Stability Analysis of Muscle-Driven Deformation in the Esophageal Wall: Insights into the Mechanisms of Corkscrew Esophagus

Corkscrew esophagus is a pathological condition in which the esophageal wall undergoes abnormal spatial deformations, such as helical twisting or localized constrictions. This phenomenon occurs transiently as the esophagus undergoes active contraction. To unravel its mechanical origins, we build a finite‑deformation model of the esophageal wall combined with an active thin‑shell outer layer that captures circular and longitudinal muscle fibers with different angle orientations and their contractile forces. The onset of buckling is identified by locating the minimum of the second variation of the total energy, which marks the critical deformation where stability is lost. Systematic variation of fiber orientation and contractile anisotropy reveals them as key determinants of stability. The resulting phase diagram highlights distinct regions of stability and instability as a function of luminal pressure and contractile properties. Using the diagram, we delineate the physiologically plausible window that precipitates corkscrew morphology. The framework links clinical observations to first‑principles mechanics and provides quantitative targets for diagnostic thresholds and muscle‑directed therapies.