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Evaluation of automated statistical shape model based knee kinematics from biplane fluoroscopy
Nora Baka1, Bart L Kaptein1, J Erik Giphart2
1Biomechanics and Imaging Group, Department of Orthopedic Surgery, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
Journal of Biomechanics
|November 12, 2013
Summary
Statistical shape models (SSMs) show promise for knee kinematics analysis using fluoroscopy, potentially reducing CT/MRI needs. This method achieved sub-millimeter and 1° precision, comparable to marker-based techniques in cadaveric and in-vivo studies.
Area of Science:
- Biomechanics
- Medical Imaging
- Orthopedics
Background:
- Current fluoroscopic knee kinematic analysis relies on patient-specific bone shapes from CT/MRI, increasing cost and radiation exposure.
- Statistical shape models (SSMs) offer a potential alternative to patient-specific models, aiming to reduce the need for CT/MRI acquisitions.
- The clinical applicability of SSM-based knee kinematics has not been extensively evaluated on key joint motion parameters.
Purpose of the Study:
- To explore the use of SSMs for computing knee kinematics from biplane fluoroscopic sequences.
- To evaluate the kinematic precision of an edge-based automated bone tracking method using SSMs.
- To investigate the relationship between bone shape accuracy and kinematic precision.
Main Methods:
- Developed SSMs for the femur and tibia-fibula using 61 training datasets.
- Evaluated kinematic precision using an edge-based automated bone tracking method with SSMs on 6 cadaveric and 10 in-vivo fluoroscopic sequences.
- Assessed precision for medial-lateral tibial shift, anterior-posterior tibial drawer, joint distraction-contraction, flexion, tibial rotation, and adduction.
Main Results:
- SSM-based kinematics achieved sub-millimeter (0.48-0.81mm) and approximately 1° (0.69-0.99°) median precision on cadaveric knees compared to bone-marker-based kinematics.
- In-vivo precision was comparable to cadaveric results when assessed using a semi-automatic reference method.
- Demonstrated that improved 3D shape reconstruction accuracy does not automatically guarantee better kinematic precision; edge fitting accuracy is more critical.
Conclusions:
- SSMs are a promising approach for knee kinematics analysis from biplane fluoroscopy, offering reduced costs and radiation dose.
- The achieved precision is comparable to established marker-based methods, though further refinement is needed to match CT-based accuracy.
- Kinematic precision is more influenced by the accuracy of edge fitting in fluoroscopic images than by overall 3D bone shape accuracy.
