Broken hip - bathroom problems

my 1.5 year old male cat, willow, recently fell off our deck and didnt land on his feet about a week ago. he broke his left hip in 3 places and may or may not have nerve damage in his right leg. he holds his stool when he is anxious, and he seems in a great mood most of the time, except that he has only passed stool twice in the past week since the accident. he is eating and drinking and alert and content. still very affectionate..but he just stares at the litterbox and wont even let us put him in it. he let us once, and he expelled quite a bit of pee and poo. that was about day 3. on day 4 he wouldnt let us put him in the box and ended up wetting himself. he was laying on his side, lifting his right leg out of the puddle and just peed all over himself and the floor and looked very upset. 

does anyone have advice on how to help him adapt to a new potty situation until he heals a bit?

Was he checked thoroughly for internal injuries? Get a very shallow box and put litter in it. If he has a place he likes to lay, put some puppy pads down, temporarily. Clean him after he pees, if he has gone on himself. I assume he is in a cat cast for the broken hip.

i agree tho this may be late and hopefully Willow is recovering. Place several (she needs 2 anyway) down and make them easy to access ie no difficulty in hopping in. Let her feel she can ho. Put it in a good location -easy to reach, not close to her food. And maybe use Paper litter for now or soft unclumping litter until she is better. Good luck!