Orthopaedics & Traumatology: Surgery & Research 101 (2015) 553–557
Available online at
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Original article
Chronic infection of unicompartmental knee arthroplasty: One-stage conversion to total knee arthroplasty C. Labruyère , V. Zeller , L. Lhotellier , N. Desplaces , P. Léonard , P. Mamoudy , S. Marmor ∗ Centre de référence en infection ostéoarticulaire, Groupe Hospitalier Diaconesses Croix Saint-Simon, 125, rue d’Avron, 75020 Paris, France
a r t i c l e
i n f o
Article history: Received 26 November 2014 Accepted 22 April 2015 Keywords: Unicompartmental knee prosthesis Infection Revision of unicompartimental knee prosthesis One-stage prosthesis exchange
a b s t r a c t Background: The main reasons for revision of unicompartmental knee arthroplasty (UKA) are loosening, wear, extension of osteoarthritis to another compartment, and infection. There have been no studies of the management of infected UKA, whose incidence varies from 0.2% to 1%. Our objective was to describe infection-related and mechanical outcomes of chronic UKA infection managed by one-stage conversion to total knee arthroplasty (TKA). Patients and methods: Consecutive patients with chronic UKA infection managed by one-stage conversion to TKA between January 2003 and December 2010 were included in a retrospective single-center study. All patients also received appropriate dual antibiotic therapy intravenously for 6 weeks then orally for 6 additional weeks. Results: During the study period, among 233 cases of infected knee arthroplasty managed at our center, 9 met the study inclusion criteria. The UKA was medial in 6 patients, lateral in 2, and patellofemoral in 1. Median age was 67 years (range, 36–83 years) and median infection duration was 9 months. In 5 patients, previous treatment with synovectomy, joint lavage, and antibiotics had failed. The following bacteria were identified: oxacillin-susceptible Staphylococci, n = 6 (S. epidermidis, n = 4; S. capitis, n = 1; and S. lugdunensis, n = 1); nutritionally deficient Streptococcus, n = 1; Enterococcus durans, n = 1; and Escherichia coli, n = 1. Median follow-up was 60 months (range, 36–96 months). No patient experienced recurrent infection or required revision surgery for infection. No medical complications limiting the use of appropriate antibiotic therapy were recorded. The mean preoperative knee and function scores were 60 and 50, respectively; corresponding mean postoperative values were 75 and 65, respectively. Discussion: UKA infection involves both the prosthesis and the native cartilage, neither of which can be treated conservatively in chronic forms. After identification of the causative organism, synovectomy and joint excision followed by same-stage TKA and combined with appropriate antibiotic therapy for 3 months is effective. Level of evidence: IV, retrospective cohort study. © 2015 Elsevier Masson SAS. All rights reserved.
1. Introduction Advantages of unicompartmental knee arthroplasty (UKA) compared to total knee arthroplasty (TKA) include preservation of bone stock, knee kinematics that more closely replicate those of the normal knee, less morbidity, and a faster recovery [1,2]. UKA produces satisfactory outcomes when used to treat incapacitating, primary or secondary, unicompartmental knee osteoarthritis. The 10-year UKA survival rate, evaluated at 70% in an early study by Marmor [3], was 90% to 95% in recent work by Argenson et al. and Lustig et al. [4,5]; and the functional outcomes were satisfactory.
∗ Corresponding author. Tel.: +33 1 44 64 16 40. E-mail address: [email protected] (S. Marmor). http://dx.doi.org/10.1016/j.otsr.2015.04.006 1877-0568/© 2015 Elsevier Masson SAS. All rights reserved.
