Mechanical performance of proximal human femur after poly-ether-ether-ketone femoral prosthesis implantation

Zhenglian ZHANG; Junying SUN; Kang SUN

ABSTRACT

BACKGROUND:

Greatly higher elastic modulus of traditional metal prosthesis than bone elastic modulus is mechanical factor for aseptic loosening of artificial joint, resulting in stress shielding, bone resorption and bone atrophy.

OBJECTIVE:

To measure femoral stress after prosthetic replacement made of carbon fiber reinforced poly-ether-ether-ketone (CF/PEEK), and compare with domestic AML prosthesis, so as to explore the application prospect of compound material in total hip femoral head prosthesis. DESIGN, TIME AND

SETTING:

Comparative analysis was performed at Orthopedics Laboratory, First Hospital of Soochow University and Institute of Biomechanical Engineering of Shanghai University from September 2002 to March 2004.MATERIALS CF/PEEK prosthesis was designed by the authors, composed of long CF/PEEK compound material as inner layer, 100 Gpa and short CF/PEEK compound material as outer layer, 20 Gpa; the layer intensity at stress center was strengthened, and the appearance and size of the CF/PEEK prosthesis simulated domestic AML cobalt alloy prosthesis (Beijing Huajiehao Company). Five pairs (10 femurs) of femurs were from fresh adult cadavers.

METHODS:

Five pairs of human cadaveric femora were divided equally into left and right groups one group received a cobalt-chrome molybdenum alloy (CoCrMo) implant and the other received CF/PEEK implant. Strain-gauge rosettes were attached to external surface of each implant and proximal femora. The loading condition simulated single-limb stance. MAIN OUTCOME

MEASURES:

strains distribution on the normal femur and femoral surface after replacement with two kinds of prostheses; shearing strain at femur-prosthesis interface of two groups.

RESULTS:

Following prosthesis implantation, the strains exhibited a progressive proximal-to-distal increase, which was similar to that in the intact femur, and the strain was maximum near the distal prosthesis. The strains on the medial and lateral surface of the femur were reduced after implantation of both types of implants. The pattern and magnitude of the strains, however, were closer to those in the intact femur after insertion of CF/PEEK prosthesis than in the CoCrMo one.

CONCLUSION:

Mechanical performance of CF/PEEK compound prosthesis is similar to bone tissue, and can provide similar strain under loading condition. Therefore, it can provide immediate postoperative stability and proximal loading transfer.