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Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_15 | Pages 73 - 73
1 Dec 2021
Cho J Goswami K Sukhonthamarn K Parvizi J Arnold W
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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.

Method

Established biofilms of Staphylococcus aureus and Escherichia coli were exposed to different irrigation solutions that included Polymyxin 500,000U/L plus bacitracin 50,000U/L, Vancomycin 1g/L, Gentamicin 80mg/L, Normal saline 0.9%, off-the-shelf Betadine 0.3%, Chlorhexidine 0.05%, Benzalkonium 1.3g/L, Sodium hypochlorite 0.125%, and Povidone-iodine 0.5%. Each experiment was conducted in a 96-well microtiter plate with a peg lid and standardized per the MBEC assay manufacturer's protocol. Following 2 minutes of solution exposure to the irrigation solution, residual biofilms were recovered by sonication. Outcome measures for antibiofilm efficacy were residual colony forming units (CFU) and optical density (690nm). Experiments were conducted in 24 replicates and the observations recorded by two blinded observers. Statistical analysis involved t-tests with Bonferonni adjustment.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_15 | Pages 34 - 34
1 Dec 2021
Goswami K Parvizi J
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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.

Method

This prospective study involving 15 institutions collected samples from 635 revision total hip(n=310) and knee(n=325) arthroplasties. Synovial fluid, tissue and swabs were obtained intraoperatively for NGS analysis. Patients were classified per 2018 Consensus definition of PJI. Treatment failure was defined as reoperation for infection that yielded positive cultures, during minimum 1-year follow-up. Concordance of the infecting pathogen cultured at failure with NGS analysis at initial revision was determined.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_15 | Pages 85 - 85
1 Dec 2021
Goswami K Shope A Wright J Purtill J Lamendella R Parvizi J
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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.

Method

In this prospective study, samples were collected from 20 patients undergoing revision TJA (10 aseptic and 10 infected) and 10 primary TJA. Synovial fluid and peripheral blood samples were obtained at the time of surgery, as well as negative field controls (skin swabs, air swabs, sterile water). All samples were shipped to the laboratory for metatranscriptomic analysis. Following microbial RNA extraction and host analyte subtraction, metatranscriptomic sequencing was performed. Bioinformatic analyses were implemented prior to mapping against curated microbial sequence databases– to generate taxonomic expression profiles. Principle Coordinates Analysis (PCoA) and Partial Least Squares-Discriminant Analysis were utilized to ordinate metatranscriptomic profiles, using the 2018 definition of PJI as the gold-standard.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_15 | Pages 59 - 59
1 Dec 2021
Chisari E Cho J Wouthuyzen M Friedrich AW Parvizi J
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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).

Method

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 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 and ANOVA.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_15 | Pages 46 - 46
1 Dec 2021
Chisari E Siqueira M Yacovelli S Goswami K Brownfield M Parvizi J
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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.

Method

A retrospective study of patients who underwent revision total hip (THA) and knee (TKA) arthroplasty between January 2019 and January 2020 was performed. All patients were aspirated prior to revision surgery and antibody testing was performed. All patients had samples harvested for culture as per standard of care. Results of the two tests and their concordance when an organism was identified were compared. A frequency table was used and a McNemar test was used to compare the two methods.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_15 | Pages 31 - 31
1 Dec 2021
Goswami K Parvizi J
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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.

Method

Fifteen institutions prospectively collected samples from 194 revision TKA and 184 revision THA between 2017–2019. Synovial fluid, tissue and swabs were obtained intraoperatively and sent to MicrogenDx (Lubbock, TX) for NGS analysis. Reimplantations were excluded. Patients were classified per the 2018 ICM definition of PJI. DNA analysis of community similarities (ANCOM) was used to identify 17 bacterial species of 294 (W-value>50) for differentiating infected vs. noninfected cases. Logistic regression with LASSO selection and random-forest algorithms were then used to build a model for predicting PJI. ICM classification was the response variable (gold-standard) and species identified through ANCOM were predictors. Patients were randomly allocated 1:1 into training and validation sets. Using the training set, a model for PJI diagnosis was generated. The entire model-building procedure and validation was iterated 1000 times.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_15 | Pages 60 - 60
1 Dec 2021
Restrepo S Groff H Goswami K Parvizi J
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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.

