Introduction. Instability continues to be the number one reason for revision in primary total hip arthroplasty (THA). Commonly, impingement precedes dislocation, inducing a levering out the prosthetic head from the liner. Impingement can be prosthetic, bony or soft tissue, depending on component positioning and anatomy. The aim of this virtual study was to investigate whether bony or prosthetic impingement occurred first in well positioned THAs, with the hip placed in deep flexion and hyperextension. Methods. Twenty-three patients requiring THA were planned for a TriFit/Trinity ceramic-on-poly cementless construct using the OPS. TM. dynamic planning software (Corin, UK). The cups were sized to best fit the anatomy, medialised to sit on the acetabular fossa and orientated at 45° inclination and 25° anteversion when standing. Femoral components and head lengths were then positioned to reproduce the native anteversion and match the contralateral leg length and offset. The planned constructs were flexed and internally rotated until anterior impingement occurred in deep flexion [Fig. 1]. The type (bony or prosthetic), and location, of impingement was then recorded. Similarly, the hips were extended and externally rotated until posterior impingement occurred, and the type and location of impingement recorded [Fig. 2]. Patients with minimal pre-operative osteophyte were selected as a best-case scenario for bony impingement. Results. 6/23 (26%) patients were planned with only a 32mm articulation (<50mm cup size), with the remaining 17 patients all planned with both 32mm and 36mm articulations (≥50mm cup size). Anterior impingement was 26% prosthetic and 74% bony with the 32mm articulations, and 100% bony with the 36mm articulations. Bony impingement in deep flexion was exclusively anterior neck on anterior inferior iliac spine. Posterior impingement was 57% prosthetic and 43% bony with the 32mm articulations, and 41% prosthetic and 59% bony with the 36mm articulations. Bony impingement in hyperextension was exclusively lesser trochanter (LT) on ischium. Of the patients planned with both 32mm and 36mm articulations, there was a 14% increase in prosthetic impingement when a 32mm head was planned (35% and 21% respectively). Discussion. Impingement in THA usually precedes dislocation and should be avoided with appropriate component positioning. We found that in hyperextension, prosthetic and bony impingement were equally common. In deep flexion, impingement was almost exclusively bony. Further studies should investigate the effects of stem version, cup orientation, liner design, cup depth, native offset and retained osteophytes on the type of impingement in THA. For any figures or tables, please contact the authors directly

Aim. metagenomic next-generation sequencing (mNGS) has shown to be a useful method for pathogen detection in prosthetic joint infections (PJI). The technique promises to minimize the PJIs without the known causative agent. Our study aimed to compare diagnostic accuracies of cultures and mNGS. Method. In this study, a meta-analysis following PRISMA recommendations was performed. PubMed and OVID Medline databases were used for article search. The studies using mNGS whole-genome sequencing method and the ones where PJI diagnosis was based on one of the currently recognized criteria were included. Studies were excluded if they comprised less than twenty cases, the ones with insufficient data for the analyses (true positive, true negative, false positive and false negative values for both mNGS and culture results) and publications with strong duplication bias. Univariate metanalysis using a random-effect model has been performed in R studio with a “meta” package. Pooled sensitivity and pooled specificity were calculated. Results. Seven studies with a total of 822 cases were included in the meta-analysis, 476 cases defined as PJI and 346 controls. Two studies used IDSA (Infectious Diseases Society of America) diagnostic criteria and the Illumina HiSeq 2500 platform for sequencing and five studies used MSIS (MusculoSkeletal Infection society). Four of those used the BGISEQ-500 sequencing platform. For one study there was no data available. Studies were performed on prosthetic hip and knee joints. Through meta-analysis, it was observed that mNGS technique is more sensitive than cultures with 90% (CI 79%– 95%) and 74% (CI 68%-79%) respectively (p=0.006). The specificity between methods was similar, for mNGS reaching 94% (CI 89%-96%) and for cultures 97% (CI 90%-99%) (p=0.285). In the PJI group, 117 new possible pathogens that were not isolated by microbiological culture were detected by the mNGS, most frequently anaerobes and coagulase-negative staphylococci both in 20/117 (17.1%) cases. Fourteen new organisms were detected in the control group and were mostly regarded as contaminants. Conclusions. Metagenomic sequencing has shown to be more sensitive than microbiological cultures in pathogen detection and thus has a great potential to improve the diagnosis and treatment of PJI. More studies on different prosthetic joints and comparing different diagnostic criteria for PJI would be needed to better understand the true diagnostic power of this method

