In the early 1970s, Bateman and Giliberty in North America and Monk in Europe introduced the bipolar endoprosthesis. This design allowed the movement between the acetabulum and the outer metal shell as well as between the high-density
polyethylene
socket and the ball of the femoral components. But the motion of two components in bipolar endoprosthesis has been argued in another several reports, depending on the type of cup and the condition of the hip until now.
The authors reviewed 20 hips of the Universal Hip Replacement bipolar endoprosthesis without acetabular reaming(A group) and 23 hips of the Universal Hip Replacemet bipolar endoprosthesis with acetabular reaming(B group). The motion and its
amount
of
the two components are also analyzed in radiologic study. The follow up period of the hip ranged from 1.5 months to 22.1 months, and the average length was 12 months.
@ES The following results were obtained.
@EN 1. In a Group, there were both of the outer and inner bearing motion in 18 cases(90.0%), and the outer bearing motion in 2 cases(10.0%). In B group, there were both of the outer and inner bearing motion in 13 cases(56.5%), and the inner
bearing
motion in 10 cases(43.5%). The ratio of both bearing motion in A group was more than those in B group(p<0.05).
2. In A group, the total average amount of the motion was 42°, the average amount of the outer bearing motion and the inner bearing motion were 30°(71.4%) and 12°(28.6%), respectively. The amount of the outer bearing motion was larger than
that
of
the iner bearing motion in A group(p<0.05).
In B group, the total average amount of the motion was 37°, the average amount or the outer bearing motion and the inner bearing motion were 10*(27.0%) and 27°(73.0%), respectively. The amount of the inner bearing motion was larger than that of
the
outer bearing motion in B group(p<0.05).
The total average amount of the motion in A group was slightly larger than that in B group, but there was no difference statistically(p>0.05).
3. In cases with 22mm head, the total average amount of the motion was 36°, the average amount of the inner bearing motion was 28*(78%).
In cases with 28mm head, the total average amount of the motion was 40°, the average amount of the inner bearing motion was 18°(45%).
The ratio of the inner bearing motion in cases with 22mm head was larger than that in cases with 28mm head(p<0.05).
The total average amount of motion in cases with 28mm head was slightly larger than that in cases with 22mm head, but there was no difference statistically(p>0.05).
4. In cases of comparative study between the cases which were followed up for less than 3 months, 3 months to 6 months and more than 6 months, there was no significant difference in the motion of 2 components and the average amount of motion
among
these 3 groups.
5. The average Harris hip score after the operation was 89.1 point in A group and 86.2 point in B group, there was no statistical difference between the two groups.
The higher the average Harris hip score was, the larger the total amount of the motion was in both group.
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