Aim: Hip resurfacing is a bone conserving procedure with respect to proximal femoral resection. For previous generations of conservative hip replacement, preservation of the natural femoral head diameter necessitated additional sacrifice of acetabular bone in order to accommodate a sufficiently thick polyethylene acetabular component. We have investigated whether the BHR offers a bone conserving procedure with respect to the acetabular bone stock.

Method: We reviewed 284 Birmingham resurfacing hip replacements (BHR), and 479, primary hip replacements, in which an uncemented acetabular component (THUA) was used. The BHR and THUA group had mean age at surgery of 55 and 65 years respectively. In 32 BHR’s and 21 THUA, pre-operative templating measurements were available for subsequent comparison with size of component implanted.

Results: Comparison of component sizes, for both implant types, confirmed bi-modal distribution according to patient gender. BHR cups, implanted by the first author, in females, were significantly smaller than those implanted, by the same author, in THUA,(p< 0.0001). Pre-operative templating overestimated component size for all groups but the difference was only significant in male BHR cases;(p=0.03). BHR cups implanted by the first author were significantly smaller than the second author, for both male (p= 0.0001) and female patients;(p< 0.001).

Conclusion: In females, BHR is bone a conserving procedure for femoral and acetabular components. In males, the procedure is not bone sacrificing when compared to THUA. Pre-operative templating can overestimate size of acetabular component that will be used for men. A significant difference was found between size of acetabular components used by two surgeons for BHR.