Instructional Course Lectures, The American Academy of Orthopaedic Surgeons - Evaluation and Treatment of Infection at the Site of a Total Hip or Knee Arthroplasty*†

Two-stage revision of infected hip prosthesis after post-operative antibiotic therapy: An observational study

Infection is a major threatening side effect after total hip arthroplasty (THA) that its management is so difficult and is accompanied by different complications. The aim of this study was to determine the outcomes of patients underwent 2-staged THA after a course of antibiotic therapy. It was an observational prospective study performed during 2009 and 2019. We managed 51 patients with infected THA using a method in which antibiotic prophylaxis was performed after THA. We followed the same protocol for treatment of patients included 2-staged revision: in first stage, removal of infected instruments were performed and insertion of a hand-made antibiotic-cement spacer was done until erythrocyte sedimentation rate and CRP were normalized. In second stage, an un-cemented prosthesis was re-implanted in femoral side and post-operative IV antibiotic were administered for a week. Patients were monitored for about 15 months. Data were analyzed. There were 3 patients developed recurrent infection required girdlestone due to the aging. One of them needed to remove implant and 2 other with 3 times of re-infection were treated by antibiotic therapy. Other 10 cases were treated first by re-changing the cement. The rate of successful treatment was 78.4% (40 of 51) after the primary surgery and antibiotic therapy. This rose to 92.1% (47 of 51) following more debridement and antibiotic therapy. The merging of staged surgical debridement, using spacer of cement-antibiotic and re-implant beside 1-week intravenous antibiotic therapy, leaded to appropriate early outcomes in this series.

Nanomechanical tribological characterisation of nanostructured titanium alloy surfaces using AFM: A friction vs velocity study

Medical-grade titanium alloys used for orthopaedic implants are at risk from infections and complications such as wear and tear. We have recently shown that hydrothermally etched (HTE) nanostructures (NS) formed on the Ti6AlV4 alloy surfaces impart enhanced anti-bacterial activity which results in inhibited formation of bacterial biofilm. Although these titanium alloy nanostructures may resist bacterial colonisation, their frictional properties are yet to be understood. Orthopaedic devices are encapsulated by bone and muscle tissue. Contact friction between orthopaedic implant surfaces and these host tissues may trigger inflammation, osteolysis and wear. To address these challenges, we performed simulation of the contact behaviour between a smooth control Ti6Al4V alloy and HTE surfaces against a hardwearing SiO₂ sphere using Atomic Force Microscopy (AFM) in Lateral Force Microscopy mode. The friction study was evaluated in both air and liquid environments at high (5 Hz) and low (0.5 Hz) scan velocities. Lower scan velocities demonstrated opposing friction force changes between the two mediums, with friction stabilising at higher velocities. The friction measured on the NS alloy surfaces was reduced by ~20% in air and ~80% in phosphate buffered saline, in comparison to the smooth control surface, displaying a non-linear behaviour of the force applied by the AFM tip. Changes in friction values and cantilever scan velocities on different substrates are discussed with respect to the Stribeck curve. Reduced friction on nanostructured surfaces may improve wear resistance and aid osseointegration.

Debridement, antibiotics and implant retention for periprosthetic joint infections: A systematic review and meta-analysis of treatment outcomes

OBJECTIVES

We aimed to assess infection control rates after DAIR in patients with periprosthetic joint infection (PJI) following joint arthroplasty and evaluate factors associated with infection control using a systematic review and meta-analysis.

METHODS

We searched MEDLINE, EMBASE, Web of Science, Cochrane databases and reference lists of relevant studies up to May 2017. Longitudinal studies conducted in patients with PJI treated exclusively by DAIR were eligible. Infection control rates were meta-analysed using random-effect models after arcsine transformation.

RESULTS

We included 93 articles based on 99 unique observational studies with data on 4897 PJIs treated by DAIR. The infection control rate for DAIR ranged from 11.1% to 100% with an overall pooled estimate of 61.4% (95% CI, 57.3-65.4) and a 95% prediction interval of 25.5% to 91.8%. Infection control rates remained generally similar for several relevant characteristics, except for evidence of variation by age, geographical location, type of infection and joint affected, duration of parenteral antibiotic therapy after the DAIR procedure, and period (year) of DAIR procedure.

CONCLUSIONS

The DAIR approach remains an option for the treatment of PJI as it is associated with acceptable infection control rates, particularly in acute postoperative infections and infections of the hip and shoulder joints.

In Vivo Assessment of Phage and Linezolid Based Implant Coatings for Treatment of Methicillin Resistant S. aureus (MRSA) Mediated Orthopaedic Device Related Infections

Staphylococcus comprises up to two-thirds of all pathogens in orthopaedic implant infections with two species respectively Staphylococcus aureus and Staphylococcus epidermidis, being the predominate etiological agents isolated. Further, with the emergence of methicillin-resistant S. aureus (MRSA), treatment of S. aureus implant infections has become more difficult, thus representing a devastating complication. Use of local delivery system consisting of S.aureus specific phage along with linezolid (incorporated in biopolymer) allowing gradual release of the two agents at the implant site represents a new, still unexplored treatment option (against orthopaedic implant infections) that has been studied in an animal model of prosthetic joint infection. Naked wire, hydroxypropyl methylcellulose (HPMC) coated wire and phage and /or linezolid coated K-wire were surgically implanted into the intra-medullary canal of mouse femur bone of respective groups followed by inoculation of S.aureus ATCC 43300(MRSA). Mice implanted with K-wire coated with both the agents i.e phage as well as linezolid (dual coated wires) showed maximum reduction in bacterial adherence, associated inflammation of the joint as well as faster resumption of locomotion and motor function of the limb. Also, all the coating treatments showed no emergence of resistant mutants. Use of dual coated implants incorporating lytic phage (capable of self-multiplication) as well as linezolid presents an attractive and aggressive early approach in preventing as well as treating implant associated infections caused by methicillin resistant S. aureus strains as assessed in a murine model of experimental joint infection.

