Q: My mother fell out of bed and broke her upper arm. She will need a shoulder replacement. She has a choice of the traditional ball in socket joint or the new reverse arthroplasty. Can you give us some idea why one might be better than the other?

A: Shoulder fractures in older adults are definitely on the rise. The upper arm bone your mother broke is called the humerus. A sudden fall from bed or even from a standing position can generate enough force to break the humeral shaft away from the humeral head. Sometimes the humeral head splits into multiple parts at the same time.

Surgery is often needed to repair or replace the shoulder. Younger patients in good health and active are more likely to have salvage surgery (save rather than replace the joint). Older patients (70 years old and older) are more likely to need a joint replacement.

The use of a reverse arthroplasty has been the implant of choice for inactive patients aged 70 or older with severe osteoporosis and now a severe fracture. In this type of implant, the ball portion of the shoulder is put where the socket used to be and the socket now goes where the ball or humeral head was located.

Patients with fracture and poor muscle function (often caused by an old unrepaired rotator cuff tear) are also good candidates for the reverse arthroplasty. The design of the reverse arthroplasty creates a much more stable shoulder joint that can function without a rotator cuff.

Certain types of fractures that aren't likely to heal seem to do well with a reverse shoulder arthroplasty. Sometimes a hemiarthroplasty is done but fails. Then it is replaced with a reverse shoulder arthroplasty. A hemiarthroplasty is the replacement of just one side of the joint -- either the head of the humerus or the cup that forms the socket).

Patients receiving a total shoulder replacement must be alert and able to participate in an active rehab program after surgery. Older adults who are inactive and perhaps who have some cognitive (thinking, memory) problems are good candidates for the reverse replacement.

Reference: James E. Voos, MD, et al. Arthroplasty for Fractures of the Proximal Part of the Humerus. In The Journal of Bone & Joint Surgery. June 2010. Vol. 92-A. No. 6. Pp. 1560-1567.