OK, here's an excerpt from the summary medical report of Dr. John T. Darby, on General Hood's wound from Gettysburg. This is almost six months after that event, and during his recovery from the loss of his leg at Chickamauga:
At this date Dec 24th [18]63, the arm can be used to enable Gen Hood to walk on crutches. Flexion and extension of the elbow is perfect. The wrist can be flexed with freedom, the fingers open or shut in the palm at will, and used in performance of the various uses for protraction. The thumb is almost perfect in varied motions; and pronation and supination exist to a considerable degree. Use of the arm, causing development of muscular power in the exterior and superior muscles will in time cause the hand to lose few of its motions.
Stephen M. Hood, The Lost Papers of Confederate General John
Bell Hood (El Dorado Hills, California: Savas Beatie, 2015), 26.
Far, far from useless. In fact, upon a causal meeting, one might not notice Hood had difficulty with his arm.