We did a follow-up study on fifty-three total hip-replacement procedures
in forty-seven patients in whom a metal-backed acetabular component was
used. The minimum follow-up was five years (average, six and one-half
years). These relatively young patients ranged in age from seventeen to
seventy-six years old (average, forty-one years old). Excluding one septic
hip and one traumatic dislocation of the acetabular component, three
sockets became loose in the remaining fifty-one hips. The results in
thirty-four patients who were forty-five years old or younger were compared
with those in a group of patients of similar age, reported by Dorr and
Takei, in whom sockets without metal backing were used. Thirteen of the
forty-three non-metal-backed sockets in their patients became loose or had
a continuous radiolucent line at least two centimeters thick around the
entire circumference of the cement on an anteroposterior radiograph, which
they referred to as impending failure. In comparison, the three loose
acetabular components in our thirty-four patients comprised a statistically
significant reduction (p less than 0.05). No acetabular components in our
series showed evidence of impending failure. We and others have reported
finite-element analyses showing that a metal backing on the acetabular
component reduces peak stresses in the bone, cement, and polyethylene.
These analytical data are now supported by the clinical data reported here;
that is, the metal backing of the acetabular component enhanced the
duration of cement fixation.