Re-Infection Outcomes Following One- And Two-Stage Surgical Revision of Infected Knee Prosthesis: A Systematic Review and Meta-Analysis

BACKGROUND

Periprosthetic joint infection (PJI) is a serious complication of total knee arthroplasty. Two-stage revision is the most widely used technique and considered as the most effective for treating periprosthetic knee infection. The one-stage revision strategy is an emerging alternative option, however, its performance in comparison to the two-stage strategy is unclear. We therefore sought to ask if there was a difference in re-infection rates and other clinical outcomes when comparing the one-stage to the two-stage revision strategy.

OBJECTIVE

Our first objective was to compare re-infection (new and recurrent infections) rates for one- and two-stage revision surgery for periprosthetic knee infection. Our second objective was to compare between the two revision strategies, clinical outcomes as measured by postoperative Knee Society Knee score, Knee Society Function score, Hospital for Special Surgery knee score, WOMAC score, and range of motion.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

MEDLINE, EMBASE, Web of Science, Cochrane Library, reference lists of relevant studies to August 2015, and correspondence with investigators.

STUDY SELECTION

Longitudinal (prospective or retrospective cohort) studies conducted in generally unselected patients with periprosthetic knee infection treated exclusively by one- or two-stage revision and with re-infection outcomes reported within two years of revision surgery. No clinical trials comparing both revision strategies were identified.

REVIEW METHODS

Two independent investigators extracted data and discrepancies were resolved by consensus with a third investigator. Re-infection rates from 10 one-stage studies (423 participants) and 108 two-stage studies (5,129 participants) were meta-analysed using random-effect models after arcsine transformation.

RESULTS

The rate (95% confidence intervals) of re-infection was 7.6% (3.4-13.1) in one-stage studies. The corresponding re-infection rate for two-stage revision was 8.8% (7.2-10.6). In subgroup analyses, re-infection rates remained generally similar for several study-level and clinically relevant characteristics. Postoperative clinical outcomes of knee scores and range of motion were similar for both revision strategies.

LIMITATIONS

Potential bias owing to the limited number of one-stage revision studies and inability to explore heterogeneity in greater detail.

CONCLUSIONS

Available evidence from aggregate published data suggest the one-stage revision strategy may be as effective as the two-stage revision strategy in treating infected knee prostheses in generally unselected patients. Further investigation is warranted.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO 2015: CRD42015017327.

Long Term Treatment Results for Deep Infections of Total Knee Arthroplasty

This study aims to identify the long-term outcomes of total knee arthroplasty (TKA) treated for deep infection. 3270 consecutive primary and 175 revision TKAs were followed prospectively. There were 39 deep infections (1.16%): 29 primary (0.9%) and 10 revision (5.7%) cases. Two-stage resection and re-implantation procedure was performed in 13 primary cases with 10/13 (77%) successfully resolved. Early (<1 month) Irrigation and Debridement (I&D) was performed in 16 primary cases with 100% success. Late (>4 months) I&D was performed in 6 cases with 5/6 (83.3%) successful. Infection following revision TKA resulted in poor outcomes with both two-stage (2/4 successful) and I&D (2/6 successful). Deep infection after primary TKA can be successfully resolved with I&D and appropriate antibiotic treatment in the early postoperative course.

Systematic review and meta-analysis of randomized controlled trials of antibiotics and antiseptics for preventing infection in people receiving primary total hip and knee prostheses

Infection rates in primary (first-time) major joint arthroplasty continue to be a significant issue. The effect of antibiotic and antiseptic prophylaxis on outcomes for this type of surgery has not been adequately reviewed. A systematic search of the main databases for randomized controlled trials (RCTs) evaluating antibiotics and antiseptics was conducted to evaluate the predetermined endpoints of infection, adverse events, costs, quality of life, and concentration levels of antibiotics. A meta-analysis using pooled effect estimates and fixed-effect and random-effect models of risk ratios (RR), calculated with 95% confidence intervals (CI), was utilized. Thirty (30) RCTs examined the effects of antibiotic and antiseptic prophylaxis on infections after primary total hip arthroplasty (THA) (total of 11,597 participants) and total knee arthroplasty (TKA) (total of 6,141 participants). For THA, preoperative systemic intravenous (i.v.) antibiotic prophylaxis may be effective in reducing the incidence of infection after THA from 6 months to ≥5 years. For TKA, there is no RCT evidence that antibiotics and/or antiseptics have any effect on infection rate. Preoperative systemic antibiotic prophylaxis in primary THA may be effective at reducing infection rate. There is no evidence that timing, route of administration, or concentration levels have an effect on reducing infections, adverse events, or costs in THA or TKA. Many of the trials included in this study were published in the 1980s and 1990s. Thus, it would be important to replicate a number of them based on current patient demographics and incidence of bacterial resistance.

Prevention of Periprosthetic Joint Infection

Periprosthetic joint infection (PJI) has moved into the first place as the cause of failure following total knee arthroplasty (TKA). Recent studies have shown that PJI results in higher mortality in patients than many cancers. The economic burden of treating PJI is likely to exceed $1 billion this year in the US. Thus, it is paramount that all efforts are invested to prevent this dreaded complication after total joint arthroplasty (TJA). This article summarizes some of the most effective and proven strategies for prevention of PJI. It is hoped that the article will be of benefit to the readers of the journal.

Two-Stage Revision Arthroplasty for Periprosthetic Hip Infection: Mean Follow-Up of Ten Years

Background. Two-stage revision hip arthroplasty is the gold standard for treatment of patients with chronic periprosthetic joint infection (PJI), but few studies have reported outcomes beyond short-term follow-up. Methods. A total of 155 patients who underwent two-stage revision arthroplasty for chronic PJI in 157 hips were retrospectively enrolled in this study between January 2001 and December 2010. The mean patient age was 57.5 years, the mean prosthetic age was 3.6 years, and the interim interval was 17.8 weeks. These patients were followed up for an average of 9.7 years. Results. At the latest follow-up, 91.7% of the patients were free of infection. The mean Harris hip score improved significantly from 28.3 points before operation to 85.7 points at the latest follow-up. Radiographically, there was aseptic loosening of the stem or acetabular components in 4 patients. In the multivariate survival analysis using a Cox regression model, repeated debridement before final reconstruction, an inadequate interim period, bacteriuria or pyuria, and cirrhosis were found to be the independent risk factors for treatment failure. Conclusion. Our data show that two-stage revision hip arthroplasty provides reliable eradication of infection and durable reconstruction of the joint in patients with PJI caused by a variety of pathogens.

