Aim

A growing number of recent investigations on the human genome, gut microbiome, and proteomics suggests that the loss of mucosal barrier function, particularly in the gastrointestinal tract, may substantially affect antigen trafficking, ultimately influencing the close bidirectional interaction between the gut microbiome and the immune system. This cross-talk is highly influential in shaping the host immune system function and ultimately shifting genetic predisposition to clinical outcome. Therefore, we hypothesized that a similar interaction could affect the occurrence of acute and chronic periprosthetic joint infections (PJI).

Aim

The efficacy of various irrigation solutions in removing microbial contamination of a surgical wound and reducing the rate of subsequent surgical site infection (SSI), has been demonstrated extensively. However, it is not known if irrigation solutions have any activity against established biofilm. This issue is pertinent as successful management of patients with periprosthetic joint infection (PJI) includes the ability to remove biofilm established on the surface of implants and necrotic tissues. The purpose of this study was to evaluate the efficacy of various irrigation solutions in eradicating established biofilm, as opposed to planktonic bacteria, in a validated in vitro model.

Aim

Surgical management of PJI remains challenging with patients failing treatment despite the best efforts. An important question is whether these later failures reflect reinfection or the persistence of infection. Proponents of reinfection believe hosts are vulnerable to developing infection and new organisms emerge. The alternative hypothesis is that later failure is a result of an organism that was present in the joint but was not picked up by initial culture or was not a pathogen initially but became so under antibiotic pressure. This multicenter study explores the above dilemma. Utilizing next-generation sequencing (NGS), we hypothesize that failures after two-stage exchange arthroplasty can be caused by an organism that was present at the time of initial surgery but not isolated by culture.

Aim

While metagenomic (microbial DNA) sequencing technologies can detect the presence of microbes in a clinical sample, it is unknown whether this signal represents dead or live organisms. Metatranscriptomics (sequencing of RNA) offers the potential to detect transcriptionally “active” organisms within a microbial community, and map expressed genes to functional pathways of interest (e.g. antibiotic resistance). We used this approach to evaluate the utility of metatrancriptomics to diagnose PJI and predict antibiotic resistance.

Aim

The clinical relevance of microbial DNA detected via next-generation sequencing (NGS) remains unknown. This multicenter study was conceived to: 1) identify species on NGS that may predict periprosthetic joint infection (PJI), then 2) build a predictive model for PJI in a developmental cohort, and 3) validate predictive utility of the model in a separate multi-institutional cohort.

Aim

Microbial identification in the setting of periprosthetic joint infections (PJI) is crucial to tailor the best combination of surgical and medical treatment. Given the high cost, low sensitivity and slow results associated with traditional cultures, s synovial fluid antibody assay was developed. We asked whether antibody testing may be used as a proxy to traditional culture in the setting of PJI.

Aim

A large body of evidence is emerging to implicate that dysregulation of the gut microbiome (dysbiosis) increases the risk of surgical site infections. Gut dysbiosis is known to occur in patients with inflammatory bowel disease (IBD), allowing for translocation of bacteria across the inflamed and highly permeable intestinal mucosal wall. The null hypothesis was that IBD was not associated with increased risk of periprosthetic joint infection (PJI) after primary total hip and knee arthroplasty. Our aim was to investigate whether a prior diagnosis of IBD was associated with a higher risk of PJI following primary total hip and knee arthroplasty.

Aim

It is traditionally stated that around 80% of all periprosthetic joint infections (PJI) are caused by well-known gram-positive organisms such as Staphylococcus aureus. With the advances in diagnostic modalities and improved abilities to isolate infective organisms, we believe the organism profile causing PJI has changed over time and includes numerous other organisms that were either not recognized as pathogens and/or considered as contaminants.

Aim

D-dimer is a widely available serum test that detects fibrinolytic activities that occur during infection. Prior studies have explored its utility for diagnosis of chronic periprosthetic joint infections (PJI), but not explored its prognostic value for prediction of subsequent treatment failure. The purpose of this study was to: (1) assess the ability of serum D-dimer and other standard-of-care serum biomarkers to predict failure following reimplantation, and (2) establish a new cutoff value for serum D-dimer for prognostic use prior to reimplantation.

Aim

Whether laminar airflow (LAF) in the operating room (OR) is effective for decreasing periprosthetic joint infection (PJI) following total joint arthroplasty (TJA) remains a clinically significant yet controversial issue. This study investigated the association between operating room ventilation systems and the risk of PJI in TJA patients.

Aim

Rifampin is considered as the antibiotic corner stone in the treatment of acute staphylococcal periprosthetic joint infections (PJI). However, if, when, and how to use rifampin has been questioned. We evaluated the outcome of patients treated with and without rifampin, and analysed the influence of timing, dose and co-antibiotic.

A growing number of recent investigations on the human genome, gut microbiome, and proteomics suggests that the loss of mucosal barrier function, particularly in the gastrointestinal tract, may substantially affect antigen trafficking, ultimately influencing the close bidirectional interaction between the gut microbiome and the immune system. This cross-talk is highly influential in shaping the host immune system and ultimately clinical infections. The hypothesis of the current study was that a change in microbiome and/or breach in GI epithelial barrier could be partially responsible for development of periprosthetic joint infections (PJI).

Multiple biomarkers of gut barrier disruption were tested in parallel in plasma samples collected as part of a prospective cohort study of patients undergoing revision arthroplasty for aseptic failures or PJI (As defined by the 2018 ICM criteria). All blood samples were collected before any antibiotic was administered. Samples were tested for Zonulin, soluble CD14 (sCD14), and lipopolysaccharide (LPS) using commercially available enzyme-linked immunosorbent assays. Statistical analysis consisted of descriptive statistics, Mann-Whitney t-test, and Kruskal-Wallis test.

A total of 134 patients were consented and included in the study. 44 were classified as PJI (30 chronic and 14 acute), and 90 as aseptic failures (26 primaries and 64 aseptic revisions). Both Zonulin and sCD14, but not LPS, were found to be significantly increased in the PJI group compared to non-infected cases (p<0.001; p=0.003). Higher levels of Zonulin were found in acute infections compared to chronic PJI (p=0.005

This prospective ongoing study reveals a possible link between gut permeability and the ‘gut-immune-joint axis’ in PJI. If this association continues to be born out with larger cohort recruitment and more in-depth analysis, it would have an immense implication in managing patients with PJI. In addition to administering antimicrobials, patients with PJI and other orthopedic infections may require gastrointestinal modulators such as pro and prebiotics.

Aims

The optimal management of an infrapopliteal deep venous thrombosis (IDVT) following total knee arthroplasty (TKA) remains unknown. The risk of DVT propagation and symptom progression must be balanced against potential haemorrhagic complications associated with administration of anticoagulation therapy. The current study reports on a cohort of patients diagnosed with IDVT following TKA who were treated with aspirin, followed closely for development of symptoms, and scanned with ultrasound to determine resolution of IDVT.

Introduction

Surgical management of PJI remains challenging with patients failing treatment despite the best efforts. An important question is whether these later failures reflect reinfection or the persistence of infection. Proponents of reinfection believe hosts are vulnerable to developing infection and new organisms emerge. The alternative hypothesis is that later failure is a result of an organism that was present in the joint but was not picked up by initial culture or was not a pathogen initially but became so under antibiotic pressure. This multicenter study explores the above dilemma. Utilizing next-generation sequencing (NGS), we hypothesize that failures after two stage exchange arthroplasty can be caused by an organism that was present at the time of initial surgery but not isolated by culture.

Aims

Failure of irrigation and debridement (I&D) for prosthetic joint infection (PJI) is influenced by numerous host, surgical, and pathogen-related factors. We aimed to develop and validate a practical, easy-to-use tool based on machine learning that may accurately predict outcome following I&D surgery taking into account the influence of numerous factors.

Aims

The aim of this study was to determine if a three-month course of microorganism-directed oral antibiotics reduces the rate of failure due to further infection following two-stage revision for chronic prosthetic joint infection (PJI) of the hip and knee.

Aim

Treatment success of debridement, antibiotics and implant retention (DAIR) is in early periprosthetic joint infection (PJI) is largely dependent on the presence or absence of a mature biofilm. In what time interval a mature biofilm develops is still unclear, and therefore, the time point at which DAIR should be disrecommended remains to be established. This large multicenter trial evaluated the failure rates of DAIR for different time intervals from index arthroplasty to DAIR in early PJI.

Background

The purpose of this multi-center, randomized clinical trial was to compare static and articulating spacers in the treatment of PJI complicating total knee arthroplasty TKA.

Introduction

Next generation sequencing (NGS) has been shown to facilitate detection of microbes in a clinical sample, particularly in the setting of culture-negative periprosthetic joint infection (PJI). However, it is unknown whether every microbial DNA signal detected by NGS is clinically relevant. This multi-institutional study was conceived to 1) identify species detected by NGS that may predict PJI, then 2) build a predictive model for PJI in a developmental cohort; and 3) validate the predictive utility of the model in a separate multi-institutional cohort.

Introduction

Femoroacetabular impingement(FAI) is a relatively common cause causes of hip pain and dysfunction in active young adults. The concept of FAI was popularized by Ganz et al in early 2000s. Surgical treatment for FAI has been widely employed over the last two decades. The long term outcome of femoroacetabular osteoplasty (FAO) and risk factors for long-term failure of FAO is less studied. The goal of this single surgeon series is to identify the long term outcome of FAO (minimum 10-year follow-up) and risk factors for surgical treatment failure in these patients.

Aims

The best marker for assessing glycaemic control prior to total knee arthroplasty (TKA) remains unknown. The purpose of this study was to assess the utility of fructosamine compared with glycated haemoglobin (HbA1c) in predicting early complications following TKA, and to determine the threshold above which the risk of complications increased markedly.

Introduction

Despite recent advances in the diagnosis of periprosthetic joint infection(PJI), identifying the infecting organism continues to be a challenge, with up to a third of PJIs reported to have negative cultures. Current molecular techniques have thus far been unable to replace culture as the gold standard for isolation of the infecting pathogen. Next- generation sequencing(NGS) is a well-established technique for comprehensively sequencing the entire pathogen DNA in a given sample and has recently gained much attention in many fields of medicine. Our aim was to evaluate the ability of NGS in identifying the causative organism(s) in patients with PJI.

Introduction

The use of irrigation solution during surgical procedures is a common and effective practice in reduction of bioburden and the risk of subsequent infection. The optimal irrigation solution to accomplish this feat remains unknown. Many surgeons commonly add topical antibiotics to irrigation solutions assuming this has topical effect and eliminates bacteria. The latter reasoning has never been proven. In fact a few prior studies suggest addition of antibiotics to irrigation solution confers no added benefit. Furthermore, this practice adds to cost, has the potential for anaphylactic reactions, and may also contribute to the emergence of antimicrobial resistance. We therefore sought to compare the antimicrobial efficacy and cytotoxicity of irrigation solution containing polymyxin-bacitracin versus other commonly used irrigation solutions.

Background

Recent reports demonstrate that Next Generation Sequencing (NGS) facilitates pathogen identification in the context of culture-negative PJI; however the clinical relevance of the polymicrobial genomic signal often generated remains unknown. This study was conceived to explore: (1) the ability of NGS to identify pathogens in culture-negative PJI; and (2) determine whether organisms detected by NGS, as part of a prospective observational study, had any role in later failure of patients undergoing surgical treatment for PJI.

