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In Vivo Performance of Third Generation Polyethylene in a Prospective Randomized Controlled Trial
e10 The Journal of Arthroplasty Vol. 25 No. 3 April 2010
Paper #10 In Vivo Performance of Third Generation Polyethylene in a Prospective Randomized Controlled Trial Kirk Kindsfater, MD, Martin W. Roche, MD, Thomas A. Gruen, MS Introduction: Third generation polyethylene offers oxidative resistance and the benefit of reduced wear; however, its adoption in knees remains limited. Little in vivo data supports in vitro wear and performance data. This study compared clinical and radiographic performance of moderately crosslinked polyethylene (MCP) to a third generation crosslinked, remelted polyethylene (CRP). Methods: This prospective, multicenter, randomized study accrued 924 knees in 767 patients between February 2005 and July 2007. The same highly polished CoCr tray and polyethylene locking mechanism was used in all cases and subjects were randomized to either the MCP (gamma irradiated in a vacuum foil package and sterilized to 4MRad) or CRP group (crosslinked to 5MRad, remelted and terminally stabilized with gas plasma). Sixty-four percent were females, 98% were diagnosed with OA, average age at surgery was 66 years, and 33 was the average BMI. Minimum 2-year (average 28.2 months; range, 18-49) clinical, radiographic, and safety data were evaluated. Results: Demographics (age at surgery, BMI, surgical time, follow-up) did not differ between the 2 groups, nor were differences observed in postoperative comparisons using American Knee Society (total and sub-scores), WOMAC, and radiographic outcomes (osteolysis, radiolucencies, stress shielding). The MCP group had 3 revisions compared to 0 for the CRP group, using removal of any component for any reason with the exception of infection as the revision definition. The 3.1 year survivorship estimates were 98.1% for MCP compared to 100% for CRP providing a log-rank P value of .08. Reasons for MCP revision were polyethylene wear, restricted range of motion, and hematoma. Discussion: The zero incidence of polyethylene failure with regard to early wear or mechanical failure in the CRP group is encouraging at short-term follow-up. However, longer-term follow-up is warranted to determine whether crosslinked, remelted polyethylene yields a definitive and enduring advantage compared to moderately crosslinked polyethylene.
Paper #10 In Vivo Performance of Third Generation Polyethylene in a Prospective Randomized Controlled Trial Kirk Kindsfater, MD, Martin W. Roche, MD, Thomas A. Gruen, MS Introduction: Third generation polyethylene offers oxidative resistance and the benefit of reduced wear; however, its adoption in knees remains limited. Little in vivo data supports in vitro wear and performance data. This study compared clinical and radiographic performance of moderately crosslinked polyethylene (MCP) to a third generation crosslinked, remelted polyethylene (CRP). Methods: This prospective, multicenter, randomized study accrued 924 knees in 767 patients between February 2005 and July 2007. The same highly polished CoCr tray and polyethylene locking mechanism was used in all cases and subjects were randomized to either the MCP (gamma irradiated in a vacuum foil package and sterilized to 4MRad) or CRP group (crosslinked to 5MRad, remelted and terminally stabilized with gas plasma). Sixty-four percent were females, 98% were diagnosed with OA, average age at surgery was 66 years, and 33 was the average BMI. Minimum 2-year (average 28.2 months; range, 18-49) clinical, radiographic, and safety data were evaluated. Results: Demographics (age at surgery, BMI, surgical time, follow-up) did not differ between the 2 groups, nor were differences observed in postoperative comparisons using American Knee Society (total and sub-scores), WOMAC, and radiographic outcomes (osteolysis, radiolucencies, stress shielding). The MCP group had 3 revisions compared to 0 for the CRP group, using removal of any component for any reason with the exception of infection as the revision definition. The 3.1 year survivorship estimates were 98.1% for MCP compared to 100% for CRP providing a log-rank P value of .08. Reasons for MCP revision were polyethylene wear, restricted range of motion, and hematoma. Discussion: The zero incidence of polyethylene failure with regard to early wear or mechanical failure in the CRP group is encouraging at short-term follow-up. However, longer-term follow-up is warranted to determine whether crosslinked, remelted polyethylene yields a definitive and enduring advantage compared to moderately crosslinked polyethylene.