The study aim was to simulate oblique spinous process abutment (SPA) in cadaveric spines and determine how this affects coupled motion in the coronal plane.

L4-S1 spinal segments from thirteen cadavers were loaded on a materials testing machine in pure compression at 1kN for 10 minutes. Reflective markers on the vertebral bodies were used to assess coronal motion using a motion analysis system. Oblique SPA was simulated by attaching moulded oblique aluminium strips to the L4 and L5 spinous processes. In each specimen, both a right- and left-sided SPA was simulated, in random order, and compression at 1kN was again applied. All tests were then repeated after endplate fracture. Coronal plane motion at baseline was compared with values following simulated SPA using Mann Whitney U-tests.

Pre-fracture, SPA increased coronal motion by 0.28° and 0.34° on right and left sides respectively, compared to baseline, only the former was significant (P=0.03). Post-fracture, SPA decreased coronal motion by 0.36° and 0.46° on right and left sides respectively, only the latter was significant (P=0.03). Simulated oblique SPA in the intact spine initiated an increase in coronal motion during pure axial loading. These findings provide limited evidence that oblique SPA may be causative in DLS.