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Updated: Aug 9, 2026
Potentiodynamic Corrosion Testing
Published on: September 4, 2016
Lessons learned from loosening of the McKee-Farrar metal-on-metal total hip replacement
C A Zahiri1, T P Schmalzried, E Ebramzadeh
1Division of Orthopaedic Surgery, Harbor-UCLA Medical Center, Torrance, California, USA.
Abstract:
Clinical and radiographic data for 15 McKee-Farrar hip replacements that had failed because of aseptic loosening (4 stem loosening, 9 cup loosening, and 2 loosening of both components) between 0.6 and 21 years (average, 8.3 years) were compared with 15 hips in which the McKee-Farrar total hip replacement has survived between 21 and 26 years. Hips that loosened were biomechanically disadvantaged compared with those that demonstrated long-term survival. Radiographic evaluation demonstrated that in hips that were revised for aseptic femoral loosening, the offset was decreased by a mean of 1.4, whereas it was increased by a mean of 4.9 mm in the surviving hips (P = .04). Further, in hips revised for aseptic loosening, the center of rotation was medialized by a mean of only 1.4 mm, whereas the center of rotation was medialized by a mean of 6.4 mm in the surviving hips (P = .1). Unfavorable biomechanics results in increased joint reaction forces that could contribute to loosening of these prostheses. Five of 6 McKee-Farrar stems revised for aseptic loosening compared with 7 of 15 surviving stems were in varus (P = .1) and, as a result, had cement mantle defects in zones III and VII. Thus, in the McKee-Farrar, similar to what has been seen in hips with metal-on-plastic bearings, curved stems are associated with varus positioning, cement mantle defects, and loosening. Wear of the metal-on-metal articulation does not appear to be the cause of failure in these cases. Wear could not be detected radiographically. At revision surgery, there was no indication of excessive bearing wear or gross metal staining of periprosthetic tissues. Microscopic analysis of tissue sections demonstrated both metal and polymethylmethacrylate particles of variable size and shape. The variability of the particles suggests that they are likely the result of loosening and that they were not generated by bearing surface wear that could cause loosening. Although it is hoped that improvements in the wear resistance of the bearing will increase survivorship, this experience and analysis of the McKee-Farrar total hip replacement illustrates the importance of the implant design, biomechanics of the reconstruction, and role of surgical implantation technique.
Insights
McKee-Farrar hip replacements that failed due to aseptic loosening showed biomechanical disadvantages compared to surviving implants. Poor stem positioning and cement mantle defects were linked to loosening, not bearing wear.
Area of Science:
- Orthopedic surgery
- Biomedical engineering
- Implant failure analysis
Background:
- Aseptic loosening is a common cause of total hip replacement failure.
- The McKee-Farrar hip replacement is a specific implant design with a history of use.
- Understanding factors contributing to implant failure is crucial for improving patient outcomes.
Purpose of the Study:
- To compare clinical and radiographic data of failed McKee-Farrar hip replacements with those that survived long-term.
- To identify biomechanical and surgical factors associated with aseptic loosening of the McKee-Farrar hip replacement.
- To investigate the role of bearing wear versus implant design and surgical technique in implant failure.
Main Methods:
- Retrospective comparison of 15 failed McKee-Farrar hip replacements (aseptic loosening) with 15 long-term surviving implants.
- Radiographic analysis of component positioning, offset, and center of rotation.
- Evaluation of stem alignment (varus) and cement mantle integrity.
- Assessment of bearing wear and periprosthetic tissue for particulate debris during revision surgery.
Main Results:
- Failed hips exhibited decreased femoral offset and less medialization of the center of rotation compared to surviving hips.
- Aseptic femoral loosening was associated with decreased offset (P=.04).
- Varus positioning of the stem and cement mantle defects in zones III and VII were observed in revised stems, suggesting a link between surgical technique and loosening, not bearing wear.
Conclusions:
- Unfavorable biomechanics, including altered offset and center of rotation, contribute to increased joint reaction forces and potential loosening.
- Curved stem designs, like the McKee-Farrar, may be associated with varus positioning, cement defects, and subsequent loosening.
- Implant design, biomechanics, and surgical technique are critical factors in the long-term survival of total hip replacements, potentially more so than bearing wear in this specific case.
