A systematic review compared complications and revision rates between cemented polyethylene glenoid (PEG) versus three modern designs of metal-backed glenoids (MBG) used in total shoulder arthroplasty.
“Although numerous studies on total shoulder arthroplasty (TSA) have aimed to find the optimal TSA design, no definite conclusions have been made. The glenoid component of TSA is divided into keel type and peg type according to its shape, and can be made of all polyethylene (PE) or be metal-backed. Both metal-backed glenoids (MBG) and cemented polyethylene glenoids (PEG) were initially used, however due to the nature of the initial MBG design, the polyethylene liner was very thin and resulted in a high wear and failure rate,” the researchers wrote. Previous research observed that MBGs resulted in high rates of failure, so the advanced MBGs were designed to combat that.
For the present study, published in BMC Musculoskeletal Disorders, the researchers queried PubMed, Cochrane Library, EMBASE, and Google Scholar. Modern MBG articles were located using search terms “total AND shoulder AND (replacement OR arthroplasty) AND (metal OR backed OR (cementless glenoid))”; cemented PEG articles were found using search terms “total AND shoulder AND (replacement OR arthroplasty) AND polyethylene.”
The searches yielded 1,186 articles for consideration. Articles were stratified into three groups based on length of follow-up: <36 months, 36–72 months, and >72 months.
Modern Metal-Backed Glenoids Lead to Favorable Outcomes
Final analysis included 35 articles encompassing data on 3,769 shoulders. Most studies (n=25) evaluated cemented PEG; the remaining 10 focused on the modern MBG. Mean age of patients in the PEG group was 66.4 years, and in the MBG group was 66.5 years; mean length of follow-up was 73.1 months and 56.1 months, respectively. The PEG group and MBG group presented the following outcomes: rate of the radiolucent line, 354/1302 (27%) vs. 47/282 (17%); loosening rate, 465/3185 (15%) vs. 22/449 (5%); and failure rate, 189/3316 (6%) vs. 11/457 (2%), respectively. In the <36-month and 36–72-month subgroup analyses, radiolucency and loosening rates were lower in the cemented PEG group, but failure rates did not largely differ. MBG had better loosening and failure outcomes in the >72-month subgroup.
“The modern MBG component, especially TM glenoid, seems to be a promising alternative to cemented PEGs, based on subgroup revision rates according to the follow-up duration and overall results of ROM and clinical scores. All polyethylene glenoids tend to increase loosening and failure over time,” the study authors concluded. They called for future studies to conduct longer-term analyses.
