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Two-stage reimplantation of septic total knee arthroplasty
Two-stage Reimplantation of Septic Total Knee Arthroplasty Report of Three Cases Using an Antibiotic-PMMA Spacer Block
James C. Cohen, MD,* William J. Hozack, M_D,-[-John M. Cuckler, MD,:[: and Robert E. Booth, Jr., MD§
Abstract: The management of an infected total knee implant is a major challenge to the orthopaedic surgeon. This ankle reviews the use of antibioticPMMA spacer block in two-stage reimplantation of septic total knee anhroplasties. In addition to serving as an antibiotic delivery system between the time of component removal and reimplantation, the antibiotic-impregnated spacer block imparts mechanical stability to the joint and decreases the morbidity during the period before reimplantation. This temporary "interposition arthroplasty" facilitates the patient's ambulation and also simplifies dissection at the time of reimplantation. Furthermore, osteoporotic bone at the time of resectioh becomes finn, good-quality bone by the time of reimplantation. Key words: septic total knee arthroplasty, antibiotic cement, infection, revision knee arthroplasty, spacer block.
that the infection could be better controlled prior to reimplantation. One major problem with this techniqiae is that the patient experiences severe disability and pain in the interval between the resection and the reimplantation, making it difficult to maintain the general vitality of the patient during this period of increased morbidity. Furthermore, the surgical dissection at the time of reimplantation is often very difficult, as the joint space is obliterated by scar and the ligaments are severely contracted. By using an antibiotic-impregnated interpositional cement block, one can avoid the morbidity of the delayed exchange procedure while at the same time making the reimplantation surgery technically much more facile. We describe our technique and present three case reports.
Infection after total knee arthroplasty has been approached in a variety of ways: antibiotics alone or in conjunction with debridement (6, 7, 12, 22), resection arthroplasty (5, 13), arthrodesis (3, 6, 13, 15, 18, 23), or reimplantation (1, 2, 6, 9-11, 14, 22). We have favored a delayed exchange arthroplasty over an immediate exchange procedure in the hope * From Michael Reese ttospital and Medical Center, Department of Orthopaedic Surgery, Chicago, Illinois. t From University of Miami School of Medicine, Department of Orthopaedics and Rehabilitation, MiamL Florida. 4: From the University of Pennsylvania, Department of Orthopaedic Surgery, Philadelphia, Pennsylvania. § From the Department of Orthopaedics, Pennsylvania Hospital and Jefferson Medical School Philadelphia, Pennsylvania. Reprint requests: William J. Hozack, MD, University of Miami School of Medicine, Department of Orthopaedics and Rehabilitation, P.O. Box 016960, Miami, FL 33101.
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Technique The techniques of revision total knee arthroplasty are well described elsewhere. The prosthesis and all cement are removed. A thorough debridement of all inflamed soft tissues is essential for a good result. Subsequently, a methylmethacrylate mold of the extension gap can be made. Eighty grams of acrylic bone cement and 2.4 g of tobramycin powder are mixed. Other antibiotics can be used, depending upon the organism and its sensitivities. The key to preparing the spacer block is to allow the cement to become fairly firm while modelling it to conform to a tibial trial of appropriate size. It is then placed in the extension gap and further adjustments are made to mold the cement to the gap while the knee is fully distracted. The cement block should be large enough to rest fully on the cortical rim of the tibia. Superior and inferior pegs are fashioned to fit into the femur and tibia, respectively. These pegs must be long enough to provide some stability but not too long to prevent easy removal. The cement is allowed to harden with the knee in the extended position, but periodic mild flexion of the knee will prevent mechanical bonding of the cement to the bone. Copious
irrigation is undertaken to prevent thermal damage from the curing cement. After the cement is hardened, reasonable stability and alignment should be present. Closure is performed in a routine fashion over closed suction drains. The block is left in position until the time of reimplantation. During this interval the patient is allowed to ambulate to weight bearing as tolerated with a knee immobilizer. The timing of the block removal and reimplantation depends upon the status of the surrounding soft tissues and the condition of the patient--at least 6 weeks is recommended. Whether this spacer should be used in cases where reimplantation is not contemplated remains uncertain. Preoperative aspiration is performed along with other laboratory tests to screen for the presence of infection. Antibiotic therapy is largely empirical and is chosen in conjunction with the infectious disease consultant. In general, parenteral antibiotics are given for 6 weeks in the first stage and then only perioperatively during the second stage. While monitoring of serum bactericidal titers has been recommended (11), we did not do this for our patients. We have used antibioticimpregnated cement for all of our reimplantation procedures.
Fig. 1. (A) Anteroposterior radiograph at time of deep infection. (B) Lateral radiograph at time of deep infection. (C) Stage 1. Cement spacer. Anteroposterior radiograph. (Figure continues)
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Case Reports Case 1 (Fig. 1) A 52-year-old w o m a n with a 25-year history of r h e u m a t o i d arthritis with multiple joint involvement had left total knee arthroplasty in February 1983. In J a n u a r y 1984 an ipsilateral fourth metatarsal resection for metatarsalgia was performed in a podiatric office. It became infected during the immediate postoperative period and was treated with local w o u n d care only. Seven weeks later, she presented to her local hospital with a 1-week history of left knee pain. A definitive diagnosis of an infected total knee arthroplasty was made, with Staphylococcus aureus cultured from both the knee aspiration and the draining Wound over the fourth metatarsal. The patient was t a k e n to the operating room o n March 27, 1984, w h e r e thick purulent material was identified u p o n opening the joint. The femoral c o m p o n e n t was loose o n gross examination. A thorough debridement was performed, with the components and all of the cem e n t removed. A Palacos cement spacer block with gentamicin was fabricated and inserted. The w o u n d was closed over drains. The foot w o u n d was also debrided of infected bone and healed slowly over several months. The knee w o u n d healed unevent-
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fully. The patient was treated with 6 weeks of intravenous vancomycin, then switched to oral clindamycin, and then switched to erythromycin over the successive 6 m o n t h s because of various mild adverse effects. The knee was painless, and the patient ambulated with a knee immobilizer and a cane. With the spacer block in place the patient had n o mediolateral instability, and examination revealed a range of m o t i o n from 5 ° to 45 ° . On October 4, 1984, approximately 6 m o n t h s after the debridement was performed, a Total Condylar III prosthesis was inserted with a 25-ram tibial plateau with tobramycin cement. Numerous operative cultures as well as a preoperative aspiration were negative. Physical therapy with a constant passive motion machine was started o n the first postoperative day. At 1 month, the patient had a range of motion from 0 ° to 95 °, with no evidence of infection. Now, 36 months since her initial treatment for the infected total knee arthroplasty, she has an excellent result without evidence of infection or loosening.
Case 2 (Fig, 2) A 74-year-old m a n had bilateral hinge-type total knee arthroplasties in 1979 for osteoarthritis. The pa-
Fig. 1. (D) Stage 1. Cement spacer. Lateral radiograph. (E) Stage 2. Reimplantation. Anteroposterior radiograph. (F) Stage 2. Reimplantation. Lateral radiograph.
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Fig. 2. (A) Anteroposterior radiograph at time of deep infection. (B) Lateral radiograph at time of deep infection. (C) stage 1. Cement spacer. Anteropostefior radiograph. (D) Stage 1. Cement spacer. Lateral radiograph. (Figure continues)
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Fig. 2. (El Stage 2. Reimplanration. Anteropostefior radiograph. (F) Stage 2. Reimplanration. Lateral radiograph.
tient developed an infection of the right knee and subsequently had resection arthroplasty. He was referred to our service on April 2, 1985, with progressive pain in his left knee and clear evidence of infection, including Staphylococcus epidermidis cultured from an aspiration. Examination revealed a flail right knee that necessitated heavy bracing and the use of a walker for ambulating. The left knee range of motion was 10° to 40 ° without instability. On April 4, 1985, exploration of the left knee revealed gross purulence along with loose components. A complete debridement was performed, including removal of the components and all of the cement. For adequate exposure, the insertion of the patellar tendon was removed with a bone block from the tibial tubercle. A tobramycin-impregnated spacer block was inserted. All cultures grew S. epidermidis; the patient was treated with parenteral cefazolin for 3 weeks, until April 30, 1985, when zeimplantation was performed using a custom Total Condylar I1[ prosthesis. The patient was continued on 6 weeks of parenteraI antibiotics, although operative cukures from the second stage were negative. The postoperative period was complicated by a superficial skin slough that was debrided and covered with a splitthickness skin graft. Thirty months after his debride-
ment, the patient has an excellent result, with 0 °100 ° of motion and no pain.
Case 3 (Fig. 3) A 62-year-old woman had a left total knee arthroplasty in July t984 that was complicated by a large soft tissue slough requiring a gastrocnemius flap. She had recurrent swelling and occasional drainage since that time. In addition, the scar tissue of the knee was erythematous, and she had only 0 °15° of flexion, On June 20, 1985, the patient had complete debridement of the components and all of the cement. The components were loose on gross examination, and there was a defect in the proximal tibia in the region of a previous sinus tract consistent with active infection. A tobramycin-impregnated spacer block was fashioned and the wound closed over drains. Operative cultures grew enterococci sensitive to amp~cillin, which the patient received parenterally for 6 weeks. During this period the patient was partial weight bearing and used two crutches. On August 5, 1985, the block was removed without difficulty and reimplantation was performed using a
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Fig. 3. (A) Anteroposterior radiograph at time of deep infection. (B) Lateral radiograph at time of deep infection. (C) Stage 1. Cement slSacer. Anteroposterior radiograph. (D) Stage 1. Cement spacer. Lateral radiograph, (Figure continues)
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Fig. 3. (E) Stage 2. Reimplantation, Anteroposterior radiograph, (F) Stage 2. Reimplanration, Lateral radiograph.
Total Condylar III prosthesis. The tissues appeared quiescent, and cultures were negative. The patient received 1 week of intravenous ampicillin and was placed on chronic oral suppressive ampicillin therapy. At 24-month follow-up evaluation, she was asymptomatic, with 90 ° of flexion and no evidence of radiographic loosening.
Discussion The patient with an infected total knee implant represents a major challenge to the orthopaedic surgeon. The management of infected total knee arthroplasties remains a controversial topic and is likely to remain so, because of the relative rarity of this disorder, the variety of treatment modalities, and the numerous significant variables that affect treatment outcome. Depending on the specifics of a given case, the following alternative methods of treatment may be appropriate for the infected total knee arthroplasty: (1) suppressive antibiotics alone; (2) incision, debridement, and antibiotics, leaving the prosthesis in situ; (3) removal of the prosthesis, with or without arthrodesis; and (4) reimplantation in either one or two stages. Before embarking on any of these treatment modalities, the patient must be
aware that eventual amputation may be necessary (12, 22). Insall et al. (11) advocated two-stage reimplanration for the salvage of infected total knee arthroplasties. The protocol consisted of thorough debridement and removal of the prosthesis and all cement, followed by 6 weeks of parenteral antibiotic therapy, with subsequent reimplantation without antibiotic cement and cessation of all antibiotic therapy. At an average follow-up period of 34 months, 9 of 11 reimplanted knees were rated good or excellent. Borden (2) also documented the advantage of delayed versus immediate reimplantation in his study of 21 cases. Rand and Bryan (14) reviewed their results in 14 knees of early reimplantation for the salvage of an infected total knee arthroplasty. Salvage was successful in six of seven patients with a low-virulence organism but only two of seven patients with a highvirulence organism. They conclude that reimplantation of a new total knee prosthesis within 2 weeks should not be done. Walker and Schurman (22) reported successful results in 9 of 11 delayed exchange arthroplasties; the other 2 eventually resulted in amputation for recurrent infection. They found that patient activity, function, and joint performance were worst after resection arthroplasty but before reimplantation. We started using an antibiotic-impregnated cement block in two-stage reimplantation for several
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major therapeutic functions: mechanical stability, spacer effect, and antibiotic delivery. Mechanically, its function as an interposition arthroplasty provides more stability to the joint and decreases the morbidity during the period between prosthesis removal and reimplantation. Since many of the patients are frail to begin with, it is especially important to maintain the patient's vitality and ambulatory status. Also, by preserving weight-bearing ambulation, the systemic disability associated with resection arthroplasty can be minimized. Furthermore, we have observed that the osteoporotic bone usually present at resection is converted into firm, good-quality surfaces at the time of reimplantation, which greatly enhances prosthesis insertion and fixation. We attribute this change to the interim weight bearing by the patient. Since the effective space at the level of the knee joint is preserved and not obliterated by scar tissue and the knee ligaments are not contracted, the dissection at the time of reimplantation is greatly simplified. The posterior capsular area is especially easy to identify. In addition, the ligaments, tendons, and capsular tissues are maintained more closely toward physiologic tension than after a simple resection. In addition to its mechanical functions, the