Aim. As the populations of patients who have multiple prosthetic joints increase these years, the fate of a single joint periprosthetic joint infection in these patients is still unknown. Risk factors leading to a subsequent infection in another prosthetic joint are unclear. Our goal is to identify the risk factors of developing a subsequent infection in another prosthetic joint and describe the organism profile to the second prosthetic infection. Method. We performed a retrospective cohort study of all PJI cases underwent surgical intervention at our institute, a tertiary care referral center over 11 years, during January 2006 to December 2016. We identified 96 patients with periprosthetic joint infection who had another prosthetic joint in place at the time of presentation. The comorbidity, number of prosthetic joints, date and type of each arthroplasty, times of recurrent infection at each prosthetic joint with subsequent debridement or 2-stage resection arthroplasty, organisms from every infection episode, the outcome of each periprosthetic joint infection in these patients were analyzed. Results. During January 2006 to May 2017, we retrospective collected 294 PJI cases (159 hips, 135 knees) in our institute. Patients with single prosthetic joint were excluded and finally 96 patients were included. Of the 96 patients, 19 (19.79%) developed a periprosthetic joint infection in a second joint. The type of organism was the same as the first infection in 12 (63.16%) of 19 patients. The time to developing a second infection averaged 2.16 years (range, 0–9.3 years). The risk factors leading to a subsequent infection in another prosthetic joint are albumin level (< 3.5 mg/dl), long-term steroid usage (> 5mg/day, > 3 months), history of necrotizing fasciitis, history of invasive dental procedure (> Grade IV procedure), 3-stage resection arthroplasty or more, and PJI caused by vacomycin-resistent enterococcus (VRE). Conclusions. A PJI might predispose patients to subsequent PJI in another prosthesis. Patients and surgeons must be aware of the risk factors contribute to this devastating complication. Most organisms in the second PJI are identical to the first one, and we believe the bacteremia may be the pathogenesis, but need further proved. The preventive policy may be needed in the future for this population who has multiple prosthetic joints

Background. The current use of a spherical prosthetic humeral head in total shoulder arthroplasty results in an imprecise restoration of the native geometry and improper placement of the center of rotation, maintained in a constant position, in comparison to the native head and regardless of glenoid component conformity. A radially-mismatched spherical head to allow gleno-humeral translation is a trade-off that decreases the contact area on the glenoid component, which may cause glenoid component wear. This finding suggests that the use of a non-spherical head with a more conforming glenoid component may reduce the risk of glenoid component wear by allowing gleno-humeral translation while increasing the contact area. A non-spherical prosthetic head more accurately replicates the head shape, rotational range of motion and gleno-humeral joint kinematics than a spherical prosthetic head, compared with the native humeral head. The combination of inversion of the bearing materials with the non-spherical configuration of the humeral head may thus decrease polyethylene wear. Aim of the present study is to evaluate in vitro wear behaviour of an all-polyethylene elliptical humeral head component against a metallic glenoid component in an anatomic configuration. Material and methods. The prosthetic components tested are from the Mirai. ®. Modular Shoulder System by Permedica S.p.A.. The prosthetic bearing components were tested in their anatomic configuration: the humeral head rubbing against the glenoid inlay, assembled over the glenoid base-plate. The glenoid insert is made of Ti6Al4V alloy coated with TiNbN. The glenoid insert, as the glenoid base-plate have the same shape which reproduce the native shape of the glenoid. Moreover, the glenoid insert has a concave articular surface described by two different radii on orthogonal planes. The vitamin E-blended UHMWPE humeral head is not spherical but elliptic-shaped with an articular surface described by two different profiles in sagittal and coronal plane. The component sizes combination tested have the greatest radial mismatches allowed between humeral head and glenoid insert. The test was performed up to 2.5 million of cycles applying a constant axial load of 756 N. Results. After 2.500.000 cycles the mean mass loss from the humeral head was 0.68 mg. The mean wear rate of the humeral head was 0.28 mg/Mc (SD 0.45 mg/Mc). The surface of the humeral heads showed an elliptical worn area with matt and polished areas with scratching. The surface of the TiNbN-coated glenoid insert counterparts did not show wear signs. Conclusion. The tested prosthetic humeral head has a non-spherical shape with an elliptical base and 2 different radii on sagittal and coronal plane. Also the tested glenoid insert has 2 different radii on sagittal and coronal planes. This components geometry leads to a radial mismatch between head and glenoid on sagittal and coronal planes. A different kinematics, allowing gleno-humeral translation while increasing the contact area, radial mismatch in different planes and the inversion of bearing materials may have a role in reducing component wear and may explain the extremely low wear rate found in the present study

