Fusions of joints, including the joint between the big toe and foot, are most often done because of degeneration of the joint, which causes substantial pain and mobility problems for the patient. There are different techniques that can be used for joint fusion, depending on the problem with the joint, the surgeon, and the available materials.
No two patients are alike, so even if they have the same procedure done, with the same materials, they will not necessarily have the same outcomes. What happened to your neighbor could be due to any number of issues and they may not necessarily happen to you.
To make your decision, bring your concerns to your surgeon and ask questions. The decisions should be based on what is best for you though, not what happened to someone else.