Managing the infected knee: as good as it gets

Graphic type differentiation of cell count data for diagnosis of early and late periprosthetic joint infection: A new method

BACKGROUND

Graphic type differentiation of cell count data of synovial aspirates is a new method for the diagnosis of early and late periprosthetic joint infection.

OBJECTIVE

The aim of the study was to analyse if the same 6 LMNE-types can be differentiated in the new Yumizen H500 cell counter as it was the case for the old cell counter ABX Pentra XL 80 of previous publications, to verify if the erythrocyte and thrombocyte curves of the new device give additional information and to calculate the difference of cell count in LMNE-type I and III (with abrasion) in the cell counter and in the manual counting chamber (Neubauer improved).

METHODS

450 aspirates of 152 total hip arthroplasties and 298 knee arthroplasties obtained for the diagnosis of periprosthetic joint infection were analysed with the Yumizen H500.

RESULTS

All LMNE-matrices of the 450 aspirates could assigned to one of the six LMNE-types. There were 76 LMNE-type I, 72 LMNE-type II, 14 LMNE-type III, 241 LMNE-type IV, 36 LMNE-type V and 12 LMNE-type VI. The erythrocyte and thrombocyte distribution curves were very helpful for differentiation of hematoma and infection. The cell count in the manual counting procedure was lower than in the cell counter: for the LMNE-type I (abrasion type) the median of the difference was 925/μL (median) and for the LMNE-type III (combined type of infection and abrasion) 3570/μL (median).

CONCLUSION

The described graphic type differentiation is a new and helpful method for differentiation of hematoma and early PJI as well as abrasion and late PJI.

Two-stage revision in periprosthetic knee joint infections

Periprosthetic joint infection (PJI) following total knee arthroplasty is one of the most catastrophic and costly complications that carries significant patient wellness as well as economic burdens. The road to efficiently diagnosing and treating PJI is challenging, as there is still no gold standard method to reach the diagnosis as early as desired. There are also international controversies with respect to the best approach to manage PJI cases. In this review, we highlight recent advances in managing PJI following knee arthroplasty surgery and discuss in depth the two-stage revision method.

One- or two-stage reimplantation for infected total knee prosthesis?

A prosthetic joint infection (PJI) is possibly the most significant potential complication of total knee arthroplasty (TKA) and is associated with substantial morbidity and socioeconomic burden. It is a devastating complication for both the patient and the surgeon alike. A two-stage revision approach for infected TKA has been the standard for surgical management; however, there is growing interest in single-stage revision surgery due to fewer procedures, reduced inpatient hospital stay and reduced costs to healthcare systems. A one-stage exchange is indicated when there is no sign of systemic sepsis and in cases where a microorganism has been isolated. It involves removal of the old prosthesis, debridement of all infected tissue, a copious washout and re-draping, and finally, re-implantation of a new prosthesis. The two-stage approach involves the use of an antibiotic spacer before the second stage is carried out. The length of time between the stages is discussed. Patients with a PJI should be managed by a multidisciplinary team. We recommend these patients are managed in specialist arthroplasty centres by high volume revision arthroplasty specialists.

A Mid-term Follow-up Study on the Reimplantation of Autoclaved Femoral and Tibial Components as Spacers for Treating Infected Total Knee Arthroplasty

Objective

Infection after total knee arthroplasty (TKA) is a rare but devastating complication. Different types of spaces have been used in two‐stage revision. The study aimed to evaluate the effect of autoclaved femoral and tibial components as spacers for treating periprosthetic infections after TKA.

Methods

A retrospective study was performed for 13 patients (five males, eight females) with a mean age of 69 ± 6 (range, 57–80) years and suffering from periprosthetic infection after TKA. They were treated with unconventional two‐stage revision from May 2008 to June 2017. In the first‐stage surgery, the autoclaved femoral and tibial components were reimplanted with a new liner as a spacer after a thorough debridement. After 4–6 months, the second‐stage surgery was performed according to the patients' requirements. The knee society score (KSS) and knee range of motion (ROM) were assessed before and after surgery. The reinfection rate was calculated.

Results

The mean duration of follow‐up was 5.7 ± 2.1 (range, 3.1–8.8) years. Culture‐positive infections comprised 69% of the cohort. All patients were able to walk 24 h after the first stage surgery, and the knee ROM could reach 90° in 1 week. Two patients (15.4%) experienced an infection recurrence. One patient was reinfected 1 year after the first stage surgery. Another patient developed reinfection 3 years after surgery but did not choose re‐revision and died of pneumonia. Only one patient underwent the second stage revision. The remaining 10 patients refused to receive a new prosthesis. At the time of the final follow‐up, six patients had slight pain in the knee while walking, and one patient required crutches to walk. There were no signs of prosthesis dislocation, rupture, deep vein thrombosis, pulmonary embolism, or delayed wound healing. No radiolucent lines or osteolysis were found. The mean KSS improved from 51 ± 10 (range, 35–63) points preoperatively to 79 ± 5 (range, 60–85) points at the final follow‐up. The average ROM before and after the first stage surgery were 62° ± 29° (range, 10°–100°) and 104° ± 9° (range, 90°–120°) (t = 4.659, P < 0.01) respectively. The infection control rate was 84.6%.

Conclusion

Reimplantation of the autoclaved original femoral and tibial components as an articulating spacer during the first stage surgery is a valuable addition for treating an infected TKA.

Diagnosis and management of infected arthroplasty

Periprosthetic joint infection (PJI) is one of the most dreadful complications after THA and TKA. Though prevention is of utmost importance in PJI management, the last decade has seen many remarkable developments in PJI diagnosis, including the introduction of several standardized PJI diagnostic definitions and biomarkers. Depending on the specific clinical situation, a myriad of treatment options for PJI are offered. Our review aims to summarize the pertinent information on PJI diagnosis and synthesize literature on the different treatment methods currently used in clinical practice. One of the most accepted PJI diagnostic definitions was developed by the Musculoskeletal Infection Society (MSIS) in 2011, later modified in the 2013 International Consensus Meeting (ICM). After promising results from studies, alpha-defensins and D-dimer were recently incorporated into the 2018 ICM PJI definition. The management choices for PJI include irrigation and debridement (DAIR), one-stage exchange arthroplasty, or two-stage exchange arthroplasty, to name a few. While two-stage revision has traditionally been the treatment of choice in the United States, there has been a growing body of evidence framing one-stage revision as a comparable choice. One-stage revision should be offered in patients meeting strict selection criteria: no sinus tract, proper soft tissue available for wound closure, appropriate bone stock, a favorable identifiable organism with encouraging antibiotic sensitivities (for cement and oral suppression later), and robust immunological status. DAIR can be considered in case of early infections with sensitive infecting organisms. Patients with multiple unsuccessful revisions or those who refuse further surgical intervention for PJI can be offered antibiotic suppression. If nothing seems to work, salvage procedures (resection arthroplasty and arthrodesis) are available as a last resort. Further research is encouraged to improve on diagnostic capabilities and develop evidence on the best treatment of choice for PJI.

