Two-stage revision surgery for infected total knee replacement offers the highest rate of success for the elimination of infection. The use of articulating antibiotic-laden cement spacers during the first stage to eradicate infection also allows protection of the soft tissues against excessive scarring and stiffness. We have investigated the effect of cyclical loading of cement spacers on the elution of antibiotics. Femoral and tibial spacers containing vancomycin at a constant concentration and tobramycin of varying concentrations were studied in vitro. The specimens were immersed and loaded cyclically to 250 N, with a flexion excursion of 45°, for 35 000 cycles. The buffered solution was sampled at set intervals and the antibiotic concentration was established so that the elution could be calculated. Unloaded samples were used as a control group for statistical comparison.

The elution of tobramycin increased proportionately with its concentration in cement and was significantly higher at all sampling times from five minutes to 1680 minutes in loaded components compared with the control group (p = 0.021 and p = 0.003, respectively). A similar trend was observed with elution of vancomycin, but this failed to reach statistical significance at five, 1320 and 1560 minutes (p = 0.0508, p = 0.067 and p = 0.347, respectively). However, cyclically loaded and control components showed an increased elution of vancomycin with increasing tobramycin concentration in the specimens, despite all components having the same vancomycin concentration. The concentration of tobramycin influences both tobramycin and vancomycin elution from bone cement. Cyclical loading of the cement spacers enhanced the elution of vancomycin and tobramycin.

We describe the use of a dental tool for the removal of excess cement during unicompartmental knee arthroplasty (UKA).

Retained excess cement following UKA is a well recognised complication. It may result in pain, impingement, loose body symptoms, vascular problems and damage to the prosthesis or structures within the lateral compartment. Symptomatic patients require additional surgery to manage such complications. The removal of excess cement becomes technically difficult during cementation of the prosthesis because there is limited surgical exposure. Consequently, the incidence of retained excess cement associated with minimally invasive knee arthroplasty ranges from 8 to 21%.

The senior author uses a ‘flat plastic’ dental instrument that is ideally shaped for use in UKA. The tool has blunt ends aligned at 90 degrees to each other which are perfectly angled to allow the rapid removal of excess cement from the femoral component and tibial tray during prosthesis insertion. It can be manoeuvred easily to break off excess bits of cement and also to retrieve them by sweeping around the prostheses from back to side. It is also used to assess alignment of the tibial tray medially and posteriorly to feel for over or under hang.

The ‘flat plastic’ dental tool helps to avoid retained excess cement and its associated complications in UKA, and is applicable in other minimally invasive arthroplasty procedures.