coach with a crutch

[BretMan]

Nearest thing I could find in the Case Book...

3.5.2 SITUATION B: The head coach from the visiting team uses a wheelchair
as a mobility device and wishes to coach in the third-base coach's box while
his/her team is at bat. RULING: As discretely as possible under the circumstances, the umpire should ask the coach if he/she has contacted the state association to determine what accommodations have been authorized for the coach's special needs. If the state association had been contacted, the coach will have documentation indicating specific participation guidelines. If the state association had not been contacted by the coach, the umpire should permit the coach to occupy the coach's box at the appropriate times, but the umpire should contact the state association as soon as possible after the contest to inform them of the situation. COMMENT: Prior to participation by a special needs student-athlete, coach or official, the state association should be contacted to determine reasonable accommodations.

If they're going to let a wheelchair be on the field, why not a crutch?