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1/1/2008

Journal: Clinical Orthopaedics and Related Research

Citation: 465:71-79, December 2007.

Authors: Carolyn Anglin, PhD, PEng; Bassam A Masri, MD, FRCSC; Jérôme Tonetti,
MD; Antony J Hodgson, PhD, PEng; Nelson V Greidanus, MD, FRCSC

Femoral neck fracture is the most common short-term concern after hip
resurfacing arthroplasty. Currently, there is little basis to decide between
neutral and valgus placement.

We loaded 10 notched cadaveric femur pairs to
failure; one side was implanted at 0[degrees] relative to the femoral neck and
the other at 10[degrees] valgus. All 20 were dual-energy xray absorptiometry-scanned.
Failure load correlated with bone mineral density.

Valgus placement increased
the fracture load by an average of 28% over neutral for specimens with normal
bone mineral density but had no effect on fracture load in specimens with low
bone mineral density. For specimens with normal bone mineral density (typical of
patients undergoing resurfacing arthroplasty), neutral-valgus placement had a
greater effect than bone mineral density, explaining 54% of the fracture load
variance. Component placement greater than 10[degrees] valgus is likely
undesirable because this can lead to an increase in component size and a greater
likelihood of notching.

To reduce fracture risk, we recommend placing the
femoral component in valgus and selecting patients with higher bone mineral
density.