Objective:To explore the risk factors of acute Kemmochi type V anterior talofibular ligament (ATFL) injury in X-ray negative children and their predictive efficacy .Methods:A retrospective cohort study was conducted to analyze the clinical data of 92 children with X-ray negative ATFL injury, who were treated at the outpatient department of Jinan Children′s Hospital from June 2023 to March 2025, including 55 boys and 37 girls, aged 5-14 years [8.8(7.0, 11.0)years]. The cause of injury was low-energy ankle sprain and X-ray examination showed no fracture, ie, X-ray negative. According to the Kemmochi classification for ATFL injury, the injury was classified as type V (Kemmochi type V group) in 42 patients and type I-IV (non-Kemmochi type V group) in 50. Gender, age, side of injury, time from injury to first visit, physical examination at the first visit [positive result of ankle inversion test, weight-bearing ability assessment, visual analogue score (VAS)], X-ray examination at the first visit (presence of os subfibulare), and musculoskeletal ultrasound examination at the first visit (swelling degree of ATFL, ankle joint effusion, enhanced blood flow signal of ATFL) were recorded in both groups. Univariate analysis and binary Logistic regression analysis were used to evaluate and determine the independent risk factors for X-ray negative Kemmochi type V ATFL injury in children. The receiver operating characteristic (ROC) curve and area under the curve (AUC) were used to evaluate the predictive efficacy of each independent risk factor for Kemmochi type V ATFL injury. Results:Univariate analysis showed significant differences between the two groups in age, VAS, ATFL swelling degree, and ankle joint effusion ( P<0.05) but no significant differences in gender, side of injury, time from injury to the first visit, positive result of ankle inversion test, weight-bearing ability assessment, presence of os subfibulare or enhanced blood flow of ATFL ( P>0.05). Binary Logistic regression analysis indicated that age ( OR=0.79, 95% CI 0.65, 0.97, P<0.05) and ATFL swelling degree ( OR=6.97, 95% CI 1.38, 35.32, P<0.05) were significantly correlated with Kemmochi type V ATFL injury in X-ray negative children. ROC curve analysis showed that the AUC for age and ATFL swelling degree were 0.65(95% CI 0.54, 0.75) and 0.78(95% CI 0.68, 0.86) and the AUC for age combined with ATFL swelling degree was 0.83(95% CI 0.74, 0.90). The optimal threshold values of age and ATFL swelling degree were 9.3 years and 1.0 mm. Conclusions:Age and ATFL swelling degree are independent risk factors for Kemmochi type V ATFL injury in X-ray negative children. Both age and ATFL swelling degree have relatively high independent predictive efficacy, and the combined predictive efficacy of the two is even higher.

Objective:To explore the risk factors of acute Kemmochi type V anterior talofibular ligament (ATFL) injury in X-ray negative children and their predictive efficacy .Methods:A retrospective cohort study was conducted to analyze the clinical data of 92 children with X-ray negative ATFL injury, who were treated at the outpatient department of Jinan Children′s Hospital from June 2023 to March 2025, including 55 boys and 37 girls, aged 5-14 years [8.8(7.0, 11.0)years]. The cause of injury was low-energy ankle sprain and X-ray examination showed no fracture, ie, X-ray negative. According to the Kemmochi classification for ATFL injury, the injury was classified as type V (Kemmochi type V group) in 42 patients and type I-IV (non-Kemmochi type V group) in 50. Gender, age, side of injury, time from injury to first visit, physical examination at the first visit [positive result of ankle inversion test, weight-bearing ability assessment, visual analogue score (VAS)], X-ray examination at the first visit (presence of os subfibulare), and musculoskeletal ultrasound examination at the first visit (swelling degree of ATFL, ankle joint effusion, enhanced blood flow signal of ATFL) were recorded in both groups. Univariate analysis and binary Logistic regression analysis were used to evaluate and determine the independent risk factors for X-ray negative Kemmochi type V ATFL injury in children. The receiver operating characteristic (ROC) curve and area under the curve (AUC) were used to evaluate the predictive efficacy of each independent risk factor for Kemmochi type V ATFL injury. Results:Univariate analysis showed significant differences between the two groups in age, VAS, ATFL swelling degree, and ankle joint effusion ( P<0.05) but no significant differences in gender, side of injury, time from injury to the first visit, positive result of ankle inversion test, weight-bearing ability assessment, presence of os subfibulare or enhanced blood flow of ATFL ( P>0.05). Binary Logistic regression analysis indicated that age ( OR=0.79, 95% CI 0.65, 0.97, P<0.05) and ATFL swelling degree ( OR=6.97, 95% CI 1.38, 35.32, P<0.05) were significantly correlated with Kemmochi type V ATFL injury in X-ray negative children. ROC curve analysis showed that the AUC for age and ATFL swelling degree were 0.65(95% CI 0.54, 0.75) and 0.78(95% CI 0.68, 0.86) and the AUC for age combined with ATFL swelling degree was 0.83(95% CI 0.74, 0.90). The optimal threshold values of age and ATFL swelling degree were 9.3 years and 1.0 mm. Conclusions:Age and ATFL swelling degree are independent risk factors for Kemmochi type V ATFL injury in X-ray negative children. Both age and ATFL swelling degree have relatively high independent predictive efficacy, and the combined predictive efficacy of the two is even higher.