The main reasons for UKA revision are loosening, extension of the osteoarthritis to another compartment, wear, and infection [6]. The frequency of periprosthetic infection after UKA is 0.2% to 1% [6–9]. A distinctive feature of UKA infection is that both the prostheses and the native cartilage are involved. Infection is an uncommon but severe complication that requires multidisciplinary surgical and medical management to both eradicate the infection and produce the best possible functional outcome. Chronic infection cannot be treated conservatively. Joint resection followed by one-stage or two-stage TKA is an option in this situation. To date, no studies have specifically addressed the management of UKA infection. The objective of this study was to describe the infection-related and mechanical outcomes of synovectomy followed by one-step TKA in patients with chronic UKA infection. We hypothesised that this one-step surgical strategy was associated with a high rate of
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C. Labruyère et al. / Orthopaedics & Traumatology: Surgery & Research 101 (2015) 553–557
infection eradication and produced functional outcomes similar to those seen after aseptic UKA revision. 2. Patients and methods A retrospective single-centre design was used. The study included consecutive patients with chronic UKA infection managed between January 2003 and December 2010 at a specialised center in osteoarticular infections. 2.1. Study population The patient characteristics were retrieved from the department database and patient medical records. Of the 233 patients with knee prosthesis infection, 9 were consecutive patients with chronic UKA infection managed by one-step conversion to TKA in 2003–2010 and were included in the study. There were 6 males and 3 females, with a median age of 65 years (range, 36–83 years) and a median body mass index of 25.5 kg/m2 (range, 20.2–29.4 kg/m2 ). Among them, 6 had a medial prosthesis, 2 a lateral prosthesis, and 1 a patellofemoral prosthesis. The reason for UKA was primary unicompartmental osteoarthritis in 5 patients, post-traumatic osteoarthritis in 3 patients, and avascular necrosis of the medial femoral condyle in 1 patient. In 2 patients, there was a history of local infection before the UKA: infected supracondylar non-union without bacteriological documentation occurred 7 years before patellofemoral UKA in 1 patient and infection of a synthetic anterior cruciate ligament 8 years before UKA in the other. Another patient experienced infection after internal fixation of a medial condylar fracture 4 months after UKA. At referral to our centre, all 9 patients had chronic knee infection with a median duration of 9 months (range, 2–84 months). A sinus tract was present in 2 patients. Furthermore, 5 patients had failed previous treatment with synovectomy, joint lavage, and antibiotics. The median number of procedures before referral to our centre was 3 (range, 1–19). 2.2. Medical and surgical management 2.2.1. Criteria used to diagnose infection Infection was suspected on the basis of clinical, radiological, and laboratory criteria. Joint aspiration was performed routinely before the surgical procedure, after stopping all antibiotics for at least 3 weeks. The results were confirmed by obtaining deep intraoperative specimens before antibiotic therapy initiation. Microbiologically documented infection was defined as recovery of the same organism from at least two intraoperative specimens [10,11]. 2.2.2. Microbiological findings A single organism was recovered in each of the 9 patients. The most common organisms were oxacillin-susceptible Staphylococci, with 6 patients (S. epidermidis, n = 4; S. capitis, n = 1; and S. lugdunensis, n = 1). There was 1 case each of nutritionally deficient Streptococcus, Enterococcus durans, and Escherichia coli. The preoperative joint aspirate was negative in 2 patients. One of them was the patient with a history of medial condylar fracture infected with E. durans, which was also recovered from the specimens taken during UKA-to-TKA conversion. The other was the patient who had a history of infected supracondylar non-union without bacteriological documentation 7 years before patellofemoral UKA; osteoarthritis extension required revision surgery 3 years after the UKA. The macroscopic appearance suggested infection and the intraoperative specimens collected before the initiation of prophylactic antibiotic therapy grew a nutritionally deficient Streptococcus. In both of these patients, the prophylactic
Fig. 1. Exchange of an infected unicompartmental knee prosthesis for a total knee prosthesis.
antibiotics started intraoperatively were continued until the results of the intraoperative specimens became available, allowing adjustment to the susceptibility profile. 2.2.3. Surgical treatment Total synovectomy was performed and the prosthesis was removed, as well as all infected tissues. One-step TKA was then carried out. A cemented posterior-stabilised prosthesis was implanted in 7 patients (Fig. 1). In the remaining 2 patients, extensive damage
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In 1 patient, severe dilated cardiomyopathy had previously contraindicated surgery, leading to the prescription of suppressive antibiotic therapy for 5 years. Stabilisation of the heart failure by implantation of a pacemaker then allowed curative strategy. All patients underwent a clinical and radiological evaluation at least 2 years after the UKA-to-TKA conversion. The International Knee Society (IKS) scores were determined to evaluate the mechanical outcome [12]. Failure to eradicate the infection was defined as recurrent infection due to the same organism or to a different organism. 3. Results Table 1 lists the main epidemiological and medical data. Median overall follow-up was 60 months (range, 36–96 months). No patient was lost to follow-up. One patient died from heart disease 2 years after the conversion, with no evidence of recurrent infection. 3.1. Infection-related outcomes and medical complications No patient experienced recurrent infection and none underwent re-operation for infection-related reasons. Complications of antibiotic therapy occurred in 2 patients: 1 had an allergy to penicillin and the other infection and thrombosis of the central venous catheter. Neither complication prevented continued treatment with appropriate antibiotics. 3.2. Functional outcomes and surgical complications Table 2 shows the IKS scores. In 4 patients, low IKS scores were ascribable to concomitant conditions: incapacitating lumbar canal stenosis, preoperative patella baja with knee stiffness, incapacitating sciatica refractory to medical treatment and requiring implantation of a transcutaneous electrical nerve stimulator, and development of osteoarthritis involving all three compartments of the contralateral knee. The IKS function score was less than 50 in these 4 patients. Two patients each experienced one surgical complication. A haematoma requiring surgical drainage developed in a patient on anti-platelet therapy. The other patient also developed a haematoma, while receiving anticoagulant therapy in an effective dose, and was treated by aspiration followed by knee manipulation under general anaesthesia. 4. Discussion
Fig. 2. Exchange of an infected unicompartmental knee prosthesis for a hinged total knee prosthesis with a medial wedge to fill the defect.
