Non-screw glenoid augmentation constructs for shoulder instability with bone loss: A biomechanical assessment of static and elastic cerclage constructs

Abstract

Purpose

This study aims to compare the biomechanical performance of elastic and static suture-based cerclage systems to traditional screw constructs in the setting of modeled glenoid bony augmentation.

Methods

Biomechanical testing was conducted on polyurethane cellular foam blocks modeling a 20 % glenoid defect repaired with a coracoid graft. Constructs consisted of an elastic suture-based cerclage, static suture-based cerclage, and a two-screw construct. Biomechanical testing was performed on material testing system, using a 7-phase, 100 cycle per phase, 1Hz, sinusoidal cyclic loading protocol, following a stair-step pattern in load control. Failure for cyclic loading was assessed at 0.8 mm linear displacement. The absolute end level for load-to-failure was 7.0 mm.

Results

Static suture-based cerclage failed at 5–50 N (Cycles 2 through 4), 2-screw constructs failed at 25–50 N (Cycle 4), and elastic suture-based cerclage failed at 100–200N (Cycles 6 and 7). Elastic cerclage exhibited superior performance compared to static cerclage beginning in Cycle 2 (p = 0.0440) and compared to SOC 2-screw construct beginning in Cycle 4 (p = 0.0118). 2-screw construct exhibited superior stability performance compared to static cerclage beginning in Cycle 3 (p = 0.0001). Elastic cerclage reached failure at 558.141 ± 4.508 N, while 2-screw construct and static cerclage reached failure at 422.009 ± 24.998 N and 366.770 ± 66.653 N, respectively. Elastic cerclage demonstrated superior biomechanical stability in load-at-failure performance to static cerclage (p < 0.0001) and the screw construct (p < 0.0001), while static cerclage demonstrated inferior biomechanical stability to the screw construct (p = 0.0343).

Conclusion

This biomechanical study comparing the performance of elastic cable and static suture tape cerclage fixation methods identified that the elastic cable cerclage exhibits a higher load-at-failure and less displacement under repetitive stress. In addition, elastic cable cerclage fixation exhibits greater strength and construct rigidity than traditional metal screw fixation.