Aim

Late acute prosthetic joint infections (PJI) treated with surgical debridement and implant retention (DAIR) have a high failure rate. The aim of our study was to evaluate treatment outcome in late acute PJIs treated with DAIR versus implant removal.

Aim

A two-stage exchange of an infected prosthetic joint (PJI) is considered the most effective surgical treatment of chronic PJIs, particularly in North America. However, reinfection rates are unacceptably high (10–20%). This could be the consequence of a persistent infection or a new infection introduced during the first or second stage of the exchange arthroplasty. We aimed to determine: i) the prevalence of positive cultures at reimplantation, ii) whether there is an association between positive cultures at reimplantation and reinfection during follow-up, and iii) if there is a microbiological correlation between primary infections, reimplantations and reinfections.

Aim

Debridement, antibiotics and implant retention (DAIR) is the recommended treatment for all acute prosthetic joint infections (PJI). However, the efficacy of DAIR and identification of risk factors for failure in patients with late acute PJI, is not well described.

Aims

The aim of this study was to examine the association between postoperative glycaemic variability and adverse outcomes following orthopaedic surgery.

Periprosthetic joint infection (PJI) is a devastating complication of total hip arthroplasty (THA). According to registry-based studies, some bearing couples are associated with an increased risk of PJI. The recent International Consensus on Periprosthetic Joint Infection stated that metal-on-metal (MOM) bearing surface appeared to be associated with a higher incidence of PJI. Based on emerging reports, the incidence of PJI appears to be different among different bearing surfaces. We conducted a multi-institutional study attempting to study this exact issue. The purpose of the study was to determine whether there was any difference in the incidence of PJI in two commonly used bearing couples (metal- on-polyethylene versus ceramic-on-polyethylene).

Based on a retrospective multi-institutional query all patients who received primary THA with MOP or COP bearing surfaces performed during 2005–2009 in two high-volume arthroplasty centers were identified. Demographic factors, comorbidities, length of hospital stay, complications and other relevant information were extracted. PJI was defined based on the MSIS (International Consensus) criteria. Multivariate analysis was performed to determine whether bearing coupling was independently correlated with PJI.

In our data, 25/2,921 (0.9%) patients with MOP and 11/2,643 (0.4%) patients with COP developed PJI. This difference was statistically significant (p=0.01). After the multivariate analysis, controlling for potential confounders (age, body mass index and length of hospital stay, Charlson comorbidity index), MOP bearing surface was found to be an independent factor correlating with higher incidence of PJI (odds ratio: 2.6, 95% confidence interval: 1.02–6.54, p=0.04).

The finding of this study, and others from centers in Europe, suggest that the bearing surface may have an influence on the incidence of PJI. Although, we had originally thought that ceramic bearing surfaces may be used in younger and healthier patients, the multivariate analyses that controlled for all these variables confirms that use of metal femoral head is an independent risk factor for development of PJI. The finding of this study is compelling and begs for future basic science mechanistic investigations.

Historical perspective: Irrigation and debridement (I&D) with modular exchange has historically been the recommended treatment for acute post-operative periprosthetic joint infection (PJI), and acute hematogenous PJI. The theory supporting this practice was that because the bacterial glycocalyx had not yet formed by these early time points, by simply debriding the intra-articular bacterial load and exchanging the modular parts, one could potentially eradicate the infection, retain the prior components, and minimise morbidity to the patient. More recently, literature is coming out suggesting that this may not necessarily be the case.

The vast majority of published research on the outcomes following I&D for treatment of PJI has focused on either cohorts of total knee arthroplasty patients or combined cohorts of total hip and knee patients. For this reason, it is difficult to tease out the differential success rate of periprosthetic hip vs. knee infections. Sherrell et al. performed a systematic review of the existing literature and created a table detailing the failure rates for various published articles on I&D for periprosthetic TKA infection.

Since it is the glycocalyx that has been thought to be the reason for treatment failure of many cases of PJI treated with I&D, many authors have implicated staphylococcal species as a predictor of a negative outcome with failure rates ranging from 30–35%. Methicillin resistant organisms have been shown to be particularly difficult to eradicate with an isolated I&D, with a 72–84% failure rate at 2 year follow-up. Interestingly, a recent study by Odum et al. suggests that neither the infecting microbe, nor the antibiotic resistance profile of the organism, as has been classically thought, actually predicts success of I&D.

Previous reports have indicated that the ability of I&D to control infection is related to the duration of symptoms and its timing relative to the index surgery. However, more recent literature is coming out to support the contrary. Koyonos et al. reviewed the outcomes of a series of 138 cases of PJI treated with I&D based on acuity of infection and concluded that an I&D has a limited role in controlling PJI regardless of acuity.

Intuitively, the physical health of the host/patient should influence the success of I&D for treatment of PJI. Several authors have shown that an immunocompromised state is a predictor of treatment failure. Furthermore, Azzam et al. reported that patients with a higher American Society of Anesthesia (ASA) score, a proxy of severity of medical comorbidities, had a significantly higher failure rate.

Although potentially appealing due to relative ease of execution and minimal surgical morbidity, the ability to successfully eradicate infection with an arthroscopic procedure may be compromised. Given the inability to perform a radical surgical debridement, nor exchange modular components, arthroscopic debridement should be used with extreme reservation in any case of PJI, regardless of the host, nature of the infecting organism, or acuity of infection.

I&D as a conservative, less morbid alternative to two-stage exchange - There is a growing body of literature to suggest that an I&D with modular component exchange may not be the benign, less morbid alternative to the ‘gold standard’ two-stage exchange arthroplasty. In fact, Fehring et al. has reported that the success of a two-stage antibiotic spacer exchange arthroplasty may be compromised by an initial I&D. They found that patients who were initially treated with an I&D only had a 66% chance of eradicating infection following a two-stage exchange arthroplasty, in contrast to historical reports of 80–90% success.

Aims

The diagnosis of periprosthetic joint infection can be difficult due to the high rate of culture-negative infections. The aim of this study was to assess the use of next-generation sequencing for detecting organisms in synovial fluid.

Next-generation sequencing (NGS) is a well-established technique for amplification and sequencing of DNA and has recently gained much attention in many fields of medicine. Our aim was to evaluate the ability of NGS in identifying the causative organism(s) in patients with periprosthetic joint infection (PJI).

In this prospective study samples were collected from 78 revision total hip arthroplasties. Synovial fluid, deep tissue and swabs were obtained at the time of surgery and shipped to the laboratory for NGS analysis. Deep tissue specimens were also sent to the institutional lab for culture. PJI was diagnosed using the Musculoskeletal infection society (MSIS) definition of PJI.

Thirty-four revisions were considered infected; culture was positive in 25 of these (25/34, 73.5%), while NGS was positive in 26 (26/34, 76.4%). Among the positive cultures, complete concordance between NGS and culture in 21 cases (21/25, 84.0%). 4 cases were discordant. Among these cases, 3 cases were culture-positive and NGS-negative, while 1 was both positive on NGS and culture for disparate organisms. Among the 9 cases of culture-negative PJI(CN-PJI), NGS was able to identify an organism in 4 cases (4/9, 44.4%). The remaining 5 cases were negative on both NGS and culture (5/9, 55.6%). Forty-four revisions were considered to be aseptic; NGS exclusively identified microbes in 7 of 44 “aseptic” revisions (15.9%) and culture exclusively isolated an organism in 3 of 44 cases (6.8%). Both NGS and culture were positive in 1 of case however the result was discordant. The remaining cases (33/44, 75.0%) were both NGS and culture negative. NGS detected several organisms in most positive samples, with a greater number of organisms detected in aseptic compared to septic cases (7 vs. 3.7, respectively).

NGS may be a promising technique for identifying the infecting organism in PJI. Our findings suggest that some cases of PJI may be polymicrobial that escape detection using conventional culture.

Aims

The aims of this study were to compare the efficacy of two agents, aspirin and warfarin, for the prevention of venous thromboembolism (VTE) after simultaneous bilateral total knee arthroplasty (SBTKA), and to elucidate the risk of VTE conferred by this procedure compared with unilateral TKA (UTKA).

Aim

Diagnosis of periprosthetic joint infection (PJI) presents a real challenge in some patients. Batteries of tests are available to reach this diagnosis. It is unknown if blood cultures have any role in diagnosis of PJI. The objective of this study was to evaluate whether blood cultures, taken in a group of patients with PJI, was useful in identifying the infecting pathogen.

The number of arthroplasties being performed increases each year. Patients undergoing an arthroplasty are at risk of venous thromboembolism (VTE) and appropriate prophylaxis has been recommended. However, the optimal protocol and the best agent to minimise VTE under these circumstances are not known. Although many agents may be used, there is a difference in their efficacy and the risk of bleeding. Thus, the selection of a particular agent relies on the balance between the desire to minimise VTE and the attempt to reduce the risk of bleeding, with its undesirable, and occasionally fatal, consequences.

Acetylsalicylic acid (aspirin) is an agent for VTE prophylaxis following arthroplasty. Many studies have shown its efficacy in minimising VTE under these circumstances. It is inexpensive and well-tolerated, and its use does not require routine blood tests. It is also a ‘milder’ agent and unlikely to result in haematoma formation, which may increase both the risk of infection and the need for further surgery. Aspirin is also unlikely to result in persistent wound drainage, which has been shown to be associated with the use of agents such as low-molecular-weight heparin (LMWH) and other more aggressive agents.

The main objective of this review was to summarise the current evidence relating to the efficacy of aspirin as a VTE prophylaxis following arthroplasty, and to address some of the common questions about its use.

There is convincing evidence that, taking all factors into account, aspirin is an effective, inexpensive, and safe form of VTE following arthroplasty in patients without a major risk factor for VTE, such as previous VTE.

Cite this article: Bone Joint J 2017;99-B:1420–30.

Revision of total hip arthroplasty (THA) is being performed with increasing frequency. However, outcomes of repeated revisions have been rarely reported in the literature, especially for severe defects. Cup revision can be a highly complex operation depending on the bone defect. In acetabular defects like Paprosky types 1 and 2 porous cementless cups maybe fixed with screws give good results. Modern trabecular metal designs improve these good results. Allografts are useful for filling cavitary defects. In acetabular defects Paprosky types 3A and 3B, impacted morselised allografts with a cemented cup technique produce good results. Difficult cases with pelvic discontinuity require reconstruction of the acetabulum with acetabular plates or large cup-cages to solve these difficult problems. However, there is still no consensus regarding the best option for reconstructing hips with bone loss. Although the introduction of ultraporous metals has significantly increased the surgeon's ability to reconstruct severely compromised hips, there remain some that cannot be managed readily using cups, augments, or cages. In such situations custom acetabular components may be required. Individual implants represent yet another tool for the reconstructive surgeon. These devices can be helpful in situations of catastrophic bone loss. Ensuring long-term outcome mechanical stability has a greater impact than restoring an ideal center of rotation.

We have done so far 15 3D Printed Individual Implants. All of them where Paprosky Type 3B defects, 10 with a additional pelvis discontinuity. The mean follow-up is 18 months. All implanted devices are still in place, no infection, no loosening.

However, despite our consecutive case series, there are no mid- to long-term results available so far. Re-revision for failed revision THA acetabular components is a technically very challenging condition.

The 3D Printed Individual Implants have a lot of advantages, like excellent surgical planning and a very simple technique (operative time, blood loss, instruments). They are a very stable construct for extensive acetabular defects and pelvic discontinuity.