to bone or ligaments required implantation of a cemented hinged prosthesis (Fig. 2). Reconstruction using wedges after performing the tibial and femoral cuts was required in 6 patients and stem extensions were used in 5 patients. Non-antibiotic cement was used for implant fixation. 2.2.4. Antibiotic therapy Antibiotic therapy was started intraoperatively, after collection of the specimens for microbiological studies. The results of the preoperative joint aspirate, when positive, were used to select the antibiotics. Two antibiotics were given intravenously for 6 weeks then orally for an additional 6 weeks.
To the best of our knowledge, there is not published study focussed specifically on the management of infected UKA, either by synovectomy or by prosthesis exchange. Although UKA infection is rare, it accounts for 3.9% of all knee prosthesis infections managed in our department. The main limitations of our study are the retrospective single-centre design and small number of patients. Nevertheless, eradication of the infection was achieved consistently. The mechanical results in our case-series were comparable to those reported after one- or two-step TKA exchange for infection [13,14] and after conversion of non-infected UKA-to-TKA [15–18]. The considerable bone and ligament damage caused by the infection and the need for a relatively extensive surgical approach to allow total resection probably contribute to adversely affect postoperative knee function. The persistence of native cartilage and small size of the prosthesis to be removed facilitate joint resection in healthy tissue, after performing the bone cuts and removing the unicompartmental
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Age/Sex
Reason for UKA
Local infection before UKA
Number of procedures before UKA/Total
Failure of treatment to eradicate the infection
Organism Aspiration
Intraoperatively
Duration of infection (months)
Type of TKA prosthesis
Reconstruction
83 years/M 64 years/M 73 years/M
Primary MTF OA Primary MTF OA Primary LTF OA
No No No
0/2 1/4 0/1
Yes Yes No
S. epidermidis – S. epidermidis
S. epidermidis Enterococcus durans S. epidermidis
5 8 84
Revision Hinged Hinged
67 years/M
Primary MTF OA
No
1/3
Yes
S. epidermidis
S. epidermidis
25
Revision
78 years/F
Avascular necrosis of medial condyle
No
0/2
Yes
E. coli
E. coli
2
Revision
71 years/M
Post-traumatic MTF OA Post-traumatic MTF OA Primary LTF OA Post-traumatic PF OA
No
1/3
No
S. lugdunensis
S. lugdunensis
5
Revision
Yes
10/19
Yes
S. capitis
S. capitis
24
Revision
Tibial stem Tibial wedges Tibial wedges and stem; femoral stem Tibial stem and femoral wedges Femoral wedges and stem; tibial stem Tibial wedges and stem Tibial wedges
No Yes
0/1 2/3
No No
S. epidermidis –
S. epidermidis Nutritionally deficient Streptococcus
8 84
Standard Revision
No No
56 years/M 51 years/F 36 years/F
M: male; F: female; UKA: unicompartmental knee arthroplasty; MTF: medial tibio-femoral; OA: osteoarthritis; LTF: lateral tibio-femoral; PF: patellofemoral; TKA: total knee arthroplasty; E. coli: Escherichia coli; S.: Staphylococci.
C. Labruyère et al. / Orthopaedics & Traumatology: Surgery & Research 101 (2015) 553–557
Table 1 Main epidemiological and medical data in the 9 patients.
C. Labruyère et al. / Orthopaedics & Traumatology: Surgery & Research 101 (2015) 553–557 Table 2 IKS scores.
Knee score Function score
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LL: consultant for Tornier and Amplitude. SM: consultant for Tornier and Depuy. Preoperatively Median (min–max)
Postoperatively Median (min–max)
60 (25–80) 50 (0–60)
75 (47–100) 65 (10–90)
IKS: International Knee Society; min: minimum; max: maximum.
