The Knee 17 (2010) 407–411

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The Knee

Intraoperatively-made cement-on-cement antibiotic-loaded articulating spacer forinfected total knee arthroplasty

Hao Shen, Xianlong Zhang, Yao Jiang ⁎, Qiaojie Wang, Yunsu Chen, Qi Wang, Junjie ShaoDepartment of Orthopedic Surgery, Division of Joint Replacement Surgery, Shanghai No. 6th people's Hospital, Shanghai Jiaotong University, Shanghai 200233, PR China

⁎ Correspondingauthor. Tel.:+8621643691818102/81E-mail address: totalknee@sina.com (Y. Jiang).

0968-0160/$ – see front matter © 2009 Elsevier B.V. Aldoi:10.1016/j.knee.2009.11.007

a b s t r a c t

a r t i c l e i n f o

Article history:Received 11 April 2009Received in revised form 25 November 2009Accepted 27 November 2009

Keywords:KneeArthroplastyInfectionTwo-stage reimplantationArticulating spacer

Cement articulating spacers have been used for the treatment of TKA infection. The disadvantages ofcommercially available pre-made mobile spacers include limitations in implant size and antibiotic dose, oftenallowing delivery of only a single antibiotic agent. Hand-made mobile spacers fail to provide a well-shaped andcongruently articular surface and have difficulties in maintaining stability. We present a method ofintraoperatively-made cement-on-cement antibiotic-loaded articulating spacer for infected total kneearthroplasty. A custommold wasmade intraoperatively with bone cement and the standard posterior stabilizedTKAprovisional componentswhichwere of the same size as the original prosthesis. Fabrication of the spacers didnot increase the overall surgical time. From 2004 to 2007, 17 infected total knee arthroplasties were treatedwithtwo-stage reimplantation. The average length of follow-up was 31 months. One patient required an above-kneeamputation for persistent infection. A knee arthrodesis was performed in one case. Ten patients receivedreimplantation with Nexgen LCCK knee implants. Articulating spacers were retained in situ in five patients. Thisarticulating spacer can help improve knee mobility and function during the interval between stages.

01,+8613901971817(mobile).

l rights reserved.

© 2009 Elsevier B.V. All rights reserved.

1. Introduction

Infection in total knee arthroplasty (TKA) is the most devastatingcomplication for both patients and surgeons alike [1–6,12,13]. A two-stage exchange currently remains to be the gold standard method formanaging chronically infected TKA, consisting of an initial debride-ment with hardware removal, a period of intravenous antibiotictherapy, and, finally, a delayed reimplantation [1–6]. Most authorsreportedly consider the functional results of two-stage exchange withan antibiotic-loaded articulating spacer to be better than those withstatic antibiotic-loaded cement spacers [7–12]. An ideal articulatingspacer both help eradicate infection and allow a good interim range ofmotion [1,11,12]. Moreover, the spacer should be composed ofmaterial with a minimal chance of biofilm formation and should notcontain or come into contact with previously infectedmaterials [8,13].

There are three commonly used types of articulating spacers: 1) atemporary prosthesis comprised of re-sterilized components or newcomponents (also called a “spacerprosthesis”) [4,5,7,10,16,19]; 2) cementspacers molded during the operation [1,3,8,11–13,18,21,23,25]; 3)preformed cement spacers [9,15,24]. Depending on the nature ofthe articulating surface, there are 3 types of intraoperatively made artic-ulating spacers: 1) the PROSTALAC systemwith ametal-on-polyethylenearticulating surface [11,12]; 2) an all-cement femoral component with apolyethylene tibial cement-covered component [18]; 3) cement-on-

cement articulating spacers [1,8,13,21,23,25]. All-cement articulatingspacers can be made [3,25] either by hand or from miscellaneous molds[1,8,13,21,23].

All-cement mobile spacers from which are made of the miscella-neous molds that are formed in the O.R. have their own particularadvantages and disadvantages. The advantages include allowing anelement of physiological motion. The option for adjustable antibioticdosing, a combination of antibiotics, and the addition of an antifungaloption (amphotericin) may be useful. Disadvantages include theadditional time required to construct the implant in the operatingroom, limited number of sizes and additional cost [20].

