Objective
This study aims to introduces a novel morphological characteristic,"Gorilla lip" sign, and evaluates its diagnostic efficacy.
Methods
A retrospective review was conducted on anteroposterior ankle X-rays from patients diagnosed with talocalcaneal coalition at our institution from January 1, 2018 to December 31, 2023, with confirmatory diagnoses obtained via CT or surgical intervention. X-rays with TCC were selected as the positive group, while the negative group comprised X-rays of children aged 9–18 years with no prior ankle surgery and CT scans ruling out TC. The“Gorilla lip” sign was characterized by any of the following findings on the sustentaculum tali : (1) osseous protuberance over half of the medial malleolus; (2) narrowed joint space and rough articular surface; (3) absent joint space. X-rays were randomly assorted and independently assessed on two occasions, two months apart, by a pediatric orthopedic resident and two pediatric orthopedic physicians with varying experience levels. Metrics such as sensitivity, specificity, likelihood ratios, and inter- and intraobserver reliability for"Gorilla lip" sign were determined.
Results
Initial sensitivity rates for"Gorilla lip" sign were 90.0%, 75.0%, and 80.0%, with second evaluations yielding 80.0%, 85.0%, and 95.0%. Specificity rates were 92.0%, 100%, and 92.0% initially, and 84.0%, 92.0%, and 92.0% subsequently. Positive likelihood ratios for the first evaluation were 11.25, infinite, and 10.00, and 5.00, 10.63, and 11.88 for the second. Negative likelihood ratios were 0.11, 0.25, 0.22 initially, and 0.24, 0.16, 0.05 subsequently. Interobserver reliability was good. Intraobserver reliability were good to excellent.
Conclusion
"Gorilla lip" sign exhibits high sensitivity and specificity, along with good to excellent inter- and intraobserver reliability, suggesting its potential as a significant radiographic marker for TCC diagnosis.