Antimicrobial megaprostheses supported with iodine

Deep infection associated with implants remains a serious complication of orthopedic surgery. We developed iodine coating for titanium implants. In this study, we performed a clinical trial of iodine-coated megaprostheses to evaluate its safety and antibacterial effects. Forty-seven patients with malignant bone tumor or pyogenic arthritis were treated using iodine-supported titanium megaprostheses between July 2008 and May 2013. The mean age was 53.6 years (range, 15-85 years). Twenty-six patients were males and 21 were females. The diagnoses included malignant bone tumor in 29 cases, infected total knee arthroplasty in 11 cases, chronic osteomyelitis due to pyogenic arthritis in six cases and loosening of total knee arthroplasty in one case. The iodine-supported implants used were 42 Kyocera Limb Salvage System and five KOBELCO K-MAX K-3. These megaprostheses were used to prevent infection in 21 patients, treat active infections in 26 patients. The mean follow-up period was 30.1 months (range, 8-50). Infection was prevented in 20 out of 21 patients. Only one patient had surgical site infection caused by Pseudomonas aeruginosa and was cured by intravenous administration of antibiotics alone without removal of the implant. In 26 treatment cases involving one- or two-stage revision surgery, infection subsided without any additional surgery. In all cases, there were no signs of infection at the time of the last follow-up. White blood cell and C-reactive protein levels returned to normal within four weeks after surgery. To confirm systemic effects of iodine, thyroid hormone levels in the blood were examined. Abnormalities of thyroid gland function were not detected. Loosening of the implants was not observed. Excellent bone ingrowth and ongrowth were found around iodine-supported megaprostheses. The iodine-supported titanium megaprostheses are highly effective and show promise for the prevention and treatment of infections in large bone defects. No cytotoxicity or adverse effects were detected with this treatment.

Acute hematogenous infection following total hip and knee arthroplasty

Forty consecutive patients (42 joints; 22 TKA, 20 THA) treated for acute hematogenous infections were reviewed. All patients underwent irrigation and debridement and exchange of the modular components. At a mean of 56 months (range, 25-124 months) recurrent infection, requiring surgery, developed in 9 of the 42 joints (21%); 8 of the 9 recurrent infections were in patients with a staphylococcal infection (P = 0.0004). Ten of the 40 patients (25%) died within 2 years of infection. Irrigation and debridement for the treatment of an acute hematogenous infection was successful in the majority of patients (76% survivorship at 2 years). Non-staphylococcal infections had a particularly low failure rate (96% survivorship at 2 years). The 2 year mortality rate among this subset of patients was strikingly high.

Candida glabrata infection following total hip arthroplasty: A case report

Candida glabrata infection following total hip arthroplasty is rare and, due to the insufficiency of standardized clinical and evidence-based guidelines, there is no appropriate therapeutic schedule. The present study reports the case of a 44-year-old patient with Candida glabrata infection following a total hip arthroplasty. The patient was successfully treated by administration of intravenous and oral voriconazole without removal of the prosthesis. This case illustrates the significance of postoperative follow-up, clinician experience and the choice of the correct antifungal agent. In this case, we found in the early stage of Candida glabrata infection, we were able to control the infection without surgery through thorough irrigation. This reduces patient suffering and economic burden.

Release of gentamicin and vancomycin from preformed spacers in infected total hip arthroplasties: measurement of concentrations and inhibitory activity in patients' drainage fluids and serum

Gentamicin (G) and vancomycin (V) concentrations in drainage fluids obtained from patients during the first 24 hours after implantation of antibiotic-loaded polymethylmethacrylate (PMMA) spacers in two-stage revision of infected total hip arthroplasty were studied. The inhibitory activity of drainage fluids against different multiresistant clinical isolates was investigated as well. Seven hips were treated by implantation of industrial G-loaded spacers. Vancomycin was added by manually mixing with PMMA bone cement. Serum and drainage fluid samples were collected 1, 4, and 24 hours after spacer implantation. Antibiotics concentrations and drains bactericidal titer of combination were determined against multiresistant staphylococcal strains. The release of G and V from PMMA cement at the site of infection was prompt and effective. Serum levels were below the limit of detection. The local release kinetics of G and V from PMMA cement was similar, exerting a pronounced, combined inhibitory effect in the implant site. The inhibitory activity of drainage fluids showed substantial intersubject variability related to antibiotic concentrations and differed according to the pathogens tested. Gentamicin and vancomycin were released from temporary hip spacers at bactericidal concentrations, and their use in combination exerted strong inhibition against methicillin-resistant S. aureus and Coagulase Negative Staphylococci strains.

Reduced re-infection rates with postoperative oral antibiotics after two-stage revision hip arthroplasty

BACKGROUND

Surgeons are often trying to decreased reinfection rates following two-stage reimplantation arthroplasty, which range from 3.2% to 13% because multiple staged revision procedures for infection can be costly and have high morbidity. We therefore asked: (1) Did the use of postoperative oral antibiotics reduce reinfection rates after 2-staged revision of THA? And (2) how did this compare with the infection rate after aseptic revision procedures?

METHODS

We identified all patients who underwent two-stage revision THA for a periprosthetic deep hip infection and found 66 patients (67 hips) who had a minimum 24 months' followup. Twenty-two of the 66 procedures (33%) were followed by a minimum of 14 days of postoperative oral antibiotics (mean, 36 days; range, 14 days to lifelong), while 44 were prescribed only immediate parenteral postoperative antibiotic therapy (mean, 1.3 days; range, 1-3 days). We then identified 407 patients (410 hips) who underwent aseptic revision hip arthroplasty and evaluated the infection rate in these patients for comparison; these patients were treated with 24 hours of postoperative parenteral antibiotics. The authors used previously described creteria to establish the presence of infection.

RESULTS

There were no reinfections in the group receiving oral postoperative antibiotics compared to six reinfections (13.6%) in the 44 patients not receiving oral antibiotics. We observed infection in 2 of the 410 hips (0.5%) revised for aseptic reasons.