Some authors have reported their methods for constructing all-cement articulating spacers made intraoperatively with miscellaneousmolds. Fehring et al. [23] used a metal mold to cast the femoralcomponent of the spacer. The surface on the tibial side was made eitherflat or curvedby the impressionof the femoral component.Durbhakula etal. [1] used a specially designed silicone mold to make spacersintraoperatively. Ha [13] reported an intraoperative mold made fromremovedcomponents andused it to create antibiotic spacerswith surfacecontours similar to those of the original total knee replacement. Hsuet al.[8] prepared articulating spacers with specially made polyproprenemolds. Suet al. [21] presentedanarticulating spacerwhichwas cast usingself-prepared molds. They were fabricated from silicone rubber.

However, all-cement articulating spacers made intraoperativelywith miscellaneous molds are without a post-cam design or with onlya tibial post [1,8,13,21,23]. A high tibial post can only maintainmedial–lateral stability. The cam is a key construct for anterior–posterior stability and the roll back mechanism. A standard post-cam

408 H. Shen et al. / The Knee 17 (2010) 407–411

design has been only used in temporary prostheses or with thePROSTALAC system [10,12,19].

We developed a simple technique to make cement-on-cementantibiotic-loaded articulating spacers that donot contain any previouslyinfected materials. The surface and size of the articulating spacer aresimilar to those of the original TKA. This technique produces a post-camposterior stabilized design in cement articulating spacers similar to thatof the original component, which prevents dislocation and improvesROM.

2. Materials and methods

Between 2004 and 2007, 17 patients with an infected TKA weretreated with a cement-on-cement antibiotic-loaded articulating spacerat our institution. The patients included 10 females and seven males,with an average age of 67 years (range, 52–76 years). The preoperativeworkup for infection consisted of a detailed clinical history and physicalexamination; radiographic evaluation; and laboratory studies. An ESRN30 mm/h combined with a CRP level N10 mg/L was considered highlysuggestive of infection. The infecting organism was determined by apositive culture result on at least two of three intraoperative cultures.

Every patient underwent a two-stage exchange with an antibiotic-loaded articulating spacer (ALAS). The initial procedure wasperformed through a medial parapatellar approach to the kneejoint. The implants and previously used bone cement were removed,followed by a thorough debridement of the infected tissue as well asany devitalized tissue. Three intraoperative culture specimens weretaken before the administration of intravenous antibiotic therapy.Cultures were taken from synovial fluid, inflamed synovial tissue andinterface membrane.

A custom mold was made intraoperatively with bone cement andthe standard posterior stabilized TKA provisional components (trials)which were the same size as the original prosthesis. Sterile paraffin oilwas used to prevent adherence of the cement to the mold. Antibiotic-loaded cement was made of gentamicin (0.5 g per 40-g package)cement mixed with vancomycin antibiotic powder (3 g per 40-g

Fig. 1. The photographs illustrate the intraoperative technique for manufacturing a cementTKA provisional component. A: A PS TKA femoral trial with sterile paraffin oil was inserted imold and the femoral part of the spacer was made. C: The same procedure was performed ocement spacer (were) are shown. F: The post and cam mechanism of the articulating space

package). The articular surface of the provisional component (femoralor tibial component) with sterile paraffin oil was inserted into a bolusof bone cement in the late doughy phase. Before complete hardeningof the cement, the component was removed. This first step took about15 min. After the bone cement had cured, the custom mold wascoated with sterile paraffin oil. A bolus of antibiotic-loaded bonecement was poured into the cement mold with firm pressure tofabricate the articulating spacer. Excess cement was removed. Thenthe spacer was separated from the mold, and the edge wassmoothened. It took about 15 min to finish this step. A similar processwas carried out on both the tibial and femoral sides (Fig. 1).

In knees with severe bone loss after removal of the infectedimplants, Kirschner wires were inserted into the components beforethe cement was completely cured, to produce stemmed articulatingspacers with additional stability.