spacer serves as an antibiotic-delivery system. Very high levels of antibiotics can be delivered to the surrounding bone and soft tissues (17, 20). Thus, in conjunction with systemic antibiotic therapy, the goal of further reducing the incidence of reinfection may be reached. In the three patients in this series, the longest period in which the cement spacer was left in place was 6 months. All of the patients that we have treated with this technique (now 15 patients) have had subsequent reimplantation of a total knee arthroplasty, except one who had a delayed knee fusion. No patient has had this spacer block left in place as a permanent solution for their infection. We cannot recommend this as an alternative, as the potential is too high for progressive bone loss created by the interaction (both biologic and mechanical) between the cement and the bone. The antibiotic treatment of infected total joint has been largely empirical. Insall (11) recommends 6 weeks of parenteral antibiotics after removal of the prosthesis, based on sensitivity studies at the serum bactericidal level of 1 : 8 or greater. Another method of delivering antibiotics to the operative area is to add them to the bone cement at the time of reimplantation (4). In general, the concentration in tissues is inversely proportional to their distance from the cement and the length of time elapsed since implantation (21). Hovelius and Josefsson (9) described an infection treated by a two-stage salvage
procedure in which gentamicin-loaded cement beads were placed in the cavity until the time of reimplantation. Unfortunately, beads serve no mechanical function. Bucholz et al. (4) showed in in vitro tests that antibiotics were released into a fluid by a diffusion process. The amount of antibiotic that is released is proportional to the surface area of the cement, the concentration in the cement, the amount of fluid around the cement, and the frequency of the turnover of this fluid. The local concentration of antibiotic during the first several days after implantation at the local tissues is much higher than that possible from systemic administration (21). Although there is much controversy concerning the duration of the therapeutic effectiveness of antibiotic-impregnated cement, there is general agreement that significant levels are found at 6 weeks (19). In animal experiments, the local concentration of antibiotic surrounding the gentamicin-impregnated cement beads was much higher than that which could have been reached using a solid antibiotic-loaded cement plug (21). Even with the higher local concentrations obtained with the antibiotic bead-delivered system, the systemic dose is low and without adverse effects (2 I). Even though the local concentrations using the solid spacer block may not be as high as that obtained with beads, we believe that the mechanical benefits of the block are substantial and justify its use. Future studies are clearly indicated to determine the required local concentration as well as to improve the type of local delivery system. In summary, we have described a technique undergoing trial by various surgeons.that can be used during a two-stage revision of an infected total knee anhroplas W. This antibiotic-impregnated cement block serves several functions--it provides mechanical stability to the knee, it acts as a mechanical spacer for ligament and soft tissue tension, and it serves as a local antibiotic-delivery system. Patient disability between resection and reimplantation is markedly decreased, and reimplantation surgery is greatly facilitated.
References 1. Bengston S, Knutson K, Lidgren L: Revision of infected knee arthroplasty. Acta Orthop Scand 57:489, 1986 2. Borden LS, Gearen PF: Infected total knee arthropIasty: a protocol for management. J Arthroplasty 2:27, 1987 3. Broderson MP, Fitzgerald RH Jr, Peterson LFA et al:
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5.
6.
7.
8.
9.
10.
1I.
12.
13.
Arthrodesis of the knee following failed total knee arthroplasty. J Bone Joint Surg 61A: 181, 1979 Bucholz HW, Elson RA, Heinert K: Antibiotic loaded acrylic cement: current concepts. Clin Orthop 190:96, 1984 Falahee MH, Matthews LS, Kaufer H: Resection arthroplasty as a salvage procedure for a knee with infection after a total arthroplasty. J Bone Joint Surg 69A:1013, 1987 Freeman MAR, Sudlow RA, Casewell MW, Radcliff SS: The management of infected total knee replacements. J Bone Joint Surg 67B:764, 1987 Grogan TJ, Dorey F, Rollins J, Amstutz HC: Deep sepsis following total knee arthroplasty. J Bone Joint Surg 68A:226, 1986 Hagemann WF, Woods GW, Tullos HS: Arthrodesis in failed total knee replacement. J Bone Joint Surg 60A:790, 1978 Hovelius L, Josefesson G: An alternative method for exchange operation of infected arthroplasty. Acta Orthop Scand 50:93, 1979 Insall JN: Infection in total knee arthroplasty, p. 42. In: AAOS Instructional Course Lectures, vol. 31. CV Mosby, St. Louis, 1982 Insall JN, Thompson FM, Brause BD: Two stage reknplantation for the salvage of infected total knee arthroplasty. J Bone Joint Surg 65A: 1087, 1983 Johnson DP, Bannister GC: The outcome of infected arthroplasty of the knee. J Bone Joint Surg 68B:289, 1986 Kaufer H, Matthews LS: Resection arthroplasty: an alternative to arthrodesis for salvage of the infected
14.