CONCLUSIONS

We believe that our findings warrant further investigation for using postoperative oral antibiotics after reimplantation for periprosthetic infection in an effort to decrease the likelihood and risks associated with additional revision arthroplasty procedures.

Two-stage reimplantation for periprosthetic knee infection: Influence of host health status and infecting microorganism

BACKGROUND

Two-stage revision is the gold standard treatment of TKA infection; nevertheless various factors may influence the success rate. The aim of our study was to assess the impact of the number of patient comorbidities together with virulence of infectious organism on prognosis of two-stage revision procedure in chronic peri-prosthetic knee infection; moreover we tried to demonstrate correlation between the presence of positive culture during re-implantation and re-infection rate.

METHODS

Thirty-eight cases of two-staged revision procedures for infected total knee arthroplasty were prospectively followed. The presence of high virulence microorganisms on the culture result and the number (more than three) of comorbidities were used as major risk factors. All cases were divided into three groups: Group 1 (10 patients without major risk factors), Group 2 (18 patients with only one major risk factor), Group 3 (10 patients with both of major risk factors).

RESULTS

After a mean follow-up of 65months (range 24-139months), there was infection recurrence in nine cases: four re-infections occurred with the same organism while five patients had re-infection with a different organism. Recurrence was higher in Group 3 (33% of the cases), lower in Group 2 (12% of the cases), whereas no infection occurred in Group 1. Finally in case of positive intraoperative cultures recurrence rate was 83%, whereas when specimens were negative we had only 12.5% of re-infections.

CONCLUSIONS

Even if standard protocol of two-stage revision has demonstrated good results when treating low-virulence infections or patients without associated risk factors, its application to more challenging condition cannot be assumed.

LEVEL OF EVIDENCE

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

Sepsis syndrome, bloodstream infections, and device-related infections

The diagnosis of sepsis is challenging given the lack of appropriate diagnostic methods and the inaccuracy of diagnostic criteria. Early resuscitation, intravenous antibiotics, and source control are crucial in the management of septic patients. The treatment of catheter-related bloodstream infection (CRBSI) often comprises 1 to 2 weeks of intravenous antibiotics plus catheter removal. Infections related to surgical devices are more difficult to manage because they require longer duration of therapy and possibly multiple surgical procedures. This review represents an update on the diagnosis and management of sepsis, catheter-related blood stream infections and some clinically important device-related infections.

How do frozen and permanent histopathologic diagnoses compare for staged revision after periprosthetic hip infections?

Histopathologic analysis of frozen tissue samples is used to aid the intraoperative diagnosis of periprosthetic hip infections, but there are concerns about reliability. The purposes of this study were to determine the rate of concordance between diagnoses of infection made with frozen and permanent sections and to assess how discrepancies affected patient outcomes. A total of 282 samples from 62 patients were collected for frozen and permanent section analysis. There was concordance in 274 samples (97%). In 1 case, discrepancies led to retention of components during persistent infection, and the patient required further revision and antibiotics until infection free. Otherwise, discrepancies did not affect patient outcomes. There is good concordance between frozen and permanent sections for diagnosing periprosthetic hip infection and rarely do these discrepancies affect management.

Prosthetic joint infections

Prosthetic joint infections represent a major therapeutic challenge for both healthcare providers and patients. This article reviews the predisposing factors, pathogenesis, microbiology, diagnosis, treatment, and prophylaxis of prosthetic joint infection. The most optimal management strategy should be identified on the basis of a number of considerations, including type and duration of infection, antimicrobial susceptibility of the infecting pathogen, condition of infected tissues and bone stock, patient wishes, and functional status.

Discrepancies between frozen and paraffin tissue sections have little effect on outcome of staged total knee arthroplasty revision for infection

BACKGROUND

Intraoperative analysis of frozen tissue samples has been used to diagnose periprosthetic joint infection in revision total knee arthroplasty, but the precision and reliability of this test throughout staged revision arthroplasty have not been well characterized. We undertook this study to determine the rate of discrepancy between frozen and permanent histopathologic samples in the diagnosis of periprosthetic infection at both the index total knee arthroplasty revision procedure and the attempted reimplantation.

METHODS

Seventy-six patients who underwent staged revision of a total knee arthroplasty for apparent infection had samples for frozen and permanent sections obtained at both the index revision procedure and subsequent reimplantation attempts. We investigated the rate of discrepancy between these frozen and permanent sections. The clinical and radiographic outcomes of patients with and without concordance between the frozen and permanent sections were reviewed.

RESULTS

Concordance was noted between 297 (97.7%) of the 304 frozen sections and the permanent sections. Seven discrepancies between diagnoses based on frozen and permanent sections were noted; however, additional samples in these patients were positive and management was not affected. Fewer discrepancies were found during the initial revision procedure (one of 92, 1%) compared with reimplantation (six of 212, 3%). The mean time to reimplantation was similar between patients with and without a discrepancy in diagnosis between the frozen and permanent sections (185 compared with 157 days). The rate of discrepancy between frozen and permanent histopathologic sections was low, and no discrepancy affected the final outcome of any patient.

CONCLUSIONS

The rate of discrepancy between frozen and permanent histopathologic samples was low for both index revision and reimplantation procedures. In rare instances of discrepancy, management should be unaffected provided a sufficient number of samples were collected.

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.

Infected tumor prostheses

Infection of tumor prostheses has been a major concern because of the extensive soft tissue dissection, long operating times, and patients' immunosuppression by cancer and adjuvant treatments. Infections most often present within 2 years postoperatively, with approximately 70% of postoperative deep infections presenting within 12 months after surgery. They are typically low organism burden infections, the pathogenesis of which is related to bacteria growing in biofilms. Staphylococci are the most common pathogens involved in prosthetic joint infections, accounting for approximately 50% of infections overall, followed by streptococci, enterococci, Enterobacteriaceae species, Pseudomonas aeruginosa, and anaerobe species. Multiple pathogens may be isolated in approximately 25% of cases, with the most common combination being coagulase-negative Staphylococcus and group-D Streptococcus. Early diagnosis and appropriate treatment are necessary. However, diagnosis may be challenging because clinical symptoms are highly variable and numerous preoperative and intraoperative diagnostic laboratory tests are nonspecific. In most cases, a 1- or 2-stage revision surgery is necessary for eradicating the megaprosthetic infection. Prevention of infection is important. The future will see technical advances for infections of tumor prostheses in areas such as microbiological diagnostics and biofilm-resistant prostheses.

