Clinical and radiological aspects of the forearm in children with congenital radioulnar synostosis: a cohort study

Introduction The upper limb functional limitations in congenital radioulnar synostosis may significantly affect the daily activities of patients. Classifications of the condition are descriptive and have limited practical application.Purpose Determine a functionally significant quantitative criterion for anatomical changes in the forearm.Material and methods 92 children (136 forearms) with congenital radioulnar synostosis were examined for  limitations in activities of daily living (ADL), health-related quality of life measured with  PedsQL questionnaire; pronation of the forearm and radiographic parameters. A comparative and  correlation analysis, ROC analysis were performed to determine the relationship between the forearm pronation and limitations of ADL.Results Statistically significant correlations were revealed between symptoms and the forearm alignment (p < 0.01, rxy = 0.5); subluxation of the ulnar head and forearm alignment (p < 0.001, rxy = 0.6); bowing deformity of the radius, forearm alignment and subluxation of the ulnar head and between the length of the forearm bones and bowing deformity of the radius (p < 0.05, rxy = 0.4 and rxy = 0.5). A statistically significant inverse correlation was revealed between symptoms and PedsQL scores (p = 0.038, rxy = –0.4). Pronation of 45° was the threshold value of the forearm alignment with a high risk of ADL limitation. The area under the ROC curve corresponding to the relationship between symptoms and the forearm alignment was 0.955 ± 0.021 (95 % CI: 0.915–0.995). There was a statistically significant (p < 0.01) decrease in the lumen of the medullary canal in the middle third of the ulnar shaft with the radius lumen being unchanged. Dorsal subluxation of the ulnar head was detected In 30 % of cases.Discussion The characteristics identified demonstrated changes in the forearm bones with functional impairments being correlated with the forearm pronation.Conclusion The correlation between the patient’s symptoms and the forearm alignment must be taken into  account in the classification and when determining indications for surgical treatment distinguishing between functional (< 45° pronation) and dysfunctional (≥ 45° pronation) options.