Aims. The diagnosis of periprosthetic joint infection (PJI) can be difficult. All current diagnostic tests have problems with accuracy and interpretation of results. Many new tests have been proposed, but there is no consensus on the place of many of these in the diagnostic pathway. Previous attempts to develop a definition of PJI have not been universally accepted and there remains no reference standard definition. Methods. This paper reports the outcome of a project developed by the European Bone and Joint Infection Society (EBJIS), and supported by the Musculoskeletal Infection Society (MSIS) and the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Implant-Associated Infections (ESGIAI). It comprised a comprehensive review of the literature, open discussion with Society members and conference delegates, and an expert panel assessment of the results to produce the final guidance. Results. This process evolved a three-level approach to the diagnostic continuum, resulting in a definition set and guidance, which has been fully endorsed by EBJIS, MSIS, and ESGIAI. Conclusion. The definition presents a novel three-level approach to diagnosis, based on the most robust evidence, which will be useful to clinicians in daily practice. Cite this article: Bone Joint J 2021;103-B(1):18–25

Aim. A substantial portion of periprosthetic joint infections (PJI) literature is comprised of observational studies. The Strengthening the Reporting of Observational Studies in Epidemiology guidelines emphasize the importance of clearly defining variables and providing diagnostic criteria. Well-defined variables in these studies play a crucial role in ensuring data consistency, fostering comparability among studies, and laying a robust foundation for evidence-based decision-making. We aimed to determine the definition of these variables and determine the objectivity of the definitions. Method. We reviewed observational studies on hip or knee PJI that focused on variables and their association with treatment outcomes. The inclusion criteria comprised studies from Jan 2017 to Jan 2023. We focused on 13 variables that were possibly subjective. These were smoking, alcohol use, diabetes mellitus, hypertension, lung disease, rheumatoid arthritis, liver diseases, kidney diseases, cardiovascular diseases, malignancy, immunosuppression, use of antibiotics, and type of infection. The reviewers examined the text of the articles, along with any available online supplements or protocols, for definitions of the selected variables. We classified a definition as objective if there was the presence of time element, severity, staging, frequencies, laboratory cut-off, medication dependence, among others. Chart review was deemed subjective. Results. We included 75 studies in the analysis. The most common factors studied were diabetes mellitus (79%), cardiovascular disease, smoking history, and rheumatoid arthritis (47% each). The variables that were objectively defined most often were antibiotic use (100%) and type of infection (95%). Smoking history (16%) and alcohol use (20%) were the least frequently objectively defined variables. Further analysis revealed that a considerable number of studies incorporated variables into their primary analyses without clear definitions. For instance, out of the 59 studies where diabetes was considered a variable, 41 studies (70%) included diabetes in their main analyses as a factor for PJI treatment outcomes, despite only 34 studies having defined this variable. Moreover, of the 34 provided definitions of diabetes mellitus, only 12 provided objective criteria for diagnosis. The rest of the provided definitions relied on “chart review” without further specification. Table 1 outlines the proportion of studies with variables defined and included in their analysis. Conclusions. Study variables were not clearly defined in most of the observational studies raising concerns about the reproducibility and reliability of findings. Our study underscores the vital need for standardized variable definitions in PJI research. Professional societies may play a crucial role in setting standards for the definition of variables. For any tables or figures, please contact the authors directly

