[Diagnostic strategies in cases of suspected periprosthetic infection of the knee. A review of the literature and current recommendations]

Knee arthrodesis with intramedullary nail in end-stage periprosthetic joint infection with extensor mechanism failure: a retrospective outcome and reinfection rate analysis of a case series

BACKGROUND

Chronic periprosthetic knee infection is a highly debilitating complication. In case of failed R-TKA, with significant bone loss and extensor mechanism failure, re-revision procedures could not even be feasible. The most appropriate therapeutic strategy in these cases remains unclear. This study aims to evaluate the clinical and subjective outcomes, as well as the reinfection rate, in nine patients with extensor mechanism failure following chronic PJI treated with knee arthrodesis using a cemented intramedullary nail with a bridging technique.

METHODS

The series included nine patients who underwent knee arthrodesis with a cemented intramedullary nail at our Institute between 2020 and 2024. All patients were treated by a single operator using a standardized two-stage revision procedure. Clinical scores (OKS and VAS), subjective scores (SF-36), postoperative limb length discrepancy, and the reinfection rate were evaluated for each patient.

RESULTS

All patients achieved good clinical and subjective scores, indicating good functional recovery and pain reduction. No patient had clinically relevant limb length discrepancy. One patient (11.1%) experienced a recurrence of infection. Literature shows that re-revision surgery with extensor mechanism reconstruction has high complication and reinfection rates, while transfemoral amputation results in lower clinical and functional scores. Knee arthrodesis ensures good functionality and a low reinfection rate.

CONCLUSIONS

Knee arthrodesis with a cemented intramedullary nail is a valid therapeutic alternative for patients with extensor mechanism failure following chronic periprosthetic infection. Patients in our study achieved good functional recovery and pain reduction. Further comparative studies with larger series are needed to confirm these results.

An overview of the current diagnostic approach to Periprosthetic Joint Infections

The diagnosis of periprosthetic joint infections (PJI) presents a formidable challenge to orthopaedic surgeons due to its complex and diverse manifestations. Accurate diagnosis is of utmost importance, as even mild pain following joint replacement surgery may indicate PJI in the absence of a definitive gold standard diagnostic test. Numerous diagnostic modalities have been suggested in the literature, and international societies have continually updated diagnostic criteria for this debilitating complication. This review article aims to comprehensively examine the latest evidence-based approaches for diagnosing PJI. Through a thorough analysis of current literature, we explore promising diagnostic strategies that have demonstrated effectiveness in identifying PJI. These strategies encompass the utilization of laboratory markers, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), alongside imaging techniques such as magnetic resonance imaging (MRI) and leukocyte scintigraphy. Additionally, we highlight the importance of synovial fluid analysis, including the potential role of alpha-defensin as a biomarker, and examine evolving international diagnostic criteria to standardize and improve diagnostic accuracy.

Early results of a novel modular knee arthrodesis implant after uncontrolled periprosthetic knee joint infection

AIM

The aim of this study is to evaluate the functional outcomes and complications after non-fusion knee arthrodesis with a modular segmental intramedullary implant used for infected total knee arthroplasty revisions.

METHODS

A retrospective review of the patients who had been surgically treated with a modular intramedullary arthrodesis implant for recurrent infection after revision TKA between January 2016 and February 2020 were included. The indications for arthrodesis were failed infected TKA with massive bone loss, deficient extensor mechanism and poor soft tissue coverage that precluded joint reconstruction with revision TKA implants. Clinical outcomes were assesed with visual analogue scale for pain (pVAS), Oxford knee score (OKS) and 12-item short form survey (SF-12). Full-length radiographs were used to verify limb length discrepancies (LLD).

RESULTS

Fourteen patients (4 male and 10 female) patients with a mean age of 69.3 (range, 59 to 81) years at time of surgery were available for final follow-up at a mean of 28.8 months (range, 24-35 months). All clinical outcome scores improved at the final follow-up (pVAS, 8.5 to 2.6, p = .01; OKS, 12.6 to 33.8, p = .02; SF-12 physical, 22.9 to 32.1, p = .01 and SF-12 mental, 27.7 to 40.2, p = .01). The mean LLD was 1.0 cm (range, + 15 - 2.3 cm). Re-infection was detected in three patients (21.4%). Two patients were managed with suppressive antibiotic treatment and a third patient required repeat 2-stage revision procedure. In one patient, a periprosthetic femur fracture was observed and treated with plate osteosynthesis.

CONCLUSION

Uncontrolled infection after total knee arthroplasty can be effectively treated with arthrodesis using a modular intramedullary nail and satisfactory functional results can be obtained.

LEVEL OF EVIDENCE

Level 4, Retrospective cohort study.

