Working Diagnosis:
Displaced fracture of the right anterior seventh costal cartilage

Treatment:
Our patient was referred to a thoracic surgeon who ordered a CT chest with IV contrast to confirm the diagnosis. He re-reviewed the prior non-contrast CT and saw the costal cartilage fracture. The patient underwent open reduction and internal fixation of the right 7th rib cartilage fracture with resection of a portion of the fractured cartilage.

Outcome:
Four months post-operatively, he continued to have pain with abdominal engagement but had returned to weightlifting and physical therapy. He had not yet returned to aerial acrobatics or to work.

Author's Comments:
Costal cartilage fractures are rare injuries typically due to high-energy blunt trauma to the chest, such as a motor vehicle accident. In sports, American football or rugby players may develop these injuries after tackles or collisions. This is the first case in the literature due to an atraumatic sports injury. Costal cartilage fractures are often missed initially as CT and x-ray imaging can be negative. Management begins with rest and pain control. The athlete can return to play with a rib protector once they are pain-free but may notice soreness for about 8 weeks. It is not known if these fractures heal to form a stable union so surgical fixation is emerging as an option for recalcitrant cases.

Editor's Comments:
This clinical case highlights the fact that costal cartilage injuries, although rare, are often misdiagnosed as intercostal muscle strains, slipping rib, and rib stress injuries in athletes presenting with atraumatic anterior chest pain.

In terms of the pathophysiology of these injuries, it is important to understand the structure and function of the sternum, ribs, and the costal cartilage connecting all the components of the rib cage. In conjunction, these elements facilitate expansion and contraction of the rib cage with respirations. Costal cartilage, compared to articular cartilage, is more adept at withstanding compression forces than tensile forces. The anterior surface of costal cartilage accommodates the highest tensile forces especially at end-inspiration and thus, it is more prone to atraumatic injury as seen in this case. In costal cartilage fractures of the 1st and 2nd ribs, there are often costochondral or chondrosternal junction injuries, but in the lower ribs damage is often seen in the middle region of the cartilage. As seen in this clinical case, the 7th rib cartilage is particularly vulnerable to injury given it is an attachment point for the 8th-10th rib cartilages, intercostal muscles, and the internal and external oblique muscles.

In terms of evaluation, the best imaging modalities to diagnose costal cartilage fracture are CT, MRI and ultrasound, but these fractures are often difficult to diagnose without calcification or concurrent sternochondral, costochondral, interchondral joint injuries. Healing of isolated cartilage damage is often not effective as cartilage lacks sufficient blood supply and stem cells to aid in repair, and the resultant chondrocyte cell death in the surrounding cartilage compromises tissue integrity and impedes appropriate repair of tissue. Given the impaired healing, findings such as hematoma, inflammation, or formation of callus that may aid in diagnosis are often not present. On CT scan, one may visualize a focal interruption in the relatively high costal cartilage density. On ultrasound, one may visualize similar focal interruption in the linear echogenic anterior margin of the hypoechogenic cartilages. On MRI, one may visualize a high signal intensity over fracture. Coronal imaging with patient prone, if tolerated, to minimize anterior chest motion may facilitate obtaining the best imaging results.

References:
McAdams et al. Chondral Rib Fractures in Professional American Football: Two Cases and Current Practice Patterns Among NFL Team Physicians. The Orthopaedic Journal of Sports Medicine, 4(2), 2325967115627623 DOI: 10.1177/2325967115627623.
Lopez et al. Cartilage Fractures and Disruptions in a Rugby Player. Clin J Sport Med _ 23(3), May 2013.
Solender GE et al. Fracture of the Costal Cartilage: Presentation, Diagnosis, and Management. The Ann Thorac Surg 2019;107, e267-e268.
Daniels SP, Kazam JJ, Yao KV, Xu HS, Green DB. Cough-induced costal cartilage fracture. Clin Imaging. 2019 May-Jun;55:161-164. doi: 10.1016/j.clinimag.2019.03.007. Epub 2019 Mar 13. PMID: 30897383.
Nummela et al. Incidence and Imaging Findings of Costal Cartilage Fractures in Patients with Blunt Chest Trauma: A Retrospective Review of 1461 Consecutive Whole-Body CT Examinations for Trauma. Radiology: February 2018;286(2); 696-704.

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