Sensitivity of knee replacement contact calculations to kinematic measurement errors.

Full Abstract

The ability to measure in vivo knee kinematics accurately makes it tempting to calculate in vivo contact forces, pressures, and areas directly from kinematic data. However, the sensitivity of contact calculations to kinematic measurement errors has not been adequately investigated. To address this issue, we developed a series of sensitivity analyses derived from a validated in vivo computational simulation of gait. The simulation used an elastic foundation contact model to reproduce in vivo contact force, center of pressure, and fluoroscopic motion data collected from an instrumented knee replacement. Treating each degree of freedom (DOF) in the simulation as motion controlled, we first quantified how errors in measured relative pose of the implant components affected contact calculations. Pose variations of +/-0.1 mm or degree over the entire gait cycle changed maximum contact force, pressure, and area by 204, 100, and 117%, respectively. Larger variations of +/-0.5 mm or degree changed these same quantities by 1157, 108, and 578%, respectively. In both cases, the largest sensitivities were to errors in superior-inferior translation and varus-valgus rotation, with loss of contact occurring on one or both sides. We then quantified how switching the sensitive DOFs from motion to load control affected the sensitivity results. Pose variations of +/-0.5 mm or degree in the remaining DOFs changed maximum contact quantities by at most 3%. These results suggest that accuracy on the order of microns and milliradians is needed to estimate contact forces, pressures, and areas directly from in vivo kinematic measurements, and that use of load rather than motion control for the sensitive DOFs may improve the accuracy of in vivo contact calculations.(c) 2008 Orthopaedic Research Society

Learn Faster Today Improve your study skills

Author information

Author/s: Fregly, Benjamin J (BJ); Banks, Scott A (SA); D'Lima, Darryl D (DD); Colwell, Clifford W (CW);

Affiliation: Department of Mechanical & Aerospace Engineering, University of Florida, 231 MAE-A Building, Box 116250, Gainesville, Florida 32611, USA.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.

Journal: Journal of orthopaedic research : official publication of the Orthopaedic Research Society (J Orthop Res), published in United States. (Language: eng)

Reference: 2008-Sep; vol 26 (issue 9) : pp 1173-9

Dates: Created 2008/07/29; Completed 2008/08/13;

PMID: 18383141, status: MEDLINE (last retrieval date: 11/6/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

External Links for this article (including full text providers, if available):

Click Electronic Full-text Provider Links to see options for finding the electronic full text links to this article. Note there may be a subscription or fee required for access to the full text. See our FAQ for information on finding FREE full text articles.

This article may also be located in paper journal collections available in many libraries. Use the Journal and Publication Information above to find the full article.

MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Aged, 80 and over
Arthroplasty, Replacement, Knee - instrumentation
Biomechanics - methods
Computer Simulation
Humans
Knee Joint - physiology
Knee Prosthesis

Knee Prosthesis
Male
Models, Biological
Range of Motion, Articular - physiology
Reproducibility of Results
Sensitivity and Specificity
Walking - physiology

These are the highest related articles currently in the database:

See 100+ related articles.