implant. However, the loss of bone tissue related to removal of the unicompartmental implant often requires the use of techniques such as bone defect filling by grafts or wedges and the implantation of more or less constrained revision prostheses with stem extensions [15–19]. The nature and distribution of the causative organisms in our study are similar to those found in a study of infected total hip arthroplasty (THA) reported by Tsukayama et al. [20] and in a THA and TKA cohort investigated by Lortat-Jacob et al. [21]. Coagulasenegative staphylococci are more common than other organisms (streptococci, enterococci, and Gram-negative rods). Thus, the bacteria responsible for UKA infection in our patients are representative of those found in joint prostheses infections overall. Factors supporting the decision to perform one-step UKAto-TKA conversion were the preoperative identification of the causative organism in the joint aspirate, the susceptibility of this organism to antibiotics, and the feasibility of complete excision. The greater ease of infected tissue removal compared to infected TKA may explain that eradication of the infection was achieved consistently, despite the use of standard antibiotic therapy regimens and of non-antibiotic cement. We believe that the best indication for one-step UKA-to-TKA conversion combined with antibiotic therapy is chronic UKA infection, recovery of the causative organism by preoperative joint aspiration, and feasibility of total infected tissue excision followed by implantation of a revision prosthesis allowing joint reconstruction. This therapeutic strategy requires the involvement of a multidisciplinary team that includes an infectious-diseases specialist in charge of prescribing and monitoring the antibiotic therapy. Another treatment option in chronic infection is two-step prosthesis exchange, which is widely used to treat chronic TKA infection [22–27]. This option has the disadvantage of requiring two surgical procedures separated by a period of limited knee function, even when a spacer is used [28]. Further joint excision during the second step holds theoretical appeal for eradicating the infection but exposes the patient to a further risk of infection during implantation of the new prosthesis. Using this strategy, Hirakawa et al. had a 25% failure rate, with one-fourth of failures due to infection by a different organism [27]. 5. Conclusion UKA infection is unique in that it involves both the prosthesis and the native cartilage, neither of which can be treated conservatively in chronic forms. The very low incidence and specific characteristics of chronic UKA infection require management by an experienced multidisciplinary team. After identification of the causative organism, total synovectomy followed by same-step TKA and combined with appropriate antibiotic therapy for 3 months is effective. Disclosure of interest CL, VZ, PL, ND, and PM declare that they have no conflicts of interest concerning this article.
References [1] Patil S, Colwell CW, Ezzet KA, D’Lima DD. Can normal knee kinematics be restored with unicompartmental knee replacement? J Bone Joint Surg Am 2005;87:332–8. [2] Newman JH, Ackroyd CE, Shah NA. Unicompartmental or total knee replacement? Five-year results of a prospective, randomised trial of 102 osteoarthritic knees with unicompartmental arthritis. J Bone Joint Surg Br 1998;80:862–5. [3] Marmor L. Unicompartmental knee arthroplasty. Ten- to 13-year follow-up study. Clin Orthop Relat Res 1988;(226):14–20. [4] Argenson JN, Chevrol-Benkeddache Y, Aubaniac JM. Modern unicompartmental knee arthroplasty with cement: a three- to ten-year follow-up study. J Bone Joint Surg Am 2002;84-A:2235–9. [5] Lustig S, Paillot JL, Servien E, Henry J, Ait Si Selmi T, Neyret P. Cemented all polyethylene tibial insert unicompartimental knee arthroplasty: a long-term follow-up study. Orthop Traumatol Surg Res 2009;95:12–21. [6] Epinette JA, Brunschweiler B, Mertl P, Mole D, Cazenave A, French Society for Hip and Knee. Unicompartmental knee arthroplasty modes of failure: wear is not the main reason for failure: a multicentre study of 418 failed knees. Orthop Traumatol Surg Res 2012;98:S124–30. [7] Whiteside LA. Treatment of infected total knee arthroplasty. Clin Orthop Relat Res 1994;(299):169–72. [8] Göksan SB, Freeman MA. One-stage reimplantation for infected total knee arthroplasty. J Bone Joint Surg Br 1992;74:78–82. [9] Morrey BF, Westholm F, Schoifet S, Rand JA, Bryan RS. Long-term results of various treatment options for infected total knee arthroplasty. Clin Orthop Relat Res 1989;(248):120–8. [10] Parvizi J, Della Valle CJ. AAOS Clinical Practice Guideline: diagnosis and treatment of periprosthetic joint infections of the hip and knee. J Am Acad Orthop Surg 2010;18:771–2. [11] Society of Unicondylar Research and Continuing Education. Diagnosis of periprosthetic joint infection after unicompartmental knee arthroplasty. J Arthroplasty 2012;27:46–50. [12] Insall JN, Dorr LD, Scott RD, Scott WN. Rationale of the Knee Society clinical rating system. Clin Orthop Relat Res 1989;(248):13–4. [13] Hanssen AD, Rand JA, Osmon DR. Treatment of the infected total knee arthroplasty with insertion of another prosthesis. The effect of antibioticimpregnated bone cement. Clin Orthop Relat Res 1994;(309):44–55. [14] Bauer T, Piriou P, Lhotellier L, Leclerc P, Mamoudy P, Lortat-Jacob A. Results of reimplantation for infected total knee arthroplasty: 107 cases. Rev Chir Orthop Reparatrice Appar Mot 2006;92:692–700 [in French]. [15] Sierra RJ, Kassel CA, Wetters NG, Berend KR, Della Valle CJ, Lombardi AV. Revision of unicompartmental arthroplasty to total knee arthroplasty: not always a slam dunk! J Arthroplasty 2013;28:128–32. [16] Oduwole KO, Sayana MK, Onayemi F, McCarthy T, O’Byrne J. Analysis of revision procedures for failed unicondylar knee replacement. Ir J Med Sci 2010;179:361–4. [17] Saragaglia D, Estour G, Nemer C, Colle P-E. Revision of 33 unicompartmental knee prostheses using total knee arthroplasty: strategy and results. Int Orthop 2009;33:969–74. [18] Châtain F, Richard A, Deschamps G, Chambat P, Neyret P. Revision total knee arthroplasty after unicompartmental femorotibial prosthesis: 54 cases. Rev Chir Orthop Reparatrice Appar Mot 2004;90:49–57 [in French]. [19] Khan Z, Nawaz SZ, Kahane S, Esler C, Chatterji U. Conversion of unicompartmental knee arthroplasty to total knee arthroplasty: the challenges and need for augments. Acta Orthop Belg 2013;79:699–705. [20] Tsukayama DT, Goldberg VM, Kyle R. Diagnosis and management of infection after total knee arthroplasty. J Bone Joint Surg Am 2003;85-A:S75–80. [21] Lortat-Jacob A, Desplaces N, Gaudias J, Dacquet V, Dupon M, Carsenti H, et al. Secondary infection of joint implants: diagnostic criteria, treatment and prevention. Rev Chir Orthop Reparatrice Appar Mot 2002;88:51–61 [in French]. [22] Walker RH, Schurman DJ. Management of infected total knee arthroplasties. Clin Orthop Relat Res 1984;(186):81–9. [23] Wasielewski RC, Barden RM, Rosenberg AG. Results of different surgical procedures on total knee arthroplasty infections. J Arthroplasty 1996;11:931–8. [24] Goldman RT, Scuderi GR, Insall JN. 2-stage reimplantation for infected total knee replacement. Clin Orthop Relat Res 1996;(331):118–24. [25] Buechel FF, Femino FP, D’Alessio J. Primary exchange revision arthroplasty for infected total knee replacement: a long-term study. Am J Orthop 2004;33:190–8. [26] Haleem AA, Berry DJ, Hanssen AD. Mid-term to long-term follow-up of twostage reimplantation for infected total knee arthroplasty. Clin Orthop Relat Res 2004;(428):35–9. [27] Hirakawa K, Stulberg BN, Wilde AH, Bauer TW, Secic M. Results of 2-stage reimplantation for infected total knee arthroplasty. J Arthroplasty 1998;13:22–8. [28] Voleti PB, Baldwin KD, Lee GC. Use of static or articulating spacers for infection following total knee arthroplasty: a systematic literature review. J Bone Joint Surg Am 2013;95:1594–9.
Available online at
ScienceDirect www.sciencedirect.com
Original article
Chronic infection of unicompartmental knee arthroplasty: One-stage conversion to total knee arthroplasty C. Labruyère , V. Zeller , L. Lhotellier , N. Desplaces , P. Léonard , P. Mamoudy , S. Marmor ∗ Centre de référence en infection ostéoarticulaire, Groupe Hospitalier Diaconesses Croix Saint-Simon, 125, rue d’Avron, 75020 Paris, France
a r t i c l e
i n f o
Article history: Received 26 November 2014 Accepted 22 April 2015 Keywords: Unicompartmental knee prosthesis Infection Revision of unicompartimental knee prosthesis One-stage prosthesis exchange
a b s t r a c t Background: The main reasons for revision of unicompartmental knee arthroplasty (UKA) are loosening, wear, extension of osteoarthritis to another compartment, and infection. There have been no studies of the management of infected UKA, whose incidence varies from 0.2% to 1%. Our objective was to describe infection-related and mechanical outcomes of chronic UKA infection managed by one-stage conversion to total knee arthroplasty (TKA). Patients and methods: Consecutive patients with chronic UKA infection managed by one-stage conversion to TKA between January 2003 and December 2010 were included in a retrospective single-center study. All patients also received appropriate dual antibiotic therapy intravenously for 6 weeks then orally for 6 additional weeks. Results: During the study period, among 233 cases of infected knee arthroplasty managed at our center, 9 met the study inclusion criteria. The UKA was medial in 6 patients, lateral in 2, and patellofemoral in 1. Median age was 67 years (range, 36–83 years) and median infection duration was 9 months. In 5 patients, previous treatment with synovectomy, joint lavage, and antibiotics had failed. The following bacteria were identified: oxacillin-susceptible Staphylococci, n = 6 (S. epidermidis, n = 4; S. capitis, n = 1; and S. lugdunensis, n = 1); nutritionally deficient Streptococcus, n = 1; Enterococcus durans, n = 1; and Escherichia coli, n = 1. Median follow-up was 60 months (range, 36–96 months). No patient experienced recurrent infection or required revision surgery for infection. No medical complications limiting the use of appropriate antibiotic therapy were recorded. The mean preoperative knee and function scores were 60 and 50, respectively; corresponding mean postoperative values were 75 and 65, respectively. Discussion: UKA infection involves both the prosthesis and the native cartilage, neither of which can be treated conservatively in chronic forms. After identification of the causative organism, synovectomy and joint excision followed by same-stage TKA and combined with appropriate antibiotic therapy for 3 months is effective. Level of evidence: IV, retrospective cohort study. © 2015 Elsevier Masson SAS. All rights reserved.
1. Introduction Advantages of unicompartmental knee arthroplasty (UKA) compared to total knee arthroplasty (TKA) include preservation of bone stock, knee kinematics that more closely replicate those of the normal knee, less morbidity, and a faster recovery [1,2]. UKA produces satisfactory outcomes when used to treat incapacitating, primary or secondary, unicompartmental knee osteoarthritis. The 10-year UKA survival rate, evaluated at 70% in an early study by Marmor [3], was 90% to 95% in recent work by Argenson et al. and Lustig et al. [4,5]; and the functional outcomes were satisfactory.
∗ Corresponding author. Tel.: +33 1 44 64 16 40. E-mail address: [email protected] (S. Marmor). http://dx.doi.org/10.1016/j.otsr.2015.04.006 1877-0568/© 2015 Elsevier Masson SAS. All rights reserved.
The main reasons for UKA revision are loosening, extension of the osteoarthritis to another compartment, wear, and infection [6]. The frequency of periprosthetic infection after UKA is 0.2% to 1% [6–9]. A distinctive feature of UKA infection is that both the prostheses and the native cartilage are involved. Infection is an uncommon but severe complication that requires multidisciplinary surgical and medical management to both eradicate the infection and produce the best possible functional outcome. Chronic infection cannot be treated conservatively. Joint resection followed by one-stage or two-stage TKA is an option in this situation. To date, no studies have specifically addressed the management of UKA infection. The objective of this study was to describe the infection-related and mechanical outcomes of synovectomy followed by one-step TKA in patients with chronic UKA infection. We hypothesised that this one-step surgical strategy was associated with a high rate of
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C. Labruyère et al. / Orthopaedics & Traumatology: Surgery & Research 101 (2015) 553–557
infection eradication and produced functional outcomes similar to those seen after aseptic UKA revision. 2. Patients and methods A retrospective single-centre design was used. The study included consecutive patients with chronic UKA infection managed between January 2003 and December 2010 at a specialised center in osteoarticular infections. 2.1. Study population The patient characteristics were retrieved from the department database and patient medical records. Of the 233 patients with knee prosthesis infection, 9 were consecutive patients with chronic UKA infection managed by one-step conversion to TKA in 2003–2010 and were included in the study. There were 6 males and 3 females, with a median age of 65 years (range, 36–83 years) and a median body mass index of 25.5 kg/m2 (range, 20.2–29.4 kg/m2 ). Among them, 6 had a medial prosthesis, 2 a lateral prosthesis, and 1 a patellofemoral prosthesis. The reason for UKA was primary unicompartmental osteoarthritis in 5 patients, post-traumatic osteoarthritis in 3 patients, and avascular necrosis of the medial femoral condyle in 1 patient. In 2 patients, there was a history of local infection before the UKA: infected supracondylar non-union without bacteriological documentation occurred 7 years before patellofemoral UKA in 1 patient and infection of a synthetic anterior cruciate ligament 8 years before UKA in the other. Another patient experienced infection after internal fixation of a medial condylar fracture 4 months after UKA. At referral to our centre, all 9 patients had chronic knee infection with a median duration of 9 months (range, 2–84 months). A sinus tract was present in 2 patients. Furthermore, 5 patients had failed previous treatment with synovectomy, joint lavage, and antibiotics. The median number of procedures before referral to our centre was 3 (range, 1–19). 2.2. Medical and surgical management 2.2.1. Criteria used to diagnose infection Infection was suspected on the basis of clinical, radiological, and laboratory criteria. Joint aspiration was performed routinely before the surgical procedure, after stopping all antibiotics for at least 3 weeks. The results were confirmed by obtaining deep intraoperative specimens before antibiotic therapy initiation. Microbiologically documented infection was defined as recovery of the same organism from at least two intraoperative specimens [10,11]. 2.2.2. Microbiological findings A single organism was recovered in each of the 9 patients. The most common organisms were oxacillin-susceptible Staphylococci, with 6 patients (S. epidermidis, n = 4; S. capitis, n = 1; and S. lugdunensis, n = 1). There was 1 case each of nutritionally deficient Streptococcus, Enterococcus durans, and Escherichia coli. The preoperative joint aspirate was negative in 2 patients. One of them was the patient with a history of medial condylar fracture infected with E. durans, which was also recovered from the specimens taken during UKA-to-TKA conversion. The other was the patient who had a history of infected supracondylar non-union without bacteriological documentation 7 years before patellofemoral UKA; osteoarthritis extension required revision surgery 3 years after the UKA. The macroscopic appearance suggested infection and the intraoperative specimens collected before the initiation of prophylactic antibiotic therapy grew a nutritionally deficient Streptococcus. In both of these patients, the prophylactic
Fig. 1. Exchange of an infected unicompartmental knee prosthesis for a total knee prosthesis.
