Acetabular Debonding: An Investigation of Porous CoatingDelamination in Hip Resurfacing Arthroplasty

To date, there have been no published investigations on the cause of acetabular debonding, a rare failure phenomenonin metal-on-metal hip resurfacing where the acetabular porous coating delaminates from the implant while remaining well fixed tothe pelvic bone.Purposes.This study aims to summarize the current understanding of acetabular debonding and to investigate thediscrepancy in rate of debonding between two implant systems.Patients and Methods.To elucidate potential causes of debonding,we retrospectively analyzed a single-surgeon cohort of 839 hip resurfacing cases. Specifically, we compared rate of debonding andmanufacturing processes between two implant systems.Results.Group 1 experienced significantly more cases of debonding thanGroup 2 cases (4.0% versus 0.0%, p value<0.0001). Implant manufacturing processes differed in surface coating, heat treatment,postmanufacturing treatment, and apex thickness. Debonded implants were more likely to have missed RAIL guidelines (p=0.04).Conclusions.We identified implant system, postoperative time, and acetabular component placement as variables contributing torate of debonding. We recommend minimizing acetabular inclination angle according to RAIL guidelines. Further, we evaluatedmanufacturing differences between the two implant systems but did not have access to proprietary data to identify the cause ofdebonding. Both implants met ASTM standards, yet only the Group 1 implant debonded. This suggests the second implant hadgreater fatigue shear strength. Because the Group 2 implant achieved a more durable interface that did not debond, we suggestthe ASTM F1160 standard for fatigue shear strength be increased to that achieved by its manufacturer.Level of Evidence II.Aretrospective evaluation of prospectively collected data