Effect of locking mechanism on fluid and particle flow through modular acetabular components.
Six modular acetabular components were evaluated to determine whether screw holes in the metal shell offer a route for fluid and debris into the acetabular bone stock. A 56-mm acetabular shell for each trial was mounted to a sealed chamber and loaded at a 25 degrees angle under axial loads of 270-2,700 N and +/- 2.5-N-m torsional load. Polystyrene microspheres (average diameter, 0.5 microm) were placed in double-deionized water at 300 mmH2O pressure in a sealed chamber above the component. The only channel between the fluid above and the collecting chamber below was through the cup-liner interface and 1 screw hole. Fluid and debris in the collecting chamber were harvested after 1,000,000 cycles. The collected sample was filtered through a 0.2-microm-pore filter and analyzed under electron microscopy for evidence of microspheres. Water and polystyrene microspheres were isolated in the collecting chamber for all trials except the Reflection cup (Smith & Nephew Orthopaedics, Memphis, TN) with a screw hole cover and the Micro-Seal cup (Whiteside Biomechanics, St. Louis, MO) with a peripheral seal. A screw placed in the screw hole of the Reflection cup failed to seal the interface. The peripheral seal around the rim of the Micro-Seal polyethylene prevented fluid and particle flow between the metal shell and polyethylene liner.
Khalily
C
C
Biomechanical Research Laboratory, Missouri Bone and Joint Center, Barnes-Jewish West County Hospital, St. Louis 63141, USA.
Tanner
M G
MG
Williams
V G
VG
Whiteside
L A
LA
D000077:Acetabulum; D001863:Bone Screws; D006801:Humans; D007595:Joint Prosthesis; D008422:Materials Testing; D008863:Microspheres; D010014:Osteolysis; D011095:Polyethylenes; D011474:Prosthesis Design; D011475:Prosthesis Failure
D011095:Polyethylenes