Bias Does Not Exist in Treating Knee Periprosthetic Joint Infection Among Patients With Substance Use Disorder

Debridement, antibiotics with implant retention (DAIR), and 2-stage revision are standard surgical interventions for treating knee periprosthetic joint infection (PJI). Patients with substance use disorder (SUD), especially addictive drug use disorder (DUD), have been shown to receive inferior medical care in many specialties compared with nonusers. The authors identified patients with a diagnosis of PJI after knee arthroplasty who received either DAIR or 2-stage revision with the Nationwide Inpatient Sample (NIS) database from 2010 to 2014. Patients were stratified into 2 groups, patients with DUD and nonusers, based on Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, criteria. Descriptive analysis was conducted to show the national trend for knee PJI treatment among the 2 patient groups. Multivariate logistic regression was used to compare the prevalence of DAIR and 2-stage revision between these 2 groups, adjusted for likely confounders, including age, sex, income, race, and comorbidities. Among the 11,331 patients with knee infection, 139 (1.23%) had DUD. Compared with nonusers, patients with DUD were significantly younger (P<.001), had more chronic conditions (P<.001), and were predominantly in lower income quartiles (P=.046). The 2 groups did not differ in sex and race (P=.072 and P=.091, respectively). The authors found that 30.22% of patients with DUD and 36.36% of nonusers received DAIR. The difference in these proportions was not statistically significant (P=.135). The results did not change after adjustment for confounding factors (P=.509). The findings suggested that bias does not exist among orthopedic surgeons who choose DAIR or 2-stage revision for knee PJI among patients with DUD. [Orthopedics. 2021;44(3):e385-e389.].

The Graphical Representation of Cell Count Representation: A New Procedure for the Diagnosis of Periprosthetic Joint Infections

Aim: This study was designed to answer the question whether a graphical representation increase the diagnostic value of automated leucocyte counting of the synovial fluid in the diagnosis of periprosthetic joint infections (PJI). Material and methods: Synovial aspirates from 322 patients (162 women, 160 men) with revisions of 192 total knee and 130 hip arthroplasties were analysed with microbiological cultivation, determination of cell counts and assay of the biomarker alpha-defensin (170 cases). In addition, microbiological and histological analysis of the periprosthetic tissue obtained during the revision surgery was carried out using the ICM classification and the histological classification of Morawietz and Krenn. The synovial aspirates were additionally analysed to produce dot plot representations (LMNE matrices) of the cells and particles in the aspirates using the hematology analyser ABX Pentra XL 80. Results: 112 patients (34.8%) had an infection according to the ICM criteria. When analysing the graphical LMNE matrices from synovia cell counting, four types could be differentiated: the type “wear particles” (I) in 28.3%, the type “infection” (II) in 24.8%, the “combined” type (III) in 15.5% and “indeterminate” type (IV) in 31.4%. There was a significant correlation between the graphical LMNE-types and the histological types of Morawietz and Krenn (p < 0.001 and Cramer test V value of 0.529). The addition of the LMNE-Matrix assessment increased the diagnostic value of the cell count and the cut-off value of the WBC count could be set lower by adding the LMNE-Matrix to the diagnostic procedure. Conclusion: The graphical representation of the cell count analysis of synovial aspirates is a new and helpful method for differentiating between real periprosthetic infections with an increased leukocyte count and false positive data resulting from wear particles. This new approach helps to increase the diagnostic value of cell count analysis in the diagnosis of PJI.

Antibiotic therapy alone does not have a high success rate in cases of unexpected positive cultures in intraoperative samples from hip and knee prosthesis revision

BACKGROUND

Unexpectedly positive bacterial cultures during prosthesis revision surgery still occur on occasion despite good preoperative diagnostics. In such cases a six-week antibiotic therapy without further surgical intervention is recommended. The aim of this study was to find out how successful this procedure is.

METHODS

In a study of 508 patients, who required revision surgery of total hip (THA, n = 231) or knee arthroplasties (TKA, n = 277) because of component loosening, biopsy was carried out before their surgery. The collected tissue samples (5) from the biopsy and the revision surgery procedure itself were analyzed according the criteria of the International Consensus Meeting (ICM). Tests revealed 11 patients (7 THA, 4 TKA) with unexpectedly positive bacterial cultures from tissue samples obtained during the revision surgery due to false negative preoperative diagnostic results. These 11 patients were treated with 6 weeks antibiotic therapy and examined with a follow-up of at least 2 years (42.2 ± 16.5 months).

RESULTS

Five patients (2 TKA, 3 THA) became reinfected, resulting in a success rate of 54.5%.

CONCLUSION

Antibiotic therapy alone of an unexpected positive intraoperative bacterial culture in prosthesis revision surgery seems to be less successful than previously assumed.

Destination Joint Spacers, Reinfection, and Antimicrobial Suppression

In this cohort of 51 patients managed with retained "destination spacers" after the resection of infected joint prostheses, the presence of preoperative sinus drainage was significantly associated with reinfection. Chronic antimicrobial suppression after destination-spacer retention did not significantly prevent reinfections.

A Novel Technique for Creating an Articulating Cement Spacer for Ankle Prosthetic Joint Infections

Total ankle arthroplasty has been increasing as a treatment for end-stage ankle arthritis. With this increase, the incidence of total ankle prosthetic infections will also increase. Treatment of these infections depends on the duration of symptoms and whether the infection is acute or chronic in presentation. The treatment of choice for chronic infections is a 2-stage procedure, the removal of implants and placement of a static cement spacer. We describe a technique for creating an articulating antibiotic cement spacer through an anterior approach in a patient with an infected total ankle arthroplasty. The articulating antibiotic cement spacer allows high doses of local antibiotics, decreases soft tissue contractures, and allows continued motion of the joint.

The diagnostic value of routine preliminary biopsy in diagnosing late prosthetic joint infection after hip and knee arthroplasty

AIMS

Biopsy of the periprosthetic tissue is an important diagnostic tool for prosthetic joint infection (PJI) as it enables the detection of the responsible microorganism with its sensitivity to antibiotics. We aimed to investigate how often the bacteria identified in the tissue analysis differed between samples obtained from preoperative biopsy and intraoperative revision surgery in cases of late PJI; and whether there was a therapeutic consequence.