The burden of periprosthetic joint infection (PJI) continues to rise and the management of this dreaded complication continues to pose challenges to the orthopaedic community. Dr Buchholz from the Endo Klinik has been credited for reporting the initial observation that addition of antibiotic to polymethylmethacrylate (PMMA) cement lead to better ability to deliver higher concentrations of antibiotic to the joint milieu and avoid administration of high doses of systemic antibiotics with potential for systemic toxicity.

Addition of antibiotics to PMMA cement has continued to be an important aspect of managing patients with chronic PJI. The rationale for this practice is that higher doses of local antibiotics can be reached without placing the patients at risk of systemic toxicity. Whether a one-stage or a two-stage exchange arthroplasty is being performed, antibiotics that can withstand the exothermic reaction of PMMA and are able to elude from cement are added at various doses to the PMMA for later delivery. Although this practice continues to be almost universal, there are a few unknowns. First of all, a recent study raised a valid question regarding this practice. Though intuitively logical, addition of antibiotics to PMMA spacers has not been scrutinised by any level 1 study and hence one is not able to prove that this practice does indeed accomplish its intended objectives of reducing recurrence or persistence of infection. Orthopaedic community is advised to seek avenues to generate this much-needed evidence. The other main unknown is how much, and in some instances which antibiotic, needs to be added to the PMMA cement. Some authorities have declared that antibiotics can be added at high doses, with an average total dose of 10.5 g of vancomycin (range, 3–16 g) and 12.5 g of gentamicin (range, 3.6–19.2 g) in one study, to PMMA cement without the fear of systemic toxicity.

In recent years, renal toxicity and other systemic adverse effects have been attributed to addition of high doses of antibiotics to cement. I have personally witnessed such adverse reactions in a few patients. Although initially I was inclined to “blame” the concurrent administration of systemic antibiotics for the renal toxicity that patients developed following insertion of spacer, selective nephrotoxicity (i.e. reaction to aminoglycoside that was only present in the spacer and not systemically administered) and resolution of the nephrotoxicity upon removal of antibiotic spacer, convinced me that our nephrology colleagues have a valid reason to be concerned about addition of high doses of antibiotics to PMMA spacers.

What has become clear is that high viscosity cements containing MA-MMA copolymers have been shown to have better antibiotic elution profiles than other PMMA formulations. So when fashioning a spacer in the operating room the surgeon needs to be aware of the differences in elution profile of antibiotics from PMMA and individualise the dose of antibiotics being added to spacer based on the type and viscosity of cement being used and the renal status of the patient. Thus, systemic toxicity caused by addition of antibiotics to cement spacer appears to be a real issue in some circumstances and this needs to be born in mind when managing patients with PJI.

There are numerous other issues related to the use of antibiotic cement spacers. In the hip, the lack of adequate offset and limited portfolio of products result in laxity in the soft tissue and subsequent dislocation of the hip. In addition, the dose and type of antibiotic in the premanufactured spacers, at least in the US, are inadequate to lead to a substantial delivery of antibiotics in the local tissues. Because of these issues, I prefer to fabricate “customised” spacers for each patient that I operate on.

Femoral revision in cemented THA might include some technical difficulties, based on loss of bone stock and cement removal, which might lead to further loss of bone stock, inadequate fixation, cortical perforation or consequent fractures. Femoral impaction grafting, in combination with a primary cemented stem, allows for femoral bone restoration due to incorporation and remodelling of the allograft bone by the host skeleton. Historically it has been first performed and described in Exeter in 1987, utilizing a cemented tapered polished stem in combination with morselised fresh frozen bone grafts. The technique was refined by the development of designated instruments, which have been implemented by the Nijmegen group from Holland. Indications might include all femoral revisions with bone stock loss, while the Endo-Clinic experience is mainly based on revision of cemented stems. Cavitary bone defects affecting meta- and diaphysis leading to a wide or so called “drain pipe” femora, are optimal indications for this technique, especially in young patients. Contraindications are mainly: septical revisions, extensive circumferential cortical bone loss and noncompliance of the patient.

Generally, the technique creates a new endosteal surface to host the cemented stem by reconstruction of the cavitary defects with impacted morselised bone graft. This achieves primary stability and restoration of the bone stock. It has been shown, that fresh frozen allograft shows superior mechanical stability than freeze-dried allografts. Incorporation of these grafts has been described in 89%. Technical steps include: removal of failed stem and all cement, reconstruction of segmental bone defects with metal mesh (if necessary), preparation of fresh frozen femoral head allografts with bone mill, optimal bone chip diameter 2–5 mm, larger chips for the calcar area (6–8 mm), insertion of an intramedullary plug including central wire, 2 cm distal the stem tip, introduction of bone chips from proximal to distal, impaction started by distal impactors over central wire, then progressive larger impactors proximal, insertion of a stem “dummy” as proximal impactor and space filler, removal of central wire, retrograde insertion of low viscosity cement (0.5 Gentamycin) with small nozzle syringe, including pressurization, and insertion of standard cemented stem. The cement mantle is of importance, as it acts as the distributor of force between the stem and bone graft and seals the stem. A cement mantle of at least 2 mm has shown favorable results. Post-operative care includes usually touch down weightbearing for 6–8 weeks, followed by 4–6 weeks of gradually increased weightbearing with a total of 12 weeks on crutches.

Relevant complications include mainly femoral fractures due to the hardly impacted allograft bone. Subsidence of tapered polished implants might be related to cold flow within the cement mantle, however, could also be related to micro cement mantle fractures, leading to early failure. Subsidence should be less than 5 mm. Survivorship with a defined endpoint as any femoral revision after 10-year follow up has been reported by the Exeter group being over 90%, while survivorship for revision as aseptic loosening being above 98%. Within the last years various other authors and institutions reported about similar excellent survivorships, above 90%. In addition, a long-term follow up by the Swedish arthroplasty registry in more than 1180 patients reported a cumulative survival rate of 94% after 15 years.

Impaction grafting might technically be more challenging and more time consuming than cement-free distal fixation techniques. It, however, enables a reliable restoration of bone stock which might especially become important in further revision scenarios in younger patients.

Venous thromboembolism (VTE) prophylaxis following total joint arthroplasty (TJA) should be individualised in order to maximise the efficacy of prophylactic measures while avoiding the adverse events associated with the use of anticoagulants. At our institution, we have developed a scoring model using the Nationwide Inpatient Sample (NIS) database, which is validated against our institutional data, to stratify patients into low- and high-risk groups for VTE. Low-risk patients are placed on aspirin 81 mg twice daily for four weeks post-operatively, and high-risk patients are placed on either a Vitamin K antagonist (warfarin), low molecular weight heparin, or other oral anticoagulants for four weeks post-operatively. All patients receive sequential pneumatic compression devices post-operatively, and patients are mobilised with physical therapy on the day of surgery. Patients who have a history of peptic ulcer disease or allergy to aspirin are also considered for other types of anticoagulation following surgery.

Risk Stratification Criteria

Major comorbid risk factors utilised in our risk stratification model include history of hypercoagulability or previous VTE, active cancer or history of non-cutaneous malignancy, history of stroke, and pulmonary hypertension. We consider patients with any of these risk factors at elevated risk of VTE and therefore candidates for formal anticoagulation.

Other minor risk factors include older age, bilateral surgery compared with unilateral, inflammatory bowel disease, varicose veins, obstructive sleep apnea, and history of myocardial infarction, myeloproliferative disorders, and congestive heart failure. Each minor criterion is associated with a score. The cumulative score is compared with a defined threshold and the score that surpasses the threshold indicates that the patient should receive post-operative anticoagulation. To facilitate the use of this scoring system, an iOS mobile application (VTEstimator) has been developed and can be downloaded from the app store.

The World Health Organization (WHO) and the Centre for Disease Control and Prevention (CDC) recently published guidelines for the prevention of surgical site infection. The WHO guidelines, if implemented worldwide, could have an immense impact on our practices and those of the CDC have implications for healthcare policy in the United States.

Our aim was to review the strategies for prevention of periprosthetic joint infection in light of these and other recent guidelines.

Cite this article: Bone Joint J 2017;99-B(4 Supple B):3–10.

Background

There are several surgical options available for patients with bilateral knee osteoarthritis including simultaneous bilateral TKA (BTKA) and staged approach. The appropriate and safe time interval between two stages is still controversial. The preset systematic review aims to determine the optimal time interval between two stages of BTKA.

Introduction

Reported data on impact of obesity on outcome of total joint arthroplasty (TJA) is mixed. The purpose of this systematic review was to evaluate the impact of obesity on surgical procedure and postoperative outcomes after total hip and knee arthroplasty.

There are a number of progressive conditions that afflict the hip and result in degenerative arthritis. Along the path of progression of the disease and prior to the development of arthritis, some of these conditions may be treatable by joint preservation procedures. Periacetabular osteotomy for developmental dysplasia of the hip (DDH), femoroacetabular osteoplasty for femoroacetabular impingement (FAI), and a variety of surgical procedures for management of early osteonecrosis of the femoral head are some examples of joint preservation of the hip. DDH is characterised by abnormal development of the acetabulum and the proximal femur that leads to suboptimal contact of the articular surfaces and the resultant increase in joint reaction forces. FAI is a condition characterised by an abnormal contact between the femoral neck and the acetabular rim. FAI is believed to exist when a triad of signs (abnormal alpha angle, labral tear, and chondral lesion) can be identified.

The question that remains is whether joint preservation procedures are able to avert the need for arthroplasty or just an intervention along the natural path of progression of the hip disease. There is an interesting study that followed 628 infants born in a Navajo reservation, including 8 infants with severe dysplasia, for 35 years. None of the children with DDH had surgical treatment and all had developed severe arthritis in the interim. The latter study and a few other natural history studies have shown that the lack of administration of surgical treatment to patients with symptomatic DDH results in accelerated arthritis. The situation is not so clear with FAI. Some believe that FAI is a pre-arthritic condition and surgical treatment is only effective in addressing the symptoms and does not delay or defer an arthroplasty. While others believe that restoration of the normal mechanical environment to the hip of FAI patients, by removing the abnormal contact and repair of the labrum, is likely to change the natural history of the disease and at minimum delay the need for an arthroplasty. There is a need for natural history studies or case series to settle the latter controversy.

Total hip arthroplasty continues to be one of the most effective procedures. Aseptic loosening compromises the long term outcome of this otherwise successful procedure. Large hemispherical cups may be used during revision surgery for patients with severe bone loss. Acetabular revision with cementless components has been remarkably successful with some series reporting no revisions for aseptic loosening at an average follow-up of 13.9 years. Another study on 186 patients (196 hips) receiving jumbo acetabular components, noted a survivorship of 98% at 4 years and 96% at 16 years. Cementless acetabular revision is now feasible for a wide range of revision situations, including some cases of pelvic discontinuity. The Paprosky classification is useful in predicting the reconstructive technique that will be required. Type I and many Type II defects may be reconstructed with standard cementless components. Many Type II and Type III defects, which involve the loss of additional structural bone, can be reconstructed with a jumbo cup. A jumbo cup is defined by Whaley et al. as a component that is >61 mm in women and >65 mm in men, a definition that is based on a shell that is >10 mm greater than the average diameter cup implanted in women and men. The jumbo cup has the advantage of an increased contact area between host bone and cup which maximises the surface area for ingrowth or ongrowth. The increased area of contact also prevents cup migration by allowing for force dissipation over a large area. Use of a jumbo cup may also decrease the need to use bone graft. In contrast to positioning the cup in the so-called high hip center, a jumbo cup can help to restore the hip center of rotation.

