Characterization of Femoral Head Taper Corrosion Features Using a 22-Year Retrieval Database.
BACKGROUND
Modularity in total hip arthroplasty has been used for decades with great success, but new findings regarding corrosion artifacts have caused a resurgence in tapered junction research. Mechanically assisted crevice corrosion (MACC) is thought to be the mechanism by which corrosive attack occurs. Myriad multi-factorial variables are known to influence the susceptibility of a modular taper junction to MACC. Some of these variables are design and manufacture related and others can be controlled by the surgeon.


OBJECTIVE
This study was performed to assess a 22-year retrieval database to determine if correlations exist between severity of corrosion artifacts and head size, time in vivo, head offset, or head material. Secondarily, the agreement of visual and semi-quantitative scoring methods was assessed using the retrieved components.


METHODS
A total of 210 femoral head tapers were scored and heads receiving high scores were measured to quantify material loss due to MACC.


RESULTS
Increased head size and increased time in vivo did not correlate to higher corrosion scores. Contrarily, there were differences in corrosion scores based on femoral head offset and material. Deviations away from a neutral offset (where neutral is defined as the alignment of femoral head center and stem taper gage point) resulted in higher scores. Cobalt-chromium-molybdenum heads were associated with higher corrosion scores and higher material loss as compared to oxidized zirconium heads.


CONCLUSIONS
Reducing the moment arm at the head-neck junction and choosing a more inert material appears to provide greater resistance to corrosion.
Smith & Nephew, 1450 Brooks Road, Memphis, TN 38116 USA.
Jacob
J
Cartner
Smith & Nephew, 1450 Brooks Road, Memphis, TN 38116 USA.
Patrick
P
Aldinger
Smith & Nephew Orthopaedic Ltd, Implant Development Centre, Leamington Spa, UK.
Chenxi
C
Li
Smith & Nephew Orthopaedic Ltd, Implant Development Centre, Leamington Spa, UK.
David
D
Collins
mechanically assisted crevice corrosion; retrievals; taper; total hip arthroplasty