Corrosion of the Head-Stem Taper Junction-Are We on the Verge of an Epidemic?: Review Article.
BACKGROUND
The modular head taper junction has contributed to the success of total hip arthroplasty (THA) greatly. Taper corrosion and wear problems reported for large and extra-large metal-on-metal bearings as well as for bi-modular THA stems have cast doubt on the benefit of the taper interface. Presently, corrosion problems are being reported for nearly all kinds of artificial hip joints incorporating metal heads, questioning taper connections in general.


OBJECTIVE
This study aimed to review the mechanical and electrochemical relationships that may lead to taper corrosion, which have been reported more commonly in recent literature, and to also review the contribution of patient characteristics and surgical techniques involved in taper assembly that may contribute to the problem.


METHODS
The search criteria "(corrosion) AND (hip arthroplasty) AND (taper OR trunnion)" and "(hip arthroplasty) AND ((pseudotumor) OR (pseudo-tumor))" in PubMed and the JAAOS were used for the literature search. In addition, the arthroplasty registers were considered.


RESULTS
Most studies acknowledge the multifactorial nature of the problem but concentrate their analysis on taper and implant design aspects, since this is the only factor that can be easily quantified. The sometimes conflicting results in the literature could be due to the fact that the other two decisive factors are not sufficiently considered: the loading situation in the patient and the assembly situation by the surgeon. All three factors together determine the fate of a taper junction in THA. There is no single reason as a main cause for taper corrosion. The combined "outcome" of these three factors has to be in a "safe range" to achieve a successful long-term taper fixation.


CONCLUSIONS
No, this is not the beginning of an epidemic. It is rather the consequence of disregarding known mechanical and electrochemical relationships, which in combination have recently caused a more frequent occurrence-and mainly reporting-of corrosion issues.
Institute of Biomechanics, TUHH Hamburg University of Technology, Denickestrasse 15, 21073 Hamburg, Germany.
Michael
0000-0002-5330-2454
M
Morlock
Institute of Biomechanics, TUHH Hamburg University of Technology, Denickestrasse 15, 21073 Hamburg, Germany.
Dennis
D
Bünte
Institute of Biomechanics, TUHH Hamburg University of Technology, Denickestrasse 15, 21073 Hamburg, Germany.
Julian
J
Gührs
Institute of Biomechanics, TUHH Hamburg University of Technology, Denickestrasse 15, 21073 Hamburg, Germany.
Nicholas
N
Bishop
assembly; chrom; cobalt; contamination; corrosion; fretting; ions; loading; taper; titanium alloy