CREEP CHARACTERISTICS OF HAND-MIXED AND VACUUM-MIXED ACRYLIC BONE-CEMENT AT ELEVATED STRESS LEVELS

Compressive creep testing of cylindrical specimens machined from two c ommercial self-polymerizing acrylic bone cements demonstrated measurab le creep strains with higher creep strains for the hand-mixed cement s pecimens compared to vacuum-mixed cement ones. The average creep strai ns of hand-mixed cement, after 6 h of constant load, ranged from 0.11% at 10.5 MPa to 14.0% at 50 MPa of applied stress. Vacuum mixing reduc ed the average creep strain to 6.7% after 6 h of applied stress at 50 MPa. There were no significant differences in the creep response betwe en the two types of acrylic cements. The difference in creep resistanc e of the two cements was reduced after vacuum mixing (P = .013), which also significantly seduced the cement's internal porosity. (C) 1995 J ohn Wiley & Sons, Inc.