Introduction. Roentgen stereophotogrammetric analysis (RSA) is currently the gold standard to measure early prosthetic migration which can predict aseptic loosening. However, RSA has some limitations such as the need for perioperative placed markers and exposure to X-radiation during follow up. Therefore, this study evaluates if low field MRI could be an alternative for RSA. Low field MRI was chosen because it is less hampered by metal artifacts of the prosthesis than high field MRI. Methods. 3D models of both the tibial component of a total knee prosthesis (Genesis II, Smith and Nephew) and the porcine tibia were made. The tibial component was implanted in the tibial bone. Consequently, 17 acquisitions with the low field MRI scanner (Esaote G-scan 0.25T) in transverse direction with a 2D PD weighted metal artifact reducing sequence PD-XMAR (TE/TR 10/1020ms, slice thickness 3mm, FOV 180×180×120 mm³, matrix size 224×224) were made. The first five acquisitions were made without repositioning the cadaver, the second twelve after slightly repositioning the cadaver within limits that are expected to be encountered in a clinical setting. Hence, in these 17 acquisitions no prosthetic-bone motions were induced. The scans were segmented and registered with Mimics. Virtual translation and rotation of the prosthesis with respect to the bone between two scans were calculated using a Procrustes algorithm. The first five scans without repositioning were used to calculate the measurement error, the following twelve to calculate the precision of low field MRI to measure prosthetic migration. Results were expressed as the maximum total point motion, mean error and 95% CI and expressed in boxplots. Results. The error of the method to measure the prosthetic position without repositioning has a mean translation between 0.09 and 0.22mm with a 95%CI between 0.30 and 0.46mm. The mean rotation was between 0.02° and 0.11° with a 95%CI between 0.18° and 0.32° with a MTPM of 0.45mm. The precision of low field MRI to measure migration with repositioning has a mean translation between 0.02 and 0.12mm with a 95%CI between 1.16mm and 1.86mm. The mean rotation was between 0.01° and 0.15° with a 95%CI between 1.78° and 3.26° with a MTPM of 2.35mm. The overall registration error was largest in the distal-proximal direction. Discussion. At the moment the low field MRI technique is not as accurate as this gold standard RSA. The accuracy of RSA varies between 0.05 and 0.5 mm for translation and 0.15 ° to 1.15 ° for rotation (95% confidence intervals). However, results are comparable with markerless RSA studies. The largest measurement error was found in the distal-proximal direction, which can be explained by the through-plane resolution of 3 mm, which is larger than the in-plane resolution of 0.8×0.8 mm². Future research should focus on improving resolution in the distal-proximal direction which would improve the precision. Moreover, an actual migration study should be performed to proof the true value of this low field MRI base markerless and X-radiation free alternative to measure prosthetic migration

Aim. Prompt recognition and identification of the causative microorganism in acute septic arthritis of native and prosthetic joints is vital to increase the chances of successful treatment. The aim of this study was to independently assess the diagnostic accuracy of the multiplex BIOFIRE® Joint Infection (JI) Panel (investigational use only) in synovial fluid for rapid diagnosis. Method. Synovial fluid samples were prospectively collected at the University Medical Center Groningen from patients who had a clinical suspicion of a native septic arthritis, early acute (post-operative, within 3 months after arthroplasty) periprosthetic joint infection (PJI) or late acute (hematogenous) PJI. JI Panel results were compared to culture-based methods as reference standard. Results. A total of 45 samples were analyzed. The BIOFIRE JI Panel showed a high specificity (100%, 95% CI 73 – 100) and positive predictive value (100%, 95% CI 79 – 100) in all patient categories. Sensitivity and negative predictive value were 83% (95% CI 36 – 99) and 88% (95% CI 47 – 99) respectively for patients with a clinical suspicion of native septic arthritis (n=12), 77% (95% CI: 46 – 94) and 63% (95% CI: 26 – 90) for patients with a clinical suspicion of a late acute PJI (n=14), and 27% (95% CI 7 – 61) and 27% (95% CI: 7 – 61) for patients with a clinical suspicion of an early acute PJI (n=19). Conclusions. The results of this pilot study indicate a clear clinical benefit of the BIOFIRE JI Panel in patients with a suspected native septic arthritis and late acute (hematogenous) PJI, but a low clinical benefit in patients with an early acute (post-operative) PJI due to the absence of low-grade microorganisms in the panel

