LAUSR

BACKGROUND The interchondral joint between the sixth and seventh costal cartilages, called synchondrosis, assists in harvesting and fabricating the microtia framework. However, its looseness often complicates the microtia surgery. We aimed to classify the interchondral joints based on looseness and identify predictors for each subtype. METHODS Electronic chart and intraoperative photographs were reviewed for consecutive microtia patients who underwent costal cartilage graft for ear reconstruction from June 2001 to February 2020. The sixth and seventh costal interchondral joint was classified in the ascending order of looseness-direct cartilaginous fusion (class I), synovial joint (class II), and loose tissue (class III)-with a minor modification from the cadaveric study of Dr. Briscoe in 1925. χ2 Tests compared the incidence of each subtype in terms of patient variables including age, sex, chest laterality, and radiologic chest deformity. Multivariate logistic regression was used for identifying independent predictors for each subtype. RESULTS Seven hundred thirty-three graft specimens were enrolled (mean age 12.1 years). Class I joint was seen in 137 (18.7%) grafts, class II in 544 (74.2%), and class III in 52 (7.1%). Female predilection was found for cartilaginous fusion (class I) (adjusted odds ratio, 1.691; P = 0.007). The incidence of loose joint (class III) was comparable, ranging from 4.6% to 12.5%, in terms of all the patient variables. CONCLUSIONS Loose interchondral joints were not uncommon in microtia surgery. Patient variables were less likely to predict this anatomical variation, necessitating some knowledge of managing the framework instability. Female patients were more likely to enable easy fabrication with directly fused costal cartilages.