Prosthetic Bearing Surfaces in an Anatomic and Reverse Total Shoulder Arthroplasty
Perhaps the most robust clinical data comparing total shoulder bearing surfaces comes from the Australian Orthopedic Association (see this link). The graph below shows less than 5% revision rate at 11 years using cross linked polyethylene in comparison to a greater than two-fold increased revision rate for non cross linked poly. These data provide a sound benchmark for comparison of alternative bearing surfaces.
This review describes some of the newer types of bearing surfaces, including those treated with vitamin E processing, ceramic heads, and pyrolytic carbon surfaces. The preponderance of this information comes from in vitro wear testing and so far no clinical data have been presented demonsrating superiority of the newer approaches over the outcomes shown in the graph above.
(1) Vitamin E-enhanced cross-linked polyethylene in model anatomic TSA had a 36% reduction in wear rates in the vitamin E-enhanced components compared with those without vitamin E processing.
(2) Although some evidence exists showing improved wear rates using ceramic heads, further data are needed to establish recommendations for both anatomic and reverse total shoulder arthroplasty. N.B., these components are not approved by the Food and Drug Administration.
(3) No published literature exists on the use of metal-on-metal interface in anatomic shoulder arthroplasty.
(4) There is little information regarding the use of a pyrocarbon bearing surface in either anatomic and reverse TSA
To put this information in perspective we should remember that glenoid component failure is determined by a number of factors that are more important than wear rates, including surgical technique (bone preparation, seating, cementing, glenohumeral stability, humeral component positioning), rotator cuff integrity, diametral mismatch of the articular surfaces, and presence or absence of metal-backing.