Introduction. The objective of our study was to determine the extent to which the quality of the biomechanical reconstruction when performing hip replacement influences gait performances. We aimed to answer the following questions: 1) Does the quality of restoration of hip biomechanics after conventional THR influence gait outcomes? (question 1), and 2) Is HR more beneficial to gait outcomes when compared with THR? (question 2). Methods. we retrospectively reviewed 52 satisfied unilateral prosthetic hip patients (40 THRs and 12 HRs) who undertook objective gait assessment at a mean follow-up of 14 months. The quality of the prosthetic hip biomechanical restoration was assessed on standing pelvic radiograph by comparison to the healthy contralateral hip. Results. We were unable to detect any statistically significant correlation between the radiographical parameters and the gait data, for THR patients. In stress conditions (inclination or declination of the ramp), the gait was more symmetric in the HR group, compared to the THR group. Discussion/Conclusions. We found that slight variations in the quality of the hip biomechanical restoration had little effect on gait outcomes of THR patients, and HR generated a more physiological gait under stress conditions than well-functioning THR

Aim. The incidence of prosthetic joint infections can be severe to monitor, as they are rare events. Recent publications from National registries points toward a significant underestimation of reported infections. The aim of this project was to develop a complication register that could report the “true” and momentaneous incidence of prosthetic infections after total knee and hip arthroplasty. Method. All patients operated with total hip arthroplasty (THA) or total knee arthroplasty (TKA) at our hospital were included in a local quality registry. All complications were reported at follow-up at 2 and 3 months for total knee and hip arthroplasties respectively, and at 1-year follow up. Both primary and revision surgeries were included. In order to monitor complications of special interest, such as deep postoperative infections, key variables were presented in a g-chart. This chart shows the number of uncomplicated surgeries between each complication (such as infection) in a bar diagram. This diagram is easily read as high bars indicate a low incidence of complications and low bars indicate a high incidence. The diagram is updated and distributed for information every month. Results. From September 2010 till December 2015 we included 2093 primary total hip arthroplasties and 272 hip revisions. The overall incidence for prosthetic infection after primary THA within 1 year after surgery was 1.8% and for hip revisions 3.4%. The momentaneous incidence in December 2015 was 3% for both primary and revision THA together. In the same period 1555 total knee arthroplasties and 155 knee revisions were included. The overall incidence of prosthetic infection after primary TKA within 1 year after surgery was 1.2% and for knee revisions 2.2%. The momentaneous incidence in December 2015 was 2.5% for primary and revision TKA together. Conclusions. Reporting the number of uncomplicated surgeries between every unwanted event or complication, such as postoperative infections, is a good method for describing rare events. This method will reveal changes in the trend at an earlier stage and can be an important tool in the work on preventing postoperative infections. A local quality register can be important in order to report a “true” incidence of postoperative infections, as the risk of underestimation is lower than in a national registry

Collection of 4–5 independent peri-prosthetic tissue samples is recommended for microbiological diagnosis of prosthetic joint infections. Sonication of explanted prostheses has also been shown to increase microbiological yield in some centres. We compared sonication with standard tissue sampling for diagnosis of prosthetic joint and other orthopaedic device related infections. We used standard protocols for sample collection, tissue culture and sonication. Positive tissue culture was defined as isolation of a phenotypically indistinguishable organism from ≥2 samples; and positive sonication culture as isolation of an organism at ≥50 cfu/ml. We compared the diagnostic performance of each method against an established clinical definition of infection (Trampuz 2011), and against a composite clinical and microbiological definition of infection based on international consensus (Gehrke & Parvizi 2013). 350 specimens were received for sonication, including joint prostheses (160), exchangeable components (76), other orthopaedic hardware and cement (104), and bone (10). A median of 5 peri-prosthetic tissue samples were received from each procedure (IQR 4–5). Tissue culture was more sensitive than sonication for diagnosis of prosthetic joint and orthopaedic device related infection using both the clinical definition (66% versus 57%, McNemar's Χ2 test p=0.016) and the composite definition of infection (87% vs 66%, p<0.001). The combination of tissue culture and sonication provided optimum sensitivity: 73% (95% confidence interval 65–79%) against the clinical definition and 92% (86–96%) against the composite definition. Results were similar when analysis was confined to joint prostheses and exchangeable components; other orthopaedic hardware; and patients who had received antibiotics within 14 days prior to surgery. Tissue sampling appears to have higher sensitivity than sonication for diagnosis of prosthetic joint and orthopaedic device infection at our centre. This may reflect rigorous collection of multiple peri-prosthetic tissue samples. A combination of methods may offer optimal sensitivity, reflecting the anatomical and biological spectrum of prosthetic joint and other device related infections

