Talk to his doctor for advice on how to deal with this potentially dangerous behavior. Men especially have trouble accepting any kind of infirmity, and his doctor might be able to get through to him. My roommate, a dear friend (and Marine veteran), has ALS (among other things). He wouldn't use his rolling walker (the kind with a seat) and was falling 4-5 times a week. All it took was a threat from me about calling his doctor and he became more conscientious about it. He doesn't always use it, but he's getting better about it.
Your husband might benefit from counseling to help him to accept this difficulty; if he won't go, either alone or with you, it may be of help for you to go individually.