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Head size and time in vivo do not correlate with THA implant taper corrosion
Investigators found cobalt-chromium-molybdenum femoral heads were associated with quantifiable taper corrosion.
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Investigators found in their study that analyzed the amount of taper corrosion in 203 femoral head retrievals, which was selected as one of the best papers at the European Hip Society Congress, that the implant’s material and offset directly correlated with taper corrosion.
Jacob Cartner, MS, presented the study that involved two types of hip replacement devices, which had been in vivo for 1 week to 10 years. He and colleagues studied taper corrosion in 166 cobalt-chromium-molybdenum (CoCrMo) heads and 37 oxidized zirconium (OxZr) femoral heads.
A difference in corrosion seen
Cartner and colleagues found the OxZr heads showed less corrosion than with the CoCrMo heads. Furthermore, according to the results, 13 CoCrMo heads had measurable material loss, which ranged from 1 µm to 103 µm.
“Our study found that despite decades of clinical success cobalt-chrome-molybdenum alloy femoral heads are still associated with a quantifiable amount of taper corrosion in outlier cases. And, while there are many factors that influence taper corrosion, our 18-year cohort showed no correlation between head size or time in vivo and severity of corrosion,” Cartner told Orthopaedics Today Europe.
Cartner and colleagues used the Goldberg Score to rank the taper surfaces of each implant. They found the head size did not correlate to a higher Goldberg Score (n = 196, R2 = 0.24); 103 femoral heads were greater than or equal to 36 mm in size and did not have statistically significant different Goldberg Scores than heads that were less than 36 mm.
The CoCrMo heads had a higher maximum depth of material loss based on vertical straightness profile measurements and this correlated with higher Goldberg Scores, Cartner and colleagues noted.
Different factors lead to corrosion
There are several factors that do correlate to taper corrosion in femoral heads, according to Cartner.
“Contrarily, head offset and material influenced the severity of corrosion. Offsets away from neutral had higher severity of corrosion scores and worst case CoCrMo heads had measurable material loss,” he said.
The investigators concluded in the study that while CoCrMo heads historically have success, they are susceptible to taper corrosion. The corrosion of an OxZr femoral head proved to be less than that of a CoCrMo femoral head.
“Worst case oxidized zirconium femoral heads exhibited lower corrosion scores and non-measurable material loss. We plan to continue our research investigating factors that influence taper corrosion in total hips,” Cartner said. – by Robert Linnehan
- Reference:
- Cartner J. Factors that influence taper corrosion: Learning from an 18-year retrieval database. Presented at: European Hip Society Annual Congress; Oct. 9-11, 2014; Stockholm.
- For more information:
- Jacob Cartner, MS, can be reached at Smith & Nephew, 1450 Brooks Rd., Memphis, TN 38116 USA; email: jacob.cartner@smithnephew.com.
Disclosure: Cartner is an employee of Smith & Nephew and owns stock in the company.