Difficult-to-treat pathogens significantly reduce infection resolution in periprosthetic joint infections

Periprosthetic joint infection (PJI) is a feared complication after arthroplasty. Our hypothesis was that PJI caused by difficult-to-treat (DTT) pathogens has a worse outcome compared with non-DTT PJI. Routine clinical data on 77 consecutive patients with confirmed PJI treated with 2-stage exchange arthroplasty were placed in DTT and non-DTT PJI groups and analyzed. The main outcome variable was that the patient was definitively free of infection after 2 years. We found definitive infection resolution in 31 patients in the DTT group (68.9%) and 28 patients (87.5%) in the non-DTT group (P < 0.05). The necessity for revision surgery until assumed resolution of infection was significantly more frequent in the DTT group with 4.72 ± 3.03 operations versus 2.41 ± 3.02 operations in the non-DTT group (P < 0.05). PJI caused by DTT bacteria is associated with significantly higher numbers of revision operations and significantly inferior definitive infection resolution.

Periprosthetic Tibial Fracture with Nonunion and Ascending Prosthetic Joint Infection: A Case Report of an Individual Treatment Strategy

Introduction:

Periprosthetic fractures are severe injuries that demand the surgeon’s full expertise and special diagnostic and therapeutic strategies. A major complication is the occurrence of an infectious nonunion, including an ascending infection from the fracture site to the arthroplasty.

Case Report:

This case report presents on a patient with a well-functioning revision total knee arthroplasty (TKA) who suffered a periprosthetic tibia fracture. Initial treatment with plating failed and the fracture had to be revised due to an infectious non-union with a multidrug-resistant Staphylococcus epidermidis, and its eradication was complicated by septic loosening of the patient’s knee arthroplasty. After multiple revisions of the nonunion, a two-stage exchange arthroplasty with a partial replacement of the distal femur due to a bone defect was necessary to obtain an acceptable result.

Conclusion:

The objective of this case report is to present an individual surgical strategy in a complex case of periprosthetic fracture and TKA with major complications. It is shown that the infection of the bone and implants is a challenging situation for surgical treatment. There is still no optimal management strategy due to missing standards as well as controversies in treatment.

Comparison of two-stage revision arthroplasty and intramedullary arthrodesis in patients with failed infected knee arthroplasty

BACKGROUND

Failed total knee arthroplasty (TKA) with significant bone loss and compromised soft-tissues is challenging and the final results are often inferior to patient's expectation. The objective of this study was to present a comparison of outcomes in patients with failed infected TKA treated with two-stage revision TKA or knee arthrodesis and to assess clinical and functional results, implant survival and infection recurrence. The hypothesis was that an arthrodesis may result in beneficial effects on patients' outcome.

METHODS

Clinical data of 81 patients with periprosthetic joint infection (PJI) of the knee joint were collected and analyzed retrospectively. Between 2008 and 2014, a total of 36 patients had been treated within a two-stage exchange procedure and reimplantation of a modular intramedullary arthodesis nail and 45 patients with revision TKA. Patients were treated according to the same structured treatment algorithm. Clinical and functional evaluation was performed using the Oxford knee score (OKS) and the visual analogue scale (VAS).

RESULTS

The mean follow-up was 32.9 ± 14.0 months. The rate of definitely free of infection at last follow-up in the arthrodesis group was 32 of 36 (88.9%) and 36 of 45 (80.0%) in the revision TKA group (p = 0.272). Mean VAS for pain in the arthrodesis group was 3.1 ± 1.4 compared to 3.2 ± 1.6 in the revision TKA group (p = 0.636). The OKS in the arthrodesis group was 38.7 ± 8.9 and 36.5 ± 8.9 (p = 0.246) in patients with revision TKA. Rate of revisions in the revision-TKA group was 2.8 ± 3.7 compared to 1.2 ± 2.4 in the arthrodesis group (p = 0.021).

CONCLUSION

Treatment of PJI needs a distinct therapy with possible fallback strategies in case of failure. A knee arthrodesis is a limb salvage procedure that showed no significant benefits on the considered outcome factors compared to revision TKA but is associated with significantly lower revision rate. After exhausted treatment modalities, a knee arthrodesis should be considered as an option in selected patients.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Periprosthetic Joint Infection of Shoulder Arthroplasties: Diagnostic and Treatment Options

Periprosthetic joint infection (PJI) is one of the most frequent reasons for painful shoulder arthroplasties and revision surgery of shoulder arthroplasties. Cutibacterium acnes (Propionibacterium acnes) is one of the microorganisms that most often causes the infection. However, this slow growing microorganism is difficult to detect. This paper presents an overview of different diagnostic test to detect a periprosthetic shoulder infection. This includes nonspecific diagnostic tests and specific tests (with identifying the responsible microorganism). The aspiration can combine different specific and nonspecific tests. In dry aspiration and suspected joint infection, we recommend a biopsy. Several therapeutic options exist for the treatment of PJI of shoulder arthroplasties. In acute infections, the options include leaving the implant in place with open debridement, septic irrigation with antibacterial fluids like octenidine or polyhexanide solution, and exchange of all removable components. In late infections (more than four weeks after implantation) the therapeutic options are a permanent spacer, single-stage revision, and two-stage revision with a temporary spacer. The functional results are best after single-stage revisions with a success rate similar to two-stage revisions. For single-stage revisions, the microorganism should be known preoperatively so that specific antibiotics can be mixed into the cement for implantation of the new prosthesis and specific systemic antibiotic therapy can be applied to support the surgery.