The disadvantages of this technique are that host bone may have to be removed to implant the cup, that bone stock is not restored by the reconstruction, and that hemispherical cups have limited applicability in situations of oblong bone stock deficiency.

Jumbo acetabular components can be used in combination with both structural and cancellous bone graft. In these cases, the cementless cup must achieve adequate contact with host bone in order to allow bone ingrowth to occur.

Aim

Different perioperative strategies have been implemented to reduce the devastating burden of infection following arthroplasty. The use of iodophor-impregnated adhesive incise drapes is one such strategy. Despite its wide adoption, there is little proof that this practice leads to a reduction of bacterial colonization. The aim of this randomized, prospective study was to evaluate the efficacy of iodophor-impregnated adhesive drapes for reducing bacterial count at the incision site.

There is no doubt that peri-prosthetic joint infection (PJI) is one the most terrible complications of joint arthroplasty. There has been a surge of interest in PJI in recent years as this problem moves to be the last frontier in joint arthroplasty.

There are a number of strategies employed for prevention of PJI. Irrigation of the surgical site with various irrigation solutions is one such strategy as it helps reduce bioburden in the wound and reduce the potential for subsequent infection.

Although the irrigation solution may work by dilution phenomenon alone, some believe that bactericidal or bacteriostatic agents may be added to the irrigation solution to increase its efficacy. Addition of antibiotics (Abx) to the irrigation solution stems from the same reasoning.

There are a number of serious issues related to the addition of Abx to the irrigation solution or in fact, for pouring into the wound (like the vancomycin powder).

Efficacy: There are no randomised prospective studies to demonstrate that addition of Abx to the irrigation solution improves “kill”. To do such a study would be logistically challenging. Basic science studies and other clinical studies with a small number of patients have failed to prove the efficacy of Abx in the irrigation solution. In fact, I would argue that the use of agents like dilute betadine is much more likely to be effective in reduction of bioburden without having many of the issues related to the use of Abx in irrigation solution.

Emergence of Resistance: Some may argue what would one lose by adding Abx to the wound or the irrigation solution. The modern society is facing an emerging catastrophe. Antimicrobial Resistance (AMR), if it persists, will kill more people than cancer by the year 2050. Annually 1000s of patients die of ESKAPE or AMR related issues. A recent task force convened by the British government produced a report about AMR which is sobering. The main finding of the task force was that continued liberal use of Abx will lead to further escalation of the AMR crisis that threatens the modern society. The guidelines by the CDC, that are about to be published, will discourage clinicians from pouring Abx into wounds and asks clinicians to exercise Abx stewardship.

Expense: There are costs associated with the use of Abx in any circumstance including their addition to irrigation solution. With over 1 million joint arthroplasties being done in the US alone, this cost can be substantial.

Hypersensitivity reactions: The use of Abx is not without problems. There have been a few fatalities associated with the use of Abx in patients with recognised and possibly unrecognised hypersensitivity to antibiotics.

Peri-prosthetic joint infection (PJI) is one the most devastating complications of joint arthroplasty. Although PJI is an infrequent complication (the reported incidence is 1%-2% in the United States), it is the most common indication for revision total knee arthroplasty in the Medicare population and the third most frequent indication for revision total hip arthroplasty. Moreover, the prevalence of PJI appears to be on the rise, with a projected number exceeding 60,000 to 70,000 cases in the United States by 2020.

It is estimated that more than 25% of revision procedures annually are attributed to PJI and this number is expected to increase in the upcoming years. The increase in the prevalence of obesity, diabetes, and other comorbidities among the patient population and the emergence of resistant infecting organisms are some of the reasons for the expected rise in the number of infections that medical community will witness.

The challenges that PJI present to the orthopaedic community are on many fronts. Prevention of PJI has proven to be a difficult task indeed. Effective strategies for prevention of PJI are being refined. The Center for Disease Control will be publishing its updated Surgical Site Prevention Guidelines in the next few months that consists of specific recommendations for prevention of PJI. In recent years, strides are made in introducing novel molecular techniques for diagnosis of PJI, which may stand to change our practices. The current surgical technique for management of PJI, besides the immense cost, fall short of delivering high success to the patients. The major problem in eradication of infection relates to formation of biofilm on the implant surface and internalization of the organisms by affected cells. Biofilm is a sophisticated structure comprising of organisms embedded in multiple layers of glycoccalyx that allows the organisms to evade host immunity and is impenetrable to antibiotics. These organisms are capable of communicating through molecular mechanisms such as quorum sensing that affords them advantage for survival in the host environment. In recent years strategies to prevent colonization of the implant surface, an essential first step in formation of biofilm, or biofilm disruption techniques have been introduced. A recent International Consensus meeting on PJI that assembled more than 350 experts identified some of the best practices in this field and identified areas in need of future research. Moving into the future, the field of orthopaedics in general and PJI in particular stand to benefit from the discoveries in the field of molecular diagnostics, metabolomics and epigenetics.

Aims

We aimed to assess the influence of ethnicity on the incidence of heterotopic ossification (HO) after total hip arthroplasty (THA).

Computer-aided surgical systems commonly use preoperative CT scans when performing pelvic osteotomies for intraoperative navigation. These systems have the potential to improve the safety and accuracy of pelvic osteotomies, however, exposing the patient to radiation is a significant drawback. In order to reduce radiation exposure, we propose a new smooth extrapolation method leveraging a partial pelvis CT and a statistical shape model (SSM) of the full pelvis in order to estimate a patient's complete pelvis. A SSM of normal, complete, female pelvis anatomy was created and evaluated from 42 subjects. A leave-one-out test was performed to characterise the inherent generalisation capability of the SSM. An additional leave-one-out test was conducted to measure performance of the smooth extrapolation method and an existing “cut-and-paste” extrapolation method. Unknown anatomy was simulated by keeping the axial slices of the patient's acetabulum intact and varying the amount of the superior iliac crest retained; from 0% to 15% of the total pelvis extent. The smooth technique showed an average improvement over the cut-and-paste method of 1.31 mm and 3.61 mm, in RMS and maximum surface error, respectively. With 5% of the iliac crest retained, the smoothly estimated surface had an RMS surface error of 2.21 mm, an improvement of 1.25 mm when retaining none of the iliac crest. This anatomical estimation method creates the possibility of a patient and surgeon benefiting from the use of a CAS system and simultaneously reducing the patient's radiation exposure.

Introduction

First-generation annealed HXLPE has been clinically successful at reducing both clinical wear rates and the incidence of osteolysis in total hip arthroplasty. However, studies have observed oxidative and mechanical degradation occurring in annealed HXLPE. Thus, it is unclear whether the favorable clinical performance of 1st generation HXLPE is due to the preservation of bearing surface tribological properties or, at least partially, to the reduction in patient activity. The purpose of this study was to evaluate the in vitro wear performance (assessed using multidirectional pin-on-disk (POD) testing) of 1^st-generation annealed HXLPE with respect to in vivo duration, clinical wear rates, oxidation, and mechanical properties.

Introduction

In THA, fretting corrosion at the head-stem taper junction has emerged as a clinical concern that may result in adverse local tissue reactions, even in patients with a metal-on-polyethylene bearing [1]. Taper junctions that employ a ceramic head have demonstrated reduced corrosion at the interface [2]. However, during revision surgery with a well-fixed stem, a titanium sleeve is used in conjunction with a ceramic head to ensure proper fit of the head onto the stem and better stress distribution. In vitro testing has suggested that corrosion is not a concern in sleeved ceramic heads [3]; however, little is known about the in vivo fretting corrosion of the sleeves. The purpose of this study was to investigate fretting corrosion in sleeved ceramic heads.

Introduction

A variety of porous coatings and substrates have been used to obtain fixation at the bone-implant interface. Clinical studies of porous tantalum, have shown radiographically well-fixed implants with limited cases of loosening. However, there has been limited retrieval analysis of porous tantalum hip implants. The purpose of this study was to investigate factors affecting bone ingrowth into porous tantalum hip implants.

The purpose of this article is to provide the reader with a seven-step checklist that could help in minimising the risk of PJI. The check list includes strategies that can be implemented pre-operatively such as medical optimisation, and reduction of the bioburden by effective skin preparation or actions taking during surgery such as administration of timely and appropriate antibiotics or blood conservation, and finally implementation of post-operative protocols such as efforts to minimise wound drainage and haematoma formation.

Cite this article: Bone Joint J 2016;98-B(1 Suppl A):18–22.

Introduction

Recent implant design trends have renewed concerns regarding metal wear debris release from modular connections in THA. Previous studies regarding modular head-neck taper corrosion were largely based on cobalt chrome (CoCr) alloy femoral heads. Comparatively little is known about head-neck taper corrosion with ceramic femoral heads or about how taper angle clearance influences taper corrosion. This study addressed the following research questions: 1) Could ceramic heads mitigate electrochemical processes of taper corrosion compared to CoCr heads? 2) Which factors influence stem taper corrosion with ceramic heads? 3) What is the influence of taper angle clearance on taper corrosion in THA?

Introduction

The release of metal debris and ions has raised concerns in joint arthroplasty. In THA metal debris and ions can be generated by wear of metal-on-metal bearing surfaces and corrosion at modular taper interfaces, currently understood to be mechanically assisted crevice corrosion (MACC) [1]. More recently, inflammatory-cell induced corrosion (ICIC) has been identified as a possible source of metal debris and/or ions [2]. Although MACC has been shown to occur at modular junctions in TKA, little is known about the prevalence of other sources. The purpose of this study was to determine the sources of metallic debris and ion release in long-term implanted (in vivo > 15y) TKA femoral components. Specific attention was paid to instances of ICIC as well as damage at the implant-bone interface.

It is strongly recommended that tissue and synovial fluid culture samples be obtained during reimplantation performed as part of a two-stage exchange arthroplasty. The incidence of positive cultures during reimplantation and the influence of positive cultures on subsequent outcome are unknown. This aim of this study was to determine the incidence of positive cultures during reimplantation and to investigate the association between positive cultures at reimplantation and the subsequent outcome

A retrospective review was conducted on 267 patients that met the Musculoskeletal Infection Society (MSIS) criteria for PJI that completed both stages of two-stage exchange arthroplasty (Table 1). Intraoperative culture results from tissue and/or synovial fluid were obtained. Cultures were positive in 33 cases (12.4%) undergoing reimplantation surgery (Figure 1). Treatment failure was assessed based on the Delphi consensus definition. Logistic regression analysis was performed to assess the predictors of positive culture and risk factors for failure of two-stage exchange arthroplasty.

Treatment failure was 45.5% for those with a positive intraoperative culture and 20.9% in those with negative cultures at the time of reimplantation. When controlling for organism virulence, comorbidities, and other confounding factors, treatment failure was higher (odds ratio [OR]: 3.3; 95% confidence interval [CI]: 1.3–4.5) and occurred at an earlier time point (hazard ratio: 2.5; 95% CI: 1.3–4.5) in patients with a positive reimplantation culture. The treatment failure rate was not different between cases with two or more positive cultures (36.4%) and one positive culture (42.8%).

Positive intraoperative cultures during reimplantation, regardless of the number of positive samples were independently associated with two times the risk of subsequent infection and earlier treatment failure. Surgeons should be aware that a positive culture at the time of reimplantation independently increases the risk of subsequent failure and needs to be taken seriously. Given the significance of these findings, future studies are needed to evaluate the optimal management of positive cultures during reimplantation surgery.

