Is the French Paradox cementing philosophy superior to the standard cementing? A randomized controlled radiostereometric trial and comparative analysis

Abstract

Aims: Highly polished stems with force-closed design have shown satisfactory clinical results despite being related to relatively high early migration. It has been suggested that the minimal thickness of cement mantles surrounding the femoral stem should be 2 mm to 4 mm to avoid aseptic loosening. The line-to-line cementing technique of the femoral stem, designed to achieve stem press-fit, challenges this opinion. We compared the migration of a highly polished stem with force-closed design by standard and line-to-line cementing to investigate whether differences in early migration of the stems occur in a clinical study.

Methods: In this single-blind, randomized controlled, clinical radiostereometric analysis (RSA) study, the migration pattern of the cemented Corail hip stem was compared between line-to-line and standard cementing in 48 arthroplasties. The primary outcome measure was femoral stem migration in terms of rotation and translation around and along with the X-, Y-, and Z- axes measured using model-based RSA at three, 12, and 24 months. A linear mixed-effects model was used for statistical analysis.

Results: Results from mixed model analyses revealed a lower mean retroversion for line-to-line (0.72° (95% confidence interval (CI) 0.38° to 1.07°; p < 0.001), but no significant differences in subsidence between the techniques (-0.15 mm (95% CI -0.53 to 0.227; p = 0.429) at 24 months. Radiolucent lines measuring < 2 mm wide were found in three and five arthroplasties cemented by the standard and line-to-line method, respectively.

Conclusion: The cemented Corail stem with a force-closed design seems to settle earlier and better with the line-to-line cementing method, although for subsidence the difference was not significant. However, the lower rate of migration into retroversion may reduce the wear and cement deformation, contributing to good long-term fixation and implant survival. Cite this article: Bone Joint J 2022;104-B(1):19-26.

Keywords: Cementing technique; Clinical Trials; Corail stem; Force-closed stem design; French paradox; Hip replacement; Migration pattern; RSA; Radiolucent lines; THA; Taper-slip stem design; arthroplasties; aseptic loosening; cementing techniques; femoral stem; hip stems; model-based RSA; radiostereometric analysis (RSA).

Fig. 1

CONSORT flowchart. CAD, computer-aided design; CN, condition number; RSA, radiostereometric analysis.

Fig. 2

Orientation of the migration coordinate system with the Corail stem (DePuy Synthes, USA).

Fig. 3

Mean retroversion (°) with standard and line-to-line cementing of the Corail stem compared with the precision of rotation around the y-axis. Line-to-line retroversion rate 12 to 24 months: 0.187 (95% confidence interval (CI) -0.031 to 0.404); standard retroversion rate 12 to 24 months: 0.369 (95% CI 0.022° to 0.717).

Fig. 4

Mean subsidence (mm) with standard and line-to-line cementing of the Corail stem compared with the precision of translation along the y-axis. Line-to-line subsidence rate 12 to 24 months: -0.143 (95% confidence interval (CI) -0.207 to 0.078); standard subsidence rate 12 to 24 months: -0.287 (95% CI -0.475 to -0.099).