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19. 20.
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22. 23.
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total knee arthroplasty, p. 283. In: AAOS Instructional Course Lectures, vol. 35. CV Mosby, St. Louis, 1986 Rand JA, Bryan RS: Reimplantafion for the salvage of an infected total knee arthroplasty. J Bone Joint Surg 65A:1081, 1983 Rand JA, Bryan RS: The outcome of failed knee arthrodesis following total knee arthroplasty. Clin Orthop 205:86, 1986 Rand JA, Bryan RS, Chao EYS: Failed total knee arthroplasty treated by arthrodesis of the knee using the Ace-Fisher apparatus. J Bone Joint Surg 69A:39, 1987 Schurman DJ, Trindade C, Hirschman HP et al: Antibiotic acrylic bone cement composites. J Bone Joint Surg 60A:978, 1978 Thornhill TS, Dalziel RW, Sledge CB: Alternatives to arthrodesis for the failed total knee arthroplasty. Clin Orthop 170:131, 1982 Trippel SB: Antibiotic-impregnated cement in total joint arthroplasty. J Bone Joint Surg 68A: 1297, 1986 Wahlig H, Dingeldein E, Bergmann R, Reuss K: The release of gentamicin from polymethylmethacrylate beads. J Bone Joint Surg 60B:270, 1978 Walenkamp GHIM, Vree TB, Van Rens TJG: Gentamicin-PMMA beads: pharmacokinefic and nephrotoxicological study. Clin Orthop 205:171, 1986 Walker RH, Schurman DJ: Management of infected total knee arthroplasties. Clin Orthop 186:81, 1984 Woods GW, Lionberger DR, Tullos MHS: Failed total knee arthroplasty: revision and arthrodesis for infection and noninfectious complications. Clin Orthop 172:184, 1983
James C. Cohen, MD,* William J. Hozack, M_D,-[-John M. Cuckler, MD,:[: and Robert E. Booth, Jr., MD§
Abstract: The management of an infected total knee implant is a major challenge to the orthopaedic surgeon. This ankle reviews the use of antibioticPMMA spacer block in two-stage reimplantation of septic total knee anhroplasties. In addition to serving as an antibiotic delivery system between the time of component removal and reimplantation, the antibiotic-impregnated spacer block imparts mechanical stability to the joint and decreases the morbidity during the period before reimplantation. This temporary "interposition arthroplasty" facilitates the patient's ambulation and also simplifies dissection at the time of reimplantation. Furthermore, osteoporotic bone at the time of resectioh becomes finn, good-quality bone by the time of reimplantation. Key words: septic total knee arthroplasty, antibiotic cement, infection, revision knee arthroplasty, spacer block.
that the infection could be better controlled prior to reimplantation. One major problem with this techniqiae is that the patient experiences severe disability and pain in the interval between the resection and the reimplantation, making it difficult to maintain the general vitality of the patient during this period of increased morbidity. Furthermore, the surgical dissection at the time of reimplantation is often very difficult, as the joint space is obliterated by scar and the ligaments are severely contracted. By using an antibiotic-impregnated interpositional cement block, one can avoid the morbidity of the delayed exchange procedure while at the same time making the reimplantation surgery technically much more facile. We describe our technique and present three case reports.
Infection after total knee arthroplasty has been approached in a variety of ways: antibiotics alone or in conjunction with debridement (6, 7, 12, 22), resection arthroplasty (5, 13), arthrodesis (3, 6, 13, 15, 18, 23), or reimplantation (1, 2, 6, 9-11, 14, 22). We have favored a delayed exchange arthroplasty over an immediate exchange procedure in the hope * From Michael Reese ttospital and Medical Center, Department of Orthopaedic Surgery, Chicago, Illinois. t From University of Miami School of Medicine, Department of Orthopaedics and Rehabilitation, MiamL Florida. 4: From the University of Pennsylvania, Department of Orthopaedic Surgery, Philadelphia, Pennsylvania. § From the Department of Orthopaedics, Pennsylvania Hospital and Jefferson Medical School Philadelphia, Pennsylvania. Reprint requests: William J. Hozack, MD, University of Miami School of Medicine, Department of Orthopaedics and Rehabilitation, P.O. Box 016960, Miami, FL 33101.
