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Soft-tissue artefact assessment during step-up using fluoroscopy and skin-mounted markers
E H Garling1, B L Kaptein, B Mertens
1Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands; Department of Radiology, Division of Image Processing, Leiden University Medical Center, Leiden, The Netherlands. E.H.Garling@lumc.nl
Journal of Biomechanics
|April 28, 2007
Summary
Soft-tissue artifacts in knee motion analysis are significant, especially after total knee arthroplasty. Plate-mounted markers showed fewer errors than strap-mounted markers, questioning the reliability of external movement registration.
Area of Science:
- Biomechanics
- Orthopedics
- Medical Imaging
Background:
- Skin-mounted markers for knee kinematics can be obscured by soft tissues, leading to inaccuracies.
- Plate-mounted or marker tree systems may reduce soft-tissue artifacts compared to individual markers.
Purpose of the Study:
- To quantify soft-tissue artifacts during knee motion after total knee arthroplasty.
- To compare the accuracy of plate-mounted versus strap-mounted marker fixation methods.
Main Methods:
- Fluoroscopy of knee motion during a step-up task in ten total knee arthroplasty patients.
- A 3D model fitting technique to reconstruct in vivo marker and implant positions.
- Randomized comparison of plate-mounted and strap-mounted marker groups.
Main Results:
- Measurement errors were larger for the thigh than the lower leg.
- Strap-mounted markers resulted in significantly more translational errors for both shank and thigh compared to plate-mounted markers.
- Soft-tissue artifacts could not be distinguished from zero across knee flexion angles for either group.
Conclusions:
- Significant soft-tissue artifacts persist with clustered skin markers, regardless of fixation method.
- The reliability of external movement analysis for clinical interpretation in small patient groups is questionable.
- Plate-mounted markers offer improved accuracy over strap-mounted markers for knee kinematics in total knee arthroplasty patients.