Method

We retrospectively reviewed the medical records of 1,363 patients with confirmed PJI (559 THA and 804 TKA) who received treatment at our institution between 2000 and 2019. Pertinent data related to demographics, microbiological findings, and outcome of treatment were collected. Organisms were differentiated using culture or confirmed by Matrix-Assisted Laser Desorption Ionization-time of flight (MALDI-tof) mass spectrometry. Statistical analysis included logistic regressions.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_15 | Pages 42 - 42
1 Dec 2021
Chisari E D'Mello D Parvizi J
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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.

Method

A matched cohort study was designed. Primary endpoint was the occurrence of PJI at 2-year. Secondary endpoints were aseptic revisions, as well as discharge to rehab facility, complications up to 30 days, and readmission up to 90 days after TJA. ICD-9 and −10 codes were used to identify patients with IBD and the control cohort. A chart review was performed to confirm diagnosis of IBD. Using our institutional database, 154 patients with IBD were identified and matched (3 to 1) for age, sex, body mass index (BMI), year of surgery, and joint affected with 462 individuals without IBD undergoing TJA.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_15 | Pages 38 - 38
1 Dec 2021
Yacovelli S Goswami K Shohat N Shahi A Parvizi J
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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.

Method

This prospective study enrolled 92 patients undergoing reimplantation between April 2015 and March 2019 who had previously undergone total hip/knee resection arthroplasty with placement of an antibiotic spacer for treatment of chronic PJI. Serum D-dimer level, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) levels were measured preoperatively for all patients. Failure following implantation was defined per the Delphi consensus criteria. Optimal cutoffs for D-dimer, ESR, and CRP were calculated based on ROC curves and compared in their association with failure following reimplantation criteria at minimum 1-year follow-up.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_15 | Pages 81 - 81
1 Dec 2021
Beldman M Löwik C Soriano A Albiach L Zijlstra W Knobben B Jutte P Sousa R Carvalho AD Goswami K Parvizi J Belden K Wouthuyzen-Bakker M
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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.

Method

Acute staphylococcal PJIs treated with surgical debridement between 1999 and 2017, and a minimal follow-up of 1 year were evaluated. Treatment failure was defined as the need for any further surgical procedure related to infection, PJI-related death, or the need for suppressive antimicrobial treatment.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_15 | Pages 62 - 62
1 Dec 2021
Wang Q Goswami K Xu C Tan T Clarkson S Parvizi J
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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.

Method

We performed a retrospective observational study on consecutive patients undergoing primary total knee arthroplasty (TKA) and total hip arthroplasty (THA) from January 2013-September 2017 in two surgical facilities within a single institution, with a minimum 1-year follow-up. All procedures were performed by five board-certified arthroplasty surgeons. The operating rooms at the facilities were equipped with LAF and turbulent ventilation systems, respectively. Patient characteristics were extracted from clinical records. PJI was defined according to Musculoskeletal Infection Society criteria within 1-year of the index arthroplasty. A multivariate logistic regression model was performed to explore the association between LAF and risk of 1-year PJI, and then a sensitivity analysis using propensity score matching (PSM) was performed to further validate the findings.


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_14 | Pages 10 - 10
1 Dec 2019
Löwik C Parvizi J Jutte P Zijlstra W Knobben B Xu C Goswami K Sousa R Carvalho AD Soriano A Wouthuyzen-Bakker M
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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.

Method

We retrospectively evaluated patients with early PJI treated with DAIR between 1996 and 2016. Early PJI was defined as a PJI that developed within 90 days after index arthroplasty. Patients with hematogenous infections, arthroscopic debridements and a follow-up less than one year were excluded. Treatment failure was defined as 1) any further surgical procedure related to infection 2) PJI-related death, or 3) long-term suppressive antibiotics, all within one year after DAIR.


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_4 | Pages 54 - 54
1 Apr 2019
Goswami K Tarabichi M Tan T Shohat N Alvand A Parvizi J
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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.

Methods

After obtaining Institutional Review Board approval and informed consent for all study participants, samples were prospectively collected from 148 revision total joint arthroplasty procedures (83 knees, 65 hips). Synovial fluid, deep tissue and swabs were obtained at the time of surgery and shipped to the laboratory for NGS analysis (MicroGenDx). Deep tissue specimens were also sent to the institutional laboratory(Thomas Jefferson University Hospital) for culture. PJI was diagnosed using the Musculoskeletal Infection Society(MSIS) definition of PJI. Statistical analysis was performed using SPSS software.