Two-stage knee arthrodesis with a modular intramedullary nail due to septic failure of revision total knee arthroplasty with extensor mechanism deficiency

BACKGROUND

Periprosthetic joint infection is a serious complication and reconstruction after failed revision total knee arthroplasty with significant bone loss and compromised soft-tissues can be challenging. Objective of this study was to assess clinical and functional results, implant survival and infection recurrence rates in patients treated with two-stage arthrodesis after failed revision TKA with extensor mechanism deficiencies due to PJI, and to identify the factors that affect outcomes after surgery.

METHODS

Thirty seven patients with PJI treated within a two-stage exchange and reimplantation of an arthrodesis nail between 2008 and 2014 were included. Systemic and local risk factors were graded preoperatively according to McPherson et al. All patients were treated according to a structured treatment algorithm. Clinical and functional evaluation was performed using the Oxford Knee Score and the Visual Analogue Scale.

RESULTS

Thirty two of 37 patients (86.5%) were graded as free of infection. Five patients (13.5%) had recurrent infection after arthrodesis with the need of revision surgery. Mean leg-length discrepancy was 2.2cm. The mean VAS for pain was three, the mean Oxford Knee Score was 38±9. Total implant survival at a 74month follow-up was 74.3% (95% CI: 45.4 to 91.1%), as determined by Kaplan-Meier survival curves. Local McPherson Score, as well as number of revisions was found to be of significant influence to the survival rate.

CONCLUSIONS

Septic failure of revision knee arthroplasty can be effectively treated with two-stage arthrodesis using a modular intramedullary nail, providing a stable and painless limb with satisfactory functional results and acceptable infection eradication rates.

Implant allergy

Osteosynthesis materials or artificial joint replacement make part of clinical routine. In case of complaints mostly mechanical causes or infections are found. Metals like nickel, chromium and cobalt or bone cement components like acrylates and gentamicine may however potentially cause intolerance reactions to implants. Correspondingly, eczema, delayed wound/bone healing, recurrent effusion, pain or implant loosening have been described as manifestation of implant allergy. In contrast to the high incidence of cutaneous metal allergy, allergies associated with implants are rare. Diagnosis of metal implant allergy is based on excluding differential diagnoses – in particular infection – and on a combined approach of allergological diagnostics by patch test and histopathology of periimplant tissue. Risk factors for allergic sensitization to implants or triggering periimplant allergic reactions in the case of preexisting cutaneous metal allergy are unknown. Despite the risk of developing complications being unclear, titanium-based osteosynthesis materials are recommended for metal-allergic patients and the use of metal-metal couplings in arthroplasty is rather not recommended for such patients. If a regular, potentially applicable CoCr-polyethylene articulation is preferred, the patient has to be well informed and has to give his written consent.

Emperor's new clothes: Is particle disease really infected particle disease?

Aseptic loosening remains the most significant long-term complication of total hip replacement. The current paradigm points to an inflammatory response to wear particles as its main trigger. Recently, there have been increasing numbers of positive bacterial isolates reported among patients with clinically absent infection. This paper reviews existing evidence on possible involvement of bacteria and microbial-associated molecular patterns in the pathology of so-called "aseptic loosening." © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1497-1504, 2016.

Outcome of total knee replacement following explantation and cemented spacer therapy

Background: Infection after total knee replacement (TKR) is one of the serious complications which must be pursued with a very effective therapeutic concept. In most cases this means revision arthroplasty, in which one-setting and two-setting procedures are distinguished. Healing of infection is the conditio sine qua non for re-implantation.

This retrospective work presents an assessment of the success rate after a two-setting revision arthroplasty of the knee following periprosthetic infection. It further considers drawing conclusions concerning the optimal timing of re-implantation.

Patients and methods: A total of 34 patients have been enclosed in this study from September 2005 to December 2013. 35 re-implantations were carried out following explantation of total knee and implantation of cemented spacer. The patient’s group comprised of 53% (18) males and 47% (16) females. The average age at re-implantation time was 72.2 years (ranging from 54 to 85 years). We particularly evaluated the microbial spectrum, the interval between explantation and re-implantation, the number of surgeries that were necessary prior to re-implantation as well as the postoperative course.

