The natural history of the bone-furlong interface Justin Cobb Vijay Kannan, Robin Richards UCL/Imperial College

What is happening in the hip?  Is the interface stable  Is there any sign of debonding?  Is the bone stress shielded?  Does a steady state develop?  Could we measure and put figures to the quality of bone At the tip At the tip At the shoulder At the shoulder At the collar At the collar

 Well fixed retrieval  Ct can show bone apposition Index case Strutting bone on metal Remodelling of cortex

What is the natural history?  How long does remodelling go on for?  When does the interface stabilise? Proximally Proximally Shoulder Shoulder Distally Distally  Can we quantify the changes?  Can we predict the future?

Methods 62 patients approached Exclusions:co-morbiditiesclaustrophobia great distances to travel 24 accepted and completed the protocol All had UCLA functional activity score

Distal Interface RIGHT ANTERIOR 1MM RIGHT POSTERIOR 1MM

Distal Interface

Conclusions Debonding no evidence at all Pedestal formation does happen Proximal stress shielding The reverse happens Surface area in contact huge and increasing proximal to the shoulder This implant will be better fixed in 20 years