The Journal of Bone and Joint Surgery, Vol 65, Issue 3 366-370, Copyright © 1983 by Journal of Bone and Joint Surgery, Inc
Frictional torque in surface and conventional hip replacement
SM Ma, JM Kabo and HC Amstutz
The frictional torque of the Trapezoidal-28 total hip replacement and the
Tharies SR-3 and SR-5 surface replacements were measured in the University
of California at Los Angeles hip-joint simulator in calf serum. Loads of as
much as 890 newtons were applied while the femoral component oscillated
through a 60-degree arc at forty cycles per minute. Frictional torque, as
measured by a ring transducer at a fixed distance from the center of
rotation, was seen to diminish as the thickness of the polyethylene
increased and was found to be relatively proportional to the diameter of
the femoral component. The torques measured in this study were found to be
twenty to 100 times smaller than the static torques to failure for
acetabular fixation that have been reported in the literature. Finally, no
permanent deformation of the thin acetabular shells attributable to the
cementing process was apparent when the recommended technique of surgical
insertion was utilized. Clinical Relevance: Surface replacement components
have been shown to generate greater frictional torques at the acetabular
bone-cement interface than do smaller-diameter conventional hip
replacements. This indicates that the local mechanical-loading conditions
of the hip joint are not the same for both types of replacements, and this
should be considered when selecting the type of arthroplasty for an
individual patient.
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