The tibial spacer was inserted first and was cemented to theproximal tibia with additional antibiotic-loaded cement so as to fit thepatient's anatomy and maintain the joint line. The femoral spacer wasthen inserted and cemented to the distal femur with antibiotic-loadedcement. Antibiotic-loaded bone cement was used in the late doughyphase to make the spacer adhere to the open bone ends, whileavoiding infiltration of cement. The range of motion, stability, andpatellar tracking was assessed. Lateral retinacular release wasperformed as necessary. A drain was inserted to diminish postoper-ative hematoma formation, and the wound was closed.

In our first case, each step of the procedure was performedsequentially by one surgeon. Thereafter, molding the femoral trial andtibial trial was carried out at the same time by two surgeons. Moldingof the femoral spacer and tibial spacer was performed in the samemanner. Each of these two steps took approximately 30 min. Webegan tomake the spacers after implant removal. At that time, the sizeof the original components could be confirmed. Thorough debride-ment, rinsing with hydrogen peroxide, soaking with povidone–iodinesolution, pulse irrigation and coagulation, which took about 40–50 min, were performed by one team of surgeons. Simultaneously, thespacer was made by another team. After the tourniquet was inflated

-on-cement antibiotic-loaded articulating spacer with the standard posterior stabilizednto the bolus of bone cement. B: Antibiotic-loaded cement was poured into the femoraln the tibial side. D–E: PS TKA trials, cement molds and surfaces of the antibiotic-loadedr (showed well) exhibited good apposition in extension and flexion.

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for the second time, spacer was fixed and the wound closed. Theentire surgical procedure took 90–120 min. The molds can be re-sterilized with ETO and re-used in another procedure.

Continuous passive motion (CPM) was used and physical therapywas implemented immediately after operation. The patients wereinstructed to increase their knee motion gradually with partial weight-bearing activity with a walker or forearm crutches. Free mobilizationwas allowed for the patients 4 weeks later.

The intraoperative cultureswere reviewed to determine the infectingorganism. After the first stage, antibiotics were given for at least 6 weeksand were continued until the infection was controlled clinically. Thelaboratory tests included the leukocyte count, erythrocyte sedimentationrate, and C-reactive protein level. Reimplantation of the new prosthesiswas performed at least 10 weeks after the first-stage operation if therewas sufficient clinical, radiographic, and laboratory evidence to supportthe absence of infection for more than 4 weeks. Previously insertedarticulating cement spacers were removed and a thorough debridementwas performed. A new prosthesis was inserted only if there were nointraoperative findings to suggest infection. Antibiotic-loaded cementcontaininggentamycin (0.5 gper40-gpackage) andvancomycin (1 gper40-g package) was used to protect the implants from bacterialcolonization. If there was any suspicion of infection, the knee wasdebrided and the two-stage exchange was repeated.

The range of motion before the first stage, before the second-stagereimplantation, and at the latest postoperative follow-up was docu-mented. The Knee Society knee and functional scores were recorded inboth the interim period and the latest follow-up. Any recurrence ofinfection and complications related to the techniquewas also recorded.

3. Results

The average duration of follow-up was 31 months (range, 18–47 months). Thearticulating spacer procedures were used in all of the patients in this case series. Thegeneral clinical data are presented in Table 1. One patient developed recurrent infectionduring the interim period. Despite repeated debridement with articulating spacerimplantation and long-term antibiotics, the infection persisted. Finally, an above-kneeamputation was carried out for this patient 7.8 months after the first-stage debridement.One complex case with extensor mechanism damage had undergone debridement threetimes. The range of motion prior to articulating spacer implantation was 0° to 30°. Thispatient received articulating spacer procedures and the infection was eradicated.11.3 months later, a knee arthrodesis was performed for pain and dysfunction.

Table 1Clinical data.

