Ultrasonography or Radiography for Suspected Pediatric Talocalcaneal Coalition.

Background: Talocalcaneal coalition is a common tarsal coalition, but incomplete ossification in children often leads to underdiagnosis using traditional radiographic signs like the "C sign" and "talar beak." Ultrasonography, which is radiation-free and detects unossified cartilage, has not been studied for pediatric talocalcaneal coalition. This study evaluates the accuracy and reliability of ultrasonography versus radiography in diagnosing suspected pediatric talocalcaneal coalition.

Methods: Eighty-six suspected talocalcaneal coalitions underwent ultrasonography, radiography, and 3-dimensional CT scanning. Three pediatric orthopaedic surgeons assessed ultrasound results and radiographic signs ("C sign" and "talar beak") for interobserver and intraobserver reliability. Using CT as the diagnostic standard, the sensitivity, specificity, positive predictive value, and negative predictive value of ultrasonography and radiographic signs were evaluated.

Results: In a cohort of 86 suspected pediatric talocalcaneal coalitions, the mean age was 12.3 years. The interobserver reliability for the "C sign" was moderate (κ=0.55), while the interobserver reliability for ultrasonography was almost perfect (κ=0.87). Using 3-dimensional CT scanning as the diagnostic standard, the specificity and sensitivity of the "C sign" for diagnosing talocalcaneal coalition in children were 86% and 54%, respectively. Ultrasonography demonstrated a sensitivity of 96% and a specificity of 98%. The "talar beak" had only 3 true positives and 25 false negatives, resulting in a sensitivity of 11%, which was statistically significant (P <0.001).

Conclusions: The "C sign" is useful but less accurate than ultrasonography for diagnosing suspected pediatric talocalcaneal coalition, while the "talar beak" is unsuitable due to low sensitivity. Ultrasonography can accurately detect pediatric talocalcaneal coalition, even in unossified cases. Compared with radiography, ultrasonography is more suitable for diagnosing suspected pediatric talocalcaneal coalition.

Level of evidence: Level III-diagnostic study.