Aims. The follow-up interval of a study represents an important aspect that is frequently mentioned in the title of the manuscript. Authors arbitrarily define whether the follow-up of their study is short-, mid-, or long-term. There is no clear consensus in that regard and definitions show a large range of variation. It was therefore the aim of this study to systematically identify clinical research published in high-impact orthopaedic journals in the last five years and extract follow-up information to deduce corresponding evidence-based definitions of short-, mid-, and long-term follow-up. Methods. A systematic literature search was performed to identify papers published in the six highest ranked orthopaedic journals during the years 2015 to 2019. Follow-up intervals were analyzed. Each article was assigned to a corresponding subspecialty field: sports traumatology, knee arthroplasty and reconstruction, hip-preserving surgery, hip arthroplasty, shoulder and elbow arthroplasty, hand and wrist, foot and ankle, paediatric orthopaedics, orthopaedic trauma, spine, and tumour. Mean follow-up data were tabulated for the corresponding subspecialty fields. Comparison between means was conducted using analysis of variance. Results. Of 16,161 published articles, 590 met the inclusion criteria. Of these, 321 were of level IV evidence, 176 level III, 53 level II, and 40 level I. Considering all included articles, a long-term study published in the included high impact journals had a mean follow-up of 151.6 months, a mid-term study of 63.5 months, and a short-term study of 30.0 months. Conclusion. The results of this study provide evidence-based definitions for orthopaedic follow-up intervals that should provide a citable standard for the planning of clinical studies. A minimum mean follow-up of a short-term study should be 30 months (2.5 years), while a mid-term study should aim for a mean follow-up of 60 months (five years), and a long-term study should aim for a mean of 150 months (12.5 years). Level of Evidence: Level I. Cite this article: Bone Jt Open 2021;2(5):344–350

Aim. Accurate diagnosis is key in correctly managing prosthetic joint infection(PJI). Shoulder PJI definition and diagnosis is challenging. Current PJI definitions, based overwhelmingly in hip/knee research, may not accurately diagnose shoulder PJI. Our aim is to compare the preoperative performance of two PJI definitions comparing it to definitive postoperative classification. Method. This is a retrospective study of patients who have undergone total shoulder revision surgery for infection between 2005 and 2022. Cases were classified using two different PJI definitions: a)the European Bone and Joint Infection Society (EBJIS) and; 2)the 2018 International Consensus Meeting(ICM) PJI specific shoulder definition. Preoperative classification was based on clinical features, inflammatory markers and synovial fluid leukocyte count and definitive classification also considered microbiology and histology results. Results. Preoperative and definitive PJI classification status of the 21 patients included were evaluated and is summarized in table 1. The shoulder specific 2018 ICM definition showed the highest agreement between preoperative and definitive classification (76.2%, k=0.153, p=0.006) compared to EBJIS (52.4%, k=0.205, p=0.006). In all cases, the classification was changed because of positive intraoperative microbiology (at least two identical isolates). Microbiology findings showed coagulase negative staphylococci, Staphyloccocus aureus and Cutibacterium acnes to be the most frequent. Four patients had polymicrobial infections. Conclusions. Both the EBJIS 2021 and 2018 ICM definitions have low accuracy in predicting shoulder PJI preoperatively. Clearly further studies with larger cohorts are in dire need focusing specifically on shoulder revision arthroplasty to improve on existing definitions. Caution is advised while extrapolating of criteria/thresholds recommended for hip/knee joints. For any tables or figures, please contact the authors directly

Aim. Although non-unions being one of the most common complication after long-bone fracture fixation, the definition of this entity remains controversial and varies widely among authors. A clear definition is crucial, not only for the evaluation of published research data but also for the establishment of uniform treatment concepts. The aim of this systematic review was to identify the definitions and different criteria used in the scientific literature to describe non-unions after long bone fractures. Method. A comprehensive literature search was performed in PubMed, Cochrane Library, Web of Science, and Embase. according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Prospective therapeutic and diagnostic clinical studies in which adult long-bone fracture non-unions were investigated as main subject were included in this analysis. Results. One hundred fifty-two studies investigating 6432 long-bone non-unions met inclusion criteria for this analysis. In total 49% (75/152) of included studies did not define non-union at all, even though non-union was their main study subject. A definition of non-union on either clinical, radiologic or time criteria could be found in 51% (77/152) of the included studies. Non-union was defined based on time criteria in 83% (64/77), on radiographic criteria in 65% (50/77), and on clinical criteria in 43% (33/77). A combination of clinical, radiologic and time criteria for definition was only found in 35% (27/77) of all the included studies that defined non-union. The time point when authors defined an unhealed fracture as a nonunion showed a considerable heterogeneity, ranging from four to 24 months. Conclusions. In the current orthopaedic trauma literature, we found a lack of consensus with regard to the definition of long bones non-unions. Therefore, a standardized definition of non-union remains unclear. Without valid and reliable definition criteria of non-unions, the establishment of standardized diagnostic and treatment algorithms as well as the comparison of studies remain difficult. The lack of a clear definition emphasizes the need for consensus-based definition of fracture non-unions based on clinical, radiographic and time criteria

