Pectus excavatum is the most common anterior chest wall deformity, affecting up to 1:400 of newborns. The current gold standard to quantify the extent of deformity is by calculating the Haller Index based on a Computed Tomography (CT)-scan. However, as such scans inescapably imply exposure to ionizing radiation, novel imaging techniques have been investigated. Three-dimensional optical surface scanning is a promising new technique to acquire the trunks' three-dimensional (3D) surface topography. Based on this 3D scan, one is able to calculate the external Haller Index that is known to highly correlate with the conventional gold standard Haller Index that is based on internal measures. Both the conventional and external Haller Index are known to be affected by the respiratory phase in which the scan is acquired, however, what is the effect of patient position on the external Haller Index, and if affected, how should one correct for this phenomenon? To investigate this, a retrospective single-centre pilot study will be conducted.

Inclusion Criteria:

• Patients that received a three-dimensional optical surface scan to quantify their pectus deformity

Exclusion Criteria:

• None

Patients that received a three-dimensional optical surface scan to quatify their pectus deformity utilizing the external Haller Index. Patients were retrospectively recruited from the 3DPECTUS study (METCZ20190048; NCT03926078).