Radiological insights into costal margin rupture injuries: patterns of associated rib and costal cartilage fractures.

Purpose: Costal margin ruptures (CMR), though rare, are often associated with rib fractures and intercostal hernia. Injuries to the costal cartilages are often poorly recognised. Surgical stabilisation of rib fractures without fixing the CMR is known to result in failure of metalwork. The aim of this study was to characterise the associated rib and costal cartilage fractures according to different categories of the Sheffield Classification of CMR injuries, thus highlighting injury patterns which are of importance with respect to patient management.

Methods: Patients characterised by the Sheffield Classification were identified. Prospective clinical data were collected at the time of presentation. Computed Tomography (CT) multiplanar and 3D images were reviewed. Data were analysed according (i) to the absence or presence of Intercostal Hernia (i.e. CMR + IH and Trans Diaphragmatic Intercostal Hernia (TDIH) versus other CMR injury categories) and (ii) according to the aetiology (Expulsive versus other, where expulsive was defined as related to coughing, sneezing, retching or vomiting). Any associated rib or other costal cartilage fractures were recorded on heatmaps, according to Chest Wall Injury Society taxonomy.

Results: There were 64 patients with Costal Margin Rupture injuries included in the study. The presence of IH in addition to CMR was associated with chronic presentation, expulsive aetiology, higher body mass index, and CMR at the level of the 9th costal cartilage. IH (p = 0.002) and expulsive aetiology (p = 0.04) were associated with presence of rib fractures, but the absence of additional costal cartilage fractures (p < 0.0001 and p = 0.001 respectively). Fractures in the IH and expulsive groups were notably more focused in distribution to the posterior sector (p < 0.0001) and with the most common fracture being one level above the CMR.

Conclusion: Posterior sector, lower level rib fractures related to coughing and other "expulsive' aetiologies may be associated costal margin rupture and intercostal hernia. The latter injuries should not be overlooked in the assessment and successful management of the patient.