Changes in knee shape and geometry resulting from total knee arthroplasty.

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Medical Imaging

Background:

• Total knee arthroplasty (TKA) alters knee shape and geometry, impacting patient pain, function, stability, range of motion, and kinematics.
• Quantitative data on these geometric changes post-TKA have been lacking, hindering a deeper understanding of individual patient experiences and outcomes.

Purpose of the Study:

• To develop a conceptual framework and analysis method for quantifying changes in knee shape and geometry following TKA.
• To prospectively apply this method to a cohort of TKA patients.

Main Methods:

• Utilized computed tomography (CT) and radiography imaging systems to capture 3D knee geometry.
• Compared pre- and post-operative knee shape and geometry in nine TKA patients (eight varus, one valgus).

Main Results:

• Significant visual and numerical changes in knee shape and geometry were observed post-TKA.
• Quantified average changes including distal condyle height variations, increased posterior condyle extension medially, increased patellofemoral distance, and increased patellar thickness.
• Noted differences in external femoral rotation and joint line distance changes throughout flexion.

Conclusions:

• This study provides the first quantitative evidence of geometric alterations after TKA, moving beyond qualitative observations.
• The developed protocol and quantitative data are essential precursors for identifying factors contributing to varied patient outcomes.
• Findings can inform improvements in implant design, selection, component positioning, and surgical techniques to enhance patient satisfaction.