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Articulating antibiotic spacers offer advantages
They may preserve bone and enhance rehabilitation while eliminating infection.
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We can all agree that thorough debridement and a two-stage exchange is the standard of care for total knee arthroplasty complicated by deep infection. Both the static and articulating spacers used in these procedures eradicate infection with similar effectiveness. However, using articulating spacers promotes greater range of motion, preserves bone, facilitates reimplantation and may enhance functional recovery.
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The usual treatment for all spacer types is a thorough debridement, placement of a spacer with antibiotic-laden cement, 6 weeks of intravenous antibiotics, and reimplantation of a new prosthesis.The spacers should contain high concentrations of antibiotics. We currently use 4.8 g of tobramycin or gentamycin and 4 g of vancomycin per 40-gram unit of cement. In the peer-reviewed literature, these doses have not been shown to cause acute renal insufficiency or other systemic side effects.
Comparisons in the literature of static and articulating spacers have shown eradication rates of approximately 90% and 92% respectively. Therefore, we can conclude that static and articulating spacers are both effective for eradication of infection.
Types of spacers
Methods for creating an articulating spacer include using a recycled femoral component, a prosthesis of antibiotic laden acrylic cement (PROSTALAC) [Johnson & Johnson] or a molded cement spacer. A review of the literature reveals eradication rates of 91% for recycled component spacers, 95% for PROSTALAC spacers and 93% for molded cement spacers. Again, these results are similar. Fehring compared static versus articulating spacers and found improved range of motion with no increase of reinfection with articulating spacers.
Likewise, Emerson also showed there was better range of motion with an articulating spacer and no increase in reinfection. More recent articles have shown improved clinical scores and range of motion when a PROSTALAC device has been utilized. Hoffman et al recently published their results using recycled femoral components and demonstrated a range of motion improved by an arc of 16°. An article published by Meek and colleagues compared septic to aseptic revision. They concluded that the PROSTALAC system, by virtue its articulating movement, may offer a functional advantage over static spacers and provide functional outcomes for septic revision equal to those of aseptic revision.
The benefits of articulating spacers are: they prevent soft tissue contracture, promote range of motion, and facilitate antibiotic delivery. I've evolved from using static spacers to recycled femoral components to articulating cement spacers in my practice. To make an articulating cement spacer, I use disposable silicone molds and cement mixed with the high concentration of antibiotics described above. The powders are sifted together multiple times to ensure a good, thorough mix. We chill the monomer in ice water to facilitate easier mixing and flow through a vacuum system; otherwise the mixture can be difficult and bulky. The femoral and tibial molds are prepared separately, and 2 disposable injection nozzles are used to mold intramedullary dowels. The femoral mold is massaged to eliminate air spaces and keep the anterior flange somewhat thin so as not to overstuff the patellofemoral articulation. The spacer is contoured with a high speed burr to make it less bulky and to facilitate motion. The tibial component is fabricated basing the mold depth on the thickness of the metal and polyethylene that was removed, while striving for minimal thickness. It will be somewhat lax to allow motion for ambulation. The spacer is implanted with intentionally poor cement technique, applied with a small amount of doughy cement into a bloody wound, to reduce adherence and allow for easier removal at time of reimplantation.
For more information:
- Adolph V. Lombardi Jr., MD, Joint Implant Surgeons, Inc., 7277 Smith's Mill Road, Suite 200, New Albany, OH 43054; 614-221-6331; lombardiav@joint-surgeons.com. He indicated that he is a consultant for Biomet.
- Durbhakula SM, Czajka J, Fuchs MD, Uhl RL. Antibiotic-loaded articulating cement spacer in the 2-stage exchange of infected total knee arthroplasty. J Arthroplasty. 2004;19:768-774.
- Emerson RH Jr, Muncie M, Tarbox TR, Higgins LL. Comparison of a static with a mobile spacer in total knee infection. Clin Orthop Relat Res. 2002;404:132-138.
- Evans RP. Successful treatments of total hip and knee infection with articulating antibiotic components: A modified treatment method. Clin Orthop Relat Res. 2004;427:37-46.
- Fehring TK, Odum S, Calton TF, Mason JB. Articulating versus static spacers in revision total knee arthroplasty for sepsis. Clin Orthop Rel Res. 2000;380:9-16.
- Goldstein WM, Kopplin M, Wall R, Berland K. Temporary articulating methylmethacrylate antibiotic spacer (TAMMAS). A new method of intraoperative manufacturing of a custom articulating spacer. J Bone Joint Surg. 2001;83-A(Suppl):92-97.
- Hofmann AA, Goldberg T, Tanner AM, Kurtin SM. Treatment of infected total knee arthroplasty using an articulating spacer: 2-12 year experience. Cin Orthop Rel Res. 2005;430:125-131.
- Meek RM, Dunlop D, Garbuz DS, McGraw R, Greidanus NV, Masri BA. Patient satisfaction and functional status after aseptic versus septic revision total knee arthroplasty using the PROSTALAC articulating spacer. J Arthroplasty. 2004;19(7):874-879.
- Lombardi AV Jr. Articulating antibiotic spacers: Standard of Care — Affirms. Paper #98. Presented at Current Concepts in Joint Replacement, Winter 2006 Meeting. Dec. 16, 2006. Orlando, FL.