Abstract
Total shoulder arthroplasty with a cemented polyethylene glenoid is a proven technology with excellent survivorship, even in young, active patients followed for over 20 years.
Despite numerous efforts to avoid cement fixation, uncemented technology has failed to improve survival even in the short and middle term, and in fact has usually yielded worse results at early follow-up – hardly promising that further follow will reveal an advantage.
There have been two approaches – metal-backed designs and all-poly “magic peg” designs. There are two major problems with metal backing: there can be technical issues and fretting failure with snap-fit mechanisms, and the stiff metal backing induces early polyethylene wear. Although some early studies report cautious optimism, larger series with careful, long follow-up have reported poor results. Some have attempted to use less-stiff metal but the value is still unclear. While early results from all-poly uncemented designs have less early failure, the wisdom of having long-term close apposition of polyethylene with bone, the large bone-removal for most large-peg designs, and the unknown long-term mechanical failure mechanisms suggest caution.
Further, early work on eliminating cement was prompted by a desire to avoid “cement disease”, while more recent studies across multiple joints suggest that loosening and bone resorption are more likely due to polyethylene particles than any effect of the cement. Since most uncemented designs stiffen the basic polyethylene surface with larger pegs or metal-backing, the wisdom of the entire effort is debatable. In 2016 optimal glenoid fixation requires cement.
