Surface extraction can provide a reference for micro-CT analysis of retrieved total knee implants

Area of Science:

• Orthopaedic biomechanics
• Biomaterials science
• Medical imaging analysis

Background:

• Retrieval analysis of orthopaedic components is crucial for understanding implant performance.
• Estimating original geometry for wear measurements is challenging, often requiring multiple scans.
• Micro-computed tomography (micro-CT) offers high-resolution imaging for quantitative analysis.

Purpose of the Study:

• To determine if articular and backside surfaces of tibial inserts can be independently segmented from micro-CT scans.
• To assess if a single tibial insert thickness can serve as a reference for other thicknesses.
• To streamline quantitative wear analysis in orthopaedic retrieval studies.

Main Methods:

• Six new tibial inserts of varying thicknesses were scanned using micro-CT.
• An automated computational method was developed to segment the surfaces.
• Variability between intact and retrieved components was quantified.

Main Results:

• Segmentation of articular and backside surfaces was successful.
• Deviations between extracted surfaces (0.0004–0.010 mm) were significantly less than baseline deviations in intact surfaces (0.0002–0.053 mm).
• A single insert thickness accurately represented surfaces of different thicknesses.

Conclusions:

• Retrieved tibial insert surfaces can be accurately represented by a single reference geometry.
• This method enhances the feasibility of micro-CT for quantitative retrieval studies.
• Reduces time and cost associated with scanning multiple reference geometries.
• Enables more detailed in vivo implant function analysis.