Abstract
1. The unreliable results of the conventional cup arthroplasty are attributed to mechanical imperfections in the reconstructed joint.
2. If its reliability can be improved, there will remain a place for cup arthroplasty, which, in relatively young and active patients, offers advantages over prosthetic replacement arthroplasty.
3. A technique of concentric cup arthroplasty is described. The new joint is shaped with precision to exact dimensions and lined with a cup designed to ensure stability, concentric movement and a uniform clearance between the moving parts.
4. The results so far are encouraging and justify continued clinical trial.