Electrochemistry measurements during hip wear simulation for high and low femoral head assembly
-
1
DePuy Synthes Joint Reconstruction, Research, United States
Introduction: Corrosion at modular junctions of orthopaedic implants has been observed, at some level, for decades[1]. The clinical concerns with large femoral head metal on metal implants have focussed additional attention on methods for assessing taper junctions[2]. This study was undertaken to assess electrochemistry differences between assembly methods for attaching the modular femoral head to the hip stem during an ISO standard hip wear simulation.
Material and Methods: A 12 station hip simulator (AMTI, Watertown, MA) was set up per ISO 14242-1 for all parameters of component orientation and loading. Both 28mm and 36mm diameter metal femoral heads (DePuy Synthes) were articulated against cross-linked UHMWPE acetabular cup inserts (DePuy Synthes). Femoral heads were assembled onto either Ti6Al4V or CoCr alloy 12/14 tapers using either a "high" or "low" assembly load method providing 3 specimens for each sample. The "high" assembly load was achieved by impactions using a surgical mallet. A 25 lb. weight placed and held for 3 seconds was designated as "low" to mimic a simple hand press assembly. A 12 station potentiostat (Gamry, Westminster, PA) was set up to measure the currents and potentials on each test cell. Custom test fixtures were built from non-conductive materials to isolate the test stations from the simulator.
Test specimens were articulated in 500 ml of bovine serum, diluted with buffered saline, with 18mg/ml protein concentration, 0.56% sodium azide and 5.6mM EDTA. Testing was conducted in 500,000 cycle intervals at 1 Hz. Current and potential measurements were made every 86,000 cycles for 600 seconds @ 100 samples/second. Currents were imported into SignalExpress (National Instruments, Austin, TX) where RMS currents were extracted and reported as an average for each interval. Statistical analysis was completed using an ANOVA (p<0.05). A total of 4 intervals or 2.0M cycles were completed for each specimen.
Results: RMS corrosion currents for the low assembly group were higher than the respective high assembly groups.
CoCr alloy tapers coupled with 36mm femoral heads had increased currents over 36mm femoral heads coupled with Ti alloy tapers for low assembly loads. No significant difference was detectable between Ti alloy or CoCr alloy tapers coupled with 28mm femoral heads. The 36mm femoral head groups had increased currents over 28mm groups under low assembly conditions.
Discussion: The corrosion currents measured under standard simulator conditions are small for both high and low assembly loads but there are statistical differences noted. It is unknown, at this time, if the values reported here are clinical significant. There is mixed information reported about the effect of head size and stem taper material on corrosion current. This requires further investigation.
Conclusion: Low assembly load of modular femoral heads to stem tapers contributes to a higher corrosion current compared with high assembly load.
For their assistance in running the tests and discussing electrochemistry results: Sophie Yang, Jason Coleman, and Randall Wood
References:
[1] Collier, J.P., et al., "Corrosion between the components of modular femoral hip prostheses", JBJS, 1992, Vol 74, pp 511-517
[2] Goldber, J.R., Gilbert, J.L., "In vitro corrosion testing of modular hip tapers", JBMR part B, Vol 64B, pp 78-93.
Keywords:
joint replacement,
corrosion,
Implant,
wear
Conference:
10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016.
Presentation Type:
Poster
Topic:
Safety and toxicity evaluation for biomaterials
Citation:
Hastings
R and
Whitaker
D
(2016). Electrochemistry measurements during hip wear simulation for high and low femoral head assembly.
Front. Bioeng. Biotechnol.
Conference Abstract:
10th World Biomaterials Congress.
doi: 10.3389/conf.FBIOE.2016.01.01575
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
27 Mar 2016;
Published Online:
30 Mar 2016.
*
Correspondence:
Dr. Dustin Whitaker, DePuy Synthes Joint Reconstruction, Research, Warsaw, IN, United States, dwhitake@its.jnj.com