Case Age(y)

Gender Dignosis Onset ofinfection

Organism Interim period

ROM Kneescore

Functscore

1 70 Female OA 0–110 S. haemolyticus 69 552 61 Female OA 0–100 Unknown 68 553 55 Male OA 0–30 S. epidermidis+

Pseudomonas45 20

4 67 Female OA 5–95 S. aureus 60.2 505 68 Female RA 5–80 S. aureus 60 506 75 Male OA 0–90 E. cloacae+Enterococcus

faecalis62 50

7 78 Female OA 0–97 S. aureus 69 608 74 Male RA 0–85 Unknown 64.6 509 68 Male OA 0–85 Pichia anomala 67.4 5510 69 Male OA 10–75 Peptostreptococcus

asaccharolyticus58 45

11 70 Female OA 5–84 S. epidermidis 64 5012 74 Male OA 3–77 S. aureus 63 5013 68 Female RA 3–100 S. epidermidis 66.4 5514 77 Male OA 0–107 P. aeruginosa 69 6015 78 Female RA 0–93 S. epidermidis 61.4 5016 71 Female OA 3–83 Unknown 61.8 5517 63 Female OA 0–85 Unknown 66 55Average 69.8 84.8 63.2 50.9

a Two cases without reimplantation were ruled out for calculation of the average interim

The reimplantation was facilitated with this technique. Ten patients received thesecond-stage reimplantation with Nexgen LCCK knee implants. Minimal soft-tissuecontracture, maintenance of the collateral ligaments and preservation of bone qualitywere found during the second-stage operation. Only one knee required rectus snip forexposure. No cases needed tibial tubercule osteotomy or V–Y quadricepsplasty. No onerequired soft-tissue flap coverage for wound closure. At the latest follow-up, none of thepatients had any evidence of infection, nor did they require chronic antibiotic therapy.

Six patients were keen to avoid any further surgery and articulating spacers wereretained in situ without recurrent infection. Because of excessive usage resulting fromover-walking, spacer fracture occurred in one patient with schizophrenia. Reimplantationwas performed in this patient 33 months after the first-stage operation. Hence, fivepatients had their articulating spacer preserved in situ for their daily life activities (Fig. 2).Their average knee scorewas64.6 and theaverage function scorewas56 atfinal follow-up.The average duration of articulating spacer in situ of these five patients was 36.8 months.There were no signs of infection in these patients.

The infecting organismwas identified in 13 cases. A single organismwas identified in11 cases andmixed growthwas found in two cases. The common bacteriawere coagulasenegative Staphylococcus (CNS) and S. aureus. Fungal infection was found in one knee.Scarce bacteria in this case series included Peptostreptococcus asaccharolyticus and Pichiaanomala. One patient with polymicrobial infection by E. cloacae and Enterococcus faecalisultimately receivedanabove-knee amputation. In fourpatients, no infecting organismwasisolated.

The average time between the two stages (10 cases) was 7.8 months (range 3.5–33.4). When spacer fracture was ruled out, the average interval period (nine cases) wasfive months. Sixteen patients were satisfied with the articulating spacer, except for onepatient with extensor mechanism damage, who complained of pain and dysfunction. Atthe latest follow-up of the articulating spacer period, the average American KneeSociety knee score was 63.2 (range 45–69), and the average function score was 50.9(range 20–60). Because of the wishes of family members or financial problems, fivepatients kept the articulating spacer in situ as the definitive treatment without anyevidence of infection. All of these patients considered the function of their knees witharticulating spacers to be much better than before the operation. In ten patients withreimplantation, the average Knee Society knee score at the latest follow-up was 83.6,and the average function score was 75.5.

The average ROM before the first stage was 84.8° (range 30°–110°) and that in theinterim was 82.3° (range 25°–95°), whereas at the latest follow-up it was 95.4° (range90°–105°). The mean flexion contracture before the first stage was 2° (range, 0°–10°),and that in the interim was 3° (range, 0°–10°), whereas that at the latest follow-up was1.3° (range, 0°–5°). The mean maximum flexion before the first stage was 86.8° (range,30°–110°), and that in the interim was 85.3° (25°–95°), whereas at the latest follow-upit was 96.7° (range, 93°–105°).

4. Discussion

A two-stage exchangewith articulating spacer is currently the goldstandard method for managing chronically infected TKA [1–6]. Themajor advantage of the articulating spacer is that it provides effective

Intervalbetweenstages(month)

Post-reimplantation Result Follow-up(month)

ion ROM Kneescore

Functionscore

ROM

0–95 3.9 90 90 0–100 Reimplantation 470–90 5.2 89 80 0–95 Reimplantation 350–25 11.3a Arthrodesis 24

5–91 33.4 88.4 70 3–95 Reimplantation 415–90 6.7 83.6 80 2–95 Reimplantation 340–85 7.8a Amputation 24

0–95 8.4 86 85 0–105 Reimplantation 2610–93 Spacer 360–87 3.5 68.8 60 0–94 Reimplantation 25

10–85 4.7 76 70 5–95 Reimplantation 22

5–85 Spacer 325–80 Spacer 385–97 3.5 83.4 70 3–95 Reimplantation 180–95 4.4 87 80 0–100 Reimplantation 263–85 Spacer 433–87 Spacer 350–80 4.5 83.6 70 0–93 Reimplantation 27

82.3 7.8 83.6 75.5 95.4 31.35

period.

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eradication of infection along with an excellent range of knee motion,both between the stages and at follow-up [7–12,22]. Because thearticulating spacer overcomes certain problems of a static spacer, suchas quadriceps shortening and scaring, capsular contracture, femoralbone stock loss, difficult subsequent exposure, and poor knee functionbetween the stages, the interim duration can been extended [1,4,7–12,14,15]. Moreover, with an acceptable range of motion and dailyfunction, some patients are keen to avoid reimplantations [16,17].

Some authors reportedly prefer to use the metal-on-polyethyleneversion such as in Hofmann's protocol, with a sterilized femoralcomponent retained for good range of motion [5–7,10]. In a recentstudy with Hofmann's protocol, Anderson et al. reported an excellentrange of knee motion with average 2° to 115° at the latest follow-up.The author pointed out that physical therapy and early mobilizationwere very important, both between stages and post-reimplantation[5]. Huang et al. also treated TKA infection with Hofmann's method.However, the range of motion after reimplantation averaged 97.6°,which was smaller than that of the previous report [16]. Neitherreport provided ROM before the first-stage surgery. Nevertheless, insome recent studies, a good range of motion at final follow-up alsowas achieved with an all-cement articulating spacer. Ha reported agood ROM (2°–104°) at final follow-up with an all-cement articulat-ing spacer [13]. Villanueva-Martínez et al. reported that the averagemotion after reimplantation was 107° with hand-made articulatingspacers [3]. The range of motion was influenced by a number offactors, such as prosthesis design, operative skills, patient compliance,early rehabilitation, and especially, preoperative ROM. Therefore, thefinal ROM with non-all cement articulation after reimplantation maynot be better than that of all-cement articulation. In the current study,a ROM of 80°–90° in the interim period was sufficient for the second-stage reimplantation, and only one knee required rectus snip forexposure. On the other hand, the metal or polyethylene surface mightdecrease the friction between articulating surface, but the major goal

Fig. 2. Lateral radiographsof active full extension (A)andflexion (B) illustrate thearticulatingspacer in situ with good range of motion; Anterior–posterior projection of the articulatingspacer (C) in situ shows good alignment and medial–lateral balance; The spacer is also incongruity with the retained patella (D).

of using the articulating spacer was the eradication of infection. Anantibiotic-loaded cement surface releases antibiotics and preventbacterial colonization. Both metal and polyethylene surfaces, whichhave no antibiotic protection, have the potential of biofilm formationby colonization of rudimentory bacteria. Antibiotic elution fromPMMA is directly dependant on the surface area of the implant andthe absolute amount of antibiotic in the cement [18]. Therefore, weprefer an all-cement surface articulating spacer for its greater volumeof antibiotic storage and larger area for antibiotic elution.

There were two recent studies reported on all-cement articulatingspacers made intraoperatively with mold methods. Ha used theremoved femoral component and polyethylene insert, which werewashed and sterilized by autoclave, to make custom molds with bonecement intraoperatively [13]. Hsu et al. manufactured articulatingspacers intraoperatively with polypropylene molds made in advance[8]. Our technique can provide the stability of a posterior stabilizingspine by intraoperative molding with the standard posterior stabi-lized TKA provisional component to prevent the spacer fromdislocation and subluxation. Compared with the technique used byHa et al., our technique does not utilize any infected implant.Compared with the technique used by Hsu et al., our molding methoddoes not require measuring the bone end to choose a mold of anappropriate size. We spentmore time on thorough debridement usingbiocides and pulse irrigation than on making spacers, becauseinfection control must be the first aim in this sort of procedure.Fabrication of the spacers did not increase the total surgical time. If thesize of the re-sterilized mold matches that of the infected prosthesis,the step of making a custom mold can be skipped.

Potential wear debris from the cement-on-cement surface ofspacers has been a concern. Theoretically, cement-on-cement artic-ulation has higher friction than the metal-on polyethylene form, andmay limit the range of motion [8]. Evans suggested that the potentialmechanical problems with the currently used articulating constructsinclude increased wear debris and fragmentation from a highcoefficient of friction with cement-on-cement articulation [18].However, according to the results of a preformed all-cement kneespacer, the wear from the interface was not much higher than thatproduced by a polyethylene-on-metal interface [9,15,24]. With anintraoperative-mademold system, the roughness of the spacers mightbe slightly higher than that of preformed all-cement spacers, but thereis no report of particle-related complications with these spacers[1,8,13]. Recently, Su et al. reported that histopathologic examinationof the soft tissue surrounding the spacer interface revealed only a fewcement particles with a mild inflammatory reaction [21]. In thepresent study, crepitation was common within the first 4 weeks, andthen the sound disappeared gradually. Thereafter, these spacersbehaved just like normal prostheses. From the retrieved spacers,mirror-like polished surfaceswere found only on the tibial surface anddistal–posterior femoral surface, which were associated with ROMand cement debris. No osteolysis or substantial bone loss was found atthe time of the revision surgery.

In our case series, spacer fracture occurred in one patient withschizophrenia who over-exercised. Reimplantation was performed33months after the first-stage operation. Over-walking appeared tobe a reason for the spacer fracture, although a greater volume ofantibiotics added into the bone cement might also play a role. Some airbubbles were produced at the time of cement polymerization becausethe cement was mixed with a large volume of antibiotics manually.When the release area of the antibiotics was enlarged with air bubbles,the mechanical strength of articulating spacer decreased at the sametime. To date, spacer fracture has not occurred in the other five patientswith articulating spacer in situ. This might be ascribed to the bettercompliance of these five patients with the recovery regimen. However,whether the articulating spacers will ultimately break is at this pointunknown. Another problem which should be given attention is that, ifthese cement spacers are left in situ for an extended period, the

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prolonged release of subinhibitory concentration of antibiotics mightstimulate the introduction of antibiotic-resistant strains. Polymethyl-methacrylate itself is also a foreign material with a rough surface, andmay provide a suitable surface area wherein bacteria can adhere.Therefore, these five patients with the articulating spacer in situ will bemonitored with regular laboratory tests for any recurrence of infection.

In conclusion, this technique utilizes an all-cement antibioticbearing articulating spacerwith surface contours and post-cam designsimilar to the original TKR. The range of motion during the interimphase eases the performance of the basic activities daily life, maintainsROM of the joint, facilitates second-stage revision, and allows thesecond stage to be delayed if necessary. The reinfection andcomplication rates were low. We routinely use the technique in thetwo-stage exchange of infected TKA. Making the mold and spacerintraoperatively does not increase the whole surgical time, but it doesrequire additional manpower. Potential mechanical problems withthis technique might restrict the use of the spacer in situ for anextended period of time. The limitations of this study are the smallnumber of patients and the lack of a control group. Furtherrandomized controlled trials with a larger cohort are needed tosupport the findings presented here.

5. Conflict of interest

None.

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