CEMENT PRESSURISATION R. Bhattacharya, F. Attar, S. Green, A. Port James Cook University Hospital, Middlesbrough & University of Durham FLANGED CUP UNFLANGED CUP VS. KREIBICH PRESENTATION 2007

INTRODUCTION Aseptic loosening of acetabular component is a common reason for revision surgery. Cement pressurisation has been shown to improve fixation. Sustained pressurization more important than peak pressure. Flanged cups first introduced in 1976 to improve cement pressurisation.

PREVIOUS STUDIES Oh, Sander, Treharne Unflanged, flanged, flanged with scallops, sunk to predetermined depth Flanged cups generated higher peak pressures and intrusion pressure Higher loading forces used to insert the flanged cups Shelley & Wroblewski Flanged and unflanged Flanged cups generated higher peak and intrusion pressure Parsch, Diehm et al Flanged and unflanged Higher peak pressure with flange but no difference in mean pressure Bannister et al 2007 (BHS). Unflanged and flanged, sunk to predetermined depth Flanged cups generated more peak pressure

AIM To evaluate difference in cement pressures (peak and mean) generated by flanged and unflanged acetabular cups.

MATERIALS AND METHODS Biomechanical study simulating clinical situation as far as practicable. Model metal acetabulum with 3 holes for pressure transducers. Cement inserted and pressurised followed by cup insertion and pressurisation. Constant static pressure of 70N generated using Lloyd Davis machine (70 N is the force that is comfortably maintained in clinical practice, shown by our pilot and previous paper). Pressure recorded using piezoelectric transducers.

MATERIALS AND METHOD 3 types of cups compared: Charnley Ogee (flanged) Exeter low profile (unflanged) Exeter contemporary (flanged) 3 sets of experiment with each type using Simplex. Repeated using CMW1. Continuous pressure reading till end of cement polymerisation.

Piezoelectric transducers

Metal acetabulum with single piezoelectric transducer in place

Lloyd Davis machine with cement pressuriser

Metal acetabulum with single pressure transducer in place Cement Pressuriser Cups The Set-up

RESULTS With Simplex Peak Pressure: Charnley Ogee > Exeter Flanged (significant) Charnley Ogee > Exeter Unflanged (significant) Exeter Unflanged > Exeter Flanged (not significant) Mean Pressure: Charnley Ogee > Exeter Flanged (significant) Charnley Ogee > Exeter Unflanged (not significant) Exeter Unflanged > Exeter Flanged (not significant)

With CMW No significant difference between the pressures (peak or mean) generated by the 3 cups. However, here also, Exeter contemporary flanged cup generated the least amount of cement pressures (peak and mean).

EXPLANATION OF RESULTS Ogee flange soft, everts out. Exeter flange harder but the beads prevent effective pressurisation. Different cements behave differently.

SUMMARY OF RESULTS Flanged cups do not consistently generate significantly higher pressures compared to unflanged cups. The beads on the outer side of the Exeter flanged cups designed to prevent bottoming out, also prevent effective pressurisation.

CONCLUSION “There’s many a slip between the CUP and the LIP” !!

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