In situ tele-thermographic measurements during PMMA spacer augmentation in temporary arthrodesis after periprosthetic knee joint infection.

Poly-Methylmethacrylate (PMMA) is widely-used in orthopaedic surgery in revision arthroplasty or as a spacer in temporary arthrodesis of periprostehtic knee joint infection during a two stage procedure. The intra-operative temperature behaviour, however, has not yet been quantified. It is known that high temperature induce thermally necrosis of surrounding bone tissue during polymerisation process. The aim was to evaluate the PMMA surface temperature during polymerisation phase in situ. We hypothesized, that temperature measured in vivo could become critical in terms of the induction of thermal bone necrosis during the polymerisation phase of PMMA. The PMMA surface was measured tele-thermographically in situ during knee arthroplasty revision surgery. Infrared pictures were analyzed for temperature peaks and changes. Measurements yielded maximum PMMA-surface-temperatures ranging from 101 to 110 degrees and a two-minute-plateau of > 100°. Hot PMMA during the polymerisation phase could potentially induce tissue (bone) necrosis. Therefore temperature of PMMA of more than 70 degrees should be avoided. Cooling of the PMMA is highly recommendable.