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_4 | Pages 56 - 56
1 Apr 2019
Goswami K Cho JE Manrique J Tan T Higuera C Della Valle C Parvizi J
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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.

Methods

Using two in vitro breakpoint assays of Staphylococcus aureus (ATCC#25923) and Escherichia coli (ATCC#25922), we examined the efficacy of a panel of irrigation solutions containing topical antibiotics (500,000U/L Polymyxin-Bacitracin 50,000U/L; Vancomycin 1g/L; Gentamicin 80mg/L), as well as commonly used irrigation solutions (Normal saline 0.9%; Povidone-iodine 0.3%; Chlorhexidine 0.05%; Castile soap 0.45%; and Sodium hypochlorite 0.125%) following 1 minute and 3 minutes of exposure. Surviving bacteria were counted in triplicate experiments. Failure to eradicate all bacteria was considered to be “not effective” for that respective solution and exposure time.

Cytotoxicity analysis in human fibroblast, osteoblast, and chrondrocyte cells exposed to each of the respective irrigation solutions was performed by visualization of cell structure, lactate dehydrogenase (LDH) activity and evaluation of vital cells. Toxicity was quantified by determination of LDH release (ELISA % absorbance; with higher percentage considered a surrogate for cytotoxicity). Descriptive statistics were used to present means and standard deviation of triplicate experimental runs.


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_4 | Pages 59 - 59
1 Apr 2019
Goswami K Tan T Tarabichi M Shohat N Parvizi J
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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.

Methods

In this prospective study samples were collected in 238 consecutive patients undergoing revision total hip and knee arthroplasties. Of these 83 patients (34.9%) had PJI, as determined using the Musculoskeletal Infection Society (MSIS) criteria, and of these 20 were culture-negative (CN-PJI). Synovial fluid, deep tissue and swabs were obtained at the time of surgery and sent for NGS and culture/MALDI-TOF. Patients undergoing reimplantation were excluded. Treatment failure was assessed using the previously described Delphi criteria. In cases of re-operation, organisms present were confirmed by culture and MALDI-TOF. Concordance of the infecting pathogen(s) at failure with the NGS analysis at the initial stage CN- PJI procedure was determined.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_17 | Pages 1 - 1
1 Dec 2018
Wouthuyzen-Bakker M Sebillotte M Lomas J Kendrick B Palomares EB Murillo O Parvizi J Shohat N Reinoso JC Sánchez RE Fernandez-Sampedro M Senneville E Huotari K Allende JMB García AB Lora-Tamayo J Ferrari MC Vaznaisiene D Yusuf E Aboltins C Trebse R Salles MJ Benito N Vila A Del Toro MD Kramer T Petersdorf S Diaz-Brito V Tufan ZK Sanchez M Arvieux C Soriano A
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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.

Method

In a large multicenter study, late acute PJIs were retrospectively evaluated. Failure was defined as: PJI related death or the need for prosthesis removal or suppressive antibiotic therapy because of persistent or recurrent signs of infection. Late acute PJI was defined as < 3 weeks of symptoms more than 3 months after the index surgery.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_17 | Pages 33 - 33
1 Dec 2018
Wouthuyzen-Bakker M Kheir M Rondon A Lozano L Moya I Parvizi J Soriano A
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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.

Method

We retrospectively evaluated all two-stage exchange procedures performed at two academic centers between 2000 and 2015. Primary culture-negative PJIs and cases in whom no intraoperative cultures were obtained during reimplantation were excluded from the analysis. One or more positive intraoperative cultures during reimplantation were considered positive for infection. Reinfection was defined as the need for additional surgical intervention after reimplantation or the need for antibiotic suppressive therapy due to persistent clinical signs of infection.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_17 | Pages 92 - 92
1 Dec 2018
Wouthuyzen-Bakker M Sebillotte M Lomas J Taylor A Palomares EB Murillo O Parvizi J Shohat N Reinoso JC Sánchez RE Fernandez-Sampedro M Senneville E Huotari K Allende JB Garcia-Cañete J Lora-Tamayo J Ferrari MC Vaznaisiene D Yusuf E Aboltins C Trebse R Salles M Benito N Vila A Del Toro MD Kramer T Petershof S Diaz-Brito V Tufan ZK Sanchez M Arvieux C Soriano A
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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.