Perioperative antibiotic prophylaxis remains one of the most important strategies for prevention of periprosthetic joint infection (PJI) with current guideline recommending a first or second generation cephalosporin. Penicillin (PCN) allergy is often reported by patients, which often results in avoidance of administration of cephalosporins due to fear of cross-reactivity. Alternative medications, such as vancomyin, are often used despite reduced antimicrobial coverage. The purpose of this study was to determine if PCN allergic patients who received vancomycin alone prior to elective primary total joint arthroplasty were at increased risk of developing a subsequent PJI.

A retrospective review of 7,602 primary total joint arthroplasties (TJAs) performed between 2005 and 2013 in two institutions were identified using a prospective institutional database. Patient reported PCN or cephalosporin allergy was electronically queried from the anesthesia note. Patients who recieved multiple prophylactic antibiotics, or had unavailable perioperative antibiotic information, or those who received medication other than cefazolin and vancomycin were excluded. PJI was determined using a cross-match with an institutional PJI database constructed from International Classification of Diseases (ICD)-9 codes. Logistic regression analysis was then performed to evaluate the risk of subsequent PJI.

The rate of PJI was 1.4% (32/2296) in patients with a reported PCN allergy that received vancomycin alone versus 1.1% (59/5306) in non-PCN allergic patients that received cefazolin alone. The multivariate analysis, with the given sample size, did not detect a statistically significant increased risk of PJI when vancomycin was administered alone (adjusted odds ratio: 1.23, 95% CI 0.6–3.1, p=0.35). While there was no significant differences in the organism profile between PJIs in both groups, the rate of PJI caused by resistant organisms was higher in patients who received vancomycin alone (11.9%, 7/59) compared to those who received cefazolin (3.1%, 1/32).

While administration of perioperative prophylactic vancomycin alone during elective primary arthroplasty does not seem to result in a higher rate of subsequent PJI, patients who received vancomycin alone and developed a PJI were more likely to develop an infection with an antibiotic resistant organism. Future studies are needed to determine the most appropriate prophylactic antibiotic for patients who undergo elective arthroplasty and report PCN allergy.

Considerable efforts have been invested into identifying risk factors for periprosthetic joint infection (PJI) after total joint arthroplasty (TJA). Preoperative identification of risk factors for developing PJI is imperative for medical optimization and targeted prophylaxis. The purpose of this study was to create a preoperative risk calculator for PJI by assessing a patient's individual risks for developing PJI with resistant organisms and S.aureus.

A retrospective review of 27117 patients (43253 TJAs) from 1999 to 2014, including 1035 PJIs, was performed. A total of 41 risk factors including demographics, comorbidities (using the Elixhauser and Charlson Index), and the number of previous TJAs, were evaluated. Multivariate analysis was performed; coefficients of the models were scaled to produce useful integer scoring. Predictive model strength was assessed employing area under the curve (AUC) analysis.

Among the 41 assessed variables, the following were significant risk factors in descending order of significance: prior surgeries (p<0.0001), drug abuse (p=0.0003), revision surgery (p<0.0001), human immunodeficiency virus (p=0.0004), coagulopathy (p<0.0001), renal disease (p<0.0001), congestive heart-failure (p<0.0001), psychoses (p=0.0024), rheumatological disease (p<0.0001), knee involvement (p<0.0001), diabetes (p<0.0001), anemia (p<0.0001), males (p<0.0001), liver disease (p=0.0093), smoking (p=0.0268), and high BMI (p<0.0001). Furthermore, presence of heart-valve disease (p=0.0409), metastatic disease (p=0.0006), and pulmonary disease (p=0.0042) increased the resistant organism PJIs. Patients with metastatic disease were also more likely to be infected with S. aureus (p=0.0002). AUCs were 0.83 for any PJI, 0.86 for resistant PJI, and 0.84 for S.aureus PJI models.

This large-scale single-institutional study has determined various risk factors for PJI. Some factors are modifiable and need to be addressed before elective arthroplasty. It is imperative that surgeons are aware of these risk factors and implement all possible preventative measures, including targeted prophylaxis, in patients with high-risk of PJI. Continued efforts are needed to find novel and effective solutions to minimize the burden PJI.

Periprosthetic joint infection (PJI) is one of the most devastating complications of total joint arthroplasty (TJA). Only a few studies have investigated PJI's impact on the most worrisome of all endpoints, mortality. The purpose of this study was to perform a large-scale study to determine the rates of PJI associated in-hospital mortality, and compare it to other surgical procedures.

The Nationwide Inpatient Sample was queried from 2002 to 2010 to assess the risk of mortality for patients undergoing revision for PJI or aseptic failures. Elixhauser comorbidity index and ICD-9 codes were used to obtain patients’ medical conditions and identify PJI. Multiple logistic-regression analyses were used to determine the associated variables with mortality. In-hospital mortality was compared to the followings: coronary-artery bypass graft, mastectomy, prostatectomy, appendectomy, kidney transplant, carotid surgery, cholecystectomy, and coronary interventional procedures.

PJI was associated with an increased risk (odds ratio 2.04) of in-hospital mortality (0.77%) compared to aseptic revisions (0.38%). The in-hospital mortality of revision THAs done for PJI (1.38%, 95%CI, 1.12–1.64%) was comparable to or higher than interventional coronary procedure (1.22%, 95%CI, 1.20–1.24%), cholecystectomy (1.13%, 95%CI, 1.11–1.15%), kidney transplantation (0.70%, 95%CI, 0.61%–0.79%) and carotid surgery (0.89%, 95%CI, 0.86%–0.93%) (Figure 1). The following comorbidities were independent risk factors for in-hospital mortality after TJA: liver disease, metastatic disease, fluid and electrolyte disorders, coagulopathy, weight loss and malnutrition, congestive heart failure, pulmonary circulation disorder, renal failure, and peripheral vascular disease.

PJI is associated with a two-fold increase in mortality and have mortality rates comparable to kidney transplantation and carotid surgery. Considering the fact that patients with PJI often require multiple surgical procedures, the rate of actual in-hospital mortality for patients with PJI may be considerably higher. Surgeons should be cognizant of the potentially fatal outcome of PJI and must emphasize the importance of infection control to reduce the risk of mortality.

Failure of a two-stage exchange arthroplasty for management of periprosthetic joint infection (PJI) poses a major clinical challenge. There is a paucity of information regarding the outcome of further surgical intervention in these patients. Thus, we aim to report the clinical outcomes of subsequent surgical intervention following a failed prior two-stage exchange.

Our institutional database was used to identify 60 patients (42 knees and 18 hips) with a failed prior two-stage exchange from infection, who underwent further surgical intervention between 1998 and 2012 and had a minimum of two years follow-up. A retrospective review was performed to extract relevant clinical information, such as mortality, microbiology, and subsequent surgeries. Musculoskeletal Infection Society criteria were used to define PJI, and treatment success was defined using the Delphi criteria as previously reported.

Irrigation and debridement (I&D) was performed after a failed two-stage exchange in 61.7% (37/60) patients. The failure rate of I&D in this cohort was 51.3% (19/37). Two patients underwent amputation after I&D due to uncontrolled infection. A total of 40 patients underwent an intended a second two-stage exchange. Reimplantation occurred in only 65% of cases (26/40), and infection was controlled in 61.6% (16/26) of patients. An interim spacer exchange was required in 15% (6/40) of the cases. Of the 14 cases that did not undergo a second stage reimplantation, 5 required amputation, 6 had retained spacers, 1 underwent arthrodesis, and 2 patients died.

Further surgical intervention after a failed prior two-stage exchange has poor outcomes. I&D has a high failure rate and many of the patients who are deemed candidates for a second two-stage exchange either do not undergo reimplantation for various reasons or fail after reimplantation. The management of PJI clearly remains imperfect, and there is a dire need for further innovations that may improve the care of these PJI patients.

Periprosthetic joint infection (PJI) is one of the most feared and challenging complications following total knee arthroplasty. We provide a detailed description of our current understanding regarding the management of PJI of the knee, including diagnostic aids, pre-operative planning, surgical treatment, and outcome.

Cite this article: Bone Joint J 2015;97-B(10 Suppl A):20–9.

Periprosthetic joint infection (PJI) is one the most devastating complications of joint arthroplasty. Although PJI is an infrequent complication (the reported incidence is 1%-2% in the United States), it is the most common indication for revision total knee arthroplasty in the Medicare population and the third most frequent indication for revision total hip arthroplasty. Moreover, the prevalence of PJI appears to be on the rise, with a projected number exceeding 60,000 to 70,000 cases in the United States by 2023.

It is estimated that more than 25% of revision procedures annually are attributed to PJI and this number is expected to increase in the upcoming years. The increase in the prevalence of obesity, diabetes, and other comorbidities among the patient population and the emergence of resistant infecting organisms are some of the reasons for the expected rise in the number of infections that medical community will witness.

The challenges that PJI presents to the orthopaedic community are on many fronts. Prevention of PJI has proven to be a difficult task indeed. Effective strategies for prevention of PJI are being refined. The Center for Disease Control will be publishing its updated Surgical Site Prevention Guidelines in the next few months that consists of specific recommendations for prevention of PJI. In recent years, strides are made in introducing novel molecular techniques for diagnosis of PJI, which may stand to change our practices. The current surgical technique for management of PJI, besides the immense cost, fall short of delivering high success to the patients. The major problem in eradication of infection relates to formation of biofilm, on the implant surface and internalization of the organisms by affected cells. Biofilm is a sophisticated structure comprising of organisms embedded in multiple layers of glycoccalyx that allows the organisms to evade host immunity and is impenetrable to antibiotics. These organisms are capable or communicating through molecular mechanisms such as quorum sensing that affords them advantage for survival in the host environment. In recent years strategies to prevent colonization of the implant surface, an essential first step in formation of biofilm, or biofilm disruption techniques have been introduced. A recent International Consensus meeting on PJI that assembled more than 350 experts identified some of the best practices in this field and identified areas in need of future research. Moving into the future, the field of orthopaedics in general and PJI in particular stand to benefit from the discoveries in the field of molecular diagnostics, metabolomics and epigenetics.

Introduction:

The safety of simultaneous bilateral knee replacement (BTKA) remains controversial. Some studies have proposed a higher incidence of serious complications, even death, following BTKA whilst others refute the latter. The objective of this meta-analysis was to evaluate the safety of BTKA.

We hypothesised that the use of tantalum (Ta) acetabular components in revision total hip arthroplasty (THA) was protective against subsequent failure due to infection. We identified 966 patients (421 men, 545 women and 990 hips) who had undergone revision THA between 2000 and 2013. The mean follow up was 40.2 months (3 months to 13.1 years). The mean age of the men and women was 62.3 years (31 to 90) and 65.1 years (25 to 92), respectively.

Titanium (Ti) acetabular components were used in 536 hips while Ta components were used in 454 hips. In total, 73 (7.3%) hips experienced subsequent acetabular failure. The incidence of failure was lower in the Ta group at 4.4% (20/454) compared with 9.9% (53/536) in the Ti group (p < 0.001, odds ratio 2.38; 95% CI 1.37 to 4.27). Among the 144 hips (64 Ta, 80 Ti) for which revision had been performed because of infection, failure due to a subsequent infection was lower in the Ta group at 3.1% (2/64) compared with 17.5% (14/80) for the Ti group (p = 0.006).

Thus, the use of Ta acetabular components during revision THA was associated with a lower incidence of failure from all causes and Ta components were associated with a lower incidence of subsequent infection when used in patients with periprosthetic joint infection.

Cite this article: Bone Joint J 2015;97-B:45–9.

