ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

1. ABSTRACT
The femoral nail which prevents a complications problem
Y. Matsumoto 1 , T. Nishimura 1 , Y. Nakanishi 2 , H. Mizuta 2 ,
N. Murayama 2 , H. Higaki 3
Recently, the incidence of proximal femoral fracture in aging patients has been
increasing. The femoral nail used for treatment is mainly made of a titanium alloy.
However, the elastic modulus of titanium alloy is very high when compared with that of
bone. This causes healing inhibition due to stress-shielding and fracture at the distal end
of the stem. These complications concern many health care professionals. Moreover,
discussion of rotation of femoral head inhibited by the lag-screw has not been
adequate 4) . Redesign of the femoral nail is suggested to resolve these problems. In this
study, we performed FEM analysis on a proposed a new femoral nail design that
integrates three kinds of biocompatible polyetheretherketone (PEEK) plastics
mechanically and thermally. The stem uses a high elastic modulus PEEK at the
intersection of the lag-screw and stem, a low elastic modulus PEEK at the intersection
of the lag-screw and stem, and a low elastic modulus PEEK at the distal end of the stem.
This aspect of the design prevents stress from concentrating and decreases the
occurrence of a diaphyseal fracture at the distal end of the stem. In addition, the
Rectangle Double Lag-screw System uses a high elastic modulus PEEK at both ends,
and a low elastic modulus PEEK at the center. This design allows strain along the axis
of the screw, which allows strain to develop in the fracture site. This strain has been
shown to promote bone remodeling. Furthermore, its rectangular design inherently
inhibits its rotation. Thus indicating the validity of our design for resolving distal stem
fractures and inhibition of femoral rotation.
2. INTRODUCTION
Recently, cases of proximal femoral fractures have been increasing due to osteoporosis
caused by an aging population 6) . The orthopedic femoral nail is used in the treatment of
this fracture type. In general, titanium is used in these femoral implants because it is
biocompatible, strong enough to use at high load articulations in the body, and it is not
magnetic, which allows for MRI examination. However, some problems can occur
when a femoral nail made from titanium is used in the healing process.
The elastic modulus of titanium is very high when compared with that of bone and, in a
1
Student, Department of Engineering, Kumamoto University, Kurokami 2-39-1, Kumamoto City,
Kumamoto Prefecture, Japan
2
Professor, Graduate School of Science and Technology, University of Kumamoto, Kurokami 2-39-1,
Kumamoto City, Kumamoto Prefecture, Japan
3
Professor, Department of Engineering, KYUSHU SANGYO University, Kokadai 2-3-1, Higashi-ku,
Fukuoka City, Fukuoka Prefecture, Japan