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Technique The techniques of revision total knee arthroplasty are well described elsewhere. The prosthesis and all cement are removed. A thorough debridement of all inflamed soft tissues is essential for a good result. Subsequently, a methylmethacrylate mold of the extension gap can be made. Eighty grams of acrylic bone cement and 2.4 g of tobramycin powder are mixed. Other antibiotics can be used, depending upon the organism and its sensitivities. The key to preparing the spacer block is to allow the cement to become fairly firm while modelling it to conform to a tibial trial of appropriate size. It is then placed in the extension gap and further adjustments are made to mold the cement to the gap while the knee is fully distracted. The cement block should be large enough to rest fully on the cortical rim of the tibia. Superior and inferior pegs are fashioned to fit into the femur and tibia, respectively. These pegs must be long enough to provide some stability but not too long to prevent easy removal. The cement is allowed to harden with the knee in the extended position, but periodic mild flexion of the knee will prevent mechanical bonding of the cement to the bone. Copious
irrigation is undertaken to prevent thermal damage from the curing cement. After the cement is hardened, reasonable stability and alignment should be present. Closure is performed in a routine fashion over closed suction drains. The block is left in position until the time of reimplantation. During this interval the patient is allowed to ambulate to weight bearing as tolerated with a knee immobilizer. The timing of the block removal and reimplantation depends upon the status of the surrounding soft tissues and the condition of the patient--at least 6 weeks is recommended. Whether this spacer should be used in cases where reimplantation is not contemplated remains uncertain. Preoperative aspiration is performed along with other laboratory tests to screen for the presence of infection. Antibiotic therapy is largely empirical and is chosen in conjunction with the infectious disease consultant. In general, parenteral antibiotics are given for 6 weeks in the first stage and then only perioperatively during the second stage. While monitoring of serum bactericidal titers has been recommended (11), we did not do this for our patients. We have used antibioticimpregnated cement for all of our reimplantation procedures.
Fig. 1. (A) Anteroposterior radiograph at time of deep infection. (B) Lateral radiograph at time of deep infection. (C) Stage 1. Cement spacer. Anteroposterior radiograph. (Figure continues)
Reimplantation of Septic TKA
Case Reports Case 1 (Fig. 1) A 52-year-old w o m a n with a 25-year history of r h e u m a t o i d arthritis with multiple joint involvement had left total knee arthroplasty in February 1983. In J a n u a r y 1984 an ipsilateral fourth metatarsal resection for metatarsalgia was performed in a podiatric office. It became infected during the immediate postoperative period and was treated with local w o u n d care only. Seven weeks later, she presented to her local hospital with a 1-week history of left knee pain. A definitive diagnosis of an infected total knee arthroplasty was made, with Staphylococcus aureus cultured from both the knee aspiration and the draining Wound over the fourth metatarsal. The patient was t a k e n to the operating room o n March 27, 1984, w h e r e thick purulent material was identified u p o n opening the joint. The femoral c o m p o n e n t was loose o n gross examination. A thorough debridement was performed, with the components and all of the cem e n t removed. A Palacos cement spacer block with gentamicin was fabricated and inserted. The w o u n d was closed over drains. The foot w o u n d was also debrided of infected bone and healed slowly over several months. The knee w o u n d healed unevent-
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fully. The patient was treated with 6 weeks of intravenous vancomycin, then switched to oral clindamycin, and then switched to erythromycin over the successive 6 m o n t h s because of various mild adverse effects. The knee was painless, and the patient ambulated with a knee immobilizer and a cane. With the spacer block in place the patient had n o mediolateral instability, and examination revealed a range of m o t i o n from 5 ° to 45 ° . On October 4, 1984, approximately 6 m o n t h s after the debridement was performed, a Total Condylar III prosthesis was inserted with a 25-ram tibial plateau with tobramycin cement. Numerous operative cultures as well as a preoperative aspiration were negative. Physical therapy with a constant passive motion machine was started o n the first postoperative day. At 1 month, the patient had a range of motion from 0 ° to 95 °, with no evidence of infection. Now, 36 months since her initial treatment for the infected total knee arthroplasty, she has an excellent result without evidence of infection or loosening.
Case 2 (Fig, 2) A 74-year-old m a n had bilateral hinge-type total knee arthroplasties in 1979 for osteoarthritis. The pa-
Fig. 1. (D) Stage 1. Cement spacer. Lateral radiograph. (E) Stage 2. Reimplantation. Anteroposterior radiograph. (F) Stage 2. Reimplantation. Lateral radiograph.
