Does the French Paradox cementing technique improve or compromise femoral stem stability? An in vitro cadaver study.

Abstract

The French Paradox (FP) technique, characterised by line-to-line cementing, has recently been applied to polished tapered stems with favourable results despite the thin cement mantle created. However, it contravenes the minimum 2-mm cement mantle described in the standard (STD) cementing technique. This experimental study aimed to compare the FP and STD cementing techniques by comparing the cement mantle thickness, micromotion, and alignment of a polished tapered stem under clinically relevant loads. Stems were implanted into 4 pairs of human cadaveric hips. Femurs within each pair were randomly allocated to receive either the STD or FP technique. 5 linear variable displacement transducers (LVDTs) were used to measure the real-time motion of the stem relative to the femur. The specimens were mounted onto a joint motion simulator and cyclically loaded with axial compression (0-1,600 N) and internal torsion (0-15 Nm). No significant differences were found in permanent migration, initial and long-term inducible motion, or stem alignment between techniques. The FP technique resulted in a thinner cement mantle (∆1.0 ± 0.2 mm). The mean permanent migration was below 20 μm, and inducible motions were below 100 μm for both techniques. Both FP and STD cementing techniques resulted in well-fixed stems with low migration and inducible motion.