Review Question - QID 4623

Elution of an antibiotic is increased with increased porosity of a cement spacer. This porosity increase can be obtained with hand mixing and avoiding the use of a vacuum-type mixing device.

Joseph et al. reviews antibiotic-impregnated cement in hip arthroplasty. They note that use of this cement in one- or two-stage revisions has lowered reinfection rates, with the spacers acting to reduce dead space while stabilizing the joint.

Cui et al. reviews antibiotic impregnated cement for TKA and THA. They report that use of greater than 2 grams of antibiotic per 40 gram unit of cement weakens the cement and that use of two antibiotics in conjunction may potentially increase elution.

The reference by Stevens et al compared Simplex and Palacos bone cement in regards to elution in a TKA mold model. They found that initial as well as weekly (9 weeks total) elution rates were greater in the Palacos spacers than the Simplex models. They recommend use of the Palacos cement in TKA model to target antimicrobial delivery while limiting the potential for systemic antibiotic-related toxicity.

Illustrations A and B show an antibiotic spacer in a two-stage revision TKA. Illustration C shows a PROSTALAC in a two-stage revision THA.

Incorrect Answers:
Answer 1: Increasing the porosity acts to weaken the biomechanic characteristics of the cement.
Answer 3: Increasing the porosity acts to decrease the cement density.
Answer 4: Increasing the porosity does not improve cement-prosthesis bonding.
Answer 5: Increasing the porosity has not been shown to alter reinfection rate.