How to avoid pilonidal cyst while laying down?

Hi everyone!

My brother (35M) recently had a pelvis fracture and has to stay still and lay for about 6-8 weeks. It’s really hard for him to move from side to side and even going to the bathroom is a challenge and probably once a day activity.

My question is how can he avoid getting pilonidal cyst? I suggested he place a donut cushion under his back/butt area, but that might cause him pain, although he will try.

I had the cyst a few years back and made my life mission to educate people on it, tell them to stay active and take care of that area altogether. He is a VERY active person, and I’m talking gym every day, marathons, triathlons, Iron Mans, etc., but this really got to him and I’m trying to help him, but I have no clue what can we do, as he is in a very limited position.

Please help! Thank you!