Method

Patients diagnosed with late acute PJI between 2005 and 2015 were retrospectively evaluated. Late acute PJI was defined as the development of acute symptoms (≤ 3 weeks) occurring ≥ 3 months after arthroplasty. Failure was defined as: i) the need for implant removal, ii) infection related death, iii) the need for suppressive antibiotic therapy due to persistent signs of infection and/or iv) relapse or reinfection during follow-up.


The Bone & Joint Journal
Vol. 100-B, Issue 8 | Pages 1125 - 1132
1 Aug 2018
Shohat N Foltz C Restrepo C Goswami K Tan T Parvizi J

Aims

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

Patients and Methods

This retrospective study analyzed data on 12 978 patients (1361 with two operations) who underwent orthopaedic surgery at a single institution between 2001 and 2017. Patients with a minimum of either two postoperative measurements of blood glucose levels per day, or more than three measurements overall, were included in the study. Glycaemic variability was assessed using a coefficient of variation (CV). The length of stay (LOS), in-hospital complications, and 90-day readmission and mortality rates were examined. Data were analyzed with linear and generalized linear mixed models for linear and binary outcomes, adjusting for various covariates.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_10 | Pages 6 - 6
1 Jun 2018
Parvizi J
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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.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_10 | Pages 130 - 130
1 Jun 2018
Parvizi J
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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.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_22 | Pages 33 - 33
1 Dec 2017
Siddiqi A Restrepo C Parvizi J
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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.

Methods

The institutional database was used to identify all patients treated at our institution between 2000 – 2015 for PJI according to the latest MSIS criteria. There were a total of 864 patients with mean age of 68 years. Synovial fluid sample and/or deep tissue samples were analyzed and cultured in all of these patients. In 371 (42.9%) patients with PJI, blood cultures were also taken. Statistical analyses were performed for correlation purposes.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_7 | Pages 126 - 126
1 Apr 2017
Parvizi J
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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.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_7 | Pages 58 - 58
1 Apr 2017
Parvizi J
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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.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_7 | Pages 40 - 40
1 Apr 2017
Parvizi J
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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.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_7 | Pages 50 - 50
1 Apr 2017
Parvizi J
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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.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_5 | Pages 22 - 22
1 Mar 2017
Mirghasemi S Rasouli M Maltenfort M Rashidinia S Parvizi J
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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.

Methods

Pubmed database was searched from 1979 to 2013 for English-language studies that compared the outcomes of each surgical approach. Comparison was carried out on unilateral TKA and two-staged BTKA as well as on different time intervals in two-staged BTKA.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_5 | Pages 23 - 23
1 Mar 2017
Mirghasemi S Maltenfort M Tabatabaee R Rasouli M Rashidinia S Parvizi J
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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.

Methods

Pubmed and Scopus databases were searched from 2000 to 2013 for English-language studies that compared the outcomes of total hip or knee arthroplasty between different body mass index (BMI) groups. Data from these studies were pooled and analyzed.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_22 | Pages 28 - 28
1 Dec 2016
Parvizi J
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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.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_22 | Pages 56 - 56
1 Dec 2016
Parvizi J
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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.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_23 | Pages 57 - 57
1 Dec 2016
Rezapoor M Tan T Maltenfort M Chen A Parvizi J
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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.

Method

A total of 96 patients undergoing open joint preservation procedure of the hip were enrolled in this prospective, randomized clinical trial of iodophor-impregnated adhesive drapes*. One half of patients (n=48) had iodophor-impregnated adhesive drapes* applied to the skin prior to incision and kept on throughout the procedure, while the other half (n=48) underwent the same surgery without the use of iodophor-impregnated adhesive drapes*. Culture swabs were taken from the surgical site at five different time points during surgery (pre-skin preparation, after skin preparation, post-incision, before subcutaneous closure, and prior to dressing application) and sent for culture and colony counts. Mixed-effects and multiple logistic regression analyses were utilized.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_17 | Pages 84 - 84
1 Nov 2016
Parvizi J
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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.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_17 | Pages 110 - 110
1 Nov 2016
Parvizi J
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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.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_5 | Pages 55 - 55
1 Feb 2016
Grupp R Otake Y Murphy R Parvizi J Armand M Taylor R
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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.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_3 | Pages 3 - 3
1 Jan 2016
MacDonald D Baykal D Underwood R Malkani AL Parvizi J Kurtz SM
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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 1st-generation annealed HXLPE with respect to in vivo duration, clinical wear rates, oxidation, and mechanical properties.

