Many trials have a small number of patients. This can make it difficult to see differences between two treatment options.
Some studies go longer than others. The length of time can make it impossible to compare results over time.
Other factors can get in the way of making comparisons. Type of implant used, general health before surgery, and amount of soft tissue cut during the operation can affect the results.
Ask your mother's orthopedic surgeon for his or her advice. He or she may be able to give you some insights to help with the decision. There may be some specific reasons why your mother should have one type over another.