Results: We reported 31.4% (11) reinfections following re-implantation surgeries. The number of the reinfections declined with increasing time interval between explantation and re-implantation. Patients who developed reinfections were operated on (re-implantation) after an average of 4.47 months. Those patients with uncomplicated course were operated on (re-implantation) after an average of 6.79 months. Nevertheless, we noticed no essential differences in outcome with regard to the number of surgeries carried out prior to re-implantation. Mobile spacers proved better outcome than temporary arthrodesis with intramedullary fixation.

Conclusion: No uniform strategy of treatment exists after peri-prosthetic infections. In particular, no optimal timing can be stated concerning re-implantation. Our data point out to the fact that a longer time interval between explantation and re-implantation reduces the rate of reinfection. From our point of view, the optimal timing for re-implantation depends on various specific factors and therefore it should be defined individually.

[Synovial biomarkers for differential diagnosis of painful arthroplasty]

BACKGROUND

The diagnosis and treatment of periprosthetic joint infection (PJI) remain true clinical challenges. PJI diminishes therapeutic success, causes dissatisfaction for the patient and medical staff, and often requires extensive surgical revision(s). At the present time, an extensive multimodal algorithmic approach is used to avoid time- and cost-consuming diagnostic aberrations. However, especially in the case of the frequent and clinically most relevant "low-grade" PJI, the current diagnostic "gold standard" has reached its limits.

EVALUATION

Synovial biomarkers are thought to close this diagnostic gap, hopefully enabling the safe differentiation among aseptic, (chronic) septic, implant allergy-related and the arthrofibrotic genesis of symptomatic arthroplasty. Therefore, joint aspiration for obtaining synovial fluid is preferred over surgical synovial tissue biopsy because of the faster results, greater practicability, greater patient safety, and lower costs. In addition to the parameters synovial IL-6, CRP, and leukocyte esterase, novel biomarkers such as antimicrobial peptides and other proinflammatory cytokines are currently highlighted because of their very high to excellent diagnostic accuracy.

CONCLUSION

Independent multicenter validation studies are required to show whether a set of different innovative synovial fluid biomarkers rather than a few single parameters is favorable for a safe "one-stop shop" differential diagnosis of PJI.

Diagnostic work-up strategy for periprosthetic joint infections after total hip and knee arthroplasty: a 12-year experience on 320 consecutive cases

Background

Elective knee and hip arthroplasty is followed by infections in currently about 0.5–2.0 % of cases – a figure which is on the increase due to the rise in primary implants. Correct diagnosis early on is essential so that appropriate therapy can be administered. This work presents a retrospective analysis of the diagnoses of patients suffering infections after total hip or knee arthroplasty.

Methods

320 patients with prosthetic joint infection (PJI) following knee or hip arthroplasty were identified. They comprised a) 172 patients with an infection after total hip arthroplasty (THA): 56 % females (n = 96) and 44 % males (n = 76) with a mean age of 70.9 (39–92) years; and 148 patients with an infection after total knee arthroplasty (TKA): 55 % females (n = 82) and 45 % males (n = 66) with a mean age of 70.7 (15–87) years.

Results

Although significantly more TKA than THA patients reported pain, erythema, a burning sensation and swelling, no differences between the two groups were observed with respect to dysfunction, fever or fatigue. However, significant differences were noted in the diagnosis of loosening (THA 55 %, TKA 31 %, p < 0.001) and suspected infection using conventional X-rays (THA 61 %, TKA 29 %, p < 0.001). FDG-PET-CT produced very good results in nearly 95 % of cases. There were no differences between THA and TKA patients regarding levels of inflammation markers. Histological evaluation proved to be significantly better than microbiological analysis.

Summary

The clinical picture may be non-specific and not show typical inflammatory symptoms for a long time, particularly in PJI of the hip. As imaging only provides reliable conclusions after the symptoms have persisted for a long time, morphological imaging is not suitable for the detection of early infections. FDG-PT-CT proved to be the most successful technique and is likely to be used more frequently in future. Nevertheless, there are currently no laboratory parameters which are suitable for the reliable primary diagnosis of PJI. Diagnosis requires arthrocentesis, and the fluid obtained should always be examined both microbiologically and histologically.

Human osteoblast damage after antiseptic treatment

PURPOSE

Antiseptics are powerful medical agents used for wound treatment and decontamination and have a high potential for defeating joint infections in septic surgery. Both chlorhexidine and polyhexanide are frequently used in clinical practice and have a broad antimicrobial range, but their effect on human osteoblasts has not been sufficiently studied. Our objective was to investigate the toxic effects of polyhexanide and chlorhexidine on human osteoblasts in vitro to evaluate their clinical applicability in septic surgery.

METHODS

We isolated and cultivated human osteoblasts in vitro and assayed the toxic effects of chlorhexidine 0.1% and polyhexanide 0.04%, concentrations commonly applied in clinical practice. Toxicity analysis was performed by visualisation of cell structure, lactate dehydrogenase (LDH) activity and evaluation of vital cells. Toxicity was evaluated by microscopic inspection of cell morphology, trypan blue staining and determination of LDH release.