antibiotics started intraoperatively were continued until the results of the intraoperative specimens became available, allowing adjustment to the susceptibility profile. 2.2.3. Surgical treatment Total synovectomy was performed and the prosthesis was removed, as well as all infected tissues. One-step TKA was then carried out. A cemented posterior-stabilised prosthesis was implanted in 7 patients (Fig. 1). In the remaining 2 patients, extensive damage
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In 1 patient, severe dilated cardiomyopathy had previously contraindicated surgery, leading to the prescription of suppressive antibiotic therapy for 5 years. Stabilisation of the heart failure by implantation of a pacemaker then allowed curative strategy. All patients underwent a clinical and radiological evaluation at least 2 years after the UKA-to-TKA conversion. The International Knee Society (IKS) scores were determined to evaluate the mechanical outcome [12]. Failure to eradicate the infection was defined as recurrent infection due to the same organism or to a different organism. 3. Results Table 1 lists the main epidemiological and medical data. Median overall follow-up was 60 months (range, 36–96 months). No patient was lost to follow-up. One patient died from heart disease 2 years after the conversion, with no evidence of recurrent infection. 3.1. Infection-related outcomes and medical complications No patient experienced recurrent infection and none underwent re-operation for infection-related reasons. Complications of antibiotic therapy occurred in 2 patients: 1 had an allergy to penicillin and the other infection and thrombosis of the central venous catheter. Neither complication prevented continued treatment with appropriate antibiotics. 3.2. Functional outcomes and surgical complications Table 2 shows the IKS scores. In 4 patients, low IKS scores were ascribable to concomitant conditions: incapacitating lumbar canal stenosis, preoperative patella baja with knee stiffness, incapacitating sciatica refractory to medical treatment and requiring implantation of a transcutaneous electrical nerve stimulator, and development of osteoarthritis involving all three compartments of the contralateral knee. The IKS function score was less than 50 in these 4 patients. Two patients each experienced one surgical complication. A haematoma requiring surgical drainage developed in a patient on anti-platelet therapy. The other patient also developed a haematoma, while receiving anticoagulant therapy in an effective dose, and was treated by aspiration followed by knee manipulation under general anaesthesia. 4. Discussion
Fig. 2. Exchange of an infected unicompartmental knee prosthesis for a hinged total knee prosthesis with a medial wedge to fill the defect.
to bone or ligaments required implantation of a cemented hinged prosthesis (Fig. 2). Reconstruction using wedges after performing the tibial and femoral cuts was required in 6 patients and stem extensions were used in 5 patients. Non-antibiotic cement was used for implant fixation. 2.2.4. Antibiotic therapy Antibiotic therapy was started intraoperatively, after collection of the specimens for microbiological studies. The results of the preoperative joint aspirate, when positive, were used to select the antibiotics. Two antibiotics were given intravenously for 6 weeks then orally for an additional 6 weeks.
