Continuum robots allow accessing surgical targets deepinside the human body by steering along 3D curves inconfined spaces. Further, they provide enhanced dex-terity compared to traditional instruments . Concen-tric Tube Robots (CTRs) are representative continuumrobots that exhibit shape change by the relative transla-tion and rotation of precurved elastic tubes, telescopicallyinserted into each other. CTRs were originally envisionedas “single-arm” robots , but are nowadays also con-sidered as parts of “multi-arm” systems for surgical pro-cedures (e.g., in the prostate  or brain ).Although mechanics-based models have been developedthat can describe the shape of a single CTR of any numberof tubes and different precurvatures [6, 2], limited workon multi-arm CTRs and their modelling has been per-formed. Contrary to prior work that considers the back-bone that houses multiple robotic arms as stiff and “de-coupled” from the motion of the flexible arms [7, 4], theproposed work accounts for the interactions between anarbitrary number of CTR arms and the flexible backbone.The theory is developed for a multi-arm continuum robotcomprising a flexible CTR backbone that houses severalCTR arms as end-effectors (see Fig. 1).