METHODS

A total of 508 patients who required revision surgery of total hip arthroplasty (THA) (n = 231) or total knee arthroplasty (TKA) (n = 277) because of component loosening underwent biopsy before revision surgery. The tissue samples collected at biopsy and during revision surgery were analyzed according to the criteria of the Musculoskeletal Infection Society (MSIS).

RESULTS

In total, 178 (113 THA, 65 TKA) were classified as infected. The biopsy procedure had a sensitivity of 93.8%, a specificity of 97.3%, a positive predictive value (PPV) of 94.9%, a negative predictive value (NPV) of 96.7%, and an accuracy of 96.1%. Of the 178 infected patients, 26 showed a difference in the detected bacteria from the biopsy and the revision surgery (14.6%). This difference required a change to antibiotic therapy in only two cases (1.1%).

CONCLUSION

Biopsy is a useful tool to diagnose PJI, but there may be a difference in the detected bacteria between the biopsy and revision surgery. However, this did not affect the choice of antibiotic therapy in most cases, rendering the clinical relevance of this phenomenon as low. Cite this article: Bone Joint J 2020;102-B(3):329-335.

C-reactive protein is not a screening tool for late periprosthetic joint infection

Background

Preoperative diagnosis of periprosthetic joint infection (PJI) is important because of the therapeutic consequences. The aim of the present study is to investigate whether the serum C-reactive protein (CRP) level can be used as a screening tool for late PJI.

Materials and methods

A cohort of 390 patients with revision surgery of total hip prostheses (200) or total knee prostheses (190) was assessed for late PJI by determining CRP serum level and performing preoperative aspiration with cultivation and intraoperative tissue analyses with cultivation and histologic examination, using the Musculoskeletal Infection Society (MSIS) and International Consensus Meeting (ICM) criteria.

Results

A total of 180 joints were rated as PJI (prevalence 46%). Of these, 42.8% (77) showed a CRP level below 10 mg/L and 28.3% (51) showed a normal CRP level of less than 5 mg/L. The 76.9% of the cases with slow-growing bacteria showed a CRP level below 10 mg/L, and 61.5% showed a normal CRP level.

Conclusions

Serum CRP level should not be used as a screening tool to rule out late PJI.

Level of evidence

Level 2 (diagnostic study).

Mycobacterium tuberculosis as a Cause of Periprosthetic Joint Infection After Total Knee Arthroplasty: A Review of the Literature

Total knee arthroplasty (TKA) has become one of the most popular and successful surgeries performed in the world. Infection remains one of the most dreaded complications following TKA, and while rare, tuberculosis as a microbial etiology remains difficult to both diagnose and treat. A review was performed using PubMed, the Cochrane Database of Systematic Reviews, and EMBASE to identify literature pertinent to Mycobacterium tuberculosis infection, TKAs, periprosthetic joint infections, and any combination of the three. The diagnosis of tuberculosis infection after TKA is difficult due to nonspecific signs and symptoms and diagnostic testing. The surgeon should use a comprehensive approach to incorporate the patient's medical history, physical exam, and blood and imaging diagnostics. Among these, bacterial culture and histopathological examination remain the gold standard of diagnosis, but Polymerase chain reaction technology offers another, more sensitive and rapid option. Treatment strategy centers around on the cornerstone of anti-tuberculosis medical therapy and surgery depending on the clinical situation. While there is a lack of primary literature and standardized guidelines for the diagnosis and treatment of tuberculosis infection after TKA, the overarching principles of the treatment of tuberculosis and the treatment of the periprosthetic infection can be implemented together. There remains room for original research and improvements in both diagnostic testing and treatment.

An Evidence-Based Clinical Prediction Algorithm for the Musculoskeletal Infection Society Minor Criteria

BACKGROUND

The diagnosis of a periprosthetic joint infection (PJI) remains a clinical challenge, as there is no uniformly accepted gold standard. In 2011, the Musculoskeletal Infection Society (MSIS) convened a work group to create a standardized definition for a PJI that could be universally adopted. Based on the MSIS criteria, the diagnosis of a PJI can be made with 1 of the 2 major criteria, or 3 of the 5 minor criteria. The purpose of this study was to determine the likelihood of having a PJI based on the number of positive minor criteria and thereby develop a prediction algorithm for differentiating between a chronic PJI and a non-PJI based on the number of positive MSIS minor criteria.

METHODS

We retrospectively reviewed 297 patients who presented to a tertiary care center between 2004 and 2014 with a failed total joint arthroplasty and subsequently underwent a PJI workup to exclude chronic PJI. Patients were divided into 2 groups: (1) PJI group and (2) non-PJI group. Patients who had a positive PJI workup and subsequently underwent a 2-stage revision for infection were included in the PJI group. Patients who had a negative clinical and diagnostic workup were included in the non-PJI group. One hundred eighty-two patients met the criteria for inclusion in the study, 91 in each group. Univariate and multiple logistic regression analyses were used to evaluate 21 independent variables in each of the 2 groups. A prediction algorithm for differentiating between a chronic PJI and a non-PJI based on independent multivariate variables was created.

RESULTS

Patients who had a PJI differed significantly (P < .05) from those who did not have a PJI with regard to 10 independent variables, which included all the MSIS minor criteria we evaluated. Five independent multivariate variables were identified to differentiate between the 2 groups: positive cultures, elevated synovial white blood cell count, elevated synovial polymorphonuclear neutrophil percentage, elevated erythrocyte sedimentation rate, and elevated C-reactive protein. The predictive probability of a PJI for all 32 combinations of these 5 variables was: 3.6% for 1 positive variable, 19.3% for 2, 58.7% for 3, 83.8% for 4, and 97.8% for 5. The chi-squared test for trend and the area under the receiver-operating characteristic curve (0.977) suggest that the model is highly predictive, with an excellent diagnostic performance in identifying a PJI.

CONCLUSIONS

Diagnosing a PJI remains a clinical challenge as there is no gold standard for diagnosis. The development of the MSIS criteria, which is based on a consensus of over 400 of the world's experts in musculoskeletal infection, was a major step forward in defining the diagnosis of a PJI. However, to our knowledge, the likelihood of having a PJI based on the number of positive minor criteria has yet to be validated or quantified. Of the 20 independent variables that were evaluated, 10 were found to be significantly associated with a PJI, including all the MSIS minor criteria evaluated. In addition, a diagnostic prediction algorithm was constructed to determine the likelihood of a PJI based on 5 binary independent multivariate variables. The relationship was also examined with a receiver-operating characteristic curve analysis. The area under the curve was 0.98, indicating excellent diagnostic performance for the MSIS minor criteria in identifying a PJI.

LEVEL OF EVIDENCE

III.

