Analyzing Alignment Error in Tibial Tuberosity-Trochlear Groove Distance in Clinical Scans Using 2D and 3D Methods

Area of Science:

• Orthopedic surgery
• Medical imaging analysis
• Biomechanical engineering

Background:

• Tibial tuberosity-trochlear groove (TT-TG) distance is crucial for surgical decisions in patellofemoral instability (PFI).
• Existing TT-TG measurements have high interrater reliability but are susceptible to errors from leg-scanner alignment.
• Quantification of alignment-induced errors in TT-TG measurements is limited in clinical literature.

Purpose of the Study:

• To quantify and specify errors in TT-TG measurements caused by leg-scanner alignment.
• To utilize detailed topographical landmarks and 3D analysis of CT scans for accurate TT-TG assessment in PFI patients.

Main Methods:

• Created 3D models from CT scans of 44 knees with PFI to identify TT-TG landmarks.
• Measured TT-TG using established 2D and 3D methods.
• Developed and validated a model to estimate differences between 2D and 3D methods based on leg-scanner orientation.

Main Results:

• Significant differences (2.7 ± 4.1 mm) were observed between 2D and 3D TT-TG measurements, with 2D measurements being longer.
• A substantial proportion (29.5%) of knees showed >5 mm difference between 2D and 3D TT-TG.
• The developed estimation model demonstrated high accuracy (adjusted r² = 1.00) in correcting alignment errors.

Conclusions:

• Three-dimensional TT-TG analysis can effectively correct for leg-scanner alignment errors.
• These corrections are significant, especially when relying solely on 2D TT-TG measurements for surgical planning.
• Awareness of alignment effects is critical for accurate 2D TT-TG interpretation in PFI surgical planning.