INTRODUCTION. The hip arthroplasty implant is currently growing up both in orthopedic and trauma practice. This increases the frequency of prosthesis revision due to implant loosening often associated with periprosthetic osteolysis that determine the failure and lead to a loss of bone substance. Nowadays there are numerous biotechnologies seeking to join or substitute the autologous or omologous bone use. These biotechnologies (mesenchymal stromal cells, growth factors and bone substitutes) may be used in such situations, however, the literature doesn't offer class 1 clinical evidences in this field of application. MATERIALS AND METHODS. We performed a literature review using the universally validated search engines in the biomedical field: PubMed / Medline, Google Scholar, Scopus, EMBASE. The keywords used were: “Growth Factors”, “Platelet Rich Plasma”, “OP-1”, “BMP”, “BMP-2”, “BMP-7”, “Demineralized Bone Matrix”, “Stem Cell”, “Bone Marrow”, “Scaffold”, “Bone Substitutes” were crossed with “hip”, “revision”, “replacement” / “arthroplasty”, “bone loss” / “osteolysis.”. RESULTS. The search led to 321 items, of these were considered relevant: as regards the growth factors 21 articles related to in vivo animal studies and 2 articles of human clinical use of BMPs and 1 single article on the use of PRP; as regards the mesenchymal stromal cells 2 items of application in animals; as regards the use of bone substitutes we have analyzed a review of this application. DISCUSSION. The use of biotechnologies in hip prosthetic revisions has produced conflicting results: autologous growth factors (PRP) have definitely been proven effective in maxillofacial surgery, in animal studies the results of BMPs are inconsistent with articles that validate their use and others that don't recommend it. Clinical application has demonstrated, today, the limited use of BMP-7 in revisions with even an increased risk of early re-mobilization, PRP appears to be rather effective only in the early stages of peri-prosthetic osteolysis. The mesenchymal cells can increase the chances of recovery and integration of the grafts but an important variable is the number of cells that are still alive after the impaction of the graft which affects their vitality. The bone substitutes appear to be safe and very useful, particularly if applied in order to implement the omologous bone, which is still the most scaffolds used in this surgery. CONCLUSIONS. The systematic review of the literature has shown an important lack of clinical studies regarding the use of biotechnologies for prosthetic revisions. It is therefore difficult to draw guidelines that regulate the application, prospective randomized clinical studies are therefore needed to validate its effectiveness

INTRODUCTION. The hip arthroplasty implant is currently growing up both in orthopedic and trauma practice. This increases the frequency of prosthesis revision due to implant loosening often associated with periprosthetic osteolysis that determine the failure and lead to a loss of bone substance. Nowadays there are numerous biotechnologies seeking to join or substitute the autologous or omologous bone use. These biotechnologies (mesenchymal stromal cells, growth factors and bone substitutes) may be used in such situations, however, the literature doesn't offer class 1 clinical evidences in this field of application. MATERIALS AND METHODS. We performed a literature review using the universally validated search engines in the biomedical field: PubMed / Medline, Google Scholar, Scopus, EMBASE. The keywords used were: “Growth Factors”, “Platelet Rich Plasma”, “OP-1”, “BMP”, “BMP-2”, “BMP-7”, “Demineralized Bone Matrix”, “Stem Cell”, “Bone Marrow”, “Scaffold”, “Bone Substitutes” were crossed with “hip”, “revision”, “replacement” / “arthroplasty”, “bone loss” / “osteolysis.”. RESULTS. The search led to 321 items, of these were considered relevant: as regards the growth factors 21 articles related to in vivo animal studies and 2 articles of human clinical use of BMPs and 1 single article on the use of PRP; as regards the mesenchymal stromal cells 2 items of application in animals; as regards the use of bone substitutes we have analyzed a review of this application. DISCUSSION. The use of biotechnologies in hip prosthetic revisions has produced conflicting results: autologous growth factors (PRP) have definitely been proven effective in maxillofacial surgery, in animal studies the results of BMPs are inconsistent with articles that validate their use and others that don't recommend it. Clinical application has demonstrated, today, the limited use of BMP-7 in revisions with even an increased risk of early re-mobilization, PRP appears to be rather effective only in the early stages of peri-prosthetic osteolysis. The mesenchymal cells can increase the chances of recovery and integration of the grafts but an important variable is the number of cells that are still alive after the impaction of the graft which affects their vitality. The bone substitutes appear to be safe and very useful, particularly if applied in order to implement the omologous bone, which is still the most scaffolds used in this surgery. CONCLUSIONS. The systematic review of the literature has shown an important lack of clinical studies regarding the use of biotechnologies for prosthetic revisions. It is therefore difficult to draw guidelines that regulate the application, prospective randomized clinical studies are therefore needed to validate its effectiveness

