Total knee arthroplasty three-dimensional kinematic estimation prevision. From a two-dimensional fluoroscopy acquired...

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Medical Imaging

Background:

• Accurate assessment of total knee arthroplasty (TKA) kinematics is crucial for evaluating implant performance and patient outcomes.
• Single fluoroscopic imaging systems with computed-assisted design (CAD) model matching offer a potential method for determining six-degree of freedom (6DoF) TKA kinematics.
• Previous accuracy reports for these systems were based on idealized laboratory conditions, potentially overestimating their real-world performance.

Purpose of the Study:

• To evaluate the true accuracy of a flat panel single plane video-fluoroscopy system using CAD model matching for TKA kinematics.
• To compare the accuracy of fluoroscopy-based TKA kinematics with simultaneously obtained optoelectronic measurements, considered the gold standard.
• To highlight the underestimation of errors associated with 2D/3D fluoroscopic registration in practical clinical settings.

Main Methods:

• A TKA was implanted into cadaveric femur and tibia.
• Thirty knee flexion cycles were simultaneously recorded using single plane fluoroscopy and an active optical tracking system.
• Kinematic data were compared using root mean square error (RMS), concordance correlation coefficient, and Bland & Altman analysis.

Main Results:

• The mean range of motion during flexion was 106°.
• RMS errors were 0.68° (flexion), 0.67° (varus-valgus), 1.02° (internal-external rotation), 1.3 mm (antero-posterior), 2.4 mm (medio-lateral), and 1.06 mm (proximo-distal).
• Significant outliers were observed, particularly in medio-lateral displacement, with extreme errors ranging from -5.4 mm to 22.1 mm.

Conclusions:

• The study identified outliers and systematic errors in all degrees of freedom, with larger standard deviations than previously published data.
• Ensuring the motion of interest is in the in-plane direction is critical for accurate fluoroscopic kinematic analysis.
• This research establishes a more realistic threshold for the detection capabilities of this TKA kinematic analysis technique in practical applications.