The incidence of total shoulder arthroplasty continues to increase. The most common reason for failure of a total shoulder arthroplasty is the glenoid component. Two styles of cemented all-polyethylene components are commonly implanted. These two styles are pegged glenoid and keel glenoid components. Data regarding the superiority of the styles has focused on radiolucent lines, complete loosening and need for revision procedures. Several retrospective and randomised controlled trials have been published to examine these endpoints. There is a trend in the literature to demonstrate decreased rates of radiolucent lines with pegged glenoid components, but a recent systematic review of available trials did not demonstrate a significant difference in the rate of radiolucent lines between the two styles. A slightly increased rate of revision was noted for the keel components. Overall pegged and keel glenoids both still represent good options in total shoulder arthroplasty

Radiolucent lines in total shoulder arthroplasty around the glenoid component are not uncommon in post-operative x-rays and the incidence varies. A certain percentage progress and as the lines enlarge can lead to component loosening. One study reported a 9% incidence at 2 years and 27% incidence at 5 years. A recent long term study (15 to 20 years) reported a 73% incidence. Radiolucent lines can be caused by anatomy (posterior glenoid wear) or pathology (inflammatory arthritis) as well as technical factors such as glenoid implant design (metal back) and improper implantation techniques where the prosthesis is not fully seated or cement is used to fill a defect. Every attempt should be made to avoid lucent lines. Minimal bone should be removed from the glenoid vault and a pressure injection type of insertion is helpful in getting the cement into the cancellous bone. Furthermore a peg type of glenoid implant rather than a keel type is preferred as this has been associated with a lower incidence of radiolucent lines