I went with my father to the orthopedic surgeon to see about getting him a shoulder replacement. The doctor talked about a partial replacement. What’s the advantage of that over a total replacement?

The shoulder is a ball and socket joint. Replacing just the top of the humeral head (ball) or just the socket (glenoid) is called a hemiarthroplasty. Most of the time only the humeral head is replaced in a hemiarthroplasty.

The benefits of hemiarthroplasty include less time in the operating room, less cost, and less blood loss. Smoothing and replacing the glenoid side increases the risk of problems. The glenoid implant is also more likely to pull loose.

Most patients get good results with humeral head replacement. They report pain relief and improved motion and strength. The overall positive outcome is improved function for daily activities.

Hemiarthroplasty is advised for younger, more active patients who have a good glenoid surface. Balanced muscle strength around the joint is also important. The only red flag about hemiarthroplasty is the result of recent long-term studies. It seems the good results deteriorate over time. Studies comparing partial to total shoulder joint replacement are looking to see if it wouldn’t be better in the long run to start with a total joint replacement.