RESULTS

Damaged cell structure could be shown by microscopy. Both antiseptics promoted LDH activity after incubation with osteoblasts. The evaluation of vital osteoblasts showed a significant decrease of vital cells.

CONCLUSIONS

Both antiseptics induced significant cell death of osteoblasts at optimum exposure. We therefore recommend cautious use of polyhexanide and chlorhexidine in septic surgery to avoid severe osteoblast toxicity.

Lipopolysaccharide-binding protein: a valuable biomarker in the differentiation between periprosthetic joint infection and aseptic loosening?

PURPOSE

The pre-operative differentiation between periprosthetic joint infection (PJI) and aseptic loosening after total hip (THA) or knee (TKA) arthroplasty is essential for successful therapy and relies in part on the use of molecular markers. The objective of this study was to assess serum levels of lipopolysaccharide-binding protein (LBP) as a diagnostic tool for PJI and to compare its accuracy with standard tests.

METHODS

One hundred and twenty patients presenting with a painful TKA or TKA with indication for surgical revision were included in this prospective, controlled, clinical trial at a single centre. Pre-operative blood and serum samples were collected and analysed for white blood cell (WBC) count, C-reactive protein (CRP) and LBP. The definite diagnosis of periprosthetic joint infection was determined on the basis of clinical, microbiological and histopathological examination.

RESULTS

LBP showed significantly higher values in PJI compared with aseptic loosening (p < 0.001) and control (p < 0.001), with a specificity of 66% and a sensitivity of 71% at a cutoff value of >7 ng/ml. In combination with CRP, the positive predictive value for PJI was at 0.67; negative predictive value with both negative was at 0.77.

DISCUSSION

Patients with PJI have elevated serum levels of LBP when compared with patients with aseptic loosening. The use of LBP in serum appears not to be a more accurate marker than CRP level in serum for detecting PJI. On the basis of these results, we cannot recommend the sole use of LBP for differentiating PJI and aseptic loosening following THA and TKA.

Optimal culture incubation time in orthopedic device-associated infections: a retrospective analysis of prolonged 14-day incubation

Accurate diagnosis of orthopedic device-associated infections can be challenging. Culture of tissue biopsy specimens is often considered the gold standard; however, there is currently no consensus on the ideal incubation time for specimens. The aim of our study was to assess the yield of a 14-day incubation protocol for tissue biopsy specimens from revision surgery (joint replacements and internal fixation devices) in a general orthopedic and trauma surgery setting. Medical records were reviewed retrospectively in order to identify cases of infection according to predefined diagnostic criteria. From August 2009 to March 2012, 499 tissue biopsy specimens were sampled from 117 cases. In 70 cases (59.8%), at least one sample showed microbiological growth. Among them, 58 cases (82.9%) were considered infections and 12 cases (17.1%) were classified as contaminations. The median time to positivity in the cases of infection was 1 day (range, 1 to 10 days), compared to 6 days (range, 1 to 11 days) in the cases of contamination (P < 0.001). Fifty-six (96.6%) of the infection cases were diagnosed within 7 days of incubation. In conclusion, the results of our study show that the incubation of tissue biopsy specimens beyond 7 days is not productive in a general orthopedic and trauma surgery setting. Prolonged 14-day incubation might be of interest in particular situations, however, in which the prevalence of slow-growing microorganisms and anaerobes is higher.

Evaluation of an interdisciplinary therapy algorithm in patients with prosthetic joint infections

PURPOSE

Current concepts in the treatment of prosthetic joint infections include prosthetic retention and exchange strategies according to published recommendations. A useful algorithm should fit for each type of prosthetic joint infection, even the most complicated situations. We present the outcome of 147 patients with prosthetic joint infections of the hip or the knee joint in an unselected population in clinical routine.

METHODS

Between November 2006 and November 2009, 147 consecutive patients with prosthetic joint infections of the hip or knee were treated according to an algorithm based on the concept published by Zimmerli et al. in 2004. Causative organism, duration of infection, patient comorbidities, surgical treatment, antibiotic treatment, and outcome of treatment were analysed retrospectively. According to the criteria duration of infection, stability of prosthesis, local and systemic risk factors, and susceptibility of the causative pathogen, patients were treated either with debridement and retention or a long-interval two-stage procedure.

RESULTS

A pathogen could be detected in 82.8% of the patients, gram-positive cocci being most common. Twenty-seven patients were treated with debridement and retention and 120 were treated with a two-stage procedure. In 68 cases difficult-to-treat pathogens could be detected, a polymicrobial infection was found in 51 patients. Definitely free of infection were 71.6% after a two-stage procedure, and 70.4% after debridement and retention.

CONCLUSIONS

Our data indicates that the applied algorithm is suitable to be applied as a day-to-day routine, and we confirmed that published results from the literature can be reproduced in an inhomogeneous patient cohort.

