Govind, G;
Henckel, J;
Taylor, S;
Mcmillan, R;
Hart, A;
Skinner, J;
(2014)
There Is A Relationship Between The In Vivo Force Acting On A Metal-On-Metal Hip Implant And The Point Within The Acetabular Cup With The Largest Wear Scar: A Novel Retrieval Study Using 3D CT, Mathematical Modelling and In Vivo Data.
Presented at: 15th EFORT Congress 2014, London, UK.
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Abstract
The human hip joint is important, both in health and disease. Its range of motion is remarkable, and thus the loads transferred through the hip can be highly variable, depending on the patient’s activity. Investigation of retrieved hip implants can give us insight into multidirectional forces and its role in implant failure. The current theory of “edge loading” has shown a quantitative relationship between the location of the primary wear scar (WS1) at the edge and the wear volume. A regression analysis of hip force data (www.ORTHOLOAD.com) was used to find lever arms LLA and GLA for these subjects, assumed equal to those for our retrievals. See below for source of other data. This allowed the 2D Free body force system to be solved for the hip and abductor forces. Using the SPSS Statistics package, the Pearson’s correlation was calculated between: 1)The resultant hip joint reaction force and the wear angle 2)The resultant abductor force and the wear angle. These were 0.634 (p=0.036) and 0.611 (p=0.046) respectively. A negative wear angle represented a WS1 posterior to the COF and a positive wear angle represented a WS1 anterior to the COF, hence the more positive the wear angle, the more anterior it was. An increase in in vivo abductor and hip joint reaction force: does not lead to edge wear results in a more positive wear angle results in a WS1 that is more anterior in the coronal plane This pilot study suggests that: anterior wear may be an important factor in enabling clinicians to make thoughtful predictions about implant failure in patients
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