Heterotopic Ossification was once a problem in ADR surgery. It is the growth of osteophytes outside the normal, healthy boundaries of the bone. In the spine this can result in bone spurs, and auto fusion.

Some of the early patients with cervical artificial disc replacement began to experience heterotopic ossification in the form of auto fusion, i.e. bony bridging around the artificial disc replacement between the two vertebrae. Such a fusion within a cervical ADR appears not to result in clinical symptoms – motion is lost over time to create an unwanted fusion. But there is no nerve compression etc. from this.

Due to surgeon feedback to the manufacturers, implants have been redesigned by some manufactures, widening the endplates of their cervical artificial disc to the point, where they cover nearly the entire endplate of the vertebrae.

This is no problem with auto fusion in lumbar artificial disc replacement patients with today`s models and surgical technique (there are reports from the late 1980ies surgeries).