Article

This study addresses the risk of femoral neck fracture associated
with resurfacing hip prostheses. A novel cemented Proximal Epiphyseal Replacement
(PER) featuring a short curved stem was investigated. METHODS: Seven pairs of
femurs were in vitro tested.
One femur of each pair was randomly assigned for PER
implantation. The contralateral femur was tested intact.
All femurs were loaded
to failure in a validated, physiological configuration.
High-speed videos
(10,000-12,000 frames/s) were acquired to identify the location of fracture
initiation. For comparison, data were included from Birmingham Hip Resurfacing
previously tested in an identical fashion (N=3). FINDINGS: Relative to the
contralateral intact femurs, the failure load of the PER and Birmingham implants
was 15.4% higher and 10.0% lower, respectively. In six of the seven PER implants,
fracture initiation (neck or inter-trochanteric) was similar to the contralateral
intact femurs, suggesting comparable stress distribution. Conversely, fracture
initiation in the Birmingham implants occurred at the lateral prosthesis rim,
which differed substantially from the intact femurs. No correlation existed
between bone quality and strengthening/weakening effect of the PER (failure load
of implant as a percentage of intact: R^2=0.067). Conversely, Birmingham
implantation weakened the femurs with lower density (R^2=0.92). Therefore, unlike
most resurfacing prostheses,
the PER seems suitable also for osteoporotic
subjects. INTERPRETATION: This study seems to confirm that resurfacing with a
Birmingham Hip tends to reduce the strength of the proximal femur. The opposite
seemed to happen with the PER, which slightly reduced the risk of neck fracture,
also in low-quality bones.
CI - Copyright (c) 2011 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS