The eburnated bone-cement interface

Background: The cement-bone interface has been well studied as the weakest link where initiation of long-term aseptic loosening occurs in cemented arthroplasty. During total knee replacement, one is often confronted with eburnated bone in patients with severe arthritis. We aimed to study shear strength of the eburnated cement-bone interface and the effect of varied surface topology of eburnated bone on this interface strength. Methods: We used blocks of ebony wood to simulate eburnated bone. They were engineered to produce three surface topologies: smooth, drill holes, and cross-hatch pattern. These were cemented to metal (steel) blocks. Each specimen was then mounted onto a loading machine that created a shear force at the simulated cement-bone interface. Force displacement curves were recorded for all specimens until interface failure. Results: The smooth surfaced blocks were found to fail at the cement-wood (bone) interface at an average force of 0.5 MPa. Both the other surface topology alterations resulted in an increased ability to withstand force (average 3.7 MPa) before failure. Examination of the failed specimens revealed a combination of failure at both interfaces as well as cement deformation. Conclusions: One must alter the smooth surface of eburnated bone when dealing with bone defects in cemented arthroplasty. The pattern employed does not make a difference to the strength of the construct. The resulting mechanical bond of the cement with bone is as strong as any component in the metal-cement-bone construct.