Customized Knee Articulating Cement Spacer with Stem Extension for Treatment of Chronic Periprosthetic Joint...

Choice of articulating spacer in selected Methicillin-resistant Staphylococcus aureus (MRSA) patients with instability that do not qualify for a second-stage revision (i.e., due to significant co-morbidities, multiple persistent infections, open wound ulcers) is challenging. To avoid a recurrent biofilm when using a cruciate-retaining (Cr/Cb) femoral implant, we have utilized a polymer femoral implant and constraint all-polyethylene (all-poly) tibia with stem extensions as a permanent spacer.

After removal of prior implants and final debridement, appropriate-sized trial femur and proper thickness all-poly tibia are selected. Two chest tubes are loaded with cement with a delivery gun to make the extension rods. A Steinmann pin is inserted into the stem of the tibial insert. The components are inserted and the knee is reduced, then flexion and extension gaps are assessed. Small adjustments can be made to fill the gaps with extra cement. If there is collateral insufficiency, a constrained polyethylene (poly) can be used with the extension rod. An appropriate antibiotic is used based on the final culture, sensitivity, and availability in powder form.

This technique has been performed on 32 MRSA prosthetic joint infection (PJI) cases, followed for a minimum of nine months (nine months to three years). The mean final range of motion was 70 ± 15 degrees (30-110 degrees). Final radiographs do not show any sign of subsidence, loosening, or failure of the spacer. Rate of eradication of infection was 97% in the remaining 31 cases. One patient required amputation due to lack of wound coverage.

Custom-made articulating spacer using all-poly tibia and a trial femur with stem extension can provide reproducible outcomes in treating PJI while maintaining mobility.