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The effect of implant malalignment on joint loading in total elbow arthroplasty: an in vitro study
James R Brownhill1, J W Pollock, Louis M Ferreira
1Hand and Upper Limb Bioengineering Laboratory, St Joseph's Health Care--London, London, ON, Canada.
Hypothesis:
Aseptic loosening is one of the leading causes of failure in total elbow arthroplasty. Incorrect implant positioning and alignment in other joints such as the knee have been found to lead to excessive loading and wear. Although similar alignment difficulties exist in the elbow, the effect of implant malalignment on wear-inducing loads is not yet known. This in vitro study determined the effect of anterior malpositioning and varus-valgus and internal-external malrotations on humeral stem loading in total elbow arthroplasty.
Methods And Materials:
Computer-navigated linked elbow arthroplasty was conducted in 8 cadaveric elbows. A modular, instrumented humeral component was used to measure loading during simulated elbow motion while the position of the ulna relative to the humerus was recorded.
Results:
Loading increased for all malaligned implant positions tested (P < .05). During simulation of implant malpositioning, combinations of internal-external and varus-valgus malrotations that tended to preserve the line of action of the elbow flexors had lower loads than combinations that did not.
Discussion:
This in vitro study showed that loading does increase after humeral component malalignment; however, further studies are required to determine the long-term effects on polyethylene wear and component loosening.