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Fig. 2. (A) Anteroposterior radiograph at time of deep infection. (B) Lateral radiograph at time of deep infection. (C) stage 1. Cement spacer. Anteropostefior radiograph. (D) Stage 1. Cement spacer. Lateral radiograph. (Figure continues)
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Fig. 2. (El Stage 2. Reimplanration. Anteropostefior radiograph. (F) Stage 2. Reimplanration. Lateral radiograph.
tient developed an infection of the right knee and subsequently had resection arthroplasty. He was referred to our service on April 2, 1985, with progressive pain in his left knee and clear evidence of infection, including Staphylococcus epidermidis cultured from an aspiration. Examination revealed a flail right knee that necessitated heavy bracing and the use of a walker for ambulating. The left knee range of motion was 10° to 40 ° without instability. On April 4, 1985, exploration of the left knee revealed gross purulence along with loose components. A complete debridement was performed, including removal of the components and all of the cement. For adequate exposure, the insertion of the patellar tendon was removed with a bone block from the tibial tubercle. A tobramycin-impregnated spacer block was inserted. All cultures grew S. epidermidis; the patient was treated with parenteral cefazolin for 3 weeks, until April 30, 1985, when zeimplantation was performed using a custom Total Condylar I1[ prosthesis. The patient was continued on 6 weeks of parenteraI antibiotics, although operative cukures from the second stage were negative. The postoperative period was complicated by a superficial skin slough that was debrided and covered with a splitthickness skin graft. Thirty months after his debride-
ment, the patient has an excellent result, with 0 °100 ° of motion and no pain.
Case 3 (Fig. 3) A 62-year-old woman had a left total knee arthroplasty in July t984 that was complicated by a large soft tissue slough requiring a gastrocnemius flap. She had recurrent swelling and occasional drainage since that time. In addition, the scar tissue of the knee was erythematous, and she had only 0 °15° of flexion, On June 20, 1985, the patient had complete debridement of the components and all of the cement. The components were loose on gross examination, and there was a defect in the proximal tibia in the region of a previous sinus tract consistent with active infection. A tobramycin-impregnated spacer block was fashioned and the wound closed over drains. Operative cultures grew enterococci sensitive to amp~cillin, which the patient received parenterally for 6 weeks. During this period the patient was partial weight bearing and used two crutches. On August 5, 1985, the block was removed without difficulty and reimplantation was performed using a
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Fig. 3. (A) Anteroposterior radiograph at time of deep infection. (B) Lateral radiograph at time of deep infection. (C) Stage 1. Cement slSacer. Anteroposterior radiograph. (D) Stage 1. Cement spacer. Lateral radiograph, (Figure continues)
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Fig. 3. (E) Stage 2. Reimplantation, Anteroposterior radiograph, (F) Stage 2. Reimplanration, Lateral radiograph.
Total Condylar III prosthesis. The tissues appeared quiescent, and cultures were negative. The patient received 1 week of intravenous ampicillin and was placed on chronic oral suppressive ampicillin therapy. At 24-month follow-up evaluation, she was asymptomatic, with 90 ° of flexion and no evidence of radiographic loosening.