Prognostic Factors for Success After Irrigation and Debridement With Modular Component Exchange for Infected Total Knee Arthroplasty

BACKGROUND

Irrigation and debridement with modular component exchange (IDMCE) can treat prosthetic joint infection (PJI) after total knee arthroplasty (TKA). Compared to 2-stage revision, IDMCE is associated with lower morbidity but may carry higher infection recurrence rates. We aimed to identify prognostic factors associated with successful IDMCE in patients with PJI.

METHODS

We identified 99 consecutive patients who underwent IDMCE following TKA PJI at a tertiary academic medical center from November 2009 through January 2016. Examined variables included age, gender, symptom duration, body mass index, Charlson comorbidity index, total protein, albumin, hemoglobin A1c, erythrocyte sedimentation rate (ESR), C-reactive protein, white blood cell count, gram stain results, final cultures, and use of long-term antibiotic suppression. Success was defined as no further operation on the ipsilateral knee. We used t tests and chi-square analyses to determine whether each preoperative factor was associated with IDMCE reoperation.

RESULTS

At mean follow-up of 2.6 years, 64 patients who underwent IDMCE were defined as successful. Thirty-five patients required one or more additional procedures for recurrent infection; of these, 20 patients underwent 2-stage revision. Patients with symptom duration of less than 2 days avoided additional surgery in 88% of cases. Elevated ESR >47 mm/h was the only variable associated with reoperation (P = .005). There were no associations among the other examined variables.

CONCLUSION

Using IDMCE for PJI after TKA required reoperation in 35% of cases. Elevated preoperative ESR laboratory values and duration of symptoms >2 days were associated with reoperation.

Preoperative PCR analysis of synovial fluid has limited value for the diagnosis of periprosthetic joint infections of total knee arthroplasties

Preoperative diagnosis of periprosthetic joint infection (PJI) is important because of the therapeutic consequences. This prospective study was designed to answer the question, if preoperative PCR analysis of the synovial fluid in addition to the culture and the CRP analysis of the blood are helpful for the diagnosis of PJI in knee arthroplasties. Before revision CRP analysis of the blood, cultivation and PCR analysis of synovial fluid of 116 knee endoprostheses were performed. During revision surgery, five tissue samples of the periprosthetic tissue were cultured and five further samples subjected to histological analysis. These analyses of the periprosthetic tissue were used to verify the results of the preoperative diagnostic methods. Twenty-seven prostheses were identified as infected (prevalence 23.3%). The combined analyses of the joint fluid cultivation and the CRP blood level resulted in a sensitivity of 77.8%, a specificity of 95.5%, a positive-predictive value of 84.0%, a negative-predictive value of 93.4% and an accuracy of 91.4%. The PCR analysis of the synovial fluid resulted in a sensitivity of 55.6%, a specificity of 82.0%, a positive-predictive value of 48.4%, a negative-predictive value of 85.9% and an accuracy of 75.9%. The sensitivity for culture of the aspirate and PCR analysis in combination with an elevated CRP level was 85.2%, the specificity 82.0%, the positive-predictive value 58.9%, the negative-predictive value 94.8% and the accuracy 82.7%. The preoperative PCR analysis of synovial fluid has only limited value in addition to the standard culture analysis.

Utility of Synovial White Blood Cell Count and Differential Before Reimplantation Surgery

BACKGROUND

Determining optimal timing of reimplantation during 2-stage exchange for periprosthetic joint infection (PJI) remains elusive. Joint aspiration for synovial white blood cell (WBC) count and neutrophil percentage (PMN%) before reimplantation is widely performed; yet, the implications are rarely understood. Therefore, this study investigates (1) the diagnostic yield of synovial WBC count and differential analysis and (2) the calculated thresholds for persistent infection.

METHODS

Institutional PJI databases identified 129 patients undergoing 2-stage exchange arthroplasty who had joint aspiration before reimplantation between February 2005 and May 2014. Persistent infection was defined as a positive aspirate culture, positive intraoperative cultures, or persistent symptoms of PJI-including subsequent PJI-related surgery. Receiver-operating characteristic curve was used to calculate thresholds maximizing sensitivity and specificity.

RESULTS

Thirty-three cases (33 of 129; 25.6%) were classified with persistent PJI. Compared with infection-free patients, these patients had significantly elevated PMN% (62.2% vs 48.9%; P = .03) and WBC count (1804 vs 954 cells/μL; P = .04). The receiver-operating characteristic curve provided thresholds of 62% and 640 cells/μL for synovial PMN% and WBC count, respectively. These thresholds provided sensitivity of 63% and 54.5% and specificity of 62% and 60.0%, respectively. The risk of persistent PJI for patients with PMN% >90% was 46.7% (7 of 15).

CONCLUSION

Synovial fluid analysis before reimplantation has unclear utility. Although statistically significant elevations in synovial WBC count and PMN% are observed for patients with persistent PJI, this did not translate into useful thresholds with clinical importance. However, with little other guidance regarding the timing of reimplantation, severely elevated WBC count and differential analysis may be of use.

Inadequacy of Joint Aspiration for Detection of Persistent Periprosthetic Infection During Two-Stage Septic Revision Knee Surgery

Despite the lack of validation, synovial aspiration remains a common practice during 2-stage septic revision total knee arthroplasty (TKA). The goal of this study was to investigate the diagnostic validity of synovial polymethylmethacrylate (PMMA) spacer aspiration of temporary knee arthrodesis to detect persistent periprosthetic joint infection before TKA reimplantation. This retrospective cohort study included 73 consecutive patients who underwent 2-stage septic revision TKA according to a standard protocol. After explantation surgery, including temporary arthrodesis with an intramedullary stabilized PMMA spacer, all patients had synovial aspiration 2 weeks before reimplantation to exclude persistent periprosthetic joint infection. Patients had a 2-week antibiotic holiday before aspiration. Sensitivity and specificity of the synovial PMMA spacer joint aspiration for the detection of periprosthetic joint infection were determined and referenced against intraoperative microbiologic and histologic samples obtained at second-stage surgery. Sensitivity of the synovial PMMA spacer aspiration was 21%. Because of poor diagnostic validity, synovial PMMA spacer aspiration cannot be recommended for routine exclusion of persistent periprosthetic joint infection before TKA reimplantation. Therefore, exclusion of persistent periprosthetic joint infection should be supplemented by other diagnostic methods, and it is not necessary to delay TKA reimplantation for PMMA spacer aspiration. [Orthopedics. 2017; 40(4):231-234.].

The DAIR (debridement, antibiotics and implant retention) procedure for infected total knee replacement - a literature review

Prosthetic joint infection (PJI) is a devastating complication in total knee arthroplasty (TKA) and third most common cause of revision of TKA with significant morbidity and surgical challenges. Treatment options include non-operative measures with long term antibiotic suppression, debridement and implant retention (DAIR), one- or two-stage revision arthroplasty, arthrodesis and amputation. Implant retention without infection is ideal and DAIR has been reported to have variable success rates depending on patient factors, duration of infection, infecting micro-organisms, choice of procedure, single or multiple debridement procedures, arthroscopic or open, antibiotic choice and duration of antibiotic use. We present a thorough literature review of DAIR for infected TKA. The important factors contributing to failure are presence of sinus, immunocompromised patient, delay between onset of infection and debridement procedure, Staphylococcal infection in particular Meticillin Resistant Staphylococcal aureus, multiple debridement procedures, retention of exchangeable components and short antibiotic duration. In conclusion DAIR can be successful procedure to eradicate infection in TKA in selective patients with factors contributing to failure taken into account.

The Mark Coventry, MD, Award: Oral Antibiotics Reduce Reinfection After Two-Stage Exchange: A Multicenter, Randomized Controlled Trial

BACKGROUND

Many patients develop recurrent periprosthetic joint infection after two-stage exchange arthroplasty of the hip or knee. One potential but insufficiently tested strategy to decrease the risk of persistent or recurrent infection is to administer additional antibiotics after the second-stage reimplantation.

QUESTIONS/PURPOSES

(1) Does a 3-month course of oral antibiotics decrease the risk of failure secondary to infection after a two-stage exchange? (2) Are there any complications related to the administration of oral antibiotics after a two-stage exchange? (3) In those patients who develop a reinfection, is the infecting organism different from the initial infection?

METHODS

Patients at seven centers randomized to receive 3 months of oral antibiotics or no further antibiotic treatment after operative cultures after the second-stage reimplantation were negative. Adult patients undergoing two-stage hip or knee revision arthroplasty for a periprosthetic infection who met Musculoskeletal Infection Society (MSIS) criteria for infection at the first stage were included. Oral antibiotic therapy was tailored to the original infecting organism(s) in consultation with an infectious disease specialist. MSIS criteria as used by the treating surgeon defined failure. Surveillance of patients for complications, including reinfection, occurred at 3 weeks, 6 weeks, 3 months, 12 months, and 24 months. If an organism demonstrated the same antibiotic sensitivities as the original organism, it was considered the same organism; no DNA subtyping was performed. Analysis was performed as intent to treat with all randomized patients included in the groups to which they were randomized. A log-rank survival curve was used to analyze the primary outcome of reinfection. At planned interim analysis (enrollment is ongoing), 59 patients were successfully randomized to the antibiotic group and 48 patients to the control group. Fifty-seven patients had an infection after TKA and 50 after a THA. There was no minimum followup for inclusion in this analysis. The mean followup was 14 months in the antibiotic group and 10 months in the control group.

RESULTS

Patients treated with oral antibiotics failed secondary to infection less frequently than those not treated with antibiotics (5% [three of 59] versus 19% [nine of 48]; hazard ratio, 4.37; 95% confidence interval, 1.297-19.748; p = 0.016). Three patients had an adverse reaction to the oral antibiotics severe enough to cause them to stop taking the antibiotics early, and four patients who were randomized to that group did not take the antibiotics as directed. With the numbers available, there were no differences between the study groups in terms of the likelihood that an infection after treatment would be with a new organism (eight of nine in the control group versus one of three in the treatment group, p = 0.087).

CONCLUSIONS

This multicenter randomized trial suggests that at short-term followup, the addition of 3 months of oral antibiotics appeared to improve infection-free survival. As a planned interim analysis, however, these results may change as the study reaches closure and the safety profile may yet prove risky. Further followup of this cohort of patients will be necessary to determine whether these preliminary results are durable over time.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Two-stage Revision for Periprosthetic Hip and Knee Joint Infections

Background:

Periprosthetic joint infection (PJI) continues to be one of the leading causes of failure following hip and knee surgery. The diagnostic workflow of PJI includes detailed clinical examination, serum markers, imaging and aspiration/biopsy of the affected joint. The goals of treatment are eradication of the infection, alleviation of pain, and restoration of joint function. Surgical management of PJI consists of debridement, antibiotics and implant retention (DAIR) and single or two-stage revision procedures. Two-stage revision remains the gold standard for treatment of PJIs. We aim to discuss the two stage procedure in this article and report the outcomes.

Methods:

The first stage of the two stages consists of removal of all components and associated cement with aggressive debridement and placement of an antibiotic-loaded cement spacer. Patients are then treated with variable periods of parenteral antibiotics, followed by an antibiotic free period to help ensure the infection has been eradicated. If the clinical evaluation and serum inflammatory markers suggest infection control, then the second stage can be undertaken and this involves removal of the cement spacer, repeat debridement, and placement of a new prosthesis.

Results:

Common themes around the two-stage revision procedure include timing of the second stage, antibiotics used in the interim period, length of the interim period before consideration of reimplantation and close liaising with microbiologists.

Conclusion:

Successful eradication of infection and good functional outcome using the two stage procedure is dependent on a multidisciplinary approach and having a standard reproducible startegy.

Trends and Outcomes in the Treatment of Failed Septic Total Knee Arthroplasty: Comparing Arthrodesis and Above-Knee Amputation

BACKGROUND

Options for treatment of a failed septic total knee arthroplasty (TKA) include arthrodesis and above-knee amputation (AKA). Little comparative data exist to help clinicians when considering these alternatives.

METHODS

A national database was queried for patients who underwent either knee arthrodesis or AKA for an infected TKA between 2005 and 2012. Procedure volumes, postoperative complications, hospital charges, length of stay, and 90-day readmission rates were evaluated.

RESULTS

A total of 2634 patients underwent arthrodesis and 5001 patients underwent AKA for septic TKA. The percentage of total patients who underwent AKA increased significantly throughout the study period compared to knee arthrodesis. Patients who underwent AKA tended to be older and have more medical comorbidities. Arthrodesis patients had a significantly higher rate of postoperative infection (14.5% vs 8.3%, P < .0001) and transfusion (55.1% vs 46.8%, P < .0001), whereas AKA patients had a higher rate of systemic complications (31.5% vs 25.9%, P < .0001) and in-hospital mortality (3.7% vs 2.1%, P < .0001). The AKA cohort had lower hospital charges ($79,686 vs $84,747, P = .004), longer length of stay (11 vs 7 days, P < .0001), and higher 90-day readmission rate (19.4% vs 16.9%).

CONCLUSION

Our data suggest that there is an increasing trend toward AKA for the treatment of a failed infected TKA when compared to arthrodesis. Comparative analysis of the outcomes of these procedures should help the clinician when weighing these alternatives.