High rate of infection control with one-stage revision of septic knee prostheses excluding MRSA and MRSE

BACKGROUND

The rate of infection control for one-stage revision of infected knee arthroplasties is unclear as are the factors influencing infection control. Such factors include duration of infection and the type of infected prosthesis.

QUESTIONS/PURPOSES

We therefore determined: (1) the rate of infection control with one-stage revision of septic knee prostheses, (2) the clinical knee scores that can be achieved, (3) whether the duration of infection or the type of prosthesis influence the level of infection control, and (4) whether different types of prostheses influence the knee scores.

METHODS

We retrospectively reviewed prospectively collected data from 63 patients who underwent one-stage revisions of septic knee endoprostheses (six unicondylar, 37 primary total knee replacement prostheses, and 20 hinged knee endoprostheses) between 2004 and 2006. All were treated locally and systemically with microorganism-specific antibiotics. For this study we excluded patients with Methicillin-resistant Staphylococcus aureus and Methicillin-resistant Staphylococcus epidermidis or unknown microorganisms. The patients were examined for infection every 3 months and Oxford and Knee Society scores were assessed at the same time. The minimum followup was 24 months (mean followup, 36 months; range, 24-70 months).

RESULTS

None of the patients with replacement unicondylar and primary total knee replacement prostheses had recurrence of infection. Three of the 20 patients with the hinged infected knee prostheses had recurrences; these three patients had chronic infections and had undergone two to three revision operations during at least a 5-year period. The likelihood of infection control was influenced by the duration of infection. The mean Knee Society knee score 24 months after surgery was 72 points (range, 20-98 points), the Knee Society function score was 71 points (range, 10-100 points), and the Oxford-12 knee score was 27 points (range, 13-44 points).

CONCLUSIONS

One-stage revision of septic knee prostheses achieved an infection control rate of 95% and higher knee scores than reported for two-stage revisions. Higher rates of recurrent infection appeared to be associated with long-term chronic infections of hinged prostheses.

[What can be done when hip prostheses fail? : New trends in revision endoprosthetics]

Revision surgery after total hip arthroplasty is increasing steadily in numbers. These procedures demand high performance from both the treating surgeon as well as the implants used. Novel developments from basic research and industrial partners extend the possibilities for treating affected patients. This article gives an overview of the state of the art in revision hip arthroplasty: new techniques and trends are outlined and presented.

[Logistic requirements and biopsy of periprosthetic infections: what should be taken into consideration?]

Preoperative diagnosis of periprosthetic infections is particularly important before revision of knee and hip arthroplasties because of the therapeutic consequences. Therefore, periprosthetic infections should be ruled out before any revision surgery is performed. Of the different diagnostic methods direct techniques which allow the direct detection of microorganisms with testing of antibiotic sensitivity are recommended. This allows microorganism-specific systemic and local antibiotic therapies and helps to reduce the risk of development of resistance. In our studies it could be shown that the time for incubation to detect microorganisms should be 14 days and that biopsy of periprosthetic tissues is superior to aspiration alone because it combines several diagnostic methods (microbiological and histological). It is preferable to repeating an aspiration when data are unclear, i.e. in cases of potentially false positives or negatives results of aspiration.

Optimizing culture methods for diagnosis of prosthetic joint infections: a summary of modifications and improvements reported since 1995

Improving diagnosis of prosthetic joint infections (PJIs) has become an increasing challenge due to a steadily rising number of patients with prosthetic implants. Based on a systematic literature search we have ascertained the evidence base for improvement of culture diagnosis. We searched PubMed/MEDLINE using the medical subject heading (MeSH) 'prosthesis-related infections' 1995 through 2010 without further restrictions. An analogous search was conducted for ISI Web of Knowledge. A total of 1409 reports were screened for original results, obtained by methods described in sufficient detail to make replication possible. We gave priority to methods for sample preparation, culture media, culture methods and incubation time. Clinical sensitivity and specificity were calculated where possible. We found evidence to support superiority of cultures obtained from the diluent after sonication of prosthetic implants in comparison with culturing tissue biopsies. Sonication parameters and accessory steps have been studied extensively, and thresholds for significant growth have been defined. Conversely, methods for processing of soft tissue biopsies have been studied to a limited extent. Culture of synovial fluid in blood culture vials has been shown to be more sensitive (90-92 %) than intraoperative swab cultures (68-76 %) and tissue cultures (77-82 %). Formal evaluation of agar media for culturing PJI specimens seemed to be lacking. The polymicrobial nature of PJIs supports the routine use of an assortment of media suitable for recovery of fastidious, slow-growing, anaerobic and sublethally damaged bacteria. A number of studies supported an incubation period for up to 14 days. Although we identified evidence-based improvements of culture methods, there is a need for more studies especially with regard to tissue biopsies. Culturing remains an important means to identify and characterize pathogenic micro-organisms and supplements the increasing number of culture-independent assays.

