Anatomic variability of the ribs and costal cartilage: A pilot study

Abstract

BACKGROUND: The rib cage is classically described as seven true ribs, three false ribs, and two floating ribs. Recent cadaveric studies have shown that there is variability in the cartilaginous attachments of the rib cage; however, these studies were done on Caucasian specimens only. We sought to determine if the anatomy of the rib cage can be assessed via computed tomography (CT) and describe the anatomic variations. METHODS: The trauma registry was used to identify recent patients evaluated by the trauma program who did not have rib fractures. These patients were sorted by race and gender and randomly assigned for review by experienced chest wall surgeons. CT scans were evaluated in three-dimensional, axial, sagittal, coronal, and tangential images to evaluate the number of ribs, aberrant anatomy, and cartilaginous attachments. Data was analyzed by SPSS v.30. RESULTS: Two hundred seventy-eight patients were evaluated with an average age of 49+/−25 years, and 54% were male. In all, 11 pairs of ribs were noted in 3.5% of patients and 13 ribs in 1% of patients. Variability was noted in the number of the lowest true ribs: sixth rib 19%, seventh rib 75%, eighth rib 6%, and a different number of true ribs on each side 5%. The number of true ribs was greater in males (6.9+/−0.5) versus females (6.8+/−0.5), p =0.008. Significantly more females had ribs that connected at the midline without sternal attachment: 24.4% (31/127) versus 14.5% (22/127), p =0.037. Comparing the right and left rib cage, 72% of patients were asymmetric. Super/infranummary pairs of ribs occur in 5% of patients. CONCLUSIONS: Significant variability from the presumed normal anatomy of the costal cartilages was seen. Compared with females, males have more true ribs. Most people do not have symmetrical rib cages, and the majority of patients exhibit variability in their costal cartilage. ( J Trauma Acute Care Surg 2026;00:000–000 Copyright © 2026 Wolters Kluwer Health, LLC. All rights reserved.) LEVEL OF EVIDENCE: Level IV.