Experimental studies of the biological response to a new bone cement

As part of the assessment of the biological properties of a new bone cement (London Hospital cement) which contains poly(ethylmethacrylate) and n-butylmethacrylate, the monomer (n-butylmethacrylate) has been compared in toxicity studies with methylmethacrylate monomer, as used in conventional bone cement. N-butylmethacrylate monomer had an LD₅₀ of 1.0 to 1.2 ml kg^–1 and was therefore only slightly more toxic than methylmethacrylate monomer (LD₅₀ 1.2 ml kg^–1) when injected intraperitoneally into mice. It did not have any more significant cardiorespiratory depressive effect on intravenous infusion into rabbits, either in single or cumulative doses, when compared with methyl monomer (repeated infusions in 12 rabbits). Both monomers caused a transient bradycardia, tachypnoea, raised central venous pressure and arterial hypotension in low doses with rapid recovery, though the effects were sustained at higher cumulative doses of 60 mg kg^–1 and above. These results demonstrate that n-butylmethacrylate monomer does not differ significantly in toxicity from the monomer used in conventional cement and can therefore be used as a component in the new material.