Mark B. Coventry Award: synovial C-reactive protein: a prospective evaluation of a molecular marker for periprosthetic knee joint infection

BACKGROUND

C-reactive protein (CRP) serum assays are a standard element of the diagnostic workup for periprosthetic joint infection (PJI). However, because CRP is a marker for systemic inflammation, this test is not specific to PJI.

QUESTIONS/PURPOSES

Our purpose was to assess whether synovial fluid and serum assays alone could differentiate between infected and uninfected revision knee arthroplasties and to determine which of these methods had the greatest diagnostic accuracy.

METHODS

We collected synovial fluid specimens from 66 patients undergoing revision total knee arthroplasty. Patients were judged uninfected or infected by standardized criteria. Synovial CRP levels were measured using an individual CRP assay (15 samples; 10 infected, five uninfected) and a multiplex immunoassay platform (59 samples; 25 infected, 34 uninfected). Results from preoperative standard serum CRP assays conducted were also collected (55 samples; 25 infected, 30 uninfected). Sensitivity, specificity, and receiver operating characteristic curve analyses were performed for each assay with a diagnosis of infection based on previously established criteria.

RESULTS

Synovial CRP concentrations differed between infected and uninfected joints in the multiplex and serum analyses. The area under the curve was 0.84 for the individual assay, 0.91 for the multiplex assay, and 0.88 for the serum CRP assay. Sensitivity and specificity were 70.0% and 100.0% for the individual enzyme-linked immunosorbent assay, 84.0% and 97.1% for the multiplex assay, and 76.0% and 93.3% for the serum CRP assay.

CONCLUSIONS

An assay measuring CRP in synovial fluid may be more accurate in diagnosing PJI than the standard serum CRP assay. We believe such an assay holds promise as a new diagnostic marker for PJI.

Two-stage revision of implant-associated infections after total hip and knee arthroplasty

Septic loosening of total hip and knee endoprostheses gains an increasing proportion of revision arthroplasties. Operative revisions of infected endoprostheses are mentally and physically wearing for the patient, challenging for the surgeon and a significant economic burden for healthcare systems. In cases of early infection within the first three weeks after implantation a one-stage revision with leaving the implant in place is widely accepted. The recommendations for the management of late infections vary by far. One-stage revisions as well as two-stage or multiple revision schedules have been reported to be successful in over 90% of all cases for certain patient collectives. But implant associated infection still remains a severe complication. Moreover, the management of late endoprosthetic infection requires specific logistics, sufficient and standardized treatment protocol, qualified manpower as well as an efficient quality management. With regard to the literature and experience of specialized orthopaedic surgeons from several university and regional hospitals we modified a commonly used treatment protocol for two-stage revision of infected total hip and knee endoprostheses. In addition to the achievement of maximum survival rate of the revision implants an optimisation of the functional outcome of the affected artificial joint is aimed for.

[Replacement of infected knee and hip endoprostheses]

Infections occur in 0.5-5% of cases after implantation of an endoprosthesis and represent one of the most severe complications of artificial joint replacements. Approximately 300,000 primary implantations for hip and knee prostheses are carried out in Germany annually with a corresponding number of early and late infections. This means that approximately 4,000-6,000 cases are to be expected annually. Periprosthetic infections normally lead to a significant loss of function and quality of life for patients and the complex remediation is costly. Therefore, preventive measures, such as perioperative prophylaxis with antibiotics, maintaining highly sterile conditions during operations and an expedient selection of patients are of substantial importance. The basic principles of an adequate restoration include identification of the pathogen, local eradication of the infection mostly after removal of the prosthesis, pathogen-oriented systemic and local antibiotic therapy and finally re-implantation of the revision prosthesis under infection-free conditions. The standard procedure for revision surgery is a two-phase replacement with maintenance of an infection-free interval before renewal of the prosthesis. The use of single-phase or multi-phase strategies, as well as the selection of cemented or cement-free revision, varies between centers as a definitive evaluation is not yet available.The most important parameters for successful treatment of periprosthetic infections have been identified as the earliest possible diagnosis, radical surgical cleansing with an adequate antibiotic therapy and successful restoration has been reported in approximately 80% of cases. Because of the complex therapy regime, treatment in specialized centers is generally recommended especially under the aspect of a demanding patient monitoring.

Is there a role for tissue biopsy in the diagnosis of periprosthetic infection?

BACKGROUND

Successful treatment of an infected joint arthroplasty depends on correctly identifying the responsible pathogens. The value of a preoperative biopsy remains controversial.

QUESTIONS/PURPOSES

We (1) compared the sensitivity and specificity of both tests separately and in combination, and (2) asked whether the combination of tissue biopsy and aspiration would improve our diagnostic yield in the evaluation of periprosthetic joint infections.

