CEMENT PENETRATION IN HIP RESURFACING ARTHROPLASTY:
FEMORAL COMPONENT DESIGN AND CEMENTATION TECHNIQUE

PE Beaulé*, W. Matar*, P. Poitras*, K. Smit* and O. May§

*University of Ottawa, Ottawa, ON, Canada

§Université de Lille 2, Lille, Nord, France

PURPOSE: Retrieval analyses of failed metal on metal hip resurfacings have shown
variability in cement penetration and mantle. Multiple factors have been shown
to influence cement penetration into the femoral head. The objective of this
study is to determine the effect of different femoral component designs used in
hip resurfacing on cement penetration.

MATERIAL AND METHODS: Femoral heads were retrieved following THR from hips with
a diagnosis of osteoarthritis. DXA scans were used to control for BMD. Six
femoral heads were resurfaced for each of the five different femoral component
designs: BHR®, ASR®, Conserve Plus®, Durom® and ReCap®. All femoral components
were implanted as per manufacturer recommendations. In addition, the BHR was
implanted using the Conserve Plus cementing technique “BHR(Conserve)” and
vice-versa for the Conserve Plus implant “Conserve(BHR)”. Femoral heads were
then sectioned. Cement mantle thickness, penetration depth and percentage of
penetration were analyzed on digital X-rays. Statistical analysis was completed
using a one-way ANOVA with Tukey correction (p<0.05).

RESULTS: Average cement penetration was statistically highest with the BHR
(65.6+/-15.2%) compared to Recap (26.1+/-5.2%), Conserve Plus (19.4+/-5.3%),
Durom (17.7+/-4.0%) and ASR (12.2+/-5.1%) (p<0.05). Cement penetration in the
BHR(Conserve) group remained statistically higher than all other implants
(36.7+/-6.6%) (p<0.05), whereas the Conserve(BHR) group did not show a
difference. The depth of cement penetration was greatest in the BHR group
(11.97+/-4.15mm) and least in the ASR group (1.42+/-0.64mm) (p<0.05). Mantle
thickness was greatest with the BHR(Conserve) group 2.92+/-0.72mm and thinnest
in the Conserve(BHR) group 0.49+/-0.22mm (p<0.05).

CONCLUSION: Cement penetration was greatest with the BHR’s low-viscosity
cementing technique. When tested with the Conserve Plus’ high viscosity
cementing technique, cement penetration was still greater than Conserve Plus,
Conserve(BHR), Recap and ASR groups. This result suggests that the implant
design itself and more specifically its clearance between prepared femoral head
and implant plays a critical role. There was great variance in the depth of
cement penetration from the 3-5mm needed to achieve proper three-dimensional
interlocking; only the Recap fell into this range. Surgeons who are offering hip
resurfacing in the treatment of osteoarthritis need to understand this since
excessive or insufficient penetration can lead to early failure.