Insufficient lateralization of the femoral component coupled with exposed reamed cancellous bone has been speculated to predispose to femoral neck fracture. The current study examined the effect of mediolateral implant position and exposed cancellous bone on the strength of the resurfaced proximal femur. Composite femurs were prepared in three configurations: (1) partial, with the implant placed at the native femoral head offset of the femur, partially exposing reamed cancellous bone; (2) proud, with a medialized implant exposing a circumferential ring of cancellous bone; and (3) complete, with a lateralized implant covering all reamed cancellous bone. Specimens were loaded to failure in axial compression. A finite element model was used to further explore the effect of exposed cancellous bone, cement mantle thickness, and relative valgus orientation on the strain distributions in the resurfaced femur. The proud group (2063 N) was significantly weaker than both the partial (2974 N, ) and complete groups (5899 N, ) when tested to failure. The partial group was also significantly weaker than the complete group when tested to failure . The finite element model demonstrated increasing levels of strain in the superior reamed cortical-cancellous bone interface with increasing degree of exposed cancellous bone. The condition of the femoral component medialized as the result of a thick cement mantle had the greatest detrimental impact on strain level in the superior reamed cancellous bone while a valgus oriented implant provided a protective effect. This study provides biomechanical evidence that exposed reamed cancellous bone significantly reduces the load-to-failure and increases maximum strains in the resurfaced proximal femur. The perceived benefit of reconstructing the femur to its native geometry may inherently weaken the proximal femur and increase femoral neck fracture risk if the femoral component is not sufficiently lateralized to cover all unsupported reamed cancellous bone. Relative valgus orientation of the implant may help to minimize the risk of neck fracture if reamed cancellous bone remains exposed following implant impaction.
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August 2010
Research Papers
The Biomechanical Consequence of Insufficient Femoral Component Lateralization and Exposed Cancellous Bone in Hip Resurfacing Arthroplasty
Michael Olsen,
Michael Olsen
Martin Orthopaedic Biomechanics Laboratory,
e-mail: michaelolsen@utoronto.ca
St. Michael’s Hospital
, 5-066 Shuter Wing, 30 Bond Street, Toronto, ON, M5B1W8 Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto
, Toronto, ON, M5B 1W8, Canada; Orthopaedic Biomechanics Laboratory, Sunnybrook Health Sciences Centre
, Orthopaedic Biomechanics Laboratory 2075 Bayview Avenue, UB 19, Toronto, ON, M4N 3M5, Canada
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Edward T. Davis,
Edward T. Davis
NHS Foundation Trust,
The Royal Orthopaedic Hospital
, The Woodlands Bristol Road South, Northfield, Birmingham, UK, B31 2AP
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Cari M. Whyne,
Cari M. Whyne
Institute of Biomaterials and Biomedical Engineering,
University of Toronto
, Toronto, ON, Canada; Orthopaedic Biomechanics Laboratory, Sunnybrook Health Sciences Centre
, Orthopaedic Biomechanics Laboratory 2075 Bayview Avenue, UB 19, Toronto, ON, M4N 3M5, Canada; Department of Surgery, Faculty of Medicine, University of Toronto
, Toronto, ON, M5B 1W8, Canada
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Rad Zdero,
Rad Zdero
Martin Orthopaedic Biomechanics Laboratory,
St. Michael’s Hospital
, 5-066 Shuter Wing, 30 Bond Street, Toronto, ON, M5B1W8 Canada
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Emil H. Schemitsch
Emil H. Schemitsch
Martin Orthopaedic Biomechanics Laboratory,
St. Michael’s Hospital
, 5-066 Shuter Wing, 30 Bond Street, Toronto, ON, M5B1W8 Canada; Department of Surgery, Faculty of Medicine, University of Toronto
, Toronto, ON, M5B 1W8, Canada
Search for other works by this author on:
Michael Olsen
Martin Orthopaedic Biomechanics Laboratory,
St. Michael’s Hospital
, 5-066 Shuter Wing, 30 Bond Street, Toronto, ON, M5B1W8 Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto
, Toronto, ON, M5B 1W8, Canada; Orthopaedic Biomechanics Laboratory, Sunnybrook Health Sciences Centre
, Orthopaedic Biomechanics Laboratory 2075 Bayview Avenue, UB 19, Toronto, ON, M4N 3M5, Canadae-mail: michaelolsen@utoronto.ca
Edward T. Davis
NHS Foundation Trust,
The Royal Orthopaedic Hospital
, The Woodlands Bristol Road South, Northfield, Birmingham, UK, B31 2AP
Cari M. Whyne
Institute of Biomaterials and Biomedical Engineering,
University of Toronto
, Toronto, ON, Canada; Orthopaedic Biomechanics Laboratory, Sunnybrook Health Sciences Centre
, Orthopaedic Biomechanics Laboratory 2075 Bayview Avenue, UB 19, Toronto, ON, M4N 3M5, Canada; Department of Surgery, Faculty of Medicine, University of Toronto
, Toronto, ON, M5B 1W8, Canada
Rad Zdero
Martin Orthopaedic Biomechanics Laboratory,
St. Michael’s Hospital
, 5-066 Shuter Wing, 30 Bond Street, Toronto, ON, M5B1W8 Canada
Emil H. Schemitsch
Martin Orthopaedic Biomechanics Laboratory,
St. Michael’s Hospital
, 5-066 Shuter Wing, 30 Bond Street, Toronto, ON, M5B1W8 Canada; Department of Surgery, Faculty of Medicine, University of Toronto
, Toronto, ON, M5B 1W8, CanadaJ Biomech Eng. Aug 2010, 132(8): 081011 (7 pages)
Published Online: July 1, 2010
Article history
Received:
September 19, 2008
Revised:
January 15, 2010
Posted:
February 2, 2010
Published:
July 1, 2010
Online:
July 1, 2010
Citation
Olsen, M., Davis, E. T., Whyne, C. M., Zdero, R., and Schemitsch, E. H. (July 1, 2010). "The Biomechanical Consequence of Insufficient Femoral Component Lateralization and Exposed Cancellous Bone in Hip Resurfacing Arthroplasty." ASME. J Biomech Eng. August 2010; 132(8): 081011. https://doi.org/10.1115/1.4001159
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