Mid-term progressive loosening of hydroxyapatite-coated femoral stems paired with a metal-on-metal bearing
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(2019) 14:225
RESEARCH ARTICLE
Open Access
Mid-term progressive loosening of hydroxyapatite-coated femoral stems paired with a metal-on-metal bearing Trevor Gascoyne1, Bryan Flynn2, Thomas Turgeon2,3 and Colin Burnell2,3*
Abstract Background: Several hydroxyapatite (HA)-coated femoral stems from a single manufacturer were identified to have aseptically loosened at mid-term follow-up despite prior radiographic appearance of osseointegration. Possible causes and associated risk factors for stem loosening were explored through radiographic review and implant retrieval analysis. Methods: Forty-six retrieved hip stems (Corail, DePuy-Synthes) were identified and grouped by bearing type: metal-on-metal (MoM), metal-on-polyethylene, and ceramic-on-ceramic. Stem lucency was graded on postoperative radiographs up to the time of revision. Stems were examined for stripping of the HA coating, taper corrosion, and bearing wear in metal-on-metal cases. Patient demographics, implant design features, and perioperative data were collected from electronic databases and patient charts. Results: Aseptic loosening occurred in 37% of cases examined. MoM bearings were associated with 7.25 times greater risk of loosening compared to other bearing types. Stem radiolucency was more prevalent for MoM cases and, although not statistically significant, demonstrated progressive lucency. Taper corrosion appeared more severe for MoM cases and correlated with proximal stem radiolucency. Removal of the HA coating from the stems was associated with both taper corrosion and MoM bearing wear. Length of implantation was a confounding factor for the MoM cases. Conclusion: This study has demonstrated a high risk of mid-term loosening of previously osseointegrated HA-coated femoral stems when paired with a MoM bearing. The mechanism of loosening appears progressive in nature and related to the MoM bearing, possibly interacting with the HA coating. If such loosening is recognized early, rapid revision may allow for retention of the femoral stem. Keywords: Hip arthroplasty, Aseptic loosening, Metal-on-metal, Hydroxyapatite, Radiolucency, Wear
Background Long-term survival of total hip arthroplasty (THA) requires excellent fixation between the host bone and the prosthesis. This fixation can be achieved via cement, bone in-growth, or bone on-growth. The latter can be promoted through the use of bone growth promoting substances, such as hydroxyapatite (HA). HA is a naturally occurring mineral found within bone composition, and its presence on the femoral component supports osseointegration of the stem [1, 2]. While primary stability of the femoral stem in cementless THA models depends on a * Correspondence: [email protected] 2 Concordia Joint Replacement Group, 310-1155 Concordia Avenue, Winnipeg, Manitoba R2K 2M9, Canada 3 Department of Surgery, University of Manitoba, Winnipeg, Manitoba, Canada Full list of author information is available at the end of the article
press fit between the bone and femoral component, longterm stability requires osseointegrat
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