Patella tendon injuries secondary to cement spacers used at first-stage revision of infected total knee replacement

We describe a series of three patients who sustained patella tendon injuries in infected total knee arthroplasties following the use of a static cement spacer at first-stage knee revision. The patella tendon injuries resulted in significant compromise to wound healing and knee stability requiring multiple surgeries. The mid-term function was poor with an Oxford score at 24 months ranging from 12 to 20. Based on our experience, we advise caution in the use of static cement spacer blocks. If they are to be used, we recommend that they should be keyed in the bone to prevent patella tendon injuries.

Arthrodesis should be strongly considered after failed two-stage reimplantation TKA

BACKGROUND

A two-stage reimplantation procedure is a well-accepted procedure for management of first-time infected total knee arthroplasty (TKA). However, there is a lack of consensus on the treatment of subsequent reinfections.

QUESTIONS/PURPOSES

The purpose of this study was to perform a decision analysis to determine the treatment method likely to yield the highest quality of life for a patient after a failed two-stage reimplantation.

METHODS

We performed a systematic review to estimate the expected success rates of a two-stage reimplantation procedure, chronic suppression, arthrodesis, and amputation for treatment of infected TKA. To determine utility values of the various possible health states that could arise after two-stage revision, we used previously published values and methods to determine the utility and disutility tolls for each treatment option and performed a decision tree analysis using the TreeAgePro 2012 software suite (Williamstown, MA, USA). These values were subsequently varied to perform sensitivity analyses, determining thresholds at which different treatment options prevailed.

RESULTS

Overall, the composite success rate for two-stage reimplantation was 79.1% (range, 33.3%-100%). The utility (successful outcome) and disutility toll (cost for treatment) for two-stage reimplantation were determined to be 0.473 and 0.20, respectively; the toll for undergoing chronic suppression was set at 0.05; the utility for arthrodesis was 0.740 and for amputation 0.423. We set the utilities for subsequent two-stage revision and other surgical procedures by subtracting the disutility toll from the utility each time another procedure was performed. The two-way sensitivity analysis varied the utility status after an additional two-stage reimplantation (0.47-0.99) and chance of a successful two-stage reimplantation (45%-95%). The model was then extended to a three-way sensitivity analysis twice: once by setting the variable arthrodesis utility at a value of 0.47 and once more by setting utility of two-stage reimplantation at 0.05 over the same range of values on both axes. Knee arthrodesis emerged as the treatment most likely to yield the highest expected utility (quality of life) after initially failing a two-stage revision. For a repeat two-stage revision to be favored, the utility of that second two-stage revision had to substantially exceed the published utility of primary TKA of 0.84 and the probability of achieving infection control had to exceed 90%.

CONCLUSIONS

Based on best available evidence, knee arthrodesis should be strongly considered as the treatment of choice for patients who have persistent infected TKA after a failed two-stage reimplantation procedure. We recognize that particular circumstances such as severe bone loss can preclude or limit the applicability of fusion as an option and that individual clinical circumstances must always dictate the best treatment, but where arthrodesis is practical, our model supports it as the best approach.

Peri-prosthetic hip infections: in favour of one-stage

Although it does offer certain obvious advantages, the one-staged revision approach in infected THA remains rare in the field of orthopaedics. Besides the reduced number of surgical interventions for patients, it is associated with a decreased inpatient hospital stay and quicker mobilisation. Furthermore, it might be the more cost-effective approach and enables a reduced duration of post-operative systemic antibiotics, usually less than 14 days in our setting. Technically speaking, the presence of a positive culture of a pre-operative aspiration and respective antibiogram are mandatory requirements. A general cemented implant fixation using topical antibiotics is the treatment of choice for single-staged procedures. The key to surgical success is based on the well-defined and detailed intra-hospital infrastructure, including a meticulous pre-operative hip aspiration regime, pre-operative planning and an aggressive intra-operative surgical approach.

Assessing the gold standard: a review of 253 two-stage revisions for infected TKA

BACKGROUND

Periprosthetic joint infection has been the leading cause of failure following TKA surgery. The gold standard for infection control has been a two-staged revision TKA. There have been few reports on mid- to long-term survivorship, functional outcomes, and fate of patients with a failed two-stage revision TKA.

QUESTIONS/PURPOSES

Therefore, we determined (1) the mid-term survivorship of two-stage revision TKA, (2) the function of patients in whom infection was controlled, and (3) the outcome of patients with a failed two-stage revision due to recurrent infection.

METHODS

We retrospectively reviewed 239 patients who underwent 253 two-stage revision TKAs for periprosthetic infection. There were 239 patients (253 knees), 104 men and 135 women, with a mean age of 70 ± 10 years at the time of two-stage revision and a mean BMI of 31.53 ± 6.74 kg/m2. During followup, we obtained WOMAC and The Knee Society Clinical Rating Scores and radiographs. The minimum followup was 1 year (median, 4 years; range, 1-17 years).

RESULTS

Thirty-three patients experienced a failed two-staged TKA. Sixteen patients experienced failure due to recurrent sepsis. There were 17 failures for aseptic causes.

CONCLUSION

The overall infection-free survivorship for two-stage revision TKA was 85% at 5 years and 78% at 10 years.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Immobilized antibiotics to prevent orthopaedic implant infections

Many surgical procedures require the placement of an inert or tissue-derived implant deep within the body cavity. While the majority of these implants do not become colonized by bacteria, a small percentage develops a biofilm layer that harbors invasive microorganisms. In orthopaedic surgery, unresolved periprosthetic infections can lead to implant loosening, arthrodeses, amputations and sometimes death. The focus of this review is to describe development of an implant in which an antibiotic tethered to the metal surface is used to prevent bacterial colonization and biofilm formation. Building on well-established chemical syntheses, studies show that antibiotics can be linked to titanium through a self-assembled monolayer of siloxy amines. The stable metal-antibiotic construct resists bacterial colonization and biofilm formation while remaining amenable to osteoblastic cell adhesion and maturation. In an animal model, the antibiotic modified implant resists challenges by bacteria that are commonly present in periprosthetic infections. While the long-term efficacy and stability is still to be established, ongoing studies support the view that this novel type of bioactive surface has a real potential to mitigate or prevent the devastating consequences of orthopaedic infection.

Intramedullary rod and cement static spacer construct in chronically infected total knee arthroplasty

Two-stage reimplantation, with interval antibiotic-impregnated cement spacer, is the preferred treatment of prosthetic knee joint infections. In medically compromised hosts with prior failed surgeries, the outcomes are poor. Articulating spacers in such patients render the knee unstable; static spacers have risks of dislocation and extensor mechanism injury. We examined 58 infected total knee arthroplasties with extensive bone and soft tissue loss, treated with resection arthroplasty and intramedullary tibiofemoral rod and antibiotic-laden cement spacer. Thirty-seven patients underwent delayed reimplantation. Most patients (83.8%) were free from recurrent infection at mean follow-up of 29.4 months. Reinfection occurred in 16.2%, which required debridement. Twenty-one patients with poor operative risks remained with the spacer for 11.4 months. All patients, during spacer phase, had brace-free ambulation with simulated tibiofemoral fusion, without bone loss or loss of limb length.