Summary Statement

This study assesses oxidation, mechanical behavior and revision reasons of 2^nd generation HXLPE used in total hip and knee arthroplasty. While oxidation was low for both X3 and E1 HXLPEs, oxidative regional variations were detected in the sequentially annealed cohort.

Summary Statement

Fretting and corrosion has been identified as a clinical problem in modular metal-on-metal THA, but remains poorly understood in modern THA devices with polyethylene bearings. This study investigates taper damage and if this damage is associated with polyethylene wear.

Introduction

The safety of simultaneous bilateral knee replacement (BTKA) remains controversial. Some studies have proposed a higher incidence of serious complications, even death, following BTKA whilst others refute the latter. The objective of this meta-analysis was to evaluate the safety of BTKA.

Developmental dysplasia of the hip (DDH) is relatively a common condition that can lead to early arthritis of the hip. Although total hip arthroplasty is the surgical treatment of choice for these patients with end stage arthritis, some patients afflicted with DDH may present early. Acetabular osteotomy, in particular Bernese or periacetabular osteotomy (PAO as described by Professor Ganz and Jeff Mast back in 1980s) may be an option with patients with symptomatic DDH who have joint space available. PAO has many advantages. First, it is performed through a single incision (modified Smith Peterson approach) without breaching the abductor mechanism. The periacetabular fragment has, hence, excellent blood supply and avascular necrosis of the acetabular portion is not an issue. In addition, the osteotomy is so versatile allowing for great mobility of the fragment to obtain coverage even in the worst of circumstances. The osteotomy does not affect the posterior column and hence allows for earlier weight bearing. Most joint preservation surgeons in North America and Europe prefer PAO to other types of osteotomy.

The indications for PAO are a patient with symptomatic DDH who has good joint space and a congruent joint. The congruency of the joint is usually determined by the abduction views (obtained at 30 degrees abduction and neutral rotation). Although the joint space may be measured on plain radiographs, in recent years some centers have been utilising cross sectional imaging, such as dGEMERIC for evaluation of the articular cartilage, which has been shown to be a good predictor of outcome for PAO.

Nanotechnology is the study, production and controlled manipulation of materials with a grain size < 100 nm. At this level, the laws of classical mechanics fall away and those of quantum mechanics take over, resulting in unique behaviour of matter in terms of melting point, conductivity and reactivity. Additionally, and likely more significant, as grain size decreases, the ratio of surface area to volume drastically increases, allowing for greater interaction between implants and the surrounding cellular environment. This favourable increase in surface area plays an important role in mesenchymal cell differentiation and ultimately bone–implant interactions.

Basic science and translational research have revealed important potential applications for nanotechnology in orthopaedic surgery, particularly with regard to improving the interaction between implants and host bone. Nanophase materials more closely match the architecture of native trabecular bone, thereby greatly improving the osseo-integration of orthopaedic implants. Nanophase-coated prostheses can also reduce bacterial adhesion more than conventionally surfaced prostheses. Nanophase selenium has shown great promise when used for tumour reconstructions, as has nanophase silver in the management of traumatic wounds. Nanophase silver may significantly improve healing of peripheral nerve injuries, and nanophase gold has powerful anti-inflammatory effects on tendon inflammation.

Considerable advances must be made in our understanding of the potential health risks of production, implantation and wear patterns of nanophase devices before they are approved for clinical use. Their potential, however, is considerable, and is likely to benefit us all in the future.

Cite this article: Bone Joint J 2014; 96-B: 569–73.

The rate of peri-prosthetic infection following total joint replacement continues to rise, and attempts to curb this trend have included the use of antibiotic-loaded bone cement at the time of primary surgery. We have investigated the clinical- and cost-effectiveness of the use of antibiotic-loaded cement for primary total knee replacement (TKR) by comparing the rate of infection in 3048 TKRs performed without loaded cement over a three-year period versus the incidence of infection after 4830 TKRs performed with tobramycin-loaded cement over a later period of time of a similar duration. In order to adjust for confounding factors, the rate of infection in 3347 and 4702 uncemented total hip replacements (THR) performed during the same time periods, respectively, was also examined. There were no significant differences in the characteristics of the patients in the different cohorts.

The absolute rate of infection increased when antibiotic-loaded cement was used in TKR. However, this rate of increase was less than the rate of increase in infection following uncemented THR during the same period. If the rise in the rate of infection observed in THR were extrapolated to the TKR cohort, 18 additional cases of infection would have been expected to occur in the cohort receiving antibiotic-loaded cement, compared with the number observed. Depending on the type of antibiotic-loaded cement that is used, its cost in all primary TKRs ranges between USD $2112.72 and USD $112 606.67 per case of infection that is prevented.

Cite this article: Bone Joint J 2014;96-B:65–9.

Introduction:

First generation highly crosslinked polyethylenes (HXPLEs) have proven successful in lowering both penetration and osteolysis rates. However, 1^st generation annealing and remelting thermal stabilization have been associated with in vivo oxidation or reduced mechanical properties. Thus, 2^nd generation HXLPEs were developed to improve oxidative stability while still maintaining material properties. Little is known about the in vivo clinical failure modes of these 2^nd generation HLXPEs.

The purpose of this study was to assess the revision reasons, wear, oxidative stability, and mechanical behavior of retrieved sequentially annealed Vitamin E diffused HXLPE in THA and TKA.

Introduction:

Degradation of modular head-neck tapers was raised as a concern in the 1990s (Gilbert 1993). The incidence of fretting and corrosion among modern, metal-on-polyethylene and ceramic-on-polyethylene THA systems with 36+ mm femoral heads remains poorly understood. Additionally, it is unknown whether metal debris from modular tapers could increase wear rates of highly crosslinked PE (HXLPE) liners.

The purpose of this study was to characterize the severity of fretting and corrosion at head-neck modular interfaces in retrieved conventional and HXLPE THA systems and its effect on penetration rates.

Background:

Previous studies regarding modular head-neck taper corrosion were largely based on cobalt chrome (CoCr) alloy femoral heads. Less is known about head-neck taper corrosion with ceramic femoral heads.

INTRODUCTION:

The diagnosis of periprosthetic joint infection (PJI) remains a serious challenge. Based on previous work, we believe that biomarkers will become the mainstay of diagnosing PJI in the future. We report on completion of our 8 year comprehensive biomarker program, evaluating the diagnostic profile of the 15 most promising synovial fluid biomarkers.

Louis Pasteur once said that: “Fortune favours the prepared mind.” As one of the great scientists who contributed to the fight against infection, he emphasised the importance of being prepared at all times to recognise infection and deal with it. Despite the many scientific discoveries and technological advances, such as the advent of antibiotics and the use of sterile techniques, infection continues to be a problem that haunts orthopaedic surgeons and inflicts suffering on patients.

The medical community has implemented many practices with the intention of preventing infection and treating it effectively when it occurs. Although high-level evidence may support some of these practices, many are based on little to no scientific foundation. Thus, around the world, there is great variation in practices for the prevention and management of periprosthetic joint infection.

This paper summaries the instigation, conduct and findings of a recent International Consensus Meeting on Surgical Site and Periprosthetic Joint Infection.

Cite this article: Bone Joint J 2013;95-B:1450–2.

Total knee replacement (TKR) is an operation that can be performed with or without the use of a tourniquet. Meta-analyses of the available Level-1 studies have demonstrated that the use of a tourniquet leads to a significant reduction in blood loss. The opponents for use of a tourniquet cite development of complications such as skin bruising, neurovascular injury, and metabolic disturbance as drawbacks. Although there may certainly be reason for concern in arteriopathic patients, there is little evidence that routine use of a tourniquet during TKR results in any of the above complications. The use of a tourniquet, on the other hand, provides a bloodless field that allows the surgeon to perform the procedure with expediency and optimal visualisation. Blood conservation has gained great importance in recent years due to increased understanding of the problems associated with blood transfusion, such as increased surgical site infection (due to immunomodulation effect), increased length of hospital stay and increased cost. Based on the authors’ understanding of the available evidence, the routine use of a tourniquet during TKR is justified as good surgical practice.

Cite this article: Bone Joint J 2013;95-B, Supple A:133–4.

Orthopaedic surgeons have accepted various radiological signs to be representative of acetabular retroversion, which is the main characteristic of focal over-coverage in patients with femoroacetabular impingement (FAI). Using a validated method for radiological analysis, we assessed the relevance of these signs to predict intra-articular lesions in 93 patients undergoing surgery for FAI. A logistic regression model to predict chondral damage showed that an acetabular retroversion index (ARI) > 20%, a derivative of the well-known cross-over sign, was an independent predictor (p = 0.036). However, ARI was less significant than the Tönnis classification (p = 0.019) and age (p = 0.031) in the same model. ARI was unable to discriminate between grades of chondral lesions, while the type of cam lesion (p = 0.004) and age (p = 0.047) were able to. Other widely recognised signs of acetabular retroversion, such as the ischial spine sign, the posterior wall sign or the cross-over sign were irrelevant according to our analysis. Regardless of its secondary predictive role, an ARI > 20% appears to be the most clinically relevant radiological sign of acetabular retroversion in symptomatic patients with FAI.

Cite this article: Bone Joint J 2013;95-B:893–9.

Direct anterior approach (DAA) using the Hueter interval for total hip replacement (THA) provides an inter-nervous and inter-muscular access to the hip joint. Although it is technically demanding, the learning curve has been shown to be around 40 cases and 6 months in a high-volume joint surgeon's practice. A level-one study has demonstrated that DAA provides equal or better results and an equivalent rate of complications when compared to the highly utilized direct lateral approach. Using the available evidence to perform a multi-criteria decision analysis we demonstrated that DAA can be the most efficient approach to perform THA. From our standpoint, there is no reason to speculate a surgical approach with such advantages will be abandoned in the future. The DAA is here to stay, and may become the gold standard for THA.

Total knee arthroplasty is an operation that can be performed with or without the use of tourniquet. Two systematic reviews and meta-analyses of the available literature have demonstrated that the use of tourniquet leads to a reduction in blood loss and also shortens the operative time. The opponents for use of tourniquet cite development of complications such as skin bruising, neurovascular injury, and metabolic disturbances as a deterrent for the use of tourniquet. Although the latter may be true for some patients such as those with previous vascular grafts, there is little evidence that routine use of tourniquet during TKA results in any of the above complications. The use of tourniquet on the other hand provides a bloodless field that allows the surgeon to perform the procedure with expediency and optimised visualisation. Blood conservation has gained extreme importance in recent years because of increased understanding of problems associated with blood transfusion such as increased surgical site infection (due to immunomodulation effect), increased length of hospital stay, increased cost and so on. Based on our understanding of the available evidence, we believe that routine use of tourniquet during TKA is justified and a good surgical practice.

A novel cementless tapered wedge femoral hip implant has been designed at a reduced length and with a geometry optimized to better fit a wide array of bone types (Accolade II, Stryker, Mahwah, USA). In this study, finite element analysis (FEA) is used to compare the initial stability of the new proposed hip stem to predicate tapered wedge stem designs. A fit analysis was also conducted. The novel stem was compared to a predicate standard tapered stem and a shortened version of that same predicate stem.

Introduction

Sequentially annealed highly crosslinked polyethylenes (HXLPEs) were introduced in total knee replacement (TKR) starting in 2005 to reduce wear and particle-induced osteolysis. Few studies have reported on the clinical performance of HXLPE knees. In this study, we hypothesized that due to the reduced free radicals, sequentially annealed HXLPE would have lower oxidation levels than gamma inert-sterilized controls.

