Over the past ten years shoulder replacement designs have significantly changed on the humeral side. In a traditional shoulder replacement design the humeral implant is held in place by a "stem" which goes down the center of the humerus (arm bone). This design has worked very well since the original shoulder repalcements were introduced in the 1950's. Recently there has been alot of interest in developing implants that either have a shorter stem or no stem at all.
Short stem and stemless designs are often promoted as being minimally invasive, requiring less surgical time, causing less pain and less blood loss. All of these claims sound good but in reality there aren't many true advantages of smaller stem designs. The surgeyr is really no less invasive. The only real advantage of these implants is that they are much, much easier to remove if a revision needs to be done in the future. It can be very difficult to remove a long stem implant and often requires an osteotomy which means breaking the bone open to get the stem out. With short stem and stemless designs the implant can be removed with much less trauma if a revision is required in the future. For this reason alone I now use a short stem design for almost all of my shoulder replacements.