Materials and Methods

103 1st-generation annealed HXLPE liners were collected at revision surgery. 39 annealed HXLPE liners were selected based on their implantation time and assigned to three equally sized cohorts (n=13 per group); short-term (1.4–2.7y), intermediate term (5.2–8.0y) and long-term (8.3–12.5y). From each retrieved liner, two 9-mm cores were obtained (one from the superior region and one from the inferior region). Sixteen cores were fabricated from unimplanted HXLPE liners that were removed from their packaging and six pins from unirradiated GUR 1050 resin served as positive controls. Multidirectional POD wear testing was conducted against wrought CoCr disks in a physiologically relevant lubricant (20 g/L protein concentration) using a 100-station SuperPOD (Phoenix Tribology, UK). Each pin had its own chamber with 15mL lubricant maintained at 37±1°C. An elliptical wear pattern with a static contact stress of 2.0 MPa was employed. Testing was carried out to 1.75 million cycles at 1.0 Hz and wear was assessed gravimetrically. POD wear rates were calculated using a linear regression of volumetric losses. In vivo penetration was measured directly using a calibrated micrometer. Oxidation was assessed on thin films obtained from superior and inferior regions of the liners (ASTM 2102). Mechanical properties were assessed using the small punch test (ASTM 2183).


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_3 | Pages 4 - 4
1 Jan 2016
MacDonald D Clarkin-Wright G Parvizi J Lee G Klein G Rimnac C Gilbert J Kurtz S
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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.

Materials and Methods

Between 2001 and 2014, 35 sleeved ceramic heads were collected during revision surgery as part of a multi-center retrieval program. The sleeves were all fabricated from titanium alloy and manufactured by 4 companies (CeramTec (n=14), Smith & Nephew (Richards, n=11), Stryker (n=5), and Zimmer (n=5)). The femoral heads were made from 3 ceramics (Alumina (n=7), Zirconia (n=11), and Zirconia-toughened Alumina (n=17)). Sleeve dimensions (length and thickness) were measured using calibrated calipers. Fretting corrosion of the sleeves and available associated stems was scored using a 4-point, semi-quantitative scoring system [4], with 1 being little-to-no damage, and 4 corresponded to severe fretting corrosion. Five sleeves could not be extracted; thus the external surface was not scored.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_2 | Pages 28 - 28
1 Jan 2016
Hanzlik J Day J Levine HB Klein GR Hartzband M Parvizi J Kraay M Rimnac C Kurtz S
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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.

Methods

126 porous tantalum acetabular shells and 7 femoral stems, were collected under an IRB-approved multicenter retrieval program. Acetabular shells that were grossly loose, cemented or complex revisions were excluded. Shells with visible bone on the surface were chosen. 20 acetabular shells (10 primary) and all femoral stems were dehydrated, embedded, sectioned, polished and bSEM imaged (Figure-1). Main shell revision reasons were infection (n=10,50%), femoral loosening (n=3,15%) and instability (n=3,15%). Analyzed implants were implanted for 2.3±1.7 years (shells) and 0.3±0.3 years (stems). Eight slices per shell and 5–7 slices per stem were analyzed. The analysis included bone area/pore area (BA/PA), BA/PA zonal depth analysis, extent of ingrowth and maximum depth of bone ingrowth. BA/PA zone depths were: Zone-1 (0–500um), Zone-2 (500–1000um) and Zone-3 (1000um-full depth). Nonparametric statistical tests investigated differences in bone measurements by location within an implant and implant type (Friedman's Variance and Kruskal-Wallis). Post-hoc Dunn tests were completed for subsequent pairwise comparisons. Spearman's rank correlation identified correlations between bone measurements and patient related variables (implantation time, age, height, weight, UCLA Activity Score). Statistical analyses were performed using PASW Statistics package.


The Bone & Joint Journal
Vol. 98-B, Issue 1_Supple_A | Pages 18 - 22
1 Jan 2016
Heller S Rezapoor M Parvizi J

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.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_2 | Pages 132 - 132
1 Jan 2016
MacDonald D Kurtz SM Kocagoz S Hanzlik J Underwood RJ Gilbert J Lee G Mont M Kraay M Klein GR Parvizi J Day J Rimnac C
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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?

