Disclosed adjustable retaining arm systems can include a multi-segmented, articulable arm that holds one or more interchangeable tools and can be made relaxed to set a desired position and made rigid to fix the desired position by adjusting tension in a cable running through the arm. The arm can quickly attach and detach from a support structure. The support structure include a cable tensioning system, sensors, control system, power system, etc. A user input device, such as a foot pedal or button on the arm, can be used by a surgeon to change the arm between relaxed and rigid states. The arm and attachable tools can be detachable, disposable and/or sterilizable, while other system components can remain mounted in a fixed location as the arm is removed and replaced. The arm can hold multiple tools in any desired orientation around subject work location.