Aim. Surgical treatment of ankle fractures comes with a substantial risk of complications, including infection. An unambiguously definition of fracture-related infections (FRI) has been missing. Recently, FRI has been defined by a consensus group with a diagnostic algorithm containing suggestive and confirmatory criteria. The aim of the current study was to report the prevalence of FRI in patients operated for ankle fractures and to assess the applicability of the diagnostic algorithm from the consensus group. Method. Records of all patients with surgically treated ankle fractures from 2015 to 2019 were retrospectively reviewed for signs of postoperative infections. Patients with suspected infection were stratified according to confirmatory or suggestive criteria of FRI. Rate of FRI among patients with confirmatory and suggestive criteria were calculated. Results. Suspected infection was found in 104 (10%) out of 1004 patients. Among those patients, confirmatory criteria were met in 76/104 (73%) patients and suggestive criteria were met in 28/104 (27%) at first evaluation. Patients with clinical confirmatory criteria (N= 76) were diagnosed with FRI. Patients with suggestive criteria were further examined with either bacterial sampling at the outpatient clinic, revision surgery including bacterial sampling, or a wait-and-see approach. Eleven (39%) of the 28 patients had positive cultures and were therefore diagnosed as having FRI at second evaluation. In total 87 (9%) patients were diagnosed with FRI according to the consensus definition. Only 73 (70%) of the 104 patients with suspected FRI had adequate bacterial sampling. Conclusions. The prevalence of FRI, applying the FRI-consensus criteria, for patients with surgically treated ankle fractures was 9%. Twenty-two percent of patients who met the confirmatory criteria had negative bacterial cultures. The current study shows that we did not have a systematic approach to patients with suspected FRI as recommended by the consensus group. A systematic approach to adequate bacterial sampling when FRI is suspected is paramount. The consensus definition of FRI and its diagnostic algorithm facilitates such an approach

Aim. There have been many attempts to define the criteria by which prosthetic joint infection (PJI) is diagnosed. Our aim is to validate the 2021 European Bone and Joint Infection Society (EBJIS) definition of PJI. Method. This is a multicenter retrospective study of patients who have undergone total hip or knee revision surgery in four different European institutions between 2013–2018. Cases with less than four intraoperative microbiology samples; no preoperative/intraoperative synovial fluid differential leukocyte count or intraoperative histology were excluded. Minimum follow-up of at least two years after revision surgery if no subsequent infection and/or the need for implant removal was also required. All cases were classified using the 2021 EBJIS, the 2018 International Consensus Meeting (ICM) and the 2013 Musculoskeletal Infection Society (MSIS) PJI definitions. Results. Definitive PJI classification according to the different definitions of the 507 patients included are presented in table 1. The EBJIS definition classifies 40.4%(205/507) of the cases as confirmed infections compared to 33.9%(p=0.038) and 29.4%(p<0.001) in 2018 ICM and 2013 MSIS classifications respectively. Compared to 2018 ICM classification it also offers significantly less undetermined cases – 5.0% vs. 11.4%(p<0.001). Free from infection Kaplan-Meyer survival curve shows significantly better outcome for EBJIS unlikely compared to confirmed subgroup(p=0.031). EBJIS likely subgroup survival is not significantly different from unlikely(p=0.529) or confirmed(p=0.717) cohorts. Among the MSIS not infected cohort the newly classified EBJIS confirmed/likely cases present higher subsequent infection rate (albeit not statistically significant) when compared to EBJIS infection unlikely cases − 16.0%(13/81) vs. 10.1%(28/277). This subsequent PJI rate is similar to the MSIS infected cohort. A similar trend is not obvious within ICM 2018 not infected subgroup. Conclusions. The EBJIS 2021 definition is shown to be the most sensitive definition while also offering a smaller number of undetermined cases. Newly diagnosed infections seem to have a similar prognosis as “classically” infected cases. For any tables or figures, please contact the authors directly

