GLENOID COMPONENT – METAL BACKED CEMENTLESS

Evidence to Decision Framework: Recommendation upgraded from limited to moderate because of a very low reported survivorship rate. 

Different modes of failure have been observed with metal backed as compared to all polyethylene components. These include gross loosening and catastrophic implant failure resulting in severe glenoid bone lose, rapid polyethylene backside wear with metal on metal contact and significant metal debris.

Metal backed cementless glenoid components have been abandoned due to poor outcomes, high revision rates and catastrophic glenoid implant failure. Gauci et al. 2018, reported a 70% failure rate with need for revision surgery and 24% survivorship at 12 years for cementless metal backed glenoid components. This is compared to 74% survivorship in the cemented polyethylene glenoid group. Modes of failure reported included polyethylene wear with metal on metal contact, instability, and rotator cuff failure. Those with preoperative posterior humeral head subluxation with a biconcave retroverted glenoid (Walch B2) were most at risk for metal backed glenoid implant failure. Clitherow et al. 2014, also reported 4.4 times higher revision rate of uncemented metal backed glenoid implants as compared to cemented all polyethylene components (P<0.001) at mean follow-up of only 3.5 years. The results from the Australian National Joint Registry Page et al.⁶⁰ also supports these findings with revision rate of 17.9% for uncemented metal backed glenoid components (Hazard Ratio 4.77; 95%CI 4.10-5.55, P<0.001) compared to 3.7% for cemented glenoid components. This data has led to most implant companies in the united states removing metal backed cementless glenoid components from the market.

Strength of Evidence (quality of evidence): Limited

Benefits & Harms:

76% failure rate; studies report ceasing use because of unfavorable outcomes.

Outcome Importance:

Critical to have knowledge of poor results associated with uncemented metal backed glenoid components.

Cost Effectiveness/Resource Utilization:

Avoidance of use of any implant with a high failure rate will prevent increased costs and additional resources need to correct these issues.

Acceptability:

This data is well known and currently metal backed cementless glenoid implants are not used.

Feasibility:

Already part of standard practice not to use as well as understanding of failures of metal backed glenoid.

Future Research:

Future studies are needed to develop and design new glenoid implants if metal backed cementless implant concept is to be pursued with a goal of improving the survivorship of the glenoid.