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

Abstract

Background:

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.

Aim:

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.

Methods:

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).

Results:

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.

Conclusions:

Both FP and STD cementing techniques resulted in well-fixed stems with low migration and inducible motion.