The use of quaternised chitosan-loaded PMMA to inhibit biofilm formation and downregulate the virulence-associated gene expression of antibiotic-resistant staphylococcus

Biomaterial-associated infections remain a serious complication in orthopaedic surgery. Treatments, including the local use of antibiotic-loaded polymethylmethacrylate (PMMA) bone cement, are not always successful because of multiantibiotic-resistant organisms. In this study, we synthesised a new quaternised chitosan derivative (hydroxypropyltrimethyl ammonium chloride chitosan, HACC) that contains a series of substitutions of quaternary ammonium and demonstrated that HACC with a 26% degree of substitution (DS; referred to as 26%HACC) had a strong antibacterial activity and simultaneously good biocompatibility with osteogenic cells. We loaded 26%HACC at 20% by weight into PMMA bone cement to investigate whether HACC in PMMA prevents bacterial biofilm formation on the surface of bone cements. Chitosan-loaded PMMA (at the same weight ratio), gentamicin-loaded PMMA and PMMA with no antibiotic were also investigated and compared. Two clinical isolates, Staphylococcus epidermidis 389 and methicillin-resistant S. epidermidis (MRSE287), and two standard strains, S. epidermidis (ATCC35984) and methicillin-resistant Staphylococcus aureus (ATCC43300), were selected to evaluate the bacterial biofilm formation at 6, 12 and 24 h using the spread plate method, confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The results showed that 26%HACC-loaded PMMA inhibited biofilm formation on its surface, while the PMMA control and chitosan-loaded PMMA were unable to inhibit biofilm formation. The gentamicin-loaded PMMA decreased the number of viable methicillin-resistant Staphylococcus strains, but its ability to inhibit biofilm formation was lower than 26%HACC-loaded PMMA. Real-time PCR demonstrated that 26%HACC-loaded PMMA markedly downregulated the expression of icaAD, which encodes essential enzymes for polysaccharide intercellular adhesion (PIA) biosynthesis, upregulated the expression level of icaR, which negatively mediates icaAD expression, and also downregulated the expression of MecA, which encodes membrane-bound enzymes known to be penicillin-binding proteins. Our study indicates that 26%HACC-loaded PMMA prevents biofilm formation of Staphylococcus, including antibiotic-resistant strains, on the surface of bone cement, and downregulates the virulence-associated gene expression of antibiotic-resistant staphylococcus, thus providing a promising new strategy for combating implant infections and osteomyelitis.

Hypertensive patients show delayed wound healing following total hip arthroplasty

BACKGROUND

Prolonged wound-discharge following total hip arthroplasty (THA) is associated with an increased risk of infection. However, the potential role of hypertension in prolonging the duration of wound healing in this population has not yet been investigated. The aim of the present study was to compare healing in this population that has not yet been investigated. The aim of the present study was to compare hypertensive and normotensive THA patients in terms of the length of time required to achieve a dry wound and the length of stay in the hospital.

METHODS

One hundred and twenty primary THA patients were evaluated. Pre-operative clinical history and physical examination revealed that 29 were hypertensive and 91 were normotensive. The two groups were statistically matched using optimal propensity score matching. The outcomes of interest were the number of days until a dry wound was observed and the duration of hospital stay.

RESULTS

The average systolic blood pressures were 150.1 mmHg and 120.3 mmHg for the hypertensive and normotensive groups, respectively. The mean number of days until the wound was dry was 3.79 for the hypertensive group and 2.03 for the normotensive group. Hypertensive patients required more days for their wounds to dry than normotensive patients (odds ratio  =  1.65, p<0.05). No significant difference in the duration of hospital stay was found between the two groups.

CONCLUSIONS

Hypertensive patients had a higher risk of prolonged wound discharge after THA than their normotensive counterparts. Patients with prolonged wound drainage are at greater risk for infection. Clinicians should pay particular attention to infection-prevention strategies in hypertensive THA patients.

Failure mode classification for tumor endoprostheses: retrospective review of five institutions and a literature review

BACKGROUND

Massive endoprostheses provide orthopaedic oncologists with many reconstructive options after tumor resection, although failure rates are high. Because the number of these procedures is limited, failure of these devices has not been studied or classified adequately. This investigation is a multicenter review of the use of segmental endoprostheses with a focus on the modes, frequency, and timing of failure.

METHODS

Retrospective reviews of the operative databases of five institutions identified 2174 skeletally mature patients who received a large endoprosthesis for tumor resection. Patients who had failure of the endoprosthesis were identified, and the etiology and timing of failure were noted. Similar failures were tabulated and classified on the basis of the risk of amputation and urgency of treatment. Statistical analysis was performed to identify dependent relationships among mode of failure, anatomic location, and failure timing. A literature review was performed, and similar analyses were done for these data.

RESULTS

Five hundred and thirty-four failures were identified. Five modes of failure were identified and classified: soft-tissue failures (Type 1), aseptic loosening (Type 2), structural failures (Type 3), infection (Type 4), and tumor progression (Type 5). The most common mode of failure in this series was infection; in the literature, it was aseptic loosening. Statistical dependence was found between anatomic location and mode of failure and between mode of failure and time to failure. Significant differences were found in the incidence of failure mode Types 1, 2, 3, and 4 when polyaxial and uniaxial joints were compared. Significant dependence was also found between failure mode and anatomic location in the literature data.

CONCLUSIONS

There are five primary modes of endoprosthetic failure, and their relative incidences are significantly different and dependent on anatomic location. Mode of failure and time to failure also show a significant dependence. Because of these relationships, cumulative reporting of segmental failures should be avoided because anatomy-specific trends will be missed. Endoprosthetic design improvements should address failure modes specific to the anatomic location.

