BACKGROUND: The use of larger femoral head sizes in total hip arthroplasty has been shown to reduce the rate of dislocation and to increase the range of motion; however, such components have been associated with unacceptably high polyethylene wear rates. Studies have shown dramatic differences in wear rates between nominally cross-linked polyethylene (i.e., polyethylene that is cross-linked during radiation sterilization) and elevated cross-linked polyethylene (i.e., polyethylene that is cross-linked to a higher degree than that obtained by radiation sterilization alone). The aim of this study was to test the effect of increased cross-linking and of increased head size on polyethylene wear rates. METHODS: Four groups of acetabular liners obtained from a single manufacturer, including 28-mm-diameter nominally cross-linked, 32-mm-diameter nominally cross-linked, 28-mm-diameter elevated cross-linked, and 32-mm-diameter elevated cross-linked polyethylene liners, were tested. Three implants from each group were tested in a twelve-station hip wear simulator with use of 90% bovine serum as a lubricant. The liners were articulated with the appropriately sized cobalt-chromium femoral head. Additional liners from each design were subjected only to the same load without motion to serve as load-soak controls to account for any weight gain due to fluid absorption. Gravimetric analysis was performed every 500,000 cycles for a total of five million cycles. RESULTS: Nominally cross-linked liners demonstrated mean wear rates of 14.97 and 16.92 mg per million cycles for the 28-mm and 32-mm head sizes, respectively. Both of the elevated cross-linked liners had significantly lower wear rates than the nominally cross-linked liners, with a mean of 1.51 and 2.57 mg per million cycles for the 28-mm and 32-mm head sizes, respectively (p < 0.001). CONCLUSION: The dramatic reduction in wear rates with polyethylene cross-linking, even with the larger head size, may increase the potential for use of 32-mm head components in total hip arthroplasty.
BACKGROUND: The use of larger femoral head sizes in total hip arthroplasty has been shown to reduce the rate of dislocation and to increase the range of motion; however, such components have been associated with unacceptably high polyethylene wear rates. Studies have shown dramatic differences in wear rates between nominally cross-linked polyethylene (i.e., polyethylene that is cross-linked during radiation sterilization) and elevated cross-linked polyethylene (i.e., polyethylene that is cross-linked to a higher degree than that obtained by radiation sterilization alone). The aim of this study was to test the effect of increased cross-linking and of increased head size on polyethylene wear rates. METHODS: Four groups of acetabular liners obtained from a single manufacturer, including 28-mm-diameter nominally cross-linked, 32-mm-diameter nominally cross-linked, 28-mm-diameter elevated cross-linked, and 32-mm-diameter elevated cross-linked polyethylene liners, were tested. Three implants from each group were tested in a twelve-station hip wear simulator with use of 90% bovine serum as a lubricant. The liners were articulated with the appropriately sized cobalt-chromium femoral head. Additional liners from each design were subjected only to the same load without motion to serve as load-soak controls to account for any weight gain due to fluid absorption. Gravimetric analysis was performed every 500,000 cycles for a total of five million cycles. RESULTS: Nominally cross-linked liners demonstrated mean wear rates of 14.97 and 16.92 mg per million cycles for the 28-mm and 32-mm head sizes, respectively. Both of the elevated cross-linked liners had significantly lower wear rates than the nominally cross-linked liners, with a mean of 1.51 and 2.57 mg per million cycles for the 28-mm and 32-mm head sizes, respectively (p < 0.001). CONCLUSION: The dramatic reduction in wear rates with polyethylene cross-linking, even with the larger head size, may increase the potential for use of 32-mm head components in total hip arthroplasty.
Authors: Nathan A Mall; Ryan M Nunley; Jin Jun Zhu; William J Maloney; Robert L Barrack; John C Clohisy Journal: Clin Orthop Relat Res Date: 2011-02 Impact factor: 4.176
Authors: Adolph V Lombardi; Michael D Skeels; Keith R Berend; Joanne B Adams; Orlando J Franchi Journal: Clin Orthop Relat Res Date: 2011-06 Impact factor: 4.176
Authors: Siôn Glyn-Jones; Geraint E R Thomas; Patrick Garfjeld-Roberts; Roger Gundle; Adrian Taylor; Peter McLardy-Smith; David W Murray Journal: Clin Orthop Relat Res Date: 2015-02 Impact factor: 4.176
Authors: Paul F Lachiewicz; Daniel S Heckman; Elizabeth S Soileau; Jimmi Mangla; John M Martell Journal: Clin Orthop Relat Res Date: 2009-08-19 Impact factor: 4.176