Two stage revision knee arthroplasty for infection with massive bone loss. A technique to achieve spacer stability

We report a technique for the intra-operative production of an antibiotic-impregnated cement spacer, reinforced with an intramedullary nail. The spacer is designed for use in cases where significant bone loss and/or ligamentous instability prevent the formation of a stable joint when using a conventional spacer during a two-stage revision knee arthroplasty. This technique has been performed in eleven patients. Nine patients have subsequently undergone a second-stage procedure. Two patients died of unrelated causes before a second-stage could be performed. In all but one case, the infection has been successfully eradicated and patients remain infection free at a mean follow-up of 32 months (range 21-64 months). We believe that the described technique is an effective alternative to the traditional spacer, in patients with significant bone loss and/or ligamentous instability. It delivers antibiotics locally, while producing a mechanically stable joint, on which the patient can mobilise, maintaining leg length and tissue tensions.

Plasma-assisted surface modification of organic biopolymers to prevent bacterial attachment

Despite many synthetic biomaterials having physical properties that are comparable or even superior to those of natural body tissues, they frequently fail due to the adverse physiological reactions they cause within the human body, such as infection and inflammation. The surface modification of biomaterials is an economical and effective method by which biocompatibility and biofunctionality can be achieved while preserving the favorable bulk characteristics of the biomaterial, such as strength and inertness. Amongst the numerous surface modification techniques available, plasma surface modification affords device manufacturers a flexible and environmentally friendly process that enables tailoring of the surface morphology, structure, composition, and properties of the material to a specific need. There are a vast range of possible applications of plasma modification in biomaterial applications, however, the focus of this review paper is on processes that can be used to develop surface morphologies and chemical structures for the prevention of adhesion and proliferation of pathogenic bacteria on the surfaces of in-dwelling medical devices. As such, the fundamental principles of bacterial cell attachment and biofilm formation are also discussed. Functional organic plasma polymerised coatings are also discussed for their potential as biosensitive interfaces, connecting inorganic/metallic electronic devices with their physiological environments.

Plasma-enhanced synthesis of bioactive polymeric coatings from monoterpene alcohols: a combined experimental and theoretical study

This paper describes the synthesis and characterization of a novel organic polymer coating for the prevention of the growth of Pseudomonas aeruginosa on the solid surface of three-dimensional objects. Substrata were encapsulated with polyterpenol thin films prepared from terpinen-4-ol using radio frequency plasma enhanced chemical vapor deposition. Terpinen-4-ol is a constituent of tea tree oil with known antibacterial properties. The influence of deposition power on the chemical structure, surface composition, and ultimately the antibacterial inhibitory activity of the resulting polyterpenol thin films was studied using X-ray photoelectron spectroscopy (XPS), water contact angle measurement, atomic force microscopy (AFM), and 3-D interactive visualization and statistical approximation of the topographic profiles. The experimental results were consistent with those predicted by molecular simulations. The extent of bacterial attachment and extracellular polymeric substances (EPS) production was analyzed using scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM). Polyterpenol films deposited at lower power were particularly effective against P. aeruginosa due to the preservation of original terpinen-4-ol molecules in the film structure. The proposed antimicrobial and antifouling coating can be potentially integrated into medical and other clinically relevant devices to prevent bacterial growth and to minimize bacteria-associated adverse host responses.

An articulating spacer to treat and mobilize patients with infected total knee arthroplasty

This retrospective study analyzed 25 consecutive patients (25 knees) with chronic deep TKA infection. During 1997-2004, patients underwent two-stage articulating spacer surgery. The original femoral component was removed, autoclaved and replaced and a new polyethylene was utilized. The second- stage procedure occurred at a mean of 11 weeks (range: 4 to 39 weeks) after spacer insertion. Mobilization was encouraged between stages. All patients were assessed at a minimum of two years (mean 54 months; range: 24-108 months) post re-implantation, and Modified Hospital for Special Surgery (HSS) knee scores were calculated. Only one patient (4%) had re-infection. Average ROM before re-implantation was 5 degrees to 112 degrees , and 3 degrees to 115 degrees at latest follow-up. HSS scores averaged 91 (Range: 65-100) at latest follow-up. Two-stage re-implantation with an articulating spacer for infected TKA effectively treats infection and gives excellent knee motion between stages, and at mid- to long-term follow-up.

The microbiology of the infected knee arthroplasty

We describe the results of a retrospective analysis of patients with microbiologically proven infection, who underwent revision TKA between 1994 and 2008. Of the 121 patients included in the study, 61 (50%) were male and 60 (50%) were female. The mean age was 71 (range 42-88) years. The most common organisms identified were Coagulase negative Staphylococcus (CNS) (49%) and Staphylococcus aureus (SA) (13%). The prevalence of CNS appears to be increasing, while that of SA and other organisms is decreasing. Vancomycin and teicoplanin were the most effective antibiotics with overall sensitivity rates of 100% and 96%, respectively. The results of our theoretical model suggest that gentamicin combined with vancomycin is the most effective empirical regimen. Staphylococcal species are the most common organisms encountered in deep infection of the knee. Gentamicin combined with vancomycin offers the most comprehensive protection and potentially allows for infected knee arthoplasties to be treated with a one-stage procedure.

The value of synovial biopsy, joint aspiration and C-reactive protein in the diagnosis of late peri-prosthetic infection of total knee replacements

We analysed the serum C-reactive protein level, synovial fluid obtained by joint aspiration and five synovial biopsies from 145 knee replacements prior to revision to assess the value of these parameters in diagnosing late peri-prosthetic infection. Five further synovial biopsies were used for histological analysis. Samples were also obtained during the revision and incubated and analysed in an identical manner for 14 days. A total of 40 total knee replacements were found to be infected (prevalence 27.6%). The aspiration technique had a sensitivity of 72.5% (95% confidence interval (CI) 58.7 to 86.3), a specificity of 95.2% (95% CI 91.2 to 99.2), a positive predictive value of 85.3% (95% CI 73.4 to 100), a negative predictive value of 90.1% (95% CI 84.5 to 95.7) and an accuracy of 89%. The biopsy technique had a sensitivity of 100%, a specificity of 98.1% (95% CI 95.5 to 100), a positive predictive value of 95.2% (95% CI 88.8 to 100), a negative predictive value of 100% and an accuracy of 98.6%. C-reactive protein with a cut-off-point of 13.5 mg/l had a sensitivity of 72.5% (95% CI 58.7 to 86.3), a specificity of 80.9% (95% CI 73.4 to 88.4), a positive predictive value of 59.2% (95% CI 45.4 to 73.0), a negative predictive value of 88.5% (95% 81.0 to 96.0 CI) and an accuracy of 78.1%. We found that biopsy was superior to joint aspiration and C-reactive protein in the diagnosis of late peri-prosthetic infection of total knee replacements.

