Creating cement keyholes (i.e. drilling simple holes in cancellous bone to allow cement filling) is a practice used in multiple scenarios in orthopaedic surgery to ensure improved fixation between the bone-cement interface and as such between bone and prosthesis. It is most commonly used in hip arthroplasty to secure fixation of the cup to the acetabulum by drilling keyholes in acetabulum. However very little research has been conducted into what the dimensions of such cement keyholes should be. The following laboratory based research was performed to provide insight into the optimum dimensions of cement keyholes.

The investigator designed a novel arrangement to enable testing of keyholes. Beechwood block models were then made to this design testing keyholes of varying diameters and depths. These were cemented with acrylic bone cement and then loaded to failure. A finite system analysis was also performed.

Results show that stresses are concentrated at the base of the keyhole. As such increasing diameter of keyhole infers greater strength, but there is no relationship between depth and strength. This has been further confirmed with finite element analysis. We suggest the width of cement keyholes bears more importance than the depth and propose drilling wide but shallow keyholes.