How do lower-limb landmarking errors impact morphometrics in total knee arthroplasty planning?

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Medical imaging analysis

Background:

• Accurate anatomical landmark identification is crucial for total knee arthroplasty (TKA) planning and implant positioning.
• Current TKA planning validation uses uniform thresholds, ignoring the clinical impact of landmark positioning errors.
• A framework is needed to quantify landmark contributions and establish risk-stratified acceptance criteria.

Purpose of the Study:

• To determine the hierarchy of anatomical landmark criticality for TKA planning using sensitivity analysis.
• To propose risk-stratified acceptance criteria for quality control in TKA planning.

Main Methods:

• A Monte Carlo sensitivity analysis (50,000 iterations) was performed on 30 patients for 14 morpho-functional metrics derived from 34 landmarks.
• Two sensitivity indices were used: Morphometrical Impact Rate (MIR) and Chatterjee coefficient (ξ).
• Empirical positioning error distributions were obtained from experienced orthopedic surgeons.

Main Results:

• Metric sensitivity varied 12-fold, with the inferior medial femoral condyle Z-coordinate being the most critical landmark.
• Malleolar landmarks showed maximal sensitivity for rotational metrics.
• Reference frame contamination, indicated by high Chatterjee coefficients, is a significant error propagation mechanism.

Conclusions:

• Landmark positioning accuracy does not directly correlate with clinical impact in TKA planning.
• A hierarchical validation framework prioritizing landmarks based on quantified clinical impact (MIR, Chatterjee coefficient) is proposed.
• Plane-defining landmarks require prioritized validation due to cascading reference frame errors.