We thank Dr. Macaulay for his kind comments and interest in our paper.
First, the 7.5% dislocation rate might have been reduced a little in
association with the use of a 32-mm head. Other variables that could have
reduced the dislocation rate were optimal orientation of the acetabular
component, the use of an acetabular component with a long posterior wall, and
repair of the transgluteal approach in three layers (including the capsule,
gluteus medius, and gluteus minimus).
Second, the suggestion that a 1-mm unipolar head might reduce acetabular
erosion is entirely justified. D'Arcy and
Devas1 noted an 11%
prevalence of acetabular erosion in association with the use of acetabular
components with 1/8-in (3.2-mm) increments. They subsequently went on to
develop a bipolar hip with 1-mm increments that had a much lower erosion
rate2. However, this
modification had two variables, the first being the change in increment of
head size and the second being the bipolar design, so the specific influence
of the 1-mm increment alone cannot be isolated.
A larger unipolar femoral head was associated with a higher erosion rate in
the report by D'Arcy and
Devas1, so we would
not recommend this option on the basis of their experience.
Third, the Oxford outcome measure is self-reported but validated and as
patients describe symptoms we believe that patient-oriented functional outcome
measures should replace those derived from physicians.
We agree with Dr. Macaulay that the displaced intracapsular femoral neck
fracture remains an unsolved injury, particularly in younger patients. We hope
that our study has made a small contribution to clarifying the management of
mobile, independent older patients.