High Complication and Revision Rates in Anatomical Total Shoulder Arthroplasty with the Combination of Polyethylene and Cementless Convertible Metal-Backed Glenoid Components: A Retrospective Cohort Study.

BACKGROUND

Historically, Metal-Backed (MB) glenoid components in anatomical total Shoulder arthroplasty (aTSA) are prone to failure primarily due to loosening between the metal and bony surface. However, newer generations of MB glenoid components have performed well in reverse shoulder arthroplasty (RSA), with convertibility being considered to be the most significant benefit of MB components. Theoretically, MB components may be a viable option in "Rotator cuff at risk" cases. The aim of this study is to compare revisions versus revision-free survivorship and highlight problems associated with using convertible MB glenoid components in aTSA.

METHODS

Between December 2015 and September 2018, aTSA was performed on 30 patients utilizing 32 implants with convertible MB glenoid (two patients were operated bilaterally). The first investigation was performed at a mean of 55.9 months (43-76) by search in the national registry for revisions with twelve cases. The second FU on all remaining patients without revisions was conducted at a mean of 54.9 months (46-71) through physical examination with fourteen patients (sixteen implants), with four patients missing. Demographic data, indications, complications, revisions, and re-operations were recorded for each patient.

RESULTS

High rates of complications led to revisions or re-operation in aTSA in combination with MB (15/32). Seven problems were associated with polyethylene (PE), which included loosening, disengagement, or wear. Eight complications were not directly associated with the MB component. There was one with loosening on the metal-bone interface side. Conversion to RSA was possible in three cases, and secondary cuff failure was seen once. High infection rates (2/32) led to a different strategy for antibiotics and preoperative preparations.

CONCLUSION

MB glenoid components caused unacceptably high complication and revision rates in aTSA. PE wear, disengagement, or loosening were the main reasons for revisions. Therefore, procedures with MB glenoid components were abandoned in aTSA.

LEVEL OF EVIDENCE

Level IV case series, treatment study.