Proposing the Retrosternal Angle as a Diagnostic Measure for Banana Sternum in Pectus Excavatum.

Background/purpose: Anteriorly convex sternum in pectus excavatum, also known as banana sternum (BS), influences decision-making during repair and, especially, the need to cross bars. However, the definition of BS remains subjective. Thus, we aim to propose the retrosternal angle (RSA) as a diagnostic measure for the discrimination of BS.

Material And Methods: Retrospective analysis of a cohort of patients who underwent a minimally invasive repair of pectus excavatum (MIRPE) between October 2016 and October 2023 at our Pectus Clinic. Five expert thoracic surgeons individually reviewed their medical photographs and chest CT scans assigning patients to BS or non-BS groups based on consensus (≥4 surgeons). RSA measurements were obtained by an independent thoracic surgeon.

Results: Among 283 cases analyzed, 50 (18%) were classified as BS and 233 (82%) as non-BS. No significant differences were found between groups in age (p = 0.62), Haller index (p = 0.11), or Correction index (p = 0.58). However, RSA was significantly lower in the BS group (141.2 ± 8.4° vs. 154.5 ± 10.3°, p < 0.0001). Receiver operating characteristic curve analysis revealed RSA as a reliable predictor of BS (AUC 0.85, p < 0.0001), with a threshold of 148.5° demonstrating 80% sensitivity and 77% specificity. Regarding potential clinical implications, 26/50 (52%) of patients defined as BS underwent bar crossing, compared with 45/232 (19%) of those not considered a BS (p < 0.0001).

Conclusion: This study proposes an objective metric, the Retrosternal Angle, to assess BS in chest CT scans, with a threshold of 148.5° showing high sensitivity and specificity. External validation of this angle and threshold is warranted in future investigations.

Type Of Study: Retrospective comparative study.

Level Of Evidence: III.