In severe cases, fractures can be repaired by means of a shoulder replacement procedure. There are several types of shoulder replacements, the most common of which is a hemiarthroplasty shoulder replacement. During this procedure the humeral surface of the joint is replaced with a metal ball and the socket is left as is. These artificial components are typically pressed into the bone with surgical cement. It may also be inserted with an uncemented technique. This procedure is generally recommended if he humeral head is fractured, but the socket is not degenerative. In certain cases the stabilising muscles around the shoulder called the rotator cuff muscles are deficient and in those cases a reverse replacement will be performed. It is simply a reversal of components that places the socket of the joint where the ball used to be, and the ball where the socket used to be.