Biomedical Engineering Reference
In-Depth Information
treatment of marble bones is very difficult because of their hardness. In these
cases, special tools made of tungsten carbide are required (ramiah
et al
.,
2006).
osteonecrosis, also known as ischaemic necrosis of bone, aseptic necrosis
or avascular necrosis (Avn), is due to a loss of the blood supply in the bone
tissue. This pathology affects approximately 20 000 new patients per year in
the USA. Although any age group may develop osteonecrosis, most patients
are between 20 and 50 years old, with the average age in the late thirties.
Patients over the age of 50 are likely to have developed osteonecrosis either
by a fracture of the hip or, more rarely, in association with disease of the
major blood vessels of the lower leg.
When a section of the bone has died, it does not heal spontaneously. Thus,
one approach to this problem is to remove the dead bone surgically and fill
the empty space with bone graft that is either taken from the patient or from
the bone bank. The success of this approach depends upon the quantity of
bone that has died. The use of synthetic biomaterials is a potential alternative
to the use of autografts and allografts. In cases where osteonecrosis attacks
larger areas such as joints, total joint replacement procedures must take
place.
Paget's bone disease, also regarded as the osteoclasts disease, is a more
common disease affecting 1-2% of white adults older than 55 years. The
disease is characterized by an increased bone turnover that affects one or
more sites throughout the skeleton. The most common affected sites are
the pelvis (70% of cases), femur (55%), lumbar spine (53%), skull (42%)
and tibia (32%) (Kanis, 1992). The prevalence of Paget's disease increases
substantially with age. Studies performed in the UK suggest that the disease
affects about 8% of men and 5% of women by the eighth decade of life
(van Staa
et al
., 2002). There are large variations in the prevalence of this
disease depending on the ethnicity and geographic location of people. It has
been reported that the UK has the highest prevalence of Paget's disease of
the bone in the world.
The rapid rate of bone turnover in Paget's disease leads to the production
of bone that has a disorganized architecture and reduced mechanical strength,
leading to an increased risk of developing deformities and pathological
fractures. In this sense, surgical intervention is frequently required for the
management of complications caused by Paget's disease. The most common
indication for surgical treatment is joint replacement for osteoarthritis, but
others include fracture fixation, osteotomy to correct bone deformity, surgery
to correct spinal stenosis and prophylactic surgery in patients with painful
pseudofractures (redden
et al
., 1981). The fixation of Pagetic fractures can
be technically challenging because of bony enlargement, deformity, hard
bone and increased vascularity (Kaplan, 1999).
