Surgeon offers advice for optimal cement fixation in primary total knee arthroplasty
He notes that surgeons should consider cementing and pressurizing both the surface and tibial stem.
Several controversies surround the fixation of primary total knee arthroplasty. At the 9th Annual Current Concepts in Joint Replacement Spring 2008 Meeting, Douglas A. Dennis, MD, offered his tips for cementing the perfect knee.
Total knee arthroplasty surgeons, who continue to debate the merits of cemented vs. uncemented components, disagree on whether to obtain fixation with central metaphyseal stems or short condylar pegs and whether both the condylar surface and the metaphyseal stem or the surface alone should be cemented.
My review of the literature still states that cement remains the gold standard of primary total knee arthroplasty fixation, Dennis said. Fixation with condylar pegs can be as good as cementing the plateau and central stem, but only if you have good uniform cement penetration of 3 mm, which is often not obtained. Therefore, full cementation of both the plateau and stem is better.
Dennis cited a study by William J. Maloney, MD, that showed a 14.4% loosening rate at a 5-year minimum follow-up of 97 total knee replacements (TKR) with surface cementation alone. Histology studies reveal excellent cement penetration in the central portion of the tibial plateau, Dennis said. However, there is inconsistent penetration peripherally as the cement can escape and, therefore, you get less penetration, he said.
To obtain the best cement fixation, surgeons must first obtain a good surgical exposure and drill the sclerotic bone to enhance the cement penetration (Figure). Use a tourniquet if there is no vascular compromise, Dennis said. He then uses a pulsatile lavage to clean the bone. Do not forget to clean the posterior aspect of the femur. Most studies show that femoral component loosening typically initiates from poor fixation of the posterior femoral condyles.
He carefully dries the bone interface to allow the cement to directly bond with the bone. I like to pressure-inject the bone using a cement gun, particularly at the periphery of the tibia. This provides a good peripheral seal to retard later ingress of osteolytic micro-particulate debris into the tibia, Dennis said. I would encourage you to consider cementing and pressurizing both the surface and tibial stem. He noted that the bone is weak centrally and not pressurizing the surface and the stem could lead to decreased fixation.
Dennis coats the back of the components with cement to decrease fat intrusion at the prosthesis-cement interface. You then firmly and uniformly impact the components, maintaining the pressure until the cement is cured, he said. Then, you want to carefully clear excess cement by cutting and removing it in large fragments and to try to avoid the creating a lot of micro-particulate cement debris, which may enhance third-body wear of the articulating surfaces.
He re-dries the posterior femoral condyles after the tibia is dislocated. Similarly, he coats the back of the component to limit bone marrow fat penetration. I typically will place a tibial trial insert before I complete impacting that component, because I do not want to create any scratching of either the tibial tray or femoral component, Dennis said.
After you have extended the knee, it is very common to get additional cement expressed from both components, Dennis said. I will subsequently perform a secondary cleaning. On the patella, if you have resected it properly, you will often cut through the subchondral bone of the lateral facet.
He will often perforate the sclerotic bone on the lateral facet of the patella and cement the patella in a routine fashion.
Image: Dennis DA
For more information:
- Douglas A. Dennis, MD, can be reached at Colorado Joint Replacement, 2535 S. Downing St., Suite 100, Denver, CO 80210; 720-524-1367; e-mail: firstname.lastname@example.org. He has indicated that he is a consultant and receives royalties from DePuy.
- Dennis DA. Cementing the perfect knee: Still a majority requirement. Paper #48. Presented at the 9th Annual Current Concepts in Joint Replacement Spring 2008 Meeting. May 18-21, 2008. Las Vegas.
- Maloney WJ, Clohisy J. Premature failure of surface cementation technique in primary total knee arthroplasty. Presented at the 2002 Annual Meeting of the American Academy of Orthopaedic Surgeons. Feb. 13-17, 2002. Dallas.