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.

Aim: A comparative in vitro study to identify which knot conþguration is the strongest and most secure in orthopaedic surgery. Background: It has been proven that monoþlament sutures are less damaging to soft tissues than multiþlament (braided) ones. However braided sutures are still popular with orthopaedic surgeons. It is thought that this is due to the knot-holding properties of braided materials. Methods: Four commonly used surgical knots were tied on a novel knot-testing rig by the same operator. They were subjected to a series of static (n=300) and pulsatile (n=380) forces in different environments, to simulate anticipated physiological demands. These tests were performed on both absorbable and non-absorbable sutures in both mono-þlament and braided form. Results: These 680 knotting tests show that the surgeonsñ knot is not always the best option in every situation and that surgeons should have a range of knots in their arsenal. Conclusions: This study has shown that monoþlament sutures can be as strong and reliable as braided materials if tied with appropriate knots. Therefore, by using a variety of knotting techniques, a surgeon may rely more heavily on monoþlament sutures, thereby reducing the soft-tissue trauma and infection risk that braided sutures involve.