Unilateral subtalar coalition: contralateral sustentaculum tali morphology

Area of Science:

• Orthopedic surgery
• Pediatric radiology
• Foot and ankle anatomy

Background:

• Subtalar coalition is a common cause of pediatric flatfoot.
• Understanding the contralateral morphology in unilateral cases is crucial for diagnosis and treatment.
• Computed tomography (CT) is a key imaging modality for evaluating subtalar joint anatomy.

Purpose of the Study:

• To measure and compare sustentaculum tali (ST) dimensions in pediatric patients with unilateral subtalar coalition.
• To determine if the contralateral (opposite) side exhibits altered morphology compared to controls.
• To investigate the relationship between middle facet (MF) and ST dimensions in these patients.

Main Methods:

• Retrospective review of CT scans from 35 pediatric patients with unilateral subtalar coalition and 33 controls.
• Measurement of anteroposterior dimensions of the MF and ST on the contralateral side (or equivalent in controls).
• Calculation of the MF/ST ratio and ST length posterior to the MF; statistical comparison between groups.

Main Results:

• Patients with unilateral subtalar coalition had a significantly smaller MF (12.86 mm vs 16.82 mm, P < .001) and a larger MF/ST ratio (0.54 vs 0.76, P < .001) on the contralateral side.
• The ST extended significantly further posterior to the MF in the coalition group (10.97 mm vs 5.24 mm, P < .001).
• High inter- and intraobserver reliability was achieved for all measurements.

Conclusions:

• The contralateral sustentaculum tali (ST) demonstrates altered morphology in pediatric patients with unilateral subtalar coalition, characterized by a smaller middle facet (MF).
• The ST significantly extends further posterior to the MF on the contralateral side in coalition patients.
• These morphological changes may offer insights into the developmental origins and pathogenesis of subtalar coalitions.