Discussion The patient with an infected total knee implant represents a major challenge to the orthopaedic surgeon. The management of infected total knee arthroplasties remains a controversial topic and is likely to remain so, because of the relative rarity of this disorder, the variety of treatment modalities, and the numerous significant variables that affect treatment outcome. Depending on the specifics of a given case, the following alternative methods of treatment may be appropriate for the infected total knee arthroplasty: (1) suppressive antibiotics alone; (2) incision, debridement, and antibiotics, leaving the prosthesis in situ; (3) removal of the prosthesis, with or without arthrodesis; and (4) reimplantation in either one or two stages. Before embarking on any of these treatment modalities, the patient must be
aware that eventual amputation may be necessary (12, 22). Insall et al. (11) advocated two-stage reimplanration for the salvage of infected total knee arthroplasties. The protocol consisted of thorough debridement and removal of the prosthesis and all cement, followed by 6 weeks of parenteral antibiotic therapy, with subsequent reimplantation without antibiotic cement and cessation of all antibiotic therapy. At an average follow-up period of 34 months, 9 of 11 reimplanted knees were rated good or excellent. Borden (2) also documented the advantage of delayed versus immediate reimplantation in his study of 21 cases. Rand and Bryan (14) reviewed their results in 14 knees of early reimplantation for the salvage of an infected total knee arthroplasty. Salvage was successful in six of seven patients with a low-virulence organism but only two of seven patients with a highvirulence organism. They conclude that reimplantation of a new total knee prosthesis within 2 weeks should not be done. Walker and Schurman (22) reported successful results in 9 of 11 delayed exchange arthroplasties; the other 2 eventually resulted in amputation for recurrent infection. They found that patient activity, function, and joint performance were worst after resection arthroplasty but before reimplantation. We started using an antibiotic-impregnated cement block in two-stage reimplantation for several
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major therapeutic functions: mechanical stability, spacer effect, and antibiotic delivery. Mechanically, its function as an interposition arthroplasty provides more stability to the joint and decreases the morbidity during the period between prosthesis removal and reimplantation. Since many of the patients are frail to begin with, it is especially important to maintain the patient's vitality and ambulatory status. Also, by preserving weight-bearing ambulation, the systemic disability associated with resection arthroplasty can be minimized. Furthermore, we have observed that the osteoporotic bone usually present at resection is converted into firm, good-quality surfaces at the time of reimplantation, which greatly enhances prosthesis insertion and fixation. We attribute this change to the interim weight bearing by the patient. Since the effective space at the level of the knee joint is preserved and not obliterated by scar tissue and the knee ligaments are not contracted, the dissection at the time of reimplantation is greatly simplified. The posterior capsular area is especially easy to identify. In addition, the ligaments, tendons, and capsular tissues are maintained more closely toward physiologic tension than after a simple resection. In addition to its mechanical functions, the spacer serves as an antibiotic-delivery system. Very high levels of antibiotics can be delivered to the surrounding bone and soft tissues (17, 20). Thus, in conjunction with systemic antibiotic therapy, the goal of further reducing the incidence of reinfection may be reached. In the three patients in this series, the longest period in which the cement spacer was left in place was 6 months. All of the patients that we have treated with this technique (now 15 patients) have had subsequent reimplantation of a total knee arthroplasty, except one who had a delayed knee fusion. No patient has had this spacer block left in place as a permanent solution for their infection. We cannot recommend this as an alternative, as the potential is too high for progressive bone loss created by the interaction (both biologic and mechanical) between the cement and the bone. The antibiotic treatment of infected total joint has been largely empirical. Insall (11) recommends 6 weeks of parenteral antibiotics after removal of the prosthesis, based on sensitivity studies at the serum bactericidal level of 1 : 8 or greater. Another method of delivering antibiotics to the operative area is to add them to the bone cement at the time of reimplantation (4). In general, the concentration in tissues is inversely proportional to their distance from the cement and the length of time elapsed since implantation (21). Hovelius and Josefsson (9) described an infection treated by a two-stage salvage
procedure in which gentamicin-loaded cement beads were placed in the cavity until the time of reimplantation. Unfortunately, beads serve no mechanical function. Bucholz et al. (4) showed in in vitro tests that antibiotics were released into a fluid by a diffusion process. The amount of antibiotic that is released is proportional to the surface area of the cement, the concentration in the cement, the amount of fluid around the cement, and the frequency of the turnover of this fluid. The local concentration of antibiotic during the first several days after implantation at the local tissues is much higher than that possible from systemic administration (21). Although there is much controversy concerning the duration of the therapeutic effectiveness of antibiotic-impregnated cement, there is general agreement that significant levels are found at 6 weeks (19). In animal experiments, the local concentration of antibiotic surrounding the gentamicin-impregnated cement beads was much higher than that which could have been reached using a solid antibiotic-loaded cement plug (21). Even with the higher local concentrations obtained with the antibiotic bead-delivered system, the systemic dose is low and without adverse effects (2 I). Even though the local concentrations using the solid spacer block may not be as high as that obtained with beads, we believe that the mechanical benefits of the block are substantial and justify its use. Future studies are clearly indicated to determine the required local concentration as well as to improve the type of local delivery system. In summary, we have described a technique undergoing trial by various surgeons.that can be used during a two-stage revision of an infected total knee anhroplas W. This antibiotic-impregnated cement block serves several functions--it provides mechanical stability to the knee, it acts as a mechanical spacer for ligament and soft tissue tension, and it serves as a local antibiotic-delivery system. Patient disability between resection and reimplantation is markedly decreased, and reimplantation surgery is greatly facilitated.
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