Chapter 11
Two-Stage Reimplantation for Infection
Giles R. Scuderi and Henry D. Clarke
Two-stage reimplantation of infected total knee arthroplasty has become the treatment of choice for most patients.1,2,3,4The treat- ment protocol is divided into three phases: (1) removal of the pros- thesis and all cement with debridement of the soft tissues and bone;
(2) six weeks of parental antibiotics; and (3) implantation of a new total knee prosthesis. To have adequate bone stock for the later reimplantation, care should be taken at the time of component removal care. While all attempts to perform a thorough debride- ment and cement removal are undertaken, overzealous debride- ment can lead to significant bone loss, complicating the reimplantation.
Following the removal of the infected components, cement spacers are placed between the femoral–tibial and patellofemoral articulations. The use of antibioticimpregnated cement beads or spacer blocks allows local delivery of high concentrations of anti- biotics. While the larger surface area of multiple beads theoreti- cally provides greater allusion of local antibiotics than from a single spacer block, no definite clinical advantage has been proven.
However, the spacer block has definite mechanical advantages over the beads. Spacer blocks facilitate ambulation prior to the reim- plantation and also allow easier exposure at the time of the later surgery.5In most cases a spacer block is fashioned using two to three 40 g batches of polymethylmethacrylate cement mixed with high doses of antibiotics. We typically use 2.4 g of tobramycin and 1 g of vancomycin per pack of cement. When mixing the anti- biotics, the lumps in the crystalline vancomycin should not be crushed. Once the cement has reached a doughy consistency it is placed into the femoral tibial space during the final stages of poly- merization. Longitudinal distraction is applied to the extremity in an effort to prevent cement interdigitation with the bone; this enables easy removal at the time of reimplantation. If large spacers are used, the heat produced by the exothermic reaction can be significant. Irrigation should be used to cool the cement block,
preventing damage to the neurovascular structures that lie only millimeters from the posterior capsule. The cement spacer can be fashioned with short pegs or stems to help provide stability.
Extending the spacer anteriorly over the distal femur and into the patellofemoral joint also helps with stability and maintains a plane between the patella and femur. The block should be suitably large to sit on cortical bone and provide stability in extension. If the block is too small and has contact predominantly with cancellous bone or is insufficient to maintain stability, further bone erosion can occur. If the intramedullary canal is opened to remove stemmed components, antibiotic-impregnated cement rods can be placed inside the canals. Use of a cement spacer usually provides enough stability to the knee to allow the patient to walk for short distances in a knee immobilizer, brace, or cast.
During the 1990s, more functional temporary spacers were developed that incorporate small metallic femoral runners and polyethylene inserts into molded polymethylmethacrylate compo- nents. One such device, the so-called PROSTALAC (prosthesis of antibiotic loaded acrylic cement) allows joint motion and weight bearing during the period prior to reimplantation.6 A range of motion up to 75 degrees has been reported with the use of this tem- porary functional spacer.6In a similar manner, some surgeons have sterilized the extracted femoral component and reinserted it tem- porarily using a small polyethylene insert on a cement block.7 Again, this can reduce the patient’s disability between debridement and staged reimplantation. If an articulating spacer is used, then attention must be paid to equalizing the flexion and extension space or dislocation may occur.
Aspiration prior to reimplantation is considered if there is clin- ical suspicion of persistent infection. However, in most cases our decision to proceed with reimplantation is determined intraopera- tively based upon the appearance of the tissues and an evaluation of histologic frozen section specimens. At the time of reimplanta- tion, adequate surgical exposure must be obtained and use of one of the previously discussed techniques, such as the quadriceps snip, may be required. Although uncemented prostheses with bone graft soaked in antibiotic solution have been used successfully in reim- plantation,8we favor the use of cemented prostheses. The use of antibiotic-impregnated cement at the time of reimplantation has been shown to be associated with a significantly lower risk of recur- rent infection.9
Significant bone loss, which requires the use of modular wedges or blocks, is often encountered at the time of reimplanta- tion. Therefore, a prosthesis system, which has a full range of
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modular augments and stem extensions, should be available at reimplantation. The use of stemmed components does not nec- essarily require that a fully constrained articulation be implanted.
Rather, the use of more constrained designs are reserved for cases with ligamentous insufficiency or instability. In the majority of reimplantations we recurrently use a cemented posterior stabi- lized prosthesis. We prefer to cement only the core prosthesis and avoid introduction of cement into the canal when stem extensions are used. This facilitates removal of the stems if subse- quent prosthesis removal is required. In very rare cases with severe bone loss, custom prostheses or modular tumor prostheses may be required; the need for these devices must be anticipated preoperatively.
The postoperative management of individual patients is depen- dent on numerous variables, including the status of the soft tissue coverage, the type of exposure required, and whether structural bone grafts were utilized. In general, antibiotics are administered intravenously until final intraoperative culture results and tissue section evaluations have been obtained. If all results are negative for infection, then antibiotics are discontinued.
CLINICAL RESULTS
Insall originally reported on the successful eradication of infected total knee replacements with the two-stage protocol in 1977.2 Windsor et al later confirmed the success of this technique when they reported on 38 reimplantations with an average follow-up of 4 years.4The two-stage protocol successfully eradicated the origi- nal deep infection in 37 knees (97.4%) and the reinfection rate was 10.5% (4 of 38 knees). Goldman reported on the largest cohort of two-stage reimplantations for infection.1The 64 knees in this study had an average follow-up of 7.5 years. Six knees (9%) became infected after reimplantation. With only two reinfections with the same organism, the infection eradication rate (97%) was identical to the findings of Windsor.4
Infection after total knee replacement is a serious and poten- tially devastating complication. Successful treatment can be obtained with the two-stage protocol. The long-term functional results, reinfection rate, and survivorship are comparable with those of revision total knee replacement.1
References
1. Goldman RT, Scuderi GR, Insall JN. Two-stage reimplantation for infected total knee replacement. Clin Orthop. 1996; 331:118–124.
152 G.R. SCUDERI AND H.D. CLARKE
2. Insall JN, Thompson FM, Brause BD. Two-stage reimplantation for the salvage of infected total knee arthroplasty. J Bone Joint Surg. 1983;
65A:1087–1098.
3. Windsor RE, Bono JV. Infected total knee replacements. J Am Acad Orthop Surg. 1994; 2:44–53.
4. 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. 1990; 72A:
272–278.
5. Booth RE, Jr, Lotke PA. The results of spacer block technique in revi- sion of infected total knee arthroplasty. Clin Orthop. 1989; 248:57–60.
6. Masri BA, Kendall RW, Duncan CP, et al. Two-stage exchange arthro- plasty using a functional antibiotic-loaded spacer in the treatment of the infected knee replacement: The Vancouver experience. Sem. Arthroplasty.
1994;5(3):122–136.
7. Hofmann AA, Kane KR, Tkach TK, Plaster RL, Camargo MP. Treatment of infected total knee arthroplasty using an articulating spacer. Clin Orthop. 1995; 321:45–54.
8. Whiteside LA. Treatment of infected total knee arthroplasty. Clin Orthop.
1994; 299:169–172.
9. Hanssen AD, Rand JA, Osmon DR. Treatment of the infected total knee arthroplasty with insertion of another prosthesis: The effect of antibiotic-impregnated bone cement. Clin Orthop. 1994; 309:44–55.
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