Infection after total hip arthroplasty is a rare but potentially devastating complication. The most common pathogens responsible for these infections are gram positive bacteria. Infection caused by fungi is uncommon. There are few reports of prosthetic joint infection caused by Candida species, and there has no report of implant preservation. We experienced the case of a patient with Candida arthritis who underwent total hip arthroplasty for hip arthrosis, and successfully could preserved prosthetic joint. A 60 year-old woman underwent total hip arthroplasty in September 2014. She had had the past of sepsis by the Candida after surgery of the duodenal cancer. After four weeks in total hip arthroplasty, she made clinic visits. Her chief complaints were low-grade fever of 1 week's duration and discharge from operative scar for THA. The patient underwent arthrocentesis of the left hip. The culture was positive for Candida tropicalis. Operation of surgical debridement and liner change was performed as soon as possible. After operation, the patient was treated with fluconazole intravenously for 28 days. She has continued to taken fluconazole by mouth. Reactivation of infection have not been in her left hip. We reported the case of a patient with Candida arthritis who underwent total hip arthroplasty. Prosthetic joint could have preserved because of early detection for infection. This is the first report of preservating implant after Candida infection in total hip arthroplasty

Reverse total shoulder arthroplasty was developed to address the treatment of patients with Cuff Tear Arthropathy. Despite of the clinical improvements seen with initial reverse shoulder replacements, several mechanical problems remain. Scapular notching has been reported between 24.5% and 96% of cases. Patients have also exhibited limited external rotation, either from impingement or slackening of remaining cuff musculature. Additionally, by medializing and moving the humerus distally, patients note a loss of the normal deltoid contour leading not only to cosmetic concerns, but possibly decreasing deltoid efficiency and creating a prosthesis with less inherent stability. Finally, although mechanical failure on the glenoid side initially was thought to be uncommon, various glenoid sided problems have been reported. Recognition of these problems led to clinical and basic science studies aimed at improving surgical technique and the design of reverse shoulder implants. During the last 10 years, our institution has been conducting biomechanical research examining the forces across the glenohumeral joint. Several different models have been created to replicate mechanical failures by integrating biomechanical information with our clinical investigations, including altering the position of the implant (tilt), the type of fixation of the implant (screw or peg), and glenoid-sided bone loss. We were able to address glenoid component failure (with initial rates of 10% in our clinical studies) by recommending locking screws to neutralize forces at the fixation site. These discoveries have reduced glenoid-sided fixation failures to less than 0.1%. In vitro kinematic function and factors that affect impingement free glenohumeral motion of reversed implants is another area of interest. The clinical relevance of impingement includes scapular-notching, pain from impingement, instability and excessive prosthetic wear. Several models that include motion in three different planes (flexion-extension, abduction-adduction and internal-external rotation) have been developed to study multiple prosthetic, technique and anatomic factors which can result from varying degrees of impingement. By integrating the results from these models into our clinical practice (e.g., selecting a more lateralized glenosphere, selecting a varus humeral component and inferiorly translating the glenoid component on the glenoid surface), we have been able to maintain low rates of notching (∼10% at 8 year follow-up). Finally, our current work involves development of a model that attempts to understand which factors might be influential in causing instability and stiffness. Thus, biomechanics research offers an excellent opportunity for interdisciplinary collaboration to solve complex clinical problems

Background. Currently, the gold standard for the microbiological diagnosis remains the culturing of preoperative aspirated joint fluid and intraoperative periprosthetic tissue samples, which give false negative results in about 7 % of cases. Lytic bacteriophages are viruses that specifically infect and lyse bacteria within their replication cycle. Aim. The aim of our study was to explore possibilities for the use of bacteriophage K for the detection of live Staphylococcus spp. bacteria in sonicate fluid of infected prosthetic joints, to possibly contribute to the development of a faster, more sensitive, specific and at the same time economical and handy method for the establishment of the right diagnosis. Material and methods. Sonicate fluid samples obtained from 104 patients with revision arthroplasty were analysed. After the optimisation two indirect phage-based methods were used: a) bioluminescence detection of bacterial intracellular ATP released by bacteriophage K mediated lysis and b) q-PCR with primers specific for bacteriophage K DNA. The results were compared with classical microbiological cultivation methods. Results. With both methods the analysis of sonicate fluid and the analysis of its over-night culture achieved 100 % specificity and predictive value, as there were no false positive results. The sensitivity of the methods was lower when analysing sonicate fluid samples directly, without cultivation. The sensitivity of qPCR detection was higher (81.25 %) compared to the sensitivity of ATP detection (62.5 %) in sonicate fluid directly as a result of 3 false negative results with the qPCR method compared to 6 false negatives with the ATP detection method. The sensitivity of the methods was significantly improved (to 94.12 %) with overnight cultivation of sonicate fluid samples prior to analysis, with no difference in detection between the methods. With both methods, with pre-cultivation of sonicate fluid samples, only one of the tested samples resulted in a false negative result. However, the same sample was negative even when tested with standard microbiological methods. In this patient, only the microbiological cultivation of the periprosthetic tissue sample was positive. The bioluminescence method took 3h with a limit of detection (LOD) in the bacterial concentration range of 10. 3. CFU/mL. The method with qPCR took 4h and had a LOD of 10. 2. CFU/mL. Conclusion. Detection of staphylococci within sonicate fluid with bacteriophage K based methods is a rapid, sensitive and specific approach

