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