Introduction

Wear debris generation in metal-on-metal (MOM) total hip arthroplasty (THA) has emerged as a compelling issue. In the UK, clinically significant fretting corrosion was reported at head-taper junctions of MOM hip prostheses from a single manufacturer (Langton 2011). This study characterizes the prevalence of fretting and corrosion at various modular interfaces in retrieved MOM THA systems used in the United States.

Introduction

The purpose of this multicenter study was to assess the oxidative stability, mechanical behavior, wear and reasons for revision of 2nd generation sequentially annealed HXLPE, X3, and compare it to 1^st generation XLPE, Crossfire. We hypothesized that X3 would exhibit similar wear rates but lower oxidation than Crossfire.

Staphylococcus aureus is one of the leading causes of surgical site infection (SSI). Over the past decade there has been an increase in methicillin-resistant S. aureus (MRSA). This is a subpopulation of the bacterium with unique resistance and virulence characteristics. Nasal colonisation with either S. aureus or MRSA has been demonstrated to be an important independent risk factor associated with the increasing incidence and severity of SSI after orthopaedic surgery. Furthermore, there is an economic burden related to SSI following orthopaedic surgery, with MRSA-associated SSI leading to longer hospital stays and increased hospital costs. Although there is some controversy about the effectiveness of screening and eradication programmes, the literature suggests that patients should be screened and MRSA-positive patients treated before surgical admission in order to reduce the risk of SSI.

Cite this article: Bone Joint J 2013;95-B:4–9.

Periprosthetic joint infection (PJI) is a devastating complication which can follow a total joint arthroplasty (TJA). Although rare, this ongoing threat undermines the success of TJA, a historically reputable procedure. It has haunted the orthopedic community for decades and several ongoing studies have provided insights and new approaches to effectively battle this multilayered problem.

In this paper, we will consider the current role of simultaneous-bilateral TKA. Based on available evidence, it is our opinion that simultaneous bilateral TKA carries a higher risk of morbidity and mortality and should be reserved for select few.

Background

The diagnosis of Periprosthetic Joint Infection (PJI) is a considerable challenge in total joint arthroplasty. The mainstay for diagnosis of PJI is a combination of serological markers, including C-reactive protein (CRP), along with joint aspirate for white cell count, differential and culture. The aim of this study was to examine the use of synovial fluid CRP in the diagnosis of PJI.

Introduction

The origins of the uncemented tapered wedge hip stem design currently offered by several orthopaedic device companies can be linked back to the cemented Straight Mueller type stem design first used in 1977. The design, a wedge shape with a taper angle of 6 degrees, maintains a single medial curvature for all sizes and increases laterally in the width to accommodate different size femurs. Although evolutionary improvements have been made over the years the basic body geometry of the stem has stayed mainly unchanged with excellent clinical survivorship. Over the past decade, the demographics of hip replacement have changed, with a large increase in younger male patients in the age range of 40 to 60 years. In this study the femoral fit of a novel tapered stem, designed to fit a wide array of patient types, is compared to a standard predicate tapered stem design.

Infection poses one of the greatest medical challenges, one further complicated by bacterial biofilm formation that renders the infection antibiotic insensitive. The goal of this investigation was to covalently link the antibiotic vancomycin (VAN) to a bone allograft so as to render the tissue inhospitable to bacterial colonization and the subsequent establishment of infection. We could achieve uniform tethering of the antibiotic to the allograft with minimal disruption of the underlying bone structure. The tethered VAN remained active against gram-positive organisms with no detectable S.aureus colonization. Additionally, the grafted VAN prevented biofilm formation, even in protected topographical niches. Attachment of the antibiotic to the allograft surface was robust-the stabilized VAN remained active for long time periods. Osteoblasts cultured on the VAN-allograft evidenced no changes in cellular phenotype. We opine that this new chimeric construct represents a superior transplantable substrate with a plethora of applications in medicine, dentistry and surgery.

Use of allograft bone has become standard for bridging defects unlikely to heal by simple fixation and routinely used in revision arthroplasties for implant stabilization. Unfortunately, this decellularized allograft provides an ideal surface for bacterial colonization, necessitating repeated surgeries, extensive debridement and lengthy antibiotic treatments. With up to 18% infection rate following allograft surgeries, a need for more effective means to prevent this process is evident. We describe a novel modification of native bone allografts that renders their surface bactericidal while increasing the effectiveness of systemic antibiotic treatments.

Allograft modification: Morselized human bone was washed extensively and sequentially coupled: 2X with Fmoc-aminoethoxyethoxyacetate (Fmoc-AEEA); deprotected with 20% piperidine in Dimethylformamide (DMF); and then coupled with vancomycin (VAN) for 12–16 hours. The VAN-bone was washed extensively with DMF and PBS for at least 1 day. VAN immuno-fluorescence: Control or VAN-bone was washed 5X with PBS, blocked with 10% FBS (1hr), incubated with rabbit anti-VAN IgG (4oC, 12h) followed by an Alexa-Fluor 488-coupled goat anti-rabbit IgG (1hr), and visualized by confocal laser microscopy. Antibiotic Activity. Equal dry weights of control and VANbone were sterilized with 70% ethanol, rinsed with PBS, and incubated with either Staphylococcus aureus (S. aureus) or Escherichia Coli (Ci=104 cfu) in TSB, 37oC, for 2, 5, 8 and 12 hrs. Antibiotic treatment: Clinical grade vancomycin was added to the solution with bacteria or following infection at a final concentration of 10μg/ml. Bacterial counts: Non-adherent bacteria were removed by washing and adherent bacteria suspended by sonication in 0.3% Tween-80 for 10mins followed by plating on 3M^® Petrifilms. Bacterial visualization: Non-adherent bacteria were removed by washing extensively with PBS and adherent bacteria stained with the Live/Dead BacLight Kit (20mins, RT) to cause viable bacteria to fluoresce green. Samples were visualized by confocal microscopy.

In comparison to controls, VAN-bone consistently reduced the graft bacterial load by ~90% at all time points. After staining and visualization of adherent bacteria, biofilm formation was apparent on controls by 12 hrs and absent from VAN-bone. E.coli, a gramnegative organism that is not sensitive to VAN, readily colonized both control and VANbone, confirming retention of VAN specificity. We then evaluated VAN-bone activity in a system that modeled systemic antibiotic therapy and antibiotic prophylaxis. In the absence of solution antibiotics, VAN-bone exhibited a significant decrease in bacterial colonization as compared to controls. When 10 μg/ml VAN was added to the medium for the last 4 h (modeling systemic antibiotic therapy), colonization of control surfaces was reduced, while colonization of VAN-allograft was almost eliminated. When 10 μg/ml VAN was added concomitantly with S. aureus, VAN-bone colonization was undetectable, while colonization of control surfaces still occurred.

We have previously described an antibiotic-tethered allograft that resists bacterial colonization. In this abstract, we test this technology with an vitro model of bone implantation in the presence of solution antibiotics. In these models, solution antibiotics failed to prevent infection of control bone while completely clearing the bacteria on VAN-bone. Furthermore, VAN bone exhibited high activity against S. aureus, a gram positive organism, whereas it was ineffective against E. coli, a gram negative organism. The specificity of the tethered antibiotic supported the view that the antibacterial properties of the allograft were related to the tethered antibiotic and not to undefined aspects of the attachment chemistry. In terms of antibacterial activity, when challenged with 104 CFU S. aureus (with concentrations reaching > 107 CFU by 24 h), the antibiotic -modified allograft consistently decreased bacterial colonization by > 90%; S. aureus inocula < 102 CFU resulted in no detectable colonization of the VAN-allograft. Thus, development of these allografts may not only combat allograft colonization but increase the effectiveness of prophylactic antibiotics to ultimately result in a new therapy for allograft-associated infection.

We performed a retrospective examination of the anteroposterior pelvic CT scout views of 419 randomly selected patients between April 2004 and August 2009 in order to determine the prevalence of cam-type femoroacetabular deformity in the asymptomatic population. The CT scans had all been undertaken for conditions unrelated to disorders of the hip. The frequency of cam-type femoroacetabular deformity was assessed by measuring the α-angle of each hip on the anteroposterior images. The α-angles were classified according to the Copenhagen Osteoarthritis Study. Among 215 male hips (108 patients) the mean α-angle was 59.12° (37.75° to 103.50°). Of these, a total of 30 hips (13.95%) were defined as pathological, 32 (14.88%) as borderline and 153 (71.16%) as normal. Among 540 female hips (272 patients) the mean α-angle was 45.47° (34.75° to 87.00°), with 30 hips (5.56%) defined as pathological, 33 (6.11%) as borderline and 477 (88.33%) as normal. It appears that the cam-type femoroacetabular deformity is not rare among the asymptomatic population. These anatomical abnormalities, as determined by an increased α-angle, appear to be twice as frequent in men as in women. Although an association between osteoarthritis and femoroacetabular impingement is believed to exist, a long-term epidemiological study is needed to determine the natural history of these anatomical abnormalities.

Purpose: Recently an orthopedic manufacturer has introduced a gender specific knee design implying that there is a substantial anatomical difference between the genders. If such concept is true then TKA prosthesis implanted in the female population over the last decades, by definition, must have suboptimal outcome when compared to the male patients. The purpose of this study was to examine the functional outcome, the incidence of complications, and the need for revision between the two genders receiving the same knee design.

Method: The study selected a matched group of 150 men and 250 women undergoing TKA at our instituion. The patients were matched for age, BMI, pre-op diagnosis, comorbidities, race, mode of fixation, and the type of implant. Other demographic, surgical, and medical factors between the two genders were similar. Both pre-op and post-op functional scores were compared between the two groups. Pre-op and post-op radiographic images were assessed for implant fit.

Results: There was a significant improvement in functional outcome as measured by Knee Society score, WOMAC, and SF-36 for all patients. The improvement in functional outcome was not different between the two groups. The incidence of complications, reoperations, and need for revision between the two genders was also not significantly different.

Conclusion: Total knee arthroplasty continues to be an effective surgical procedure. Both genders appear to enjoy relief of pain and improvement of function equally. Based on this retrospective study the use of non-gender specific knee prosthesis did not seem to result in suboptimal outcome in female patients. There appears to be little merit in introduction of gender specific knee designs when previous non-gender specific prosthesis appeared to function well in both genders.

Purpose: Hip arthroscopy has been used at an increasing frequency over the last few years. Majority of patients undergoing hip arthroscopy are young and active individuals who seek definitive therapy for a painful hip condition and wish to avoid undergoing a hip replacement. Although relatively successful, complications following hip arthroscopy occur. This multi-institutional study presents a worrisome and previously unrecognized complication of hip arthroscopy, namely chondrolysis that lead to accelerated development of end-stage arthritis.

Method: Using the computerized database in each institution, patients undergoing total hip arthroplasty between 1999–2008 who had received hip arthroscopy prior to arthroplasty were identified. 39 patients were identified to have undergone at least one hip arthroscopy on the affected hip prior to arthroplasty. There were 21 female and 18 male patients. The mean age of patients at the time of hip arthroscopy was 45.9 years. Data regarding demographics, comorbidities, preoperative diagnosis, number of previous procedures, and the details of the surgical procedure were compiled. Radiographs were evaluated.

Results: The median time from arthroscopy to arthroplasty was 14.8 months (range 2.2 months to 7 years). Fourteen patients (35%) underwent THA within 12 months of a previous hip arthroscopy and in nine of these patients the indication for hip arthroscopy was labral tear debridement. These patients despite having none to minimal arthritis at the time of arthroscopy developed accelerated arthritis within a year that necessitated hip replacement.