PATIENTS AND METHODS

We prospectively followed 120 patients with suspected infection of a total joint arthroplasty: 64 with THAs and 56 with TKAs. All patients had aspiration with culture and biopsy.

RESULTS

The sensitivity was 83% for aspiration, 79% for biopsy, and 90% for the combination of both techniques. The specificity was 100% for aspiration and biopsy and the combination. The overall accuracy was 84%, 81%, and 90%, respectively.

CONCLUSIONS

Our data suggest tissue biopsy alone offers no clear advantage over joint aspiration. However, the combination of both techniques provides improved sensitivity and accuracy. We recommend the use of tissue biopsy as an adjunct to joint aspiration in the diagnosis of total joint infection.

LEVEL OF EVIDENCE

Level II, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Revision of late periprosthetic infections of total hip endoprostheses: pros and cons of different concepts

Many concepts have been devised for the treatment of late periprosthetic infections of total hip prostheses. A two-stage revision with a temporary antibiotic-impregnated cement spacer and a cemented prosthesis appears to be the most preferred procedure although, in recent times, there seems to be a trend towards cementless implants and a shorter period of antibiotic treatment. Because of the differences in procedure, not only between studies but also within studies, it cannot be decided which period of parenteral antibiotic treatment and which spacer period is the most suitable. The fact that comparable rates of success can be achieved with different treatment regimens emphasises the importance of surgical removal of all foreign materials and the radical debridement of all infected and ischaemic tissues and the contribution of these crucial procedures to the successful treatment of late periprosthetic infections.

Two-stage cementless revision of infected hip endoprostheses

Cementless two-stage revision of infected total hip prostheses lacks the possibility of local antibiotic protection of the implant at the time of reimplantation, which leads to the concern that this protocol may not sufficiently eradicate periprosthetic infection. Moreover, early implant loosening as much as 18% and stem subsidence as much as 30% have been reported. To determine whether a cementless revision could eradicate infection and achieve sufficient implant stability, we prospectively followed 36 patients with two-stage revisions for septic hip prostheses. We used a uniform protocol of a 6-week spacer interval, specific local and systemic antibiotic therapies, and cementless modular revision stems. The minimum followup was 24 months (mean, 35 months; range, 24-60 months). In one patient, the spacer was changed when the C-reactive protein value failed to normalize after 6 weeks, and the reimplantation was performed after an additional 6 weeks. No infections recurred. There was no implant loosening and a 94% bone-ingrowth fixation of stems. Subsidence occurred in two patients. The Harris hip score increased from a preoperative mean of 41 to 90 at 12 months after reimplantation and later. Using cementless prostheses in two-stage revisions of periprosthetic infections of the hip in combination with a specific local and systemic antibiotic therapy seems to eradicate infection and provide implant stability.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

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.

[Ligament instability in total knee arthroplasty--causal analysis]

Ligament instability is a common reason for revision total knee arthroplasty (TKA). A meticulous analysis of the type of instability is very important in order to revise such a knee successfully. The objective of this study was to analyze the different reasons for ligament instability in revision TKA. A total of 135 knee revisions performed by one surgeon were analyzed pre- (clinical and x-ray) and intraoperatively for the cause of failure. X-ray analysis included the assessment of each component for position. Intraopertive analysis included stability testing in extension and 30 degrees , and 90 degrees of flexion, wear pattern, patella motion (shifting and tilting) and patella height. In 32.6 % of all cases, ligament instability was the primary reason for revision. In another 21.6%, ligament instability was identified as a secondary reason for revision. Analysis of the different instability forms showed combined instability in extension and flexion as the most common cause, followed by isolated instability in flexion (31.8%) and isolated instability in extension (9.1%). The high correlation between instability and malpositioning of the prostheses was obvious. Often, an isolated femoral malposition, in particular for rotation, was found, as well as an isolated malposition of the tibia component. In summary, ligament instability is a common reason for revision TKA. Many different forms of instability can be found either as isolated or combined instability types. Correct anatomical positioning of the components and balanced ligaments in the different extension and flexion positions are important for good clinical results, a stable joint, good function and longevity.

The fate of the unexpected positive intraoperative cultures after revision total knee arthroplasty

Of a consecutive series of 692 revision total knees at 3 centers, intraoperative cultures were unexpectedly found to be positive in 41 cases (5.9%). Of the 41, 29 (71%) cases had a single positive intraoperative culture and were determined to be a probable false positive based on absence of any other evidence of infection, of which 5 were treated with extended course of intravenous antibiotics after hospital discharge and the remaining 24 received no further treatment. None of these 24 patients manifested any sign of infection at follow-up, averaging 46 months (range, 24-74 months). Twelve patients were determined to have probable type 1 periprosthetic infection, 11 of which were treated with a course of antibiotics. Two of these patients became reinfected within a year. A single positive intraoperative culture after revision total knee arthroplasty does not mandate further treatment in the absence of any other signs of infection.