Damage Patterns at the Head-Stem Taper Junction Helps Understand the Mechanisms of Material Loss

Background:\ud Material loss at the taper junction of metal-on-metal total hip replacements (MOM THRs) has been implicated in their early failure. The mechanisms of material loss are not fully understood; analysis of the patterns of damage at the taper can help us better understand why material loss occurs at this junction.\ud Methods:\ud We mapped the patterns of material loss in a series of 155 MOM-THRs received at our centre by scanning the taper surface using a roundness-measuring machine. We\ud examined these material loss maps to develop a five-tier classification system based\ud on visual differences between different patterns. We correlated these patterns to\ud surgical, implant and patient factors known to be important for head-stem taper damage.\ud Results:\ud We found that 63 implants had ‘minimal damage’ at the taper (material loss