Conclusion: Hip arthroscopy can cause accelerated degenerative arthritis of the hip in some patients. We believe the subset of our patients who developed arthritis so early after hip arthroscopy may have suffered chondrolysis and/or chondral injury during the arthroscopy that resulted in progressive and aggressive arthritis of the hip within 12 months. Hip arthroscopy should be reserved for a select group of patients. All measures to minimize the possibility of chondrolysis and/or chondral injury should be exercised.

Purpose: Femoroacetabular impingement (FAI) is recognized as an etiological risk factor for hip arthritis. The potential for joint preserving surgical techniques that may delay the progression to early arthritis and retard the possibility of arthroplasty at a young age is promising. This study presents the outcome of surgical treatment of FAI through a less invasive technique performed through a modified Smith-Peterson approach without hip dislocation, or arthroscopy.

Method: Using an institutional database, a total of 72 patients (80 hips) with radiographic and clinical diagnosis of FAI who underwent direct anterior femoroacetabular osteoplasty (FAO) were identified. Preoperative and postoperative functional evaluation was performed on these patients. The operative findings were recorded in detail and evaluated with regard to outcome.

Results: Intraoperative diagnosis of labral tear and osteochondral lesions in the anterosuperior acetabulum was confirmed in all cases. The surgical approach provided adequate access to allow labral repair and osteoplasty of the femoral neck and the acetabulum, whenever needed. There were no intraoperative complications. All patients experienced a significant improvement in function as measured by modified Harris hip and SUSHI scores. Majority (85%) of the patients were satisfied with the outcome of the surgery. In addition, Health Survey SF-36 showed most patients felt their health had improved significantly. The predictors of poor outcome were previous hip scope, lack of labrum for repair, large chondral lesions, and workman’s compensation status.

Conclusion: This study presents the early results of a less invasive surgical treatment for femoroacetabular impingement. This ongoing study shows that the described technique seems to be a viable approach for treatment of this painful condition in the young.

Purpose: The purpose of our study is to compare hips to knees in regards to the cost per increase in function, to determine the relationship of economic investment to improved quality of life.

Method: During the year 2005, a total of 23 TKA and 41 THA revisions were performed for aseptic mechanical failure. Patients were enrolled prospectively and quality of life questionnaires including the SF-36, WOMAC, Harris Hip Score (HHS), and Knee Society Score (KSS) were collected prior to and following their procedure at two year follow-up. The total cost of the procedure including the hospital, implant, and surgeon fee were implemented in a cost effectiveness model to calculate the mean cost per SF-36, WOMAC, and HHS or KSS point gained. Demographical variables and co-morbidities were collected to determine risk factors for low cost-effectiveness.

Results: The majority of patients had significant improvement in SF-36, WOMAC, HHS and KSS scales. Patients with THA revisions experience a cost per point increase for HHS of $3,000, and $500 per point SF-36 compared to knee patients who experienced a cost per point increase for KSS of $2,000, and $2,800 per point SF-36. The WOMAC exhibited similar cost effectiveness in the subscales of pain, stiffness and functioning.

Conclusion: There are few studies that have compared the cost effectiveness of total joint arthroplasty revision procedures. Given the increasing cost of health care expenditures, prioritization of funding for the different health practices will become necessary. This study demonstrates that revision THA and TKA are relatively cost effective procedures compared to other non-orthopaedic interventions.

Introduction: Clinical experience has shown that addressing variations in bone morphology is important in the development of successful hip implant designs. Numerous studies of femoral bone morphology have been published utilizing various techniques. This study has developed a method which consistently measures large quantities of 3-dimensional digital femura geometry segmented from computed tomography (CT) scans and can accurately make anatomical measurements from these images

Methods: CT images of left femora on five hundred fifty six left femura (57% male, 43% female), consisting of 69% Caucasian, 16% Asian and 14% unknown were analyzed. The average age was 66 years, ranging from 40 to 93 years. Segmentation of the outer cortical, inner cortical, and marrow boundaries were consistently performed over all CT scans. The positions identified on the reference bone are transformed to the equivalent position on the clinical bone images, from which the dimensional data is extracted and stored. The mediolateral width (MLW), medial offset (MO) and lateral offset (LO) were measured in 10mm increments, ranging from 20mm above the lesser trochanter (LT) to 130mm below the lesser trochanter. The canal flare index was defined as a ratio of the mediolateral width at a section 20mm above the lesser trochanter to the mediolateral width at the isthmus level.

Results: The mean mediolateral width at 20mm above the lesser trochanter was 47.0 ± 4.5 (35.1–61.8; n=556). Noble reported 45.4 ± 5.3 (31.0–60.0; n=200), Husmann reported in a neck oriented study 46.3 ± 6.9 (27.6–63.6; n=310) and Laine reported 47.1 ± 4.9 (n=50). The mean medial offset at a section 20mm above the lesser trochanter was 25.1 ± 2.9 (16.7–33.4). In the study by Husmann, a mean of 25.0 ± 5.2 (9.4–45.5) was reported. The mean canal flare index was 4.49 ±.8. Noble reported a mean canal flare index of 3.80 ±.074, Husmann 3.81 ±.83 and Laine 4.3 ±.93.

Discussion: In general, the study showed minor differences to published data of proximal bone morphology. However, this more powerful study has shown that there is a higher mean canal flare index than determined by Noble and a similar mean canal flare index as determined by Laine. As reported by Laine, the canal flare index varies significantly with the placement of measurements in the canal. In this study the measurements were performed in a plane oriented by the femoral neck as a hip stem would be placed. The CFI over the isthmus width showed a greater correlation than previously shown by Noble. The novel software tool allows for anatomical measurements that can be applied to an unlimited population size enabling further applications and studies.

Persistent wound drainage after total joint arthroplasty (TJA) has been associated with a higher incidence of superficial and deep periprosthetic infection but the predictors for prolonged drainage and its outcome have not been thoroughly studied.

A consecutive series of 7,153 TJA cases performed between 2000 and 2006 at our institute, were recruited into this study. There were 301 cases (4.2%) of persistent wound drainage, defined as discharge from the wound for > 48 hours. The cases were matched in a 2:1 ratio for type of surgery, joint replaced, and date of surgery.

This study identified higher BMI (p< 0.005), malnutrition as defined by serum albumin< 3.4g/dl (p< 0.04), longer operative time (p< 0.01), and higher medical comorbidities, in particular diabetes (p< 0.001) as important risk factors for persistent wound drainage. In addition, patients in the drainage group were more likely to have a peak INR of > 1.5 (p< 0.001) during their hospital stay. Patients with wound drainage had a significantly lower hemoglobin postoperatively (p< 0.01) that necessitated greater number of postoperative allogenic transfusions (p=0.004). The hospital length of stay for the drainage group was also significantly higher (p< 0.005). One of the major risk factors for development of deep infection was prolonged drainage (> 7 days). In the deep hematoma and periprosthetic subgroups, the mean of delay in treatment was 6 days in those with retention of the prosthesis and successful outcome, and 9.5 days for those with failure of incision and drainage leading to resection arthroplasty (p= 0.03).

72% of the patient were successfully treated by oral or intravenous antibiotics. 27% required at least one re-operation for deep hematoma and 13% developed deep periprosthetic infection, resulting in 6% rate of resection arthroplasty. 1.5% of those with drainage remained in girdlestone status.

This study suggests early surgery for persistent drainage and avoidance of aggressive anticoagulation.

Periprosthetic infection (PPI) remains the most dreaded and difficult complication of total joint arthroplasty. Although there is no definite diagnostic test for PPI, synovial leukocyte count and neutrophil percentage have been reported to have high sensitivity and specificity. However, leukocytes and neutrophils introduced into the joint during a traumatic aspiration can skew results and undermine the predictive value of this diagnostic test. This study intends to determine the diagnostic value of implementing a corrective formula frequently used in traumatic spinal taps to adjust for serum leukocytes introduced into the joint fluid during a bloody tap.

We conducted a review of all TKA aspirations of infected and non-infected patients performed at our institute from 2000 to 2005.

The following inclusion criteria were used:

(a) a red cell count (RBC) was performed on the aspirate, and

Patients with inflammatory arthropathy or those who underwent reimplantation after PPI were excluded. Strict criteria for diagnosis of PPI were used. We previously determined at our institute the cut-off values for fluid leukocyte count (> 1760 cells/μl) and neutrophil percentage (> 73%).

The adjusted fluid leukocyte counts were calculated using the following formula:

Wadjusted = WBCobserved – [(WBCblood * RBC-fluid/RBCblood)] predicted.

A similar formula was implemented to calculate the adjusted absolute neutrophil counts.

Our cohort included 73 infected and 32 aseptic total knee arthroplasties that fulfilled the above criteria. After correcting for introduced red blood cells, cell counts of 3 infected patients dropped below the cut-off value, while the remaining 70 maintained a high cell count. However, the 3 infected patients had initial cell counts below our reported cut-offs. Of the 32 non-infected patients, 10 patients had false positive cell counts due to the presence of extremely high numbers of blood RBC. Five of the 10 false positive aspirates successfully corrected to levels below the thresholds used to diagnose infection. The aspirates that corrected had a greater number of introduced RBCs, an initial higher cell count, and 20 times more fluid WBC deducted from the initial cell count.

The corrective formula can safely adjust for RBC found in a traumatic tap and detect false positive results among non-infected TKA without compromising the diagnosis of infection. Adjusted aspirates of non-infected TKA can be expected to decrease below zero due to one of the following: adherence of the introduced systemic WBC to the joint synovium, greater rate of lysis of the introduced systemic WBC compared to the systemic RBC, laboratory errors in performing fluid cell counts.

The differential diagnosis of pain after total knee arthroplasty (TKA) should always include periprosthetic infection (PPI). The current diagnostic tools vary in sensitivity, specificity, and predictive value. Currently there is no test with an absolute accuracy for diagnosis of PPI. Furthermore, cost effectiveness of investigations has become an important issue in recent years as increased expenses can place an unnecessary heavy burden on the medical system.

We retrospectively evaluated 296 patients who underwent revision TKA at our institution during 2000–2005 and had preoperative erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) performed. The criteria used for diagnosing infection were a positive intraoperative culture on solid media, presence of an abscess or sinus tract that communicated with the joint, positive preoperative aspiration culture, and/or elevated fluid cell count and neutrophil differential of the aspirated fluid. The sensitivity, specificity, and predictive values of ESR and CRP were determined. Combinations were performed in parallel that necessitate both tests to be negative to rule out infection. The cost of each serological test was compared to that of other commonly used screening modalities.

One hundred and sixteen patients (39%) were classified as infected and 180 patients (61%) were considered non-infected. The sensitivity, specificity, positive predictive value, and negative predictive value for the ESR were: 91%, 72%, 68%, and 93%. The sensitivity, specificity, positive predictive value, and negative predictive value for the CRP were: 94%, 74%, 70%, and 95%. The sensitivity and negative predictive value for the combined studies were 96% and 95%, respectively. However, five infected patients (4%) had a normal

ESR and CRP. An organism was cultured on solid media in 4 of the 5 cases. ESR and CRP were the least costly of all the preoperative tests including radionuclide imaging and joint fluid analysis. ESR and CRP are important preoperative tests in diagnosis of PPI and their ability to clench the diagnosis in the majority of cases should not be underestimated. When combined, these simple serological tests have improved sensitivity and negative predictive value to rule out infection.