• AAOS 2011 Focus: Redefining Success in Revision TKA Surgery

  • AAOS 2011 Focus: Redefining Success in Revision TKA Surgery

  • This monograph is based on several AAOS 2011 presentations, including clinical outcomes of traditional and emerging techniques in bone loss and infection management, with a focus on metaphyseal fixation.

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Articulating antibiotic spacers eliminate infection, improve ROM

SAN DIEGO – Patients recovering from total knee arthroplasty (TKA) may develop infections as early as 6 weeks after surgery, further complicating the recovery process and often requiring reoperation. When using a two-stage approach, surgeons can choose from a variety of spacers, including static and articulating spacers. Although static spacers effectively eradicate infection prior to reimplantation,1,2 they do not promote proper mobility or wound healing, which can ultimately lead to more serious complications such as deep vein thrombosis and pulmonary embolism.3

Figure 1
Figure: Radiograph of knee with an articulating spacer in-situ.
Source: Anderson JA

Over the years, researchers have conducted several studies that compared infection and range of motion (ROM) results with articulating vs. static spacers. Hofmann and colleagues4 conducted one study that found patients experienced both infection eradication and improved ROM at 30-months follow-up with articulating spacers. In this study, surgeons removed and autoclaved femoral and tibial components and debrided infected tissue in 26 patients. They then used articulating spacers made up of a resterilized femur and an all-polyethylene tibia to allow for improved ROM and partial mobility prior to reimplantation.

Results of the Hofmann study showed that, “effective eradication of infection, with very good range of knee motion and patient mobility, were achieved,” said John A. Anderson, MD, and his colleagues Mathias P. Bostrom, MD and Thomas P. Sculco, MD at the Hospital for Special Surgery (HSS; New York, NY).

Methods

To further evaluate the use of articulating spacers in patients with post-TKA infections, the HHS group conducted a retrospective study between 1997 and 2004. Anderson presented a study-related poster at the 2011 annual meeting of the American Academy of Orthopaedic Surgeons that outlined methods, two-stage surgical techniques and results of his team’s retrospective study. 5

Anderson’s 6- to 12-year follow-up study included 19 patients with chronic post-TKA infections, comprising 12 women and seven men with an average age of 64 (range: 45 to 87 years).

During stage one, surgeons aspirated the knee pre- and intraoperatively and identified positive cultures in approximately 84% of patients, who then were treated with organism-specific antibiotics. Surgeons removed infected joint fluid in the remaining 16% of patients.

After removing the prosthesis and bone cement, surgeons irrigated and debrided the infected tissue. The team used articulating antibiotic spacers with autoclaved femoral components and new tibial polyethylene inserts, with 48% of patients receiving a new polyethylene patella. Surgeons used antibiotic-laden cement containing, in most cases, tobramycin and vancomycin (3.6 g and 2 g, respectively). The implantation was done with cement in a nearly hardened state, allowing for easy removal of the spacer in the second stage.

In these delayed-reimplantation scenarios, Anderson’s team instructed each patient to mobilize immediately after stage one, including continuous passive motion (CPM), physical therapy and weight-bearing activities, as tolerated. For 6 weeks, patients received IV antibiotics to further eliminate and prevent infection. Patients then underwent reimplantation of new components an average of 11 weeks (range: 4 to 39 weeks) after first-stage procedures.

Table

Outcomes

Anderson’s findings were similar to Hofmann’s 1995 results.

“We assessed mid- to long-term outcomes following articulating antibiotic spacer placement during a two-stage protocol for infected TKA and found that it provided effective eradication of infection with excellent range of knee motion, both between stages and at follow-up,” said the authors. Anderson also reported no evidence of reimplantation complications in his study.

The table above compares HSS’s study results with outcomes from similar research conducted by Hofmann, Emerson and Cuckler.

Conclusion

In addition to activities that increase ROM between stages and after reimplantation, “we strongly emphasize that…surgeons should liaise regularly with their microbiology colleagues in order to tailor appropriate antibiotic therapy,” the authors said.

By using articulating metal-on-polyethylene spacers and early physical therapy, patients reported better outcomes with articulating spacers than with static spacers in terms of ROM, flexion and overall mobility.

Summary

References

  1. Hanssen AD. Managing the infected knee: as good as it gets. J Arthroplasty. 2002;17(4 Suppl 1): 98-101.
  2. Windsor RE, Insall JN, Urs WK, et al. Two-stage reimplantation for the salvage of total knee arthroplasty complicated by infection: further follow-up and refinement of indications. J Bone Joint Surg Am. 1990;72:272-278.
  3. Fehring TK, Odum S, Calton TF, Mason JB. Articulating versus static spacers in revision total knee arthroplasty for sepsis. The Ranawat Award. Clin Orthop Relat Res. 2000;380:9-16.
  4. Hofmann AA, Kane KR, Tkach TK, et al. Treatment of infected total knee arthroplasty using an articulating spacer. Clin Orthop Relat Res. 1995;321:45-54.
  5. Anderson JA, Poultsides L, Bruni D, et al. An articulating spacer with autoclaved femoral component for infected TKA: minimum 6-year follow-up. Poster presented at: American Academy of Orthopaedic Surgeons 2011 Meeting; February 15-19, 2011; San Diego.
  6. 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.
  7. Cuckler JM. The infected total knee: management options. J Arthroplasty. 2005;20(4 Suppl 2):33-36.
  8. Hofmann AA, Goldberg T, Tanner AM, Kurtin SM. Treatment of infected total knee arthroplasty using an articulating spacer: 2- to 12-year experience. Clin Orthop Relat Res. 2005;430:125-131.

John A. Anderson, MD, has no direct financial interest in the products discussed in this article, nor is he a paid consultant for any companies mentioned.