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Ultrasound improves preoperative Wassel classification of thumb polydactyly in children
1Department of Orthopaedics, National Clinical Research Center for Children and Adolescents' Health and Diseases, Ministry of Education Key Laboratory of Child Development and Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China; Chongqing Key Laboratory of Structural Birth Defect and Reconstruction, Chongqing, China.
Background:
The Wassel classification for thumb polydactyly relies on radiographs; however, invisible unossified cartilage in young children can lead to misclassification and suboptimal surgical planning. This study evaluated whether ultrasound improves the accuracy of polydactyly classification compared with radiographs.
Materials And Methods:
This prospective study included 31 cases of radial polydactyly initially classified as Wassel type IV or type II based on radiographs. All patients underwent preoperative ultrasound to identify potential cartilaginous connections between the proximal and distal phalanges. The ultrasound findings were compared against intraoperative exploration, which served as the gold standard for final classification.
Results:
Ultrasound correctly identified cartilaginous connections in the majority of cases, achieving an overall diagnostic accuracy of 93.5%. Thirty eight per cent of radiologic type IV cases were reclassified as type III, and 10% of radiologic type II cases were reclassified as type I after ultrasound detection of hidden connections. The accuracy was 100% for types IV-C and II, whereas type IV-D presented a diagnostic challenge with 75% accuracy. Overall diagnostic accuracy of ultrasound for polydactyly classification was high, with only a small number of misclassifications.
Conclusions:
Radiograph-based Wassel classification may misclassify thumb polydactyly in children due to unossified cartilage. Ultrasound allows direct visualization of cartilaginous connections and improves preoperative classification accuracy. Combined use of ultrasound and radiographs provides a more reliable anatomical assessment and may help optimize surgical planning and outcomes.
