The effect of cement restrictors on the occlusion of the humeral canal: an in vitro comparative study of 2 devices.

An in vitro study investigated the efficacy of cement restrictor devices on cement containment and penetration within the humerus. Eight pairs of preserved humeri were prepared using advanced cementing technique followed by insertion of 1 of 2 cement restrictors. Low-viscosity cement was injected followed by sham humeral stem insertion. Each specimen was sectioned into transverse 10-mm slices. Slices were photographed and digitized to quantify the cement/stem and canal cross-sectional area. Cement penetration was determined from the ratio of cement area to canal area. A significant increase in cement penetration was observed among slices from distal to proximal for both restrictors (P = .02). There was no significant difference in cement penetration, leakage, or migration between restrictors. Five of the 8 specimens migrated, with means of 21.5 +/- 25.0 mm and 24.0 +/- 36.0 mm for the polyethylene and silicone restrictors. Leakage or migration resulted in a significant decrease in cement penetration with the polyethylene restrictors (P = .001). In the silicone restrictor group, migration resulted in decreased cement penetration (P = .04). When using advanced cementing techniques, intramedullary restrictors allow improved cement penetration; however, they do not ensure cement containment.