The Influence of Head Size and Sex on the Outcome of Birmingham Hip Resurfacing
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The Journal of Bone and Joint Surgery (American). 2010
Callum W. McBryde, MD, FRCS(Tr&Orth)1, Kanthan Theivendran, MRCS1, Andrew M.C.
Thomas, FRCS1, Ronan B.C. Treacy, FRCS(Tr&Orth)1 and Paul B. Pynsent, PhD1
1 Research and Teaching Centre, Royal Orthopaedic Hospital, Bristol Road
South, Northfield, Birmingham B31 2AP, United Kingdom. E-mail address for C.W.
Investigation performed at the Royal Orthopaedic Hospital, Birmingham, United
Background Hip resurfacing has gained popularity for the
treatment of youngand active patients who have arthritis. Recent
literature has demonstrated an increased rate of revision among
female patients as compared with male patients who have undergone hip
resurfacing. The aim of the present study was to identify any
differences in survival or functional outcome between male and female
patients with osteoarthritis who were managed with metal-on-metal hip resurfacing.
Methods A prospective collection of data on all patients
undergoing Birmingham Hip Resurfacing at a single institution was
commenced in July 1997. On the basis of the inclusion and exclusion
criteria,1826 patients (2123 hips, including 799 hips in female
patients and 1324 hips in male patients) with a diagnosis of
osteoarthritis who had undergone the procedure between July 1997 and
December2008 were identified. The variables of age, sex,
preoperative Oxford Hip Score, component size used, surgical
approach, lead surgeon, and surgeon experience were analyzed. A
multivariate Cox proportional hazard survival model was used to
identify which variables were most influential for determining
Results The mean duration of follow-up was 3.46 years
(range, 0.03 to10.9 years). The five-year cumulative survival rate
for the655 hips that were followed for a minimum of five years was97.5% (95% confidence interval, 96.3% to 98.3%). There were
forty-eight revisions. Revision was significantly associated with
female sex (hazard rate, 2.03 [95% confidence interval,1.15 to
3.58]; p = 0.014) and decreasing femoral component size hazard rate
per 4-mm decrease in size, 4.68 [95% confidence interval, 4.36 to
5.05]; p < 0.001). Revision was not associated with age (p = 0.88),
surgeon (p = 0.41), surgeon experience (p = 0.30), or surgical
approach (p = 0.21). A multivariate analysis including the covariates
of sex, age, surgeon, surgeon experience, surgical approach, and
femoral component size demonstrated that sex was no longer
significantly associated with revision when femoral component size
was included in the model (p = 0.37).Femoral component size alone
was the best predictor of revision when all covariates were analyzed
(hazard rate per 4-mm decrease in size, 4.87 [95% confidence
interval, 4.37 to 5.42]; p <0.001).
Conclusions The present study demonstrates that although
female patients initially may appear to have a greater risk of
revision, this increased risk is related to differences in the
femoral component size and thus is only indirectly related to sex.
Patient selection for hip resurfacing is best made on the basis of
femoral head size rather than sex.