Aim. Accurate diagnosis is key in correctly managing prosthetic joint infection (PJI). Our aim is to compare the preoperative performance of three PJI definitions comparing it to definitive postoperative classification. Method. This is a multicenter retrospective study of patients who have undergone total hip or knee revision surgery in four different European institutions. For this specific study, cases with no preoperative synovial fluid differential leukocyte count and less than four intraoperative microbiology samples were excluded. Cases were classified using the 2021 EBJIS, the 2018 International Consensus Meeting (ICM) and the 2013 Musculoskeletal Infection Society (MSIS) PJI definitions. Preoperative classification was based on clinical features, inflammatory markers and synovial fluid leukocyte count and microbiology results. Results. Preoperative and definitive PJI classification status of the 384 patients included are presented in figure 1. EBJIS definition showed the highest agreement between preoperative and definitive classification (k=0.86, CI95% 0.81–0.90, p<0.001) compared to ICM 2018 (k=0.80, CI95% 0.75–0.84, p<0.001) or MSIS 2013 (k=0.70, CI95% 0.62–0.77, p<0.001). Compared to its respective definitive classification: EBJIS preoperative unlikely result shows 86.8% (95%CI 81.3%–91.2%) sensitivity and 87.7% (95%CI 83.3%–91.1%) negative predictive value (NPV); ICM 2018 preoperative not infected result shows 83.5% (95%CI 77.4%–88.5%) sensitivity and 86.2% (95%CI 81.9%–88.6%) NPV and; MSIS 2013 preoperative not infected result shows 63.9% (95%CI 55.0%–72.1%) sensitivity and 84.3% (95%CI 81.1%–87.1%) NPV. Around half of the preoperative EBJIS likely (45.8%) and ICM 2018 inconclusive (54.5%) turn out to be infected postoperatively. If we consider the more sensitive definition (EBJIS) as the gold standard: ICM 2018 preoperative not infected result shows 75.1% (95%CI 68.5%–81.0%) sensitivity and 78.3% (95%CI 73.9%–82.2%) NPV and; MSIS 2013 preoperative not infected result shows 42.1% (95% CI 35.2%–49.4%) sensitivity and 62.0% (59.2%–64.8) NPV. Conclusions. The EBJIS 2021 definition is not only the most sensitive definition as it was shown to be the most effective in preoperatively ruling out PJI when there is a negative result. For any tables or figures, please contact the authors directly

The orientation of an acetabulum or an acetabular prosthesis may be described by its inclination and anteversion. Orientation can be assessed anatomically, radiographically, and by direct observation at operation. The angles of inclination and anteversion determined by these three methods differ because they have different spatial arrangements. There are therefore three distinct definitions of inclination and anteversion. This paper analyses the differences between the definitions and provides nomograms to convert from one to another. It is recommended that the operative definitions be used to describe the orientation of prostheses and that the anatomical definitions be used for dysplastic acetabula

