Helical Instability of the Esophageal Wall: Stability Analysis of Active Muscle‑Driven Deformations

Corkscrew esophagusa is pathological condition characterized by abnormal spiral deformations of the esophagus. To unravel its mechanical origins, we build a finite‑deformation model of the esophageal wall augmented by an active thin‑shell outer layer that captures circular and longitudinal muscle fibers with different angle orientations and their contractile forces. Stability is quantified via a bifurcation analysis in which a small non‑axisymmetric disturbance is imposed on the finite‑deformation base state, the governing equations are linearized, and the problem is cast as a self‑adjoint eigenvalue problem. The smallest eigenvalue obtained from the Rayleigh quotient that represents the second variation of the total energy identifies the critical defromation factor at which buckling emerges. Parameter sweeps demonstrate that the circumferential to longitudinal contractile strengths are the dominant control variable; plotting contractility against the luminal pressure yields a phase diagram that cleanly separates stable and unstable regimes. 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.