blood components

BONE, DISORDERS OF BONE MARROW BIOPSY

B

Biopsy needle

extracts marrow

sample

Site of bone

marrow

BONE MARROW BIOPSY

LOCATION