Impact of polyethylene glenoid cementation technique on cement mantle integrity and stability after cyclic loading: a CT and biomechanical study.

BACKGROUND: There are no generally accepted guidelines for polyethylene (PE) glenoid component cementation techniques. In particular, it is not known whether the backside of a PE glenoid should be fully or partially cemented, or not cemented at all. We hypothesized that cementing technique has an impact on cement mantle volume and integrity as well as on biomechanical stability, measured as micromotion under cyclic loading.

METHODS: To address this question, three different cementation techniques of a single two-peg PE glenoid design into a polyurethane foam were compared with regard to (a) the quality and quantity of the cement mantle and (b) the biomechanical stability after cyclic loading in vitro. Eight identically cemented glenoids per group were used. Group A with cement application only into the peg holes, group B with additional complete cement mantle application on the backside of the glenoid and group C as group B but with additional standardized drill holes in the surface of the glenoid bone for extra cement interdigitation. All glenoids underwent cyclic edge loading by 105 cycles according to ASTM F2028-14. Before and after loading, cement mantle evaluation was performed by Xtreme CT and biomechanical strength and loosening were evaluated by measuring the relative motion of the implants.

RESULTS: The cement mantle at the back of the implant was incomplete in group A as compared to group B and C, in which the complete PE backside was covered with a homogenous cement mantle. The cement mantle was thickest in group C, followed by group B (p=0.006) and group A (p<0.001). We did not detect any breakage of the cement mantle in any of the three groups after testing. Primary stability during the cyclic loading was similar in all groups after the running-in phase (up to 4,000 cycles). Gross loosening did not occur in any implant.

CONCLUSIONS: Coverage of the PE glenoid with cement was reproducible in fully cemented groups B and C as compared to relevant cement defects in the group A. The addition of cement to the back of the PE glenoid and additional drill holes in the glenoid surface did not improve primary stability in the tested setting.