Preformed gentamicin spacers in two-stage revision hip arthroplasty: functional results and complications

Two-stage revisions with antibiotic-loaded spacers have gained popularity for treating infected hip-joint arthroplasties. The aim of this prospective study was to assess patient functionality between stages and treatment impact on duration of hospital stay and to describe related complications. Sixty-one consecutive patients with infected hip arthroplasties underwent two-stage revision with preformed spacer implantation. Mean Harris Hip and Merle d'Aubigné scores between the two stages were 39.9 and 7.6, respectively. Forty-six patients (75.4%) were able to leave hospital between stages. Spacer dislocation occurred in 16.4%. No cases of spacer breakage were noted. Preformed cement spacers provide acceptable functional outcome between revision hip arthroplasty stages and facilitate the surgical procedure without increasing mechanical complication rates.

Cementless two-staged total hip arthroplasty with a short term interval period for chronic deep periprosthetic infection. Technique and long-term results

BACKGROUND

The two-staged exchange with delayed reimplantation is the most reliable method to treat a deep periprosthetic infection after a total hip arthroplasty (THR). Nether uniform recommendations for the technique of cementless reimplantation, nor long term clinical and radiological results are reported.

MATERIALS AND METHODS

Our protocol is performed under short term antibiosis with cementless primary porous hip implants to treat chronic deep periprosthetic infections following THR. A retrospective study was performed to evaluate the clinical and radiological long term outcome and the rate of persistent infection of 14 patients.

RESULTS

In a five year minimum follow up persistent infection was observed twice in a two-staged revision THR. A dislocation of the hip components was observed in three cases, and could be surgically treated in twice and by wearing a hip-brace in one case. We could not find a loosening of THR components. Three patients had a good or excellent, 11 patients a fair or bad functional outcome. There was a significant correlation between functional outcome and length of interval of prosthesis exand reimplantation.

CONCLUSION

Patients have an increased comfort resulting from a short, CRP depending time interval between ex- and reimplantation. Functional outcome is the better the shorter the interval is. The reinfection rate is comparable to those of cemented revision THR's with a long term interval. We could observe advantages in a reduced amount of bone loss and better osseous integration of the uncemented implants, compared to cemented implants reviewing literature. Alterations of acetabular bone stock and soft tissue are responsible for a high rate of instability of the THR. An inaccurate gait pattern is caused by gluteal weakness in the majority of patients. Repeated surgical intervention and duration of immobilization have to be minimalized.

Modern treatment of infected total knee arthroplasty with a 2-stage reimplantation protocol

The purpose of this study was to determine if 2-stage reimplantation for the treatment of infected total knee arthroplasty (TKA) is still effective for treating contemporary pathogens, many of which are multidrug resistant (MDR). The medical records of all cases of infected TKAs from April 1998 to March 2006 were retrospectively reviewed for data on infecting organism and success of treatment. Of 72 patients (75 knees), with a minimum of 2 years of follow-up, who completed the protocol, the infection was eradicated in 90.7% (68/75 knees). Thirty-one (91.2%) of 34 of MDR infections and 42 (91.3%) of 46 of non-MDR infections were successfully treated. These results support previous studies that demonstrated the effectiveness of a 2-stage reimplantation protocol with a standard 1:8 minimal bactericidal titer for treating infections after TKA, including MDR organisms.

Infection following Bone Tumor Resection and Reconstruction with Tumoral Prostheses: A Literature Review

Bone resection is the choice treatment of malignant bone tumors. Tumor prosthesis is one of the most common solutions of reconstruction following resection of bone tumor located to the metaphysis of long bones. Periprosthetic infections are a frequent complication of limb-salvage surgery which is largely due to prolonged and repeated surgeries, as well as to the immunocompromised condition of these patients due to neoplastic treatment. Furthermore, the large exposure of tissues during this type of surgery and the dissection across vascular distributions also contributes to the high risk of infection. The authors reviewed the literature discussing the incidence of infections of tumor prosthesis implanted following resection of bone tumors, taking into account the different sites of implantation. In the English literature, the highest risk of infection which led to limb amputation was observed after proximal tibia resection and this difference was considered to be due to the poor condition of soft tissue and also after pelvic resection due to huge dead space after sarcoma resection not filled by implant. Independent of the location, the management of infected prosthesis is similar. That is, after one or more attempts at debridement and antibiotic therapy, it consists of implant removal and insertion of a new implant in a one- or two-stage procedure, with a decreased risk of failure with the two-stage procedure.

Two stage hip revision in periprosthetic infection: results of 41 cases

BACKGROUND

two-stage revision is considered the best treatment approach for the eradication of chronic joint infection. We report the outcome of 41 consecutive patients with infected hip prostheses, treated between 2000 and 2005, with two-stage revision using an antibiotic-loaded cement spacer.

METHODS

Patients underwent a treatment protocol which included clinical and radiographic evaluation, laboratory investigations, hip aspiration, 99mTc-MDP and 99mTc-leukocyte-labeled scintigraphy and intraoperative assessment. All patients were diagnosed with a late chronic infection and classified as B-host according to the Cierny-Mader classification system. 9 patients out of 41 (22%) required a second interim treatment period, with exchange of the spacer. The proportion of methicillin-resistant Staphylococcus was similar between the one-spacer group and two-spacer group (28% vs 33%), whereas the proportion of patients with three or more risk factors was significantly higher in the two-spacer group than in the one-spacer group (28% vs 55%, respectively).

RESULTS

Forty patients had final reimplantation, one patient had a resection arthroplasty. At an average follow-up of 5.3 years no recurrence of infection occurred. The average post-operative Harris hip score improved from 41 to 80.

CONCLUSIONS

In the treatment of two-stage revision arthroplasty the adherence to the protocol proved to be effective for infection eradication and final reimplantation.

Pre- and postoperative assessment in joint preserving and replacing surgery

Advances in imaging technology have increased its suitability for diagnosing musculoskeletal disease. Modification of imaging techniques and improved image quality have led to increased use of computed tomography and magnetic resonance imaging in the assessment of postoperative complications. This article discusses the indications, pre- and postoperative imaging findings, and postoperative complications of knee and hip arthroplasty, articular cartilage repair, and high tibial osteotomy.

