Biomedical Engineering Reference
In-Depth Information
replacement of joint components destroyed by a congenital degenerative
process may be exemplified by the total hip joint replacement that is needed
in patients born with congenital hip dysplasia. This condition may evolve, in
its worst progression, into a painful destruction of the articular surfaces of
the acetabulum and of the head of the femur at a relatively young age (before
65 years of age, after which the mechanical-based degenerative affection of
osteoarthrosis is more common).
restoration of the anatomical, and possibly mechanical, integrity of a
congenital bone defect is seldom encountered; it is mostly exemplified by
the partial development (or lack of development) of a bone segment like in
the partial agenesis of ulna, radius, tibia or fibula.
13.2 Operative techniques
A wide range of operative techniques have been developed in orthopaedic
surgery. They can be grouped in broad categories, the most important of
which are osteosynthesis, joint replacement and bone replacement.
13.2.1 Osteosynthesis
osteosynthesis is one of the most common operative techniques in orthopaedic
surgery, both in elective orthopaedics and in traumatology. it consists of
the union of two or more bone fragments, after their proper alignment has
been previously gained. The union is mechanically stabilized by a means of
screws, nails, plates and several other mechanical devices which are required
to remain effective until the biological process of fracture healing has restored
the bone segment as a single entity. Materials used in osteosynthesis are, then,
required to possess both mechanical properties adequate to take the load in
the injured bone segment and, at the same time, biological properties able
to keep them in apposition with bone for a period of time during which they
must not hamper or interfere with the bone healing process and, if possible,
should support and promote it.
Despite several devices being made with materials with a very good
biocompatibility or, even, bioactivity, devices used for osteosynthesis should
be removed after a period of time, which should not be longer than one year
from the implantation, in every patient and not only in growing children
(lovell
et al
., 1999).
13.2.2 Joint replacement
A joint may be exemplified as a structure which connects two bone segments,
allowing them a variable degree of reciprocal motion. Sliding joints are
generally enveloped by a fibrous 'joint capsule' which completely seals the