Prosthetic joint infection continues to remain a diagnostic challenge for unhappy primary arthroplasty of hip and knees. There is increasing dependence upon alpha-defensin test to make key decisions like whether to revise or not & to decide between one-stage versus two-stage. Aim. This study aims to assess diagnostic accuracy of alpha-defensin test in determining prosthetic hip & knee infection and to provide guidance for appropriate use of this novel but expensive investigation. Methods. Retrospective review of all alpha-defensin investigated patients in an orthopaedic institute between February 2015 & March 2017 was performed. Clinical and radiological outcomes including re-infections, re-operations were analysed and alpha-defensin outcomes were compared with that of other available investigations. Results. Of total 52 tests performed (17 hips & 35 knees), 3 were positive. On comparison with intra-operative culture (gold standard), sensitivity is 100%. All suspected prosthetic hip infections have good clinical outcomes following their decisions being made based upon alpha-defensin test. Among the negative knee test results, 6 patients developed signs of infection in the post-operative period, 4 of which have been revised with washout, poly exchange or full revision. Conclusion. No single clinical investigation can accurately predict prosthetic joint infection in revision for suspected infection. Alpha-defensin test, however, is a useful adjunct to intra-operative surgeon's findings & pre-operative investigations to decide for crucial decisions like whether to revise or not & for deciding between single and two stage

Introduction. The limited field of view with less-invasive hip approaches for total hip arthroplasty can make a reliable cup positioning more challenging. The aim of this study was to evaluate the accuracy of cup placement between the traditional transgluteal approach and the anterior approach in a routine setting. Objectives. We asked if the (1) accuracy, (2) precision, and (3) number of outliers of the prosthetic cup orientation differed between three study groups: the anterior approach in supine position, the anterior approach in lateral decubitus position, and the transgluteal approach in lateral decubitus position. Methods. In a retrospective comparative study we compared the inclination and anteversion of the cup after total hip arthroplasty (THA) in a consecutive series of 325 patients (350 hips). The transgluteal approach group consisted of 67 hips operated in lateral decubitus position; the anterior approach in supine position consisted of 127 operated and the anterior approach in lateral decubitus position consisted of 156 hips. The aim of the cup orientation was Lewinnek's safe zone defined by an inclination of 40±10° and an anteversion of 15°±10°. The postoperative cup orientation was determined using a validated computer-assisted method based on statistical shape modeling. This method allows the virtual creation of an accurate three-dimensional pelvic model for each individual patient based on the two-dimensional anteroposterior pelvic radiograph. The inclination and anteversion was then calculated relative to the anterior pelvic plane – a natural reference plane for the calculation of inclination and anteversion. Accuracy was defined as the difference from the cup orientation to Lewinnek's target value. Precision was defined as the standard deviation of the two angles. Outliers were characterized by an anteversion or inclination angle outside of Lewinnek's safe zone. Results. (1) The accuracy of the anterior approach in supine position did not differ compared to the transgluteal approach, but differed to the anterior approach in supine position for inclination (p=0.882; p<0.001) (Figure 1) and anteversion (p = 0.014; p<0.001) (Figure 2). (2) The precision of the anterior approach in supine position was significantly higher compared to the transgluteal approach (p<0.001) and the anterior approach in lateral decubitus position for anteversion (p<0.001 for both groups) and inclination (p<0.001 for both groups) (Figure 3). (3) There was a significantly reduced number of outliers for the anterior approach in supine position compared to the anterior approach in lateral position (p=0.001) but not in comparison to the transgluteal approach (p=0.999) (Figure 2). Conclusions. The anterior approach in supine position results in a more precise placement of the prosthetic cup both for inclination and anteversion. Cup placement with less-invasive approaches does not lead to a higher variability of cup placement despite the more limited surgical field of view. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction. Throughout the world the number of large joint arthroprosthetic implants continues to increase and consequently the number of septic complications with prosthesis mobilizations, periprostehtic bone loss or non-unions. The implant of large resection prosthesis (megaprosthesis) in selected patients could be a good solution both in hip and knee infected prosthesis with bone defects. The two stage techniques with a first operation to debride, prosthesis components removal and antibiotic spacer implantation followed by a subsequent final prosthetic implant offer great results even in highly complex patients. Objectives. The purpose of this study is to evaluate retrospectively the outcome after the implantation of megaprosthesis of the lower limbs in prosthetic infected revision. Methods. We have retrospectively evaluated all the patients we have treated with implantation of megaprosthesis in septic prosthesis revision. Between January 2008 and January 2014 we have treated 25 patients: 18 cases of hip revision and 7 cases of knee revision. All patients were treated with a two steps procedure. Results. We obtained good results from a clinical, laboratory and radiological point of view with restoration of the function of the affected limb in 22/25 cases. In 3/25 cases the infection recurred and an additional surgery was necessary. Conclusions. Megaprosthesis in large septic revision can be considered, in extreme cases appropriately selected, an available solution for the orthopedic surgeon able to restore function to the patient. The two steps procedure gives the best results with safety and lower infection recurrence creating a membrane (Chamber Induction Technique) that can protect the prosthesis in a safe environment. This type of complex surgery must be performed in specialized centers where knowledge and technologies are present

