Radiolucent lines on immediate postoperative cemented acetabular component radiographs between the PMMA bone cement mantle and bone are an indicator of an increased risk of early loosening. The cause of these lines has yet to be identified. Thermal and chemical necrosis, fluid interposition and cement shrinkage have all been suggested in the literature. The aim of the study reported here was to take an engineering approach – eliminating confounding variables present during surgery – to quantify the size of the interstice created by cement shrinkage when a 50 mm diameter flanged acetabular cup is implanted in a model acetabulum with a 52 mm hemispherical bore under controlled conditions using vacuum and non-vacuum mixed cement. Irrespective of the mixing method used, a significant interstice was created between the bone cement and the mock acetabulum. When the cement was mixed under vacuum the interstice created between the mock acetabulum and the cement mantle was 0.60 mm ± 0.09 mm; when the cement was mixed under non-vacuum conditions the interstice created was 0.39 mm ± 0.15 mm. Possible explanations for radiolucent lines are discussed.

PMMA 骨水泥罩和骨之间的术后即刻骨水泥髋臼假体 X 光片上的射线可透线是早期松动风险增加的指标。这些线条的原因尚未确定。热和化学坏死、流体介入和水泥收缩都已在文献中提出。此处报告的研究的目的是采用一种工程方法——消除手术过程中存在的混杂变量——量化当直径为 50 毫米的带凸缘的髋臼杯植入具有 52 毫米直径的模型髋臼时，由骨水泥收缩产生的间隙大小。使用真空和非真空混合水泥在受控条件下制造半球形孔。无论使用何种混合方法，在骨水泥和模拟髋臼之间产生了明显的间隙。当水泥在真空下混合时，模拟髋臼和水泥罩之间产生的间隙为 0.60 mm ± 0.09 mm；当水泥在非真空条件下混合时，产生的空隙为 0.39 毫米 ± 0.15 毫米。讨论了射线可透线的可能解释。