Methods

100 femoral head-stem pairs were analyzed for evidence of fretting and corrosion. A matched cohort design was employed in which 50 ceramic head-stem pairs were matched with 50 CoCr head-stem pairs based on implantation time, lateral offset, stem design and flexural rigidity. Fretting corrosion was assessed using a semi-quantitative scoring scale where a score of 1 was given for little to no damage and a score of 4 was given for severe fretting corrosion. The head and trunnion taper angles were measured using a roundness machine (Talyrond 585, Taylor Hobson, UK). Taper angle clearance is defined as the difference between the head and trunnion taper angles.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_1 | Pages 26 - 26
1 Jan 2016
Arnholt C Kocagoz S MacDonald D Gilbert J Parvizi J Malkani AL Klein GR Kraay M Rimnac C Kurtz S
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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.

Methods

1873 retrieved TKA components were collected from 2002–2013 as part of a multi-center, IRB-approved retrieval program. Of these, 52 CoCr femoral condyles were identified as long term TKA (Average: 17.9±2.8y). These components were predominantly revised for loosening, PE wear and instability. 40/52 of the components were primary surgeries. Components were examined using optical microscopy to confirm the presence of 5 damage mechanisms (polyethylene failure, MACC corrosion of modular tapers, corrosion damage between cement and backside, third-body wear, and ICIC). Third-body wear was evaluated using a semi-quantitative scoring method based on the percentage of damaged area. A score of 1 had minimal damage and a score of 4 corresponded to severe damage. Polyethylene components were scored using the Hood method and CoCr components were scored similarly to quantify metal wear. The total area damaged by ICIC was quantified using photogrammetry. Images were taken using a digital SLR with a calibrated ruler in the same focal plane. Using known pixel dimensions, the ICIC damaged area was calculated.


Orthopaedic Proceedings
Vol. 97-B, Issue SUPP_16 | Pages 53 - 53
1 Dec 2015
Tan T Manrique J Gomez M Chen A Parvizi J
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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.


Orthopaedic Proceedings
Vol. 97-B, Issue SUPP_16 | Pages 58 - 58
1 Dec 2015
Tan T Maltenfort M Chen A Shahi A Madden A Parvizi J
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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.


Orthopaedic Proceedings
Vol. 97-B, Issue SUPP_16 | Pages 59 - 59
1 Dec 2015
Tan T Springer B Parvizi J Chen A
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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.


Orthopaedic Proceedings
Vol. 97-B, Issue SUPP_16 | Pages 56 - 56
1 Dec 2015
Shahi A Tan T Chen A Maltenfort M Parvizi J
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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.


Orthopaedic Proceedings
Vol. 97-B, Issue SUPP_16 | Pages 55 - 55
1 Dec 2015
Gomez M Manrique J Tan T Chen A Parvizi J
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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.


Orthopaedic Proceedings
Vol. 97-B, Issue SUPP_1 | Pages 116 - 116
1 Feb 2015
Parvizi J
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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.


Orthopaedic Proceedings
Vol. 97-B, Issue SUPP_1 | Pages 107 - 107
1 Feb 2015
Parvizi J
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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.

Methods:

A computerised literature search was conducted to identify all citations, between 1966 to 2005, concerning BTKA. All the English-language abstracts were obtained. A multistage assessment was then used to identify articles fulfilling the inclusion criteria for the study. All randomised, prospective studies reporting the outcome of BTKA were included. Details of any reported data were extracted and extensive analysis of relevant variables carried out.


Orthopaedic Proceedings
Vol. 96-B, Issue SUPP_12 | Pages 27 - 27
1 Jul 2014
Parvizi J
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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.

Methods

A computerised literature search was conducted to identify all citations, between 1966 to 2005, concerning BTKA. All the English-language abstracts were obtained. A multistage assessment was then used to identify articles fulfilling the inclusion criteria for the study. All randomised, prospective studies reporting the outcome of BTKA were included. Details of any reported data were extracted and extensive analysis of relevant variables carried out.


Orthopaedic Proceedings
Vol. 96-B, Issue SUPP_8 | Pages 29 - 29
1 May 2014
Parvizi J
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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.


The Bone & Joint Journal
Vol. 96-B, Issue 5 | Pages 569 - 573
1 May 2014
Sullivan MP McHale KJ Parvizi J Mehta S

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.