Published in:
01-02-2014 | Symposium: 2013 Hip Society Proceedings
Taper Design Affects Failure of Large-head Metal-on-metal Total Hip Replacements
Published in: Clinical Orthopaedics and Related Research® | Issue 2/2014
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Background
Large-head metal-on-metal (MoM) hip arthroplasties have demonstrated poor survival. Damage at the taper-trunnion junction is a contributing factor; however, the influence of junction design is not well understood.
Questions/purposes
(1) Does taper type affect fretting, corrosion, and volumetric wear at the junction? (2) Do taper types have different wear patterns? (3) Does larger offset or head diameter increase fretting, corrosion, and wear? (4) Is the extent of fretting and corrosion associated with earlier failure?
Methods
Taper damage in 40 retrieved heads was subjectively graded for fretting and corrosion, and wear was determined with high-resolution confocal measurement. Taper types (11/13, 12/14, and Type 1) differed by angle, distal diameter, and contact length; Type 1 were thinnest and 11/13 had longer contact lengths.
Results
Fretting scores were higher in 11/13 than in Type 1 tapers. Volumetric wear and wear rates did not differ among types. Uniform, circumferential, and longitudinal wear patterns were observed in all types, but fretting, corrosion, and wear did not differ among the patterns. Head diameter and lateral offset did not correlate with fretting, corrosion, or wear. No correlation was found between fretting, corrosion, or wear and length of implantation.
Conclusions
In general, thicker tapers with longer contact lengths were associated with greater fretting scores, whereas no relationship was found among the three designs for corrosion scores or volumetric wear. This finding suggests that trunnion diameter and engagement length are important factors to consider when improving taper-trunnion junction design.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.