Eccentric reaming is superior to augmented components in B2 glenoids: a biomechanical study

Abstract

Background

Primary glenohumeral arthritis is typically associated with glenoid retroversion and posterior bone loss. Glenoid component fixation remains a weak link in the survivorship of anatomical total shoulder arthroplasty, particularly in the B2 glenoid. The aim of this study was to compare biomechanical properties of 2 glenoid preparation techniques in a B2 glenoid bone loss model.

Methods

This was a biomechanical cyclic loading study. Thirty sawbone shoulder models were generated from a computed tomography scan of a scapula with a B2 glenoid and 15° retroversion. The study consisted of 2 groups with ‘low’ correction (A groups), 2 groups with ‘high’ correction (B groups), and a control. Group A1 consisted of a 7° eccentric ream and a standard component; group A2 consisted of a 15° posteriorly augmented glenoid component (7° correction); group B1 consisted of a 12° anterior ream and standard component; group B2 used a 25° posteriorly augmented component (12° correction); group C (control) consisted of a standard component inserted in retroversion with no correction. Mechanical stability testing was performed through cyclic loading and resulting displacement was determined at 1, 10, 1000, 10,000, 50,000, and 100,000 cycles to assess for loosening.

Results

A total of 26 samples were included in the analysis, all reaching 100,000 cycles. Displacement increased significantly from baseline to 100,000 cycles in all groups (P < .05). At 100,000 cycles, the B1 group (1.4 mm ± 0.19) had significantly less displacement then the A2 (2.0 mm ± 0.29) and B2 (2.2 mm ± 0.49) (P = .0.005) groups. There were no significant differences in translational forces between any of the groups at 100,000 cycles.

Conclusions

Our data demonstrated that the use of higher degree posteriorly augmented components resulted in statistically greater translational displacement over time compared with high-side reaming and use of a standard component. Further prospective clinical studies are needed to confirm these findings.