Treatment of infected total hip arthroplasty with a 2-stage reimplantation protocol: update on "our institution's" experience from 1989 to 2003

Infection is a devastating complication of total hip arthroplasty (THA). This study aimed to determine whether 2-stage reimplantation is still effective for treating contemporary pathogens, including multidrug-resistant organisms. Records of all cases of infected THAs from 1989 to 2003 were reviewed for data on organism, presence of drug resistance, use of an antibiotic-impregnated spacer, type of reimplant, and success of treatment. Of the 87 protocol patients with 2 years of follow-up, 94.3% (82) underwent reimplantation. The original infection was eradicated in 80 of the 84 hips (78/82 patients), a success rate of 95%. All 21 multidrug-resistant infections were eradicated. There were no major differences in eradication rates when the period was split into 3 sections. These results support previous studies from our institution which demonstrated the effectiveness of a 2-stage reimplantation protocol with a standard 1:8 minimal bactericidal titer for treating infections after THA, including those due to methicillin-resistant organisms.

[Nuclear medical imaging in case of painful knee arthroplasty]

RATIONALE

The aim of the present study was to calculate the overall diagnostic accuracy of nuclear medical imaging in patients with painful knee arthroplasty.

MATERIAL AND METHODS

This retrospective study of all patients (n=87) where a (99m)Tc-triple phase bone scintigraphy (TPBS; n=120) and (99m)Tc-anti-granulocyte scintigraphy (BW 250/183; n=20) for a painful knee arthroplasty was performed between 2003 and 2007.

RESULTS

A total of 87 patients with 94 knee arthroplasties were examined to detect septic and aseptic loosening and to differentiate between them. The sensitivity, specificity, the positive and negative predictive value and accuracy of TPBS for the detection of septic knee arthroplasty loosening was 100%, 85%, 55%, 100%, 73% and for BW 250/183 was 91%, 66%, 76%, 85%, 80% for sepsis, respectively. A significant increase in diagnostic accuracy with 94%, 88%, 89%, 95% und 89% (p <0.001) could be achieved when both methods were used in combination.

CONCLUSION

Both methods alone have high negative predictive values, but the combination of both is complementary and significantly increases the diagnostic accuracy and positive predictive value for final diagnosis of knee arthroplasty loosening.

Nuclear medicine and the infected joint replacement

Nearly 700,000 hip and knee arthroplasties are performed annually in the United States. Although the results in most cases are excellent, implants do fail. Complications like heterotopic ossification, fracture, and dislocation are now relatively rare and easily diagnosed. Differentiating aseptic loosening, the most common cause of prosthetic joint failure, from infection, is important because their treatments are very different. Unfortunately, differentiating between these 2 entities can be challenging. Clinical signs of infection often are absent. Increased peripheral blood leukocytes, erythrocyte sedimentation rate, and C-reactive protein levels are neither sensitive nor specific for infection. Joint aspiration with Gram stain and culture is the definitive diagnostic test. Its specificity is in excess of 90%; its sensitivity is variable, however, ranging from 28% to 92%. Plain radiographs are neither sensitive nor specific and cross-sectional imaging modalities, such as computed tomography and magnetic resonance imaging, can be limited by hardware-induced artifacts. Radionuclide imaging is not affected by orthopedic hardware and is the current imaging modality of choice for suspected joint replacement infection. Bone scintigraphy is sensitive for identifying the failed joint replacement, but cannot be used to determine the cause of failure. Neither periprosthetic uptake patterns nor performing the test as a 3-phase study significantly improve accuracy, which is only about 50-70%. Thus, bone scintigraphy typically is used as a screening test or in conjunction with other radionuclide studies. Combined bone gallium imaging, with an accuracy of 65-80%, offers only modest improvement over bone scintigraphy alone. Presently, combined leukocyte/marrow imaging, with approximately 90% accuracy, is the radionuclide imaging procedure of choice for diagnosing prosthetic joint infection. In vivo leukocyte labeling techniques have shown promise for diagnosing musculoskeletal infection; their role in prosthetic joint infection has not been established. (111)In-labeled polyclonal immunoglobulin lacks specificity. (99m)Tc-ciprofloaxicin does not consistently differentiate infection from aseptic inflammation. (18)F-fluorodeoxyglucose positron emission tomography has been extensively investigated; its value in the diagnosis of prosthetic joint infection is debatable.

Effect of age on cytokine response in an experimental model of osteomyelitis

To study the effect of age on cytokine response in an experimental model of osteomyelitis. Forty adult male Wistar rats received a stainless steel needle, intramedullarly in the left tibia. Young rats (3 months old) and old rats (22 months old) were allotted in: Group A: Sterile implant. Group B: Sterile implant + slime producing S. aureus. Rats were sacrificed 9 weeks after surgery. Determinations: Cytokines (ELISA) in blood and in tibia extract and the number of bacteria in tibia and implant. The Wilcoxon, Mann-Whitney U tests were used (P < or = 0.01 significant). Infection was detected in every old rat receiving S. aureus, and in 7 of 10 young rats. In blood: prior to surgery, old rats presented higher IL-2 and lower IL-4 levels. Surgery alone did not induce significant changes in old rats; surgery + S. aureus induced significant increases of IL-2 and IL-10 in young rats, and of IL-6 in old rats. Tibia analysis S. aureus group showed increased levels of: IL-10 in young rats, and IL-1beta in old rats. In experimentally induced osteomyelitis, significant differences were observed in cytokine response with regard to age.

Evaluation and management of the infected total hip and knee

Infection should be in the differentia for any painful total hip or knee. A thorough history and physical, complete set of radiographs and appropriate labs including C-reactive protein and erythrocyte sedimentation rate are essential in the initial evaluation. Ancillary tests such as aspiration and nuclear imaging may be helpful in unclear cases or when labs are concerning for infection. It is essential that all antibiotics are discontinued several weeks prior to gram stain and culture, if possible, to reduce the number of false negative test results. Classifying infection into acute versus late infection aids in the treatment plan. For acute infections presenting within 2 to 4 weeks of symptom onset, irrigation and debridement with polyethylene liner exchange and retention of components may be possible. When attempting component retention, thorough debridement and rapid treatment of the infection prior to the accumulation of any biofilm is paramount for a successful outcome. Other important prognostic factors to consider include the virulence of the microorganism as well as the immune status of the host. Despite expeditious management, irrigation and debridement of acute total hip and knee infections frequently leads to recurrent infection. Thus, patients should be counseled accordingly. Further management may be needed following an initial attempt at component retention. These options include resection arthroplasty with or without re-implantation, long term antibiotic suppressive therapy, arthrodesis and even above the knee amputation in rare circumstances. For chronic infections, a successful outcome depends on several factors including the baseline health status of the patient, implant removal with a thorough debridement followed by culture specific antibiotic treatment. Furthermore, methods of monitoring for persistent infection include following laboratory values such as the C-reactive protein, erythrocyte sedimentation rate, and cultures from joint aspirations. Whether to perform a direct exchange versus a delayed revision arthroplasty for chronic total hip and knee infections can be debated. Several published series have reported successful outcomes with single stage procedures when patients are carefully selected. However, the majority of chronic infections in the United States are treated with two stage resection, since this method has consistently provided the highest cure rates, with many current studies demonstrating >90% success.

