Cement/implant interface gaps explain the poor results of CMW3 for femoral stem fixation: a cadaver study of migration fatigue and mantle morphology.

摘要

>Background: Norwegian Arthroplasty Register (NAR) reported that CMW3 cement performed poorly for femoral stem fixation.>Methods: Collared, satin-finished stems (Ra = 0.35μm) were implanted into cadaver femora using CMW3 and Simplex as control. Cement mantle function was quantified by stem migration after 300,000 cycles of “stair-climbing”. Cement cracks and interface gaps were quantified in transverse sections.>Results: The variances of the CMW3 migrations were substantially and significantly higher (p < 0.0001): subsidence (CMW3 = -32(SD42)μm, Simplex = -7(SD9)μm, p = 0.16); retroversion (CMW3 = 0.60(SD0.25)°, Simplex = 0.37(SD0.04)°, p = 0.08). Crack length-densities were similar (CMW3 = 50(SD15)μm/mm², Simplex = 45(SD12)μm/mm², p = 0.30). CMW3 had significantly more non-apposed stem/cement interface: 52(SD17)% versus 33(SD8)% (p = 0.040).Migrations were predicted by fraction of non-apposed stem/cement interface (retroversion: R² = 0.80, p < 0.0001, subsidence: R² = 0.46, p = 0.016) but not by cement cracks or non-apposed cement/bone interface (R² < 0.05, p = 0.49—0.77)>Interpretation: This study showed that increased stem/cement non-apposition resulted in increased stem migration. Early migration is known to correlate with revision risk. Therefore, the higher stem-revision risk for CMW3 cement reported by the NAR may have been due to inferior and variable stem/cement apposition.