Three-dimensional measurement of cemented femoral stem stability: an in vitro cadaver study

• Published in: Clinical biomechanics (Bristol) Vol. 15; no. 4; pp. 248 - 255
• Main Authors: Speirs, A.D, Slomczykowski, M.A, Orr, T.E, Siebenrock, K, Nolte, L.-P
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-05-2000
• Subjects: Aged; Aged, 80 and over; Biomechanics; Cement; Cementation; Femoral components; Femur; Hip prostheses; Hip Prosthesis; Humans; Implants (surgical); In Vitro Techniques; Micromotion; Microsensors; Middle Aged; Motion; Prosthesis Design; Prosthesis Failure; Stability; Total hip replacement; Biomechanics; Total hip replacement; Micromotion; Femoral components; Cement
• ISSN: 0268-0033; 1879-1271
• DOI: 10.1016/S0268-0033(99)00079-0

Objective. To compare the in vitro stability of two cemented hip stem designs: Stem I was a collarless, double-tapered, highly polished implant; Stem II had a collar and matt finish.
Background. Stability of the femoral component of a hip implant is important for its long-term clinical success. Excessive migration or cyclic motion can increase the risk of early implant failure.
Methods. The stems were implanted in paired human cadaver femurs, and custom-designed micromotion sensors were used to measure three-dimensional motions of the stems at proximal, middle and distal locations during simulated in vivo loading cycles.
Results. This study found that despite ‘rigid’ fixation, cemented stems exhibit detectable motions under a limited number of cycles of simulated physiologic loads. At four times the donor body weight, Stem I showed a subsidence of 90 μm, compared to 25 μm of Stem II (
P<0.05). In contrast, the proximal end of Stem II exhibited greater cyclic motions in the medial–lateral direction (
P<0.05).
Conclusions. The different motion patterns could be due to the design differences, such as surface finish and geometry.
Relevance
Implant design is an important factor related to the behavior of the cement/bone interface and the overall success of the implant. This study compares in vitro micromotion of two cemented femoral prostheses with differing proximal designs.