Management of falls after total knee arthroplasty

This study evaluated 78 patients who fell after total knee arthroplasty. Eight patients (10.3%) had soft-tissue injuries that led to a poor clinical course (deep infection, unplanned return to the operating room, temporary or permanent resection arthroplasty, or knee arthrodesis). Factors related to a poor clinical course included copious bleeding from the surgical wound immediately after falling, falling within 8 weeks of arthroplasty, and rupturing the parapatellar surgical wound and quadriceps repair. Patients who fall and have bleeding from their surgical wound should receive emergency surgical irrigation and debridement. A treatment protocol for patients who fall after total knee arthroplasty is presented.

Advancements in molecular epidemiology of implant infections and future perspectives

Implant infection remains the major and often irreducible complication in clinical use of biomaterials, demanding new therapeutic and preventive strategies. Etio-pathogenesis of biomaterials-related infections is being more and more studied, and various virulence bacterial factors have progressively been identified, but little is still known about the weight of the distinct molecules in the context of specific peri-implant infection sites. Molecular epidemiology has become recently integrated into the research on implant infections. What distinguishes molecular epidemiology from the simple molecular biology is that the use of molecular techniques is applied to the study of the distribution and prevalence of virulence and resistance genes in collections of bacterial clinical isolates from implant infections. Here, the authors comment on the range of molecular techniques available, reviewing the various applications of molecular epidemiology to the study of implant infections and providing some experimental examples related to the field of orthopaedic implant infections. They highlight the new opportunities arising from molecular epidemiology of designing measures useful to prevent and treat implant infections. The knowledge of the relative weight of virulence factors and of their regulatory mechanisms at molecular level can open the way to new strategies also including gene therapies aimed at silencing or knocking out crucial genes responsible for the aggressive tools (adhesins, biofilm production, antibiotic resistance) of the aetiological agents of implant-related infections.

Antibiotic-loaded cement articulating spacer for 2-stage reimplantation in infected total knee arthroplasty: a simple and economic method

We presented a simple and economic method of preparing articulating antibiotic-loaded cement spacers for treatment of infection after total knee arthroplasty. From 1996 to 2004, 28 infected total knee arthroplasties were treated with 2-stage reimplantation. Static spacers were used in 7 knees, and articulating spacers were used in 21 knees. A minimum of 2 years' follow-up after final treatment was evaluated. In the static group, 1 (14%) knee had recurrence of infection. In the articulating group, 2 (9%) knees had recurrence of infection with the original organism. Patients receiving articulating spacer had better range of motion, better knee score, and less bone loss than patients with static spacer.

[Results of reimplantation for infected total knee arthroplasty: 107 cases]

PURPOSE OF THE STUDY

The purpose of this study was to assess the results of reimplantations of total knee arthroplasties complicated by infection. Outcome was assessed in terms of eradicated infection and function.

MATERIAL AND METHODS

This retrospective multicentric study included 107 cases of infected total knee arthroplasties treated by changing the implants. Seventy-seven patients had a two-stage revision and thirty had a one-stage procedure. Patients were reviewed with a minimal 2-year and an average 52-month follow-up.

RESULTS

Revision arthroplasty (one- or two-stage) eradicated infection in two out of three patients. With a two-year follow-up, revision arthroplasty was successful in 77% of patients without any sepsis risk factor, in 65% of patients with one risk factor and in 33% of patients with at least two risk factors. After reimplantation for total knee arthroplasty infection, overall function outcome was good (KS knee score: 74.8 after two-stage revision and 75.5 after one-stage revision, NS). After two-stage procedures, the knee outcome was excellent in one-third of patients, good in another third and fair or poor in the final third. After one-stage reimplantation, 40% of the knees had an excellent outcome, 30% a good outcome and 30% a fair or poor outcome. Regarding functional outcome, overall results were fair (KS function score 62.5 for one-stage and two-stage revisions). Functional outcome was fair or poor in 42% of patients with a two-stage procedure and in 55% of patients with a one-stage revision (NS).

DISCUSSION

Our study was unable to disclose any difference between one-stage and two-stage revision for eradicating infection. Unfavorable systemic and local conditions decreased the rate of success after revision total knee arthroplasty for infection. Length of infection before reimplantation, number of surgical procedures and bacterial virulence or resistance were not, in our series, predicting factors for failure of septic revision total knee arthroplasty. No difference was found for the clinical and functional results between one-stage and two-stage procedures. Functional outcome was fair or poor for half of the patients after septic revision total knee arthroplsty. The use of an external device between the two procedures for two-stage revision significantly decreased the functional outcome compared with the use of a spacer. Articulated spacers did not offered any advantage compared with a static spacer for functional outcome.

Pasteurella multocida infection of a total knee arthroplasty after a "dog lick"

The patient we report here underwent a total knee arthroplasty (TKA) which got infected with P. multocida after her dog had licked a small wound at the third toe of the same foot. Despite a correct treatment comprising synovectomy and cleansing, and an active antibiotic treatment for 3 months, the patient was readmitted for persistent infection of the same knee 2 weeks after the end of the antibiotic treatment. Sampling during surgery allowed for the growth of a P. multocida isolate proven by a molecular method to be identical to the previously isolated strain. This recurrent P. multocida infection was treated by a two-step change of the TKA comprising a 2-month period of antibiotic treatment between the two surgical interventions.

Is there a role for extended antibiotic therapy in a two-stage revision of the infected knee arthroplasty?

All major studies have incorporated the use of prolonged courses of parenteral or oral antibiotic therapy in the management of two-stage revision of an infected total knee arthroplasty. We present a series of 59 consecutive patients, all with microbiologically-proven deep infection of a total knee arthroplasty, in whom a prolonged course of antibiotic therapy was not routinely used. The mean follow-up was 56.4 months (24 to 114).

Of the 38 patients who underwent a staged exchange, infection was successfully eradicated in 34 (89%) but recurrent or persistent infection was present in four (11%). Our rate of cure for infection is similar to that reported elsewhere. We conclude that a prolonged course of antibiotic therapy seems not to alter the incidence of recurrent or persistent infection. The costs of the administration of antibiotics are high and such a regime may be unnecessary.