In a patient support structure (10) comprising a computer (28), a controller (29), support assemblies (3, 4, 5, 6), a trunk translator subassembly (123), a rail assembly (2), support structures (10, 11) and angulation and roll subassemblies (66, 66'), the trunk translator subassembly (123) is configured for translational movement and comprises a trolley (124) and a linear actuator (134a) with a position sensor which is linked to the computer (28) to co-ordinate operations of the patient support structure.
