The main goal of interposition surgery is to ease pain where the surfaces of the elbow joint are rubbing together. A piece of tendon or other soft tissue forms a “spacer” that separates the surfaces of the joint. Interposition arthroplasty is different than a fusion surgery. Fusion simply binds the joint together, and the elbow loses much movement. Interposition arthroplasty can help take away pain while allowing the elbow joint to retain some movement.