Aims. Patients with cauda equina syndrome (CES) require emergency imaging and surgical decompression. The severity and type of symptoms may influence the timing of imaging and surgery, and help predict the patient’s prognosis. Categories of CES attempt to group patients for management and prognostication purposes. We aimed in this study to assess the inter-rater reliability of dividing patients with CES into categories to assess whether they can be reliably applied in clinical practice and in research. Methods. A literature review was undertaken to identify published descriptions of categories of CES. A total of 100 real anonymized clinical vignettes of patients diagnosed with CES from the Understanding Cauda Equina Syndrome (UCES) study were reviewed by consultant spinal surgeons, neurosurgical registrars, and medical students. All were provided with published category definitions and asked to decide whether each patient had ‘suspected CES’; ‘early CES’; ‘incomplete CES’; or ‘CES with urinary retention’. Inter-rater agreement was assessed for all categories, for all raters, and for each group of raters using Fleiss’s kappa. Results. Each of the 100 participants were rated by four medical students, five neurosurgical registrars, and four consultant spinal surgeons. No groups achieved reasonable inter-rater agreement for any of the categories. CES with retention versus all other categories had the highest inter-rater agreement (kappa 0.34 (95% confidence interval 0.27 to 0.31); minimal agreement). There was no improvement in inter-rater agreement with clinical experience. Across all categories, registrars agreed with each other most often (kappa 0.41), followed by medical students (kappa 0.39). Consultant spinal surgeons had the lowest inter-rater agreement (kappa 0.17). Conclusion. Inter-rater agreement for categorizing CES is low among clinicians who regularly manage these patients. CES categories should be used with caution in clinical practice and research studies, as groups may be heterogenous and not comparable. Cite this article: Bone Joint J 2023;105-B(9):1007–1012

Aim. Our goal is to assess diagnostic accuracy of synovial fluid testing in diagnosing prosthetic joint infection (PJI) as defined by the European Bone and Joint Infection Society (EBJIS). In addition to differential leukocyte count, simples and inexpensive biomarkers such as synovial fluid C-reactive protein (CRP), adenosine deaminase (ADA) and alpha-2-macrogloblulin(A2M) were also investigated and its possible role in increasing accuracy assessed. Method. Between January/2013 and December/2019 total hip or knee arthroplasty revision cases (regardless of preoperative diagnosis) were prospectively included provided enough synovial fluid for biomarker analysis was collected and at least four tissue samples, as well as the implant for sonication, were gathered for microbiological study. Definitive diagnosis was classified according to the new EBJIS PJI definition. Using receiver operating characteristic curves, we determined cutoff values as well as diagnostic accuracy for each marker. Results. Out of 364 revision arthroplasties performed, 102 fully respected inclusion criteria. There were 58 unlikely, 8 likely and 36 confirmed infections. Synovial fluid total leukocyte count, proportion of polymorphonuclear neutrophils (PMN), CRP, ADA and A2M were significantly different between groups. Area under the curve was 0.94 for total leucocyte count, 0.91 for proportion of PMN, 0.90 for CRP, 0.82 for ADA and 0.76 for A2M. Sensitivity, specificity, and predictive values for statistically optimal but also selected rule-in and rule-out cutoffs values are shown in Table 1. Interpreting a raised level of CRP(>2.7mg/L) or ADA(>60U/L) together with high leukocyte count (>1470 cells/μL) or proportion of PMN (>62.5%) significantly increases specificity and positive predictive value for affirming PJI. Conclusions. Differential leukocyte count cutoffs proposed by the EBJIS PJI definition are shown to perform well in ruling out (<1,500 cells/μL) and ruling in (>3,000 cells/μL) PJI. Adding simple and inexpensive biomarkers such synovial CRP or ADA is helpful in interpreting inconclusive results. For any tables or figures, please contact the authors directly

