Hello,
I can understand your father's health.
He is having some issues presently for which he needs treatment;
1) Chronic Pancreatitis - if he is having recurrent pain at abdomen, which is not so much relieved by medications, than there are some minimal invasive techniques, which relieve the pain symptoms of the patients.
2) D12 vertebral fracture - this is the main issue at present, and mainly responsible for the pain in the legs. There are some advanced procedures, which can easily be done in this age group to heal tue fracture.
3) Osteoporosis - vertebral fracture in this age group, suggest that patient is having the osteoporosis, which decreases the strength of bone and leads to fracture.
4) Muscles weakness - because of prolonged hospitalization, muscle leads to weakness.
Why he leads to pleural effusion that is to be enquired as it leads to suspicion of others diseases.
Next Steps
As there are multiple issues with your father, I need to know more about him, so that I can tell you what can be done more. You can connect me on Practo. As these things can be treatable.
Health Tips
1) Good physiotherapy of the legs
2) mobilize the patient as much as possible with support.