Re Thomas Sherman's wound on the right leg by a musket ball at Port Hudson on May 27, '63.
Seems there were aggravating factors involved in Sherman's actual wound.
Below is a description of the injury:-
..."The wound was extensive and the tissue greatly lacerated. ...(In the weeks afterwards) the examining surgeon found the wound had been very tightly sewn up with one continuous suture. When the suture was cut, there was a large discharge of decomposing coagula, pus, and bone splinters. His constitutional symptoms had assumed a most aggravated character. .....
....Fragments of bone were discharged day by day. It was decided that surgery was his only hope for recovery, and an amputation at the middle third of the thigh was performed.......his improvement was slow..........In May 1864......his stump had shrunk and impaired the fit of his artificial leg."...
(Source- 'Medical Histories of Union Generals' by Jack Welsh, @ pp. 299-300)
From this description, suggest his stump had shrunk to such an extent, largely due to his unusually high loss of bone mass caused by the continuous discharge of bone fragments/splinters reported, following the wounding.