The effect of under-reaming on the cup/bone interface of a press fit hip replacement.
This paper explores the effect of under-reaming on micromotion at the cup/bone interface of a press-fit acetabular cup. A cadaver experiment was performed on 11 acetabuli implanted with a cementless acetabular cup. The loading profile simulated hip impingement at the extremes of motion and subluxation relocation of the hip joint. Micromotion of each cup was measured in a custom made jig with linear variable differential transducers. A CAT scan and DEXA scan of the acetabulum and femoral head respectively were used to construct a three-dimensional patient specific finite element model of the hemi-pelvis. The model predicted cup micromotion under loading conditions and stresses in the acetabulum as a result of cup insertion. Micromotion was then calculated as a function of variable bone density and variable degree of underreaming. Simulated cup insertion with under-reaming of 2 mm or more approached or exceeded the yield strength of bone in acetabula with reduced bone mass density.
Zivkovic
I
I
Biomechanics Research Laboratory, University of Illinois at Chicago, 842 West Taylor Street, Room 1039, Chicago, IL 60607-7039, USA.
Gonzalez
M
M
Amirouche
F
F
D000077:Acetabulum / Q000502:physiology* / Q000601:surgery*; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D003198:Computer Simulation; D005270:Femur Head / Q000502:physiology* / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008954:Models, Biological; D009038:Motion; D013314:Stress, Mechanical