Thoracic posture-related morphological changes in patients with pectus excavatum versus healthy controls

Cases of severe pectus excavatum presenting with worsening cardiopulmonary symptoms in the upright position have been reported. However, the underlying mechanism remains unclear. We evaluated posture-related morphological changes of the thorax in patients with pectus excavatum.

Chest morphology was evaluated preoperatively using upright and supine computed tomography in 21 patients with pectus excavatum and 35 healthy volunteers. The minimum anterior-posterior thoracic diameter, depression depth, and Haller index on horizontal sections, as well as the T6-12 plumb line distance on sagittal sections, were compared between the 2 positions.

In patients with pectus excavatum (median age, 22 years; 18 males and 3 females), the minimum anterior-posterior diameter was smaller (4.5 vs 5.1 cm, P < 0.001) and the Haller index was greater (10.1 vs 6.4, P < 0.001) in the upright position than in the supine position. The T6-T12 plumb line distance was longer in the upright position (2.4 vs 0.8 cm, P < 0.001), while the depression depth showed no significant difference. Healthy volunteers exhibited similar changes. The degree of spinal curvature increased in the upright position due to the anterior shift of the lower thoracic vertebrae, resulting in a shorter anterior-posterior diameter, irrespective of chest wall deformity. One patient with dyspnoea only in the upright position exhibited compression of the right inferior pulmonary vein only on upright computed tomography.

The minimum anterior-posterior diameter is shorter in the upright position. This may explain the worsening of cardiopulmonary symptoms in patients with severe pectus excavatum when in an upright position.Clinical trial registration number: UMIN000036438 https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000041519.