Comparison of a static with a mobile spacer in total knee infection

Patients with infections of a total knee arthroplasty were stratified by medical status. Twenty-six knees in 26 patients treated with a static antibiotic-impregnated polymethylmethacrylate block spacer before 1995 were compared with 22 knees in 22 patients treated after 1995 with a mobile articulating spacer. Both groups were treated with 6 weeks of parenteral antibiotics and had reimplantation within 6 to 12 weeks after placement of the spacer. Followup for the patients who had block spacers was an average 7.5 years (range, 2.8-12.7 years), and followup for the patients with a mobile spacer was an average of 3.8 years (range, 2.6-6.4 years). Results showed that the patients with the mobile spacers had significantly better average range of motion at followup compared with patients who had block spacers (107.8degrees compared with 93.7degrees). The reinfection rate was the same between the two groups at 36 months, 7.6% (two of 26) for the patients with block spacers and 9% (two of 22) for the patients with mobile spacers. Extended followup available for the patients who had block spacers revealed a late reinfection rate of 23% (six of 26) with a new organism. There was no difference in the reinfection rate, with new or old organisms, in healthy hosts compared with patients with as many as two medical problems.