Biomet Cementing University

Dr Thierry Scheerlink

Dr. Thierry Scheerlink, MD
Prosthesis team
Department of Orthopaedics and Traumatology
AZ-VUB
Brussels
Belgium

Optimising cement mantle quality through adequate bone preparation, correct cement handling and proper implant selection - a much debated topic

Improving cement - bone interdigitation
Cement interdigitation into strong trabecular bone is crucial and can be enhanced by proper bone preparation and cementing technique. Removal of all debris (fat, blood and week or loose bone) after broaching is best performed with the aid of a brush and most important pulsed lavage. Before cement insertion, it is important to keep the bone bed as dry as possible to avoid entrapment of blood between the bone and the cement.

Cement interdigitation can also be enhanced by correct timing of cement insertion. If the cement is inserted too early, its low viscosity will not prevent backflow of blood from the trabecular bone. If the cement is inserted too late, its viscosity will be too high to allow it to flow into trabecular bone. Retrograde cement injection with a cement gun allows for good filling of the femoral canal at the distal part of the stem, which typically is difficult to achieve when finger packing the cement.

Cement pressurisation plays a major role in improving cement interdigitation into cancellous bone. After the cement is injected, the proximal femur is sealed and cement pressure is increased and then maintained until insertion of the stem. During insertion of the stem, placing a finger at the level of the calcar will help prevent various stem position and will limit cement outflow and dropping of the intramedullary pressure. Maintaining high intramedullary cement pressure is important throughout - before stem insertion, during stem insertion and up to full cement cure.

The implant - cement interface
The implant - cement interface is often neglected, but its role should not be underestimated. It is important that the upper surface of the cement is clean and dry to avoid debris being interposed between implant and cement. For the same reason, stem insertion should be performed slowly and steadily, preventing air from getting into the cement. If the cemented stem is undersized compared to the femoral canal or the broach, it should be kept strictly immobile during cement curing. The slightest movement before cement curing could create a cavity compromising mechanical implant stability.

Cement mantle thickness - a much debated topic
Cement mantle characteristics are dictated by bone preparation and cement pressurization. The shapes of the broach and the implant and their respective difference in size are important as well. Good long-term results have been published for femoral hip implants cemented with a “thin” cement mantle as well as for those surrounded by a “thick” cement mantle. However, respecting the attributes and design philosophy of each implant is crucial.