3-D Weight-Bearing CT Mapping of Ankle Joint Space: Reproducibility and Challenges

Overview

This study demonstrates the feasibility of a semi-automated 3-D joint space mapping (JSM) technique using weight-bearing CT (WBCT) to assess ankle joint space width (JSW). The method showed quantifiable inter-operator reproducibility and test-retest repeatability in a mixed clinical population, highlighting challenges related to segmentation and motion artefact.

Background

Weight-bearing computed tomography (WBCT) has become increasingly important in foot and ankle imaging, offering realistic visualization of joint space width and bone alignment under physiological load. Traditional JSW assessments often rely on single-value measurements or 2-D planes, which may not capture the complex 3-D joint geometry. Previous 3-D JSW measurement techniques depend heavily on bone segmentation accuracy and have rarely reported reproducibility metrics. This study applies a semi-automated 3-D JSM approach, previously used at the hip and knee, to the ankle for the first time.

Data Highlights

Key Findings

• The semi-automated JSM method was feasible for 3-D ankle JSW assessment using WBCT in a clinical population.
• Inter-operator reproducibility and test-retest repeatability were quantitatively evaluated, supporting reliability of the technique.
• Motion artefact led to exclusion of 16.6% of cases, indicating a limitation in image acquisition quality.
• JSW measurement accuracy depends on segmentation performance and imaging resolution, with blurring effects addressed by an optimized blur model.
• The method enables detailed mapping of four distinct joint space patches: talar dome-medial gutter, lateral gutter, talonavicular, and posterior subtalar joints.

Clinical Implications

The JSM technique using WBCT provides a reproducible and detailed 3-D assessment of ankle joint spaces under physiological load, potentially improving evaluation of degenerative changes and deformities. Clinicians should be aware of the impact of motion artefact and segmentation accuracy on measurement reliability. This method may enhance preoperative planning and monitoring of ankle pathologies by providing comprehensive joint space data beyond traditional 2-D measurements.

Conclusion

This study validates a semi-automated 3-D JSW mapping approach for the ankle using WBCT, demonstrating reproducibility and highlighting challenges such as motion artefact and segmentation dependency. The technique offers a promising tool for advanced ankle joint assessment in clinical practice.

References

1. Authors 2013-2017 -- Cone-beam CT technology and WBCT in foot and ankle imaging
2. TT et al. -- Joint Space Mapping (JSM) methodology and application at hip and knee
3. Royal National Orthopaedic Hospital Database -- WBCT imaging protocol and patient selection