Aim. Synovial fluid investigation is the best alternative to diagnose prosthetic joint infection (PJI) before adequate microbiological/histology sampling during revision surgery. Although accurate preoperative diagnosis is certainly recommended, puncturing every patient before revision arthroplasty raises concerns about safety and feasibility issues especially in difficult to access joint (e.g., hip), that often require OR time and fluoroscopy/ultrasound guidance. Currently there is no clear guidelines regarding optimal indications to perform preoperative joint aspiration to diagnose PJI before revision surgery. The main goal of this study is to determine the accuracy of our institutional criteria using the new European Bone and Joint Infection Society (EBJIS) PJI definition. Method. We retrospectively evaluated every single- or first-stage for presumed aseptic or known infected revision total hip/knee arthroplasty procedures between 2013–2020. Preoperative clinical and laboratory features were systematically scrutinized. Cases with insufficient information for accurate final PJI diagnosis (i.e., no perioperative synovial fluid examination or no multiple cultures including sonication of removed implant) were excluded. Preoperative joint aspiration is recommended in our institution if any of the following criteria are met: 1) elevated CRP and/or ESR; 2) early failure (<2 years) or repeat failure; 3) high clinical suspicion/risk factors are present. Performance of such criteria were compared against final postoperative EBJIS definition PJI diagnosis. Results. A total of 364 revision THAs or TKAs were performed during the study period. After excluding 258 cases with insufficient information, a total of 106 patients were ultimately included. 38 (35,8 %) were classified as confirmed infections, 10 (9.4 %) as likely infected and 58 (54.7%) as infection unlikely. Of those, 37 confirmed infection cases, 9 likely infected cases and 32 infection unlikely cases did have indication for preoperative synovial fluid collection before revision surgery. Institutional criteria showed 95.8 % Sensitivity, 44.83 % Specificity, 92.9 % Negative Predictive Value (NPV) and 59 % Positive Predictive Value (PPV). Conclusions. Sensitivity and NPV of the aforementioned institutional criteria are very high even with the use of the more sensitive EBJIS PJI definition. As such they seem to be a valid alternative in selecting patients that should be punctured before revision arthroplasty. They identify the vast majority of infected patients while saving a significant number of patients from unnecessary procedures

Aim. Cutibacterium acnes, a skin commensal, is responsible for 5–10% of prosthetic joint infections (PJI). All current microbiological definitions of PJI require two or more identical commensal isolates to be recovered from the same procedure to diagnose PJI and rule out contamination. Unlike coagulase negative staphylococci, C.acnes shows a highly stereotypical susceptibility profile making impossible to phenotypically assess the clonal relationship of isolates. In order to determine the clonal relationship of multiple C.acnes isolates recovered from arthroplasty revisions, we analyzed by multi-locus sequence typing (MLST) C.acnes isolates grown from orthopedic device-related infections (ODRI) in a reference center for bone and joint infection. Methods. Laboratory records from January 2009 to January 2014 were searched for monomicrobial C.acnes ODRI with growth of C. acnes in at least 2 intraoperative and/or preoperative samples. Clinical, biological and demographic information was collected from hospital charts. All corresponding isolates biobanked in cryovials (−80°C) were subcultured on anaerobic blood agar, and identification confirmed by MALDI-TOF-MS. C.acnes isolates were typed using the MLST scheme described by Lomholt et al. Plasmatic pre-operative C-reactive protein (CRP) levels were determined using DimensionEXL (Siemens). A threshold of 10 mg/L was used to determine serologically positive ODRIs from negatives. Results. Over a 5-year period, 37 cases of monomicrobial C.acnes ODRI were diagnosed in our center. Among these 37 cases, 113/153 C.acnes isolates were cryopreserved. 110/113, corresponding to 36/37 cases, were typed by MLST: 14/36 (39%) ODRI cases were found to feature isolates belonging to two or more different STs and were qualified to be heteroclonal whereas 22/36 (61%) of ODRI cases were found to feature isolates belonging to the same ST and were qualified to be homoclonal. Homoclonal infections were significantly more likely to have elevated CRP levels compared to heteroclonal cases (p=0.0011, Fisher test). Patients with only two positive intraoperative samples had significantly lower CRP values than patients with three or more positive intraoperative samples (12,7mg/L vs 67mg/L; p=0,01, homoscedastic two-tailed Student's t test). Conclusions. This study suggests that what is classified microbiologically as C.acnes ODRIs comprises: i) true homoclonal infections eliciting an inflammatory response, ii) heteroclonal infections lacking inflammatory response where C.acnes could be an innocent bystander and iii) false positives where no strain achieves true microbiological significance. Our study shows that a stricter threshold of 3 intraoperative positive samples could be more adequate than 2. These results reinforces the need for a more specific definition of C.acnes ODRI

