CT-based quantitative assessment of talar neck geometry: development of a standardized protocol and reliability...

To define reproducible computed tomography (CT)-based parameters for quantifying talar neck geometry and to evaluate their inter- and intra-observer reliability.

Thirty-five CT studies of adult feet without talar pathology were randomly selected from a prospectively maintained database. Multiplanar reconstructions were standardized along the talar axes to define reference planes. Five morphometric parameters were measured: declination angle, inclination angle, torsion angle, and medial and lateral talar neck lengths. Two fellowship-trained orthopedic surgeons and one musculoskeletal radiologist independently performed all measurements twice, four weeks apart, using DICOM viewer software. Inter- and intra-observer reliability were calculated using two-way random effects intraclass correlation coefficients (ICC).

All parameters were identifiable and measurable on the standardized CT planes across all studies. Inter-observer reliability was excellent for inclination angle (ICC 0.92, 95% CI 0.87-0.96) and good for declination angle (ICC 0.81, 95% CI 0.69-0.89); torsion angle showed poor reliability (ICC 0.41, 95% CI 0.20-0.61). Medial and lateral neck lengths demonstrated good reliability (ICC 0.77-0.83). Intra-observer reliability across observers was good to excellent (ICC > 0.80 for all parameters except torsion).

We have established a standardized CT-based protocol for assessing talar neck geometry with good-to-excellent reliability for most parameters. The proposed framework enables consistent quantification of talar neck alignment and could be potentially useful for facilitating evaluation of fracture reduction and correction planning in talar malunions.