Summary.Clinical studies have shown that second-generation femoral cementing techniques at total hip replacement result in a superior fixation of the femoral stem. In an effort to determine what benefits further developments in cementing techniques would provide, we compared the morphology of the cement mantles produced by traditional finger-packing and gun-insertion techniques. The porosity of the cement mantles was quantified using computerised image analysis. The finger-packing technique caused large air inclusions that resulted in large pores in the substance of the cement mantle, whereas the cement-gun technique did not result in any individual pore with an equivalent diameter greater than 3 mm. The mean porosity of cement mantles prepared using the finger-insertion technique was 8.3%, whereas the mean porosity in gun-prepared mantles was 1.7%. The use of a cement gun significantly reduced the porosity of femoral cement mantles (P=0.02). Reduction of defects in the substance of the cement mantle may account for the increased survival of femoral prostheses inserted when second-generation techniques were used. Further reduction of the porosity of the cement mantle could not be expected to produce as dramatic a clinical improvement in prosthesis fixation.
Rsum.Les tudes clinique ont montr que la pratique des techniques de cimentation fmorale de deuxime gnration au niveau du remplacement total de la hanche aboutissent une meilleure fixation de la tige fmorale. Afin de dterminer quels seraient les avantages prsntes par de nouveaux progrs dans le domaine de ces techniques de cimentation, nous avon compare la morphologie des enveloppes en ciment ralise par bourrage traditionnel au doigt et par insertion au pistolet. La porosit des enveloppes en ciment a t quantife par lanalyse dimage informatises. La technique de bourrage au doigt provoque des ponches dair plus importantes causant lapparition de larges pores dans la substance de lenveloppe en ciment, la technique dinsertion au pistolet ne provoque aucune formation de pores individuals quivalents dun diametre suprieur a 3 mm. La porosit moyenne des enveloppes en ciment insres au doigt atteint 8.3%, celle des enveloppes insres au pistolet slevant a 1.7%. Lemploi dun pistolet ciment a rduit de manire considrable la porosit des enveloppes fmorales en ciment (P=0.02). Il est probable que ce phnomne explique laccroissement de la survie des prothses femorales insres laide des techniques de deuxieme gnration. On ne sattend pas a ce quun accroissement supplmentaire de la rduction de la porosit de lenveloppe en ciment aboutisse une amlioration clinique aussi radicale au niveau de la fixation des prothses.