Should I take this further?

Hi there everybody, I would like your opinions please. A bit of a back story first, then the event in question. I have finished chemo and had a bilateral mastectomy. I also have other preexisting medical conditions, the total result of all, is that I now use a wheelie walker for stability and (ha ha) safety. I was getting physio and also hydrotherapy for a very stiff left shoulder where the pectoral muscle had shortened and tightened. In the process of having this therapy, my right shoulder went apeshit. Turns out to be the painful stage of adhesive capsulitis, also known as frozen shoulder. So now, therapy for both stuffed up shoulders...yayyy!!!. Off I go for my physio last Tuesday. Finish physio, now headed to the car. my husband ended up parking elsewhere than prearranged, so he had come to the physio department looking for me, but I had already finished so he was walking some distance behind me and saw it all. There was me...tootling along....down a slight slope..and at the bottom was a tank trap!!! The wheel of my walker got trapped in the drain (set into the concrete). Walker stopped, I kept going...right over the top. My hubby said it was like the Grand National...all he saw was my bum and my legs in mid air. Then he heard the crunch and the howls from me. Rushed to emergency...yippee... Because I.m on Clexane (blood thinners), twice daily for the past year, and will be for the rest of my life, they had to do a head ct to make sure I didn't have a brain bleed. (Wrong place to check, would have needed a proctoscope for that, but I digress as usual). Brain (ostensibly) all good. Five stitches in my head, landed of the worst of the two bad shoulders and did a rib on the right side too (thanks to osteoporosis). Kept the other broken ribs company which I already had. Was kept in hospital from the Tuesday and discharged on the Sunday. Missed my Herceptin and oncologist appointment which I was supposed to have on that Wednesday. So, Herceptin late by five days, which had me more hopping mad, (well twitching mad was the best I could do). Am I being unreasonable in my expectations that I should be able to use my walker on hospital property, on an approved walkway, in a responsible manner? I was not taking a shortcut across the car park. or doing a cross country walk over uneven ground. Evidently to make any sort of claim, I would have to prove negligence on the part of the hospital. I do not believe for one minute, that in the forty so (or thereabout) years that this drain has been there, that someone else pushing a sweety trolley for the Pink Ladies, or a trolley with some medical equipment, linen trolley, theatre trolley, wheelchair or walker has not been caught in this drain before. I did actually see the drain, I just did not see the slots in in until it was too late. The pictures show the grate the evening of the event, and the ones sprayed yellow were afterwards, when the hospital sprayed them. The other photo shows the slope and position of the drain. I had no option but to go over it.