Final answer:
The indications for a total hip arthroplasty include osteoarthritis, which is the most common cause of hip disability, and severe femoral fractures that disrupt blood supply and may lead to necrosis.
Step-by-step explanation:
An indication for a total hip arthroplasty, which is the medical term for hip replacement surgery, includes osteoarthritis of the hip joint, which is the most common cause of hip disability. This surgery can be used to alleviate the pain and loss of joint mobility associated with osteoarthritis. Another indication for hip arthroplasty could be a severe femoral fracture, especially if it leads to disruption of the blood supply to the femoral head and neck resulting in necrosis. However, conditions such as effusion (fluid in the joint) or a pelvic fracture are not typical indications for hip replacement surgery as the first line of treatment.