TIP OF THE MONTH: August/September 2013
Bone Slurry: Superior Fixation for Cementless TKA
Second-Place Winning Article, 2013 Paper of the Year Competition
by Theresa Pecina, OTC, ST
In our constantly busy total joint replacement practice, we carry out approximately ninety percent of all the primary total knees using a cementless knee system that promotes bone ingrowth into the prosthetic femoral and tibial components. Studies with a ten-year clinical follow-up have shown that cementless Total Knee Arthroplasty (TKA) using morselized autogenous bone chips, or slurry, as biologic cement, can yield excellent results (Hofmann, Scott, 2002). In a study executed by Dr. Aaron Hofmann, patients consented to a staged bilateral TKA, where slurry was applied to one knee, and not the other. The implants were removed at the second TKA six to 49 weeks later, and back scattered electron imaging showed significantly more bone in the porous coating of the implants treated with slurry (Hofmann, Bloebaum, Rubman, Bachus, Plaster, 1992). Hofmann considered it free bone morphogenetic protein (BMP), and felt it made a significant positive impact on the patient’s recovery (Hofmann 2007).
As a result of our literature review, we have devised a system to obtain a “slurry graft” which generates the consistency needed to improve adherence to the implant interface of both the femoral and the tibial components. The slurry graft also has the capability to be used on non-cemented patellar prosthetics. The items needed for the slurry harvest procedure include a sigmoid suction tubing set, a sterile suction trap, and a patellar reaming device The sigmoid tip is important because the marrow deep in the femoral canal is rich in BMP (Hofmann, 2007).
To prepare for the graft harvesting procedure, the surgical scrub needs to cut off the end of the sigmoid suction, leaving the curve intact.
The tubing that comes attached to the suction tip is not necessary, and can be discarded. On the back table, the scrub may choose to place extra toweling to protect the integrity of the back table drape, and can have the patellar clamp and reamer set up for fast use.
While the surgeon is accessing the femoral and tibial intramedullary canals using the large starter drill, the scrub will connect the sigmoid suction to the suction trap, and then to the primary suction. The sigmoid suction is then passed into the femoral canal as far as possible, being careful to keep the trap upright to avoid losing the graft to the suction canister. This action may require several in and out passes in pursuance of maximum bone marrow collection. The scrub may then also suction up any finely ground cancellous bone that is produced by the drilling of the canals.
The items needed for the slurry harvest procedure include a sigmoid suction tubing set, a sterile suction trap, and a patellar reaming device.
The suction trap is then disconnected from the suction tubing, and placed in an upright position on the back table to “rest”. Once the surgeon has resected the distal femur, the two pieces can then be saved on the back table for harvesting. Place one of the two pieces in the patellar clamp, and begin reaming it with the patellar reamer, saving all the fine cancellous bone possible and placing the reamings into a medicine cup (exhibit 3).
Repeat the above process using the bone from the proximal tibia resection, and also with any other large pieces of bone that will fit into the patellar clamp. If there is no patellar reaming system available, the scrub can scrape the back of the bone with a large curette. It is important to be sure the graft harvested is of a fine consistency of cancellous bone, avoiding having any cartilage incorporated into it (exhibit 4). When the marrow collected from the femoral canal has “rested” for a while, fat will begin to form at the top of the aspirated fluid. This is then carefully poured off and discarded, leaving the good marrow in the suction trap. Mix the finely ground bone with the marrow to produce the slurry graft. This is then left to sit briefly, allowing any fat to accumulate at the top, where it can again be carefully poured off. The desired consistency of the remaining slurry should be approximately that of a granular paste, similar to that of tomato paste. There should be no large chunks of bone, or cartilage present (exhibit 5).
In preparation for implantation, a freer or a cobb elevator can be used to coat the back of the implants with a fine layer of slurry, being careful not to apply an excessive amount (exhibit 6). This technique can cause a fair amount of splatter when implanting, so surgery team members must take the appropriate steps to ensure their protection. After implantation, any extra slurry is then carefully irrigated away.
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About the Author
Theresa Pecina has worked for Johnson County Orthopedics at Olathe Medical Center in Olathe, Kansas for 25 years as their private scrub/ Orthotech. Pecina loves working in surgery, but also enjoys being in the office, and working with patients. Janet Scalet, Dr. Bohn’s nurse practitioner, also helped contributed to this article.
• Bloebaum, Roy D, Rubman, Marc H, Hofmann, Aaron A. “Bone Ingrowth into Pourous Coated Tibial Components Implanted with Autograft Bone Chips: Analysis of Ten Consecutively Retrieved Implants.” Journal of Arthoplasty. 7.4. (1992): 483-493. Print.
• Hofmann, Aaron A. “Cementless Fixation for TKA: It is as good as gold.” Orthopedics Today. (2007): Web. 12 May. 2013.
• Hofmann, Aaron A and Scott, David F. “Cementless Total Knee Arthoplasty.” Surgical Techniques in Total Knee Arthoplasty. Springer, 2002. 262-271. Print.