Biomedical Engineering Reference
In-Depth Information
patients' quality of life as well as the economic burden placed by these
operations on the healthcare system.
What are the factors that make implants vulnerable to failure? How can
revision rates be decreased? Clinical outcomes of joint arthroplasty operations
are dependent on many different factors including the total volume of operations
performed by the surgeon, patient variables such as age, weight, bone quality,
gender and activity, design parameters of the implant and the material proper-
ties. The lack of a widespread registry in the US has precluded the elucidation of
the relative importance of some of these factors. Nevertheless, from the
available data, it is clear that joint dislocation, implant loosening, peri-prosthetic
osteolysis and fractures are some major occurrences requiring the revision of
joint implants (Bozic et al., 2009). In the recent years, there have been a surge of
technologies involving material development because wear particles associated
with articulating surfaces are one problem clearly associated with bone
resorption and implant loosening and minimizing wear has been a clear solu-
tion. This chapter will focus on UHMWPE and its development as a joint
replacement material from this perspective but it is important to keep in mind
that clinical outcomes are dependent on a complicated set of factors only one of
which is the material.
3.2
Early development of joint bearing couples
There were attempts at repairing damaged joint surfaces by placing materials
such as wood in between the joint surfaces in the 1800s, but the first real joint
replacement is credited to Smith-Petersen and his mold arthroplasty in 1923,
which involved covering the debrided joint surfaces with molds to allow for
natural repair of the joint (Smith-Petersen, 1948). He used glass, reinforced glass
and other materials such as Formica as interpositional devices. In 1939, a
cobalt±chromium alloy called Vitallium was introduced for mold arthroplasty
(Venable et al., 1937). An alternative design was the short-stem prosthesis,
where the femoral head replacement material was augmented by a short stem
fixed into the femur for added stability. Such prostheses were made of poly-
methylmethacrylate (PMMA) (Judet and Judet, 1950), which was later replaced
by cobalt±chromium alloys (Thomson, 1952). Short-stem prostheses were
followed by long-stem prostheses, where the length of the intermedullary stem
was increased for added stability under weight-bearing conditions (Moore and
Bohlman, 1943). The first total joint arthroplasty is credited to Wiles in 1938
(Wiles, 1957), where he used a stainless steel ball articulating against a stainless
steel acetabular cup. A similar design made of cobalt±chromium designed by
McKee and Farrar was the next generation of arthroplasty device overcoming
the in vivo corrosion observed with stainless steel and decreasing the impinge-
ment of the femoral neck on the acetabular rim (McKee and Watson-Farrar,
1966).
