Introduction: Since 1992 over 3000 custom-made cemented titanium femoral components have been implanted during total hip replacement in our centre.

Stems are machined using CAD-CAM. Measurements are made from screened AP and lateral x-rays of known magnification. Normal joint centre is recreated by controlling offset and vertical height of the femoral component.

Method: Joint centre and limb length were analysed radiologically in consecutive 100 patients following total hip replacement for unilateral arthritis. Joint centre was defined relative to the pelvis and femur.

The anatomical axis and offset of the femur were defined using a screened x-ray of known magnification taken to show maximum offset. Femoral centre height was defined relative to the greater trochanter.

Results: In general, acetabular joint centre was placed medial and high, tending to reduce limb length slightly. Conversely, on the femoral side the tendency was to leave the component proud, producing an increase in limb length. Most patients had limb length restored to within 6mm of normal.

This study confirms the effectiveness of the Belfast Custom Stem in restoring joint centre and limb length.