Comparison of efficacy of multi-modality spinal cord monitoring [SCM] (SSEP & MEP) in surgery of paediatric deformity using two classification systems I (traditional) vs. II (modified). SSEP SCM has low sensitivity in a normal spinal cord; this is only marginally improved with additional MEP monitoring. Traditional definitions of a ‘false’ positive' test ignores anaesthetic & surgical interventions following notification of altered SCM signals. Retrospective, paediatric cohort. 232 patients; mean age 14 years (26% males). 68% idiopathic scoliosis; 62% posterior surgery. Primary: Post-operative neurologic deficit. Secondary: significant (>50%↓ amplitude) SSEP or any MEP loss. PPV- Positive predictive value, NPV- Negative predictive value; LR+ve- Positive likelihood ratio, LR-ve Negative likelihood ratio; N/C – Not calculable. Efficacy of SCM is determined by definitions of ‘false positive’. System II classification was more efficacious and reflects current surgical practice

Pedicle screws allow for biomechanically secure fixation of the spine. However if they are misplaced they may effect the strength of the fixation, damage nerve roots or compromise the spinal cord. For these reasons image guidance systems have been developed to help with the accuracy of screw placement. The accuracy of pedicle screw placement outside the lumbar spine is not well published. To determine the accuracy of pedicle screw placement using CT scanning post operatively. Cortex perforations were graded in 2mm steps. Prospective observational study. Plain x-rays are inaccurate for determining screw placement and therefore high definition CT scanning was used. The screw positioning on the post-operative CT scans was independently determined by a research registrar who was not present at the time of surgery. Screw position and clinical sequelae of any malposition. Thirty patients (13 F:17 M) with segmental instability. Twelve were for metastatic disease, seven for trauma, seven for spondylolisthesis, three for atlanto-axial instability and one for a vertebral haemangioma. All patients were operated on by the senior author. One hundred and seventy six pedicle screws were inserted in the thirty patients over the 20 month study period. Six screws violated the lateral cortex of the pedicle but none perforated the medial cortex. There were no adverse neurological sequelae. The findings from this study will serve as a good comparison with future studies on pedicle screw placement, which may claim to improve accuracy and safety by the use of image guidance systems, electrical impedance or malleable endoscopes

Aim

Apart from other biomarkers isolated in the synovial fluid, alpha-defensin appears to be a promising diagnostic tool to confirm a periprosthetic joint infection (PJI) in the hip or knee. The purpose of this study was to evaluate the sensitivity and specificity of an alpha defensin lateral flow (ADLF) test compared to usual standard classifications in the diagnostic management of PJI.

Aim. Propionibacterium acnes is a skin commensal colonizing the deeper structures of the pilous bulb. It is responsible for 5–10% of lower limb prosthetic joint infections (PJI) but accounts for as many as 50% of shoulder arthroplasty infections. P. acnes PJIs characteristically feature limited systemic inflammation, limited polymorphonuclear infiltration and clinical signs compatible with aseptic loosening. All current microbiological definitions of PJI require two or more identical commensal isolates to be recovered from the same procedure to diagnose PJI to increase specificity and rule out contamination. Whereas the antimicrobial susceptibility patterns of coagulase negative staphylococci are highly polymorphic and commonly allow the ready distinction of unrelated strains, P. acnes shows a highly stereotypical susceptibility profile and it is impossible to phenotypically assess the clonal relationship of isolates. In order to determine the clonal relationship of multiple P. acnes isolates recovered from arthroplasty revisions, we analyzed by multi-locus sequence typing (MLST) P. acnes isolates grown from PJI in a reference center for bone and joint infection. Method. We retrospectively selected all cases of microbiologically documented monomicrobial PJI caused by P. acnes diagnosed in our center from January 2009 to January 2014. Microorganisms were identified by MALDI-TOF mass spectrometry (Bruker Daltonics). All corresponding P.