CPR Distance

This calculator is designed to assist in calculating the theoretical Contact Patch to Rim (CPR) distance.

This calculator assists in the calculation of the CPR distance in patients with hip resurfacing or total hip arthroplasty with a metal-on-metal (MoM) bearing. It takes into account implant design, size and orientation of the acetabular component. The current state of the knowledge (20/7/2016) is that if the CPR distance is less than 10 mm there is an increased risk of elevated metal ions and adverse soft tissue reaction due to edge loading1;2.

The CPR Distance Calculator is designed by Assoc. Prof. William L. Walter2 using DJ Langton et al. method3 based on hip contact forces published by Bergmann4.

1Reconstructive Review Oct 2015. MOS Algorithm used with EOS imaging to interpret MHRA Warning for 46-48mm MOM Arthoplasty. Clarke I
2The 2012 Otto Aufranc Award: The Interpretation of Metal Ion Levels in Unilateral and Bilateral Hip Resurfacing. Van Der Straeten, Catherine Clinical Orthopaedics and Related Research®, 2013, Vol.471
3Blood metal ion concentrations after hip resurfacing arthroplasty: a comparative study of articular surface replacement and Birmingham Hip Resurfacing arthroplasties. Langton, D J. The Journal of bone and joint surgery. British volume, October 2009, Vol.91(10), pp.1287-95
4Hip contact forces and gait patterns from routine activities. J Biomech. 2001; 34:856-871. G Bergmann.

By using the calculator, you accept this disclaimer in full. If you disagree with any part of this disclaimer, you must not use the calculator. Assoc. Prof. William L. Walter owns the intellectual property rights to the calculator. However, you may use the calculator for the stated purposes only. Whilst every effort has been made to ensure that the calculator is correct, its completeness or accuracy is not warranted and there is no commitment to ensure that the calculator is kept up to date.

To the maximum extent permitted by law, all representations, warranties and conditions relating to the calculator and the use of same (including, without limitation, any warranties implied by law in respect of satisfactory quality, fitness for purpose and/or the use of reasonable care and skill) are excluded. Assoc. Prof. William L Walter will not be liable for any costs, losses, expenses or damages (including whether direct or indirect, consequential, special, economic or financial including any loss of profits) whatsoever that may be incurred through the use of the calculator.

Nothing in this disclaimer will limit or exclude any liability however caused that is not permitted under Australian law or cannot be excluded under Australian law. This limitation and exclusion of liability governs all liabilities that are the subject matter of the disclaimer, including liabilities arising in contract, in tort (including negligence) and for breach of statutory duty.