[Two-stage procedure to exchange septic total hip arthroplasties with late periprosthetic infection. Early results after implantation of a reverse modular hybrid endoprosthesis]

BACKGROUND

Between January 2001 and January 2005 we performed the exchange of infected total hip arthroplasties in 40 cases.

MATERIAL AND METHODS

We applied a two-stage procedure when implant salvage was not possible. Our treatment algorithm included complete removal of the infected material, thorough débridement, and repeated revisions until cultures were negative. We then implanted a cemented acetabular polyethylene cup with specific antibiotic addition and a cementless modular stem (reverse modular hybrid endoprosthesis). Appropriate intravenous and oral antibiotic therapy was prescribed.

RESULTS

A total of 18 women and 22 men (age 48-86 years) were followed up for 4-48 months (mean: 12 months). Up to now 38 have remained infection free; in two cases the treatment failed and a resection arthroplasty had to be performed. There were eight complications intraoperatively (shaft fractures); four of them were treated conservatively and four needed additional stabilization. The mean hip score improved from 21 points initially to 81 points at the last examination. All details are listed in table form. Two-stage revision hip arthroplasty for infection using the inverse modular hybrid technique seems to be a safe and reliable method. Further investigation and a larger number of patients are necessary to confirm these preliminary results.

Nanosurfaces and nanostructures for artificial orthopedic implants

Nanomaterials and structures, such as nanoparticles, nanofibers, nanosurfaces, nanocoatings, nanoscaffolds and nanocomposites, are considered for various applications in orthopedics and traumatology. This review looks at proposed nanotechnology inspired applications for implants from the perspective of the orthopedic industry. Investigations support consistently the theory that most nanomaterials in various physical forms are able to enhance the cell response selectively for biological tissue integration or increase the strength and wear resistance of current orthopedic materials. At this stage, most of the studies are at the laboratory scale or in early in vivo testing. Significant basic and applied research and development is needed to realize their full clinical potential and biological, manufacturing, economic and regulatory issues have to be addressed. Nevertheless, a crucial factor for success is well-coordinated multimethod and multidiscipline teamwork with profound industrial and medical expertise.

Incidence and risk factors for surgical infection after total knee replacement

Surgical site infection (SSI) after total knee replacement (TKR) is a devastating complication. We performed a retrospective study of all consecutive TKRs performed during a 2-y period. Surgical site infection (SSI) was defined by standard criteria. All patients were examined 1 y following surgery. Of 180 patients undergoing TKR, 10 (5.6%) developed a superficial (3, 1.7%) or deep (7, 3.9%) SSI. Two independent risk factors for SSI were detected: left knees became infected more often (9/ 92, 9.8%) than right knees (1/88, 1.1%) (Relative Risk 6.7 +/- 95% CI 1.7-26.8); and 7/72 (9.7%) patients receiving a type-1 prosthesis developed infection versus 3/104 (3.1%) receiving a type-2 prosthesis (RR 4.7, 95% CI 1.18-18.4). Investigation of the operating room revealed 3 problems: there was significant traffic through the door on the left of the patient; a nonstandard horizontal-flow air conditioner had been installed above that door; a tool-washing sink was in use on the other side of that door. Infection control guidelines were rehearsed: the sink was removed, the air conditioner was disconnected, and the door was locked. In a prospective survey performed 2 y later only 1/45 patients (2.2%) undergoing TKR developed a superficial SSI (p = 0.5). Correction of independent risk factors for infection following TKR led to a decrease in SSI rate.

Risk factors associated with acute hip prosthetic joint infections and outcome of treatment with a rifampinbased regimen

BACKGROUND AND PURPOSE

Acute prosthetic infection is a serious problem. We report factors related to the incidence of acute infection and results of combined joint debridement and prolonged rifampicin-based antibiotic therapy.

PATIENTS AND METHODS

Between 1998 and 2004, 14 acute infections occurred after 819 primary hip arthroplasties. The association between patient-related and surgical factors and the risk of infection were analyzed. Infections were treated with multiple joint lavage, debridement, 2 weeks of antibiotic therapy, and then oral antibiotics for a minimum of 6 months.

RESULTS

There was a correlation between having a body mass index (BMI) of >or=30, and also more than 2 co-morbidities, and an increased risk of infection. Diabetes was a potential risk factor. Following our regime of treatment, 11 of 14 patients retained their prosthesis. 2 of 3 who required resection arthroplasty underwent successful staged revision, while the third patient had no further surgery because of being deemed unfit.

INTERPRETATION

Primary joint replacement was salvaged in 11 of 14 patients. When successful re-implantation was included, 13 of 14 patients had a mobile prosthetic joint without further infection.

[FDG-PET: a new diagnostic approach in hip prosthetic replacement]

Infection following hip arthroplasties can present a diagnostic challenge. No test is 100 % sensitive and 100 % specific; this prospective study was undertaken to evaluate the utility of FDG-PET imaging for diagnosing infected joint replacements. 24 hip joint replacements were studied prospectively and we have complete diagnoses with clinical signs and symptoms, laboratory test, radiography, joint aspiration, radionuclide imaging including FDG-PET, and histopathologic examination. 11 of 24 prostheses were infected. The sensitivity and specificity of PET for detecting infection associated with prostheses were 64,3 % and 64,7 % respectively, in our hands. FDG imaging is not useful in patients with suspected prosthetic infection like a screening test.