Pressurization techniques are used to improve the cement/bone interface at hip arthroplasty. Ultra-high-molecular-weight polyethylene (UHMWPE) cement restrictors leave particulate debris at insertion; biodegradable restrictors may therefore be preferable. We compared the migration behavior of 2 such cement restrictors. A prospective randomized study with 16 patients per group using either a UHMWPE or a biodegradable restrictor was performed. Comparison of intraoperative measurements and postoperative radiographs determined restrictor migration. Mean migration was 3.0 vs 0.5 cm (biodegradable vs UHMWPE, Mann-Whitney U test, P < .002); median, 2.9 vs 0.4; SD, 1.8 vs 0.4; and range, 0.6 to 6.4 vs 0 to 1.2. Our study found that the biodegradable restrictor allowed significantly more migration than the UHMWPE restrictor. Although there are theoretical advantages in avoiding UHMWPE restrictors, the current biodegradable alternative is actually inferior and its use cannot be endorsed.