Propionibacteria are organisms of low virulence, although they do cause deep periprosthetic infections. The aim of this study was to show that Propionibacteria do not always cause a significant rise in ESR and CRP. Between May 2001 and May 2004, we identified 77 patients with prosthetic joint replacements colonised with Propionibacteria, 47 males and 30 females. There were 47 hip joint replacements, 27 knee joint replacements, 2 endoprosthetic replacements of the femur and 1 shoulder joint replacement. We retrieved successfully the medical records of 66 patients in order to identify the number of patients treated for an infected prosthetic joint arthroplasty. The pre-operative values of ESR and CRP were recorded. For the purposes of this study, an ESR rate of 30mm/hr or higher and a CRP level of 10mg/lt or higher were considered to be suggestive of infection and were deemed a positive result. All of the 77 patients had both ESR and CRP measured pre-operatively. In only 16 (21%) both ESR and CRP were higher than 30mm/hr and 10mg/l respectively. In 33 patients (43%) with prosthetic joint replacements colonised with Propionibacteria, the pre-operative values of ESR and CRP were normal. 23 patients were treated for an infected prosthetic joint arthroplasty. In 7 (30%) of those patients both ESR and CRP were normal. This suggests that normal pre-operative values of ESR and CRP in suspected failed prosthetic joint replacements might not exclude infection, if the causative organism is of low virulence such as Propionibacteria

Periprosthetic joint infections are one of the most dreaded and complex complications of total joint arthroplasty, with fungal infection accountting for less than 1% of the cases. Treatment is challenging due to the lack of scientific evidence. We report a case of a Candida albicans total hip arthroplasty (THA) infection and performed a review of the literature. We report a case of a 79 year old women with an early THA infection (less of one month) from the primary surgery. She presented with pain and serous drainage from the operative wound and for that was submited to surgical debridement and revision of polyethilene. Cultures where taken (steril) and empirical vancomicin and rifampicin treatment was initiated. Because of persistent complains and drainage, the patient was submitted to another surgery. Cultures were taken at the time of surgery. A cement spacer impregnated with gentamicin was placed after implant removal. Cultures isolated Candida albicans. In light of this new evidence fluconazole was added to the previous scheme. After introduction of fluconazole, the clinical evolution was good. Drainage stoped 1 week after, and the wound closed. The inflammatory markers became normal shortly after. Leg pain became better. The patient was given oral suppressive treatment with fluconazole and was discharged, weight bearing as tolerated. A total of 4 mouths of treatment is programmed with close follow-up, untill the second staged revision is programmed. Prosthetic fungal infections are rare with most of the published articles being case reports. A substantial delay in diagnosis may occur because culture results are sometimes interpreted as contamination and there is a need for obtaining multiple samples, prolonged culture, and special staining. The best results are being reported with a long period of oral antifungal treatment and a two staged joint revision but there is an absence of standardized clinical and evidence-based treatment guidelines

Aim

Prosthetic joint infection (PJI) due to Candida spp. is a severe complication of arthroplasty but is little reported. This study describes Candida PJI epidemiology, management, and outcome.