Will New Metal Heads Restore Mechanical Integrity of Corroded Trunnions?

Authors:
Aditya Derasari
Aditya Derasari
Houston Methodist Orthopedics & Sports Medicine
Houston | United States
Jonathan E Gold
Jonathan E Gold
Institute of Orthopedic Research and Education
Sabir Ismaily
Sabir Ismaily
Institute of Orthopedic Research and Education
United States
Philip C Noble
Philip C Noble
Institute of Orthopedic Research and Education
United States
Stephen J Incavo
Stephen J Incavo
Houston Methodist Hospital
Houston | United States

J Arthroplasty 2017 04 11;32(4):1356-1359. Epub 2016 Oct 11.

Houston Methodist Orthopedics & Sports Medicine, Houston, Texas.

Background: Metal wear and corrosion from modular junctions in total hip arthroplasty can lead to further unwanted surgery. Trunnion tribocorrosion is recognized as an important contributor to failure. This study was performed to determine if new metal heads restore mechanical integrity of the original modular junction after impaction on corroded trunnions, and assess which variables affect stability of the new interface created at revision total hip arthroplasty.

Methods: Twenty-two trunnions, cobalt-chromium (CoCr) and titanium alloy (TiAIV), (CoCr, n = 12; TiAIV, n = 10) and new metal heads were used, 10 trunnions in pristine condition and 12 with corrosion damage. Test states were performed using an MTS Machine and included the following: 1, Assembly; 2, Disassembly; 3, Assembly; 4, Toggling; and 5, Disassembly. During loading, three-dimensional motion of the head-trunnion junction was measured using a custom jig.

Results: There were no statistical differences in the tested mechanical properties between corroded and pristine trunnions implanted with a new metal femoral head. Average micromotion of the head versus trunnion interface was greatest at the start of loading, stabilizing after approximately 50 loading cycles at an average of 30.6 ± 3.2 μm.

Conclusion: Corrosion at the trunnion does not disrupt mechanical integrity of the junction when a CoCr head is replaced with a CoCr trunnion. However, increased interface motion of a new metal head on a corroded titanium trunnion requires additional study. The evaluation of ball head size on mechanical integrity of trunnions would also be a potential subject of future investigation, as increasing the ball head size at the time of revision is not uncommon in revisions today.

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http://dx.doi.org/10.1016/j.arth.2016.10.007DOI Listing

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April 2017
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