To the best of our knowledge, there is not published study focussed specifically on the management of infected UKA, either by synovectomy or by prosthesis exchange. Although UKA infection is rare, it accounts for 3.9% of all knee prosthesis infections managed in our department. The main limitations of our study are the retrospective single-centre design and small number of patients. Nevertheless, eradication of the infection was achieved consistently. The mechanical results in our case-series were comparable to those reported after one- or two-step TKA exchange for infection [13,14] and after conversion of non-infected UKA-to-TKA [15–18]. The considerable bone and ligament damage caused by the infection and the need for a relatively extensive surgical approach to allow total resection probably contribute to adversely affect postoperative knee function. The persistence of native cartilage and small size of the prosthesis to be removed facilitate joint resection in healthy tissue, after performing the bone cuts and removing the unicompartmental
556
Age/Sex
Reason for UKA
Local infection before UKA
Number of procedures before UKA/Total
Failure of treatment to eradicate the infection
Organism Aspiration
Intraoperatively
Duration of infection (months)
Type of TKA prosthesis
Reconstruction
83 years/M 64 years/M 73 years/M
Primary MTF OA Primary MTF OA Primary LTF OA
No No No
0/2 1/4 0/1
Yes Yes No
S. epidermidis – S. epidermidis
S. epidermidis Enterococcus durans S. epidermidis
5 8 84
Revision Hinged Hinged
67 years/M
Primary MTF OA
No
1/3
Yes
S. epidermidis
S. epidermidis
25
Revision
78 years/F
Avascular necrosis of medial condyle
No
0/2
Yes
E. coli
E. coli
2
Revision
71 years/M
Post-traumatic MTF OA Post-traumatic MTF OA Primary LTF OA Post-traumatic PF OA
No
1/3
No
S. lugdunensis
S. lugdunensis
5
Revision
Yes
10/19
Yes
S. capitis
S. capitis
24
Revision
Tibial stem Tibial wedges Tibial wedges and stem; femoral stem Tibial stem and femoral wedges Femoral wedges and stem; tibial stem Tibial wedges and stem Tibial wedges
No Yes
0/1 2/3
No No
S. epidermidis –
S. epidermidis Nutritionally deficient Streptococcus
8 84
Standard Revision
No No
56 years/M 51 years/F 36 years/F
M: male; F: female; UKA: unicompartmental knee arthroplasty; MTF: medial tibio-femoral; OA: osteoarthritis; LTF: lateral tibio-femoral; PF: patellofemoral; TKA: total knee arthroplasty; E. coli: Escherichia coli; S.: Staphylococci.
C. Labruyère et al. / Orthopaedics & Traumatology: Surgery & Research 101 (2015) 553–557
Table 1 Main epidemiological and medical data in the 9 patients.
C. Labruyère et al. / Orthopaedics & Traumatology: Surgery & Research 101 (2015) 553–557 Table 2 IKS scores.
Knee score Function score
557
LL: consultant for Tornier and Amplitude. SM: consultant for Tornier and Depuy. Preoperatively Median (min–max)
Postoperatively Median (min–max)
60 (25–80) 50 (0–60)
75 (47–100) 65 (10–90)
IKS: International Knee Society; min: minimum; max: maximum.
implant. However, the loss of bone tissue related to removal of the unicompartmental implant often requires the use of techniques such as bone defect filling by grafts or wedges and the implantation of more or less constrained revision prostheses with stem extensions [15–19]. The nature and distribution of the causative organisms in our study are similar to those found in a study of infected total hip arthroplasty (THA) reported by Tsukayama et al. [20] and in a THA and TKA cohort investigated by Lortat-Jacob et al. [21]. Coagulasenegative staphylococci are more common than other organisms (streptococci, enterococci, and Gram-negative rods). Thus, the bacteria responsible for UKA infection in our patients are representative of those found in joint prostheses infections overall. Factors supporting the decision to perform one-step UKAto-TKA conversion were the preoperative identification of the causative organism in the joint aspirate, the susceptibility of this organism to antibiotics, and the feasibility of complete excision. The greater ease of infected tissue removal compared to infected TKA may explain that eradication of the infection was achieved consistently, despite the use of standard antibiotic therapy regimens and of non-antibiotic cement. We believe that the best indication for one-step UKA-to-TKA conversion combined with antibiotic therapy is chronic UKA infection, recovery of the causative organism by preoperative joint aspiration, and feasibility of total infected tissue excision followed by implantation of a revision prosthesis allowing joint reconstruction. This therapeutic strategy requires the involvement of a multidisciplinary team that includes an infectious-diseases specialist in charge of prescribing and monitoring the antibiotic therapy. Another treatment option in chronic infection is two-step prosthesis exchange, which is widely used to treat chronic TKA infection [22–27]. This option has the disadvantage of requiring two surgical procedures separated by a period of limited knee function, even when a spacer is used [28]. Further joint excision during the second step holds theoretical appeal for eradicating the infection but exposes the patient to a further risk of infection during implantation of the new prosthesis. Using this strategy, Hirakawa et al. had a 25% failure rate, with one-fourth of failures due to infection by a different organism [27]. 5. Conclusion UKA infection is unique in that it involves both the prosthesis and the native cartilage, neither of which can be treated conservatively in chronic forms. The very low incidence and specific characteristics of chronic UKA infection require management by an experienced multidisciplinary team. After identification of the causative organism, total synovectomy followed by same-step TKA and combined with appropriate antibiotic therapy for 3 months is effective. Disclosure of interest CL, VZ, PL, ND, and PM declare that they have no conflicts of interest concerning this article.
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