Bruce your note of Fletch Taylor losing his arm led me to dig a bit into some medical info I have buried on a shelf. As many know amputation was the most common civil war operation. What is not well known is that upper extremity amputation was relatively safe, only about a 25% mortality rate. If performed within 24 hours of injury infection rate was comparatively low, if done by a competent surgeon, and recovery would be typical for primary wound healing of the upper arm or about 3 - 6 weeks. All bets were off if it got infected. Taylor would have been lucky in that the kidnapped surgeon would have had only one patient, his instruments and he himself would have been "clean" i.e not covered in the filth of a whole battles worth of wounded soldiers, and the operator would not have been under time pressure thus more likely to do things right.

Thus a first week August amputation of the arm may very well have been up and about by the 2nd week of September. Not a 100% by any means but far from bed bound.

John R