Postoperative lung geometric repositioning after right upper lobectomy: the role of thoracic morphology configuration

Right upper lobectomy (RUL) is the most frequently performed lobectomy for lung cancer, yet postoperative functional loss varies widely among patients. We hypothesized that thoracic morphology constrains three-dimensional (3D) repositioning of the residual lung after RUL, leading to characteristic bronchial axis deviation and rotation-like deformation, and that these geometric changes might be associated with postoperative residual-lobe expansion.

We retrospectively analyzed 26 patients who underwent RUL (2016-2018), including five with middle lobe atelectasis (MLA). Paired pre- and postoperative computed tomography was used to quantify residual-lobe volumes and geometric markers (thoracic morphology, sagittal bronchial axis deviation of B4/5 and B6, and plane-based rotation-like deformation) and to test their associations with repositioning patterns and postoperative expansion.

Two distinct residual-lung repositioning patterns were identified: a B6-dominant pattern, in which the superior segment (S6) ascended to occupy the postoperative apical space (Type B6), and a B4/5-dominant pattern, in which the middle lobe migrated cranially (Type B4/5). Type B6 was associated with barrel-shaped thoraces, whereas Type B4/5 was associated with flatter thoraces [thoracic height-to-anteroposterior diameter (H/AP) ratio, P=0.001; 8th-rib angle, P<0.001]. Rotation-like deformation patterns differed between the two types and supported their geometric distinction. However, neither thoracic morphology, repositioning pattern, bronchial axis deviation, nor rotation-like metrics were associated with postoperative middle-plus-lower lobe volume expansion (Type B6 vs. Type B4/5, P=0.42; H/AP ratio, P=0.28; 8th-rib angle, P=0.61; ΔB4/5, P=0.06; ΔB6, P=0.65; ΔY, P=0.68; ΔX, P=0.69). MLA occurred in both patterns (Type B6, n=2; Type B4/5, n=3) and was associated with reduced postoperative expansion [middle + lower volume ratio (post/pre), P=0.02] but showed no distinctive geometric predictors.

Thoracic morphology influences 3D residual-lung repositioning after RUL, producing characteristic geometric patterns. Nevertheless, these geometric responses alone do not explain postoperative residual-lobe expansion, highlighting the need to integrate functional determinants with geometric assessment.