Shoulder resection arthroplasty is surgery performed to repair a shoulder acromioclavicular (AC) joint. The procedure is most commonly recommended for AC joint problems resulting from osteoarthritis or injury.

A resection arthroplasty involves the surgical removal of the last 0.5 in (1.3 cm) of the collarbone. This removal leaves a space between the acromion and the cut end of the collarbone where the AC joint used to be. The joint is replaced by scar tissue, which allows movement to occur, but prevents the rubbing of the bone ends. The end result of the surgery is that the flexible connection between the acromion and the collarbone is restored. The procedure is usually performed by making a small 2 in (5 cm) incision in the skin over the AC joint. In some cases, the surgery can be done arthroscopically. In this approach, the surgeon uses an endoscope to look through a small hole into the shoulder joint. The endoscope is an instrument of the size of a pen, consisting of a tube fitted with a light and a miniature video camera, which transmits an image of the joint interior to a television monitor. The surgeon proceeds to remove the segment of collarbone through a small incision with little disruption of the other shoulder structures.

From http://www.answers.com/topic/shoulder-resection-arthroplasty