THERMAL ASPECTS OF THE USE OF POLYMETHYLMETHACRYLATE IN LARGE METAPHYSEAL DEFECTS IN BONE - A CLINICAL REVIEW AND LABORATORY STUDY

The potential necrotizing effects of the heat produced by the exotherm ic polymerization process has raised questions regarding the use of po lymethylmethacrylate (PMMA) in orthopedic surgery. An experimental mod el was used to: (1) analyze the amplitude and distribution of heat in bone taken from autopsy specimens when large metaphyseal defects (simu lating tumor excision) were filled with curing PMMA and (2) to observe any significant necrotizing temperatures. The experimental design inc luded two experimental groups of five distal femora into which either a small- or large-bore defect was made in the lateral epicondylar regi on. These defects were filled with either one or two packs of PMMA cem ent, and temperature probes were used to record temperature elevations at the cement core, the bone-cement interface, and the surrounding 1- , 2-, 3-, and 5-mm bone intervals. To simulate physiologic temperature and fluid environment, the experiment was conducted in a 37-degrees- normal saline bath. There is clinical evidence suggesting that the lar ge amounts of PMMA used in tumor reconstructive surgery (often two pac ks or more) may lead to thermal necrosis of remaining tumor cells in t he curetted cavity. This may explain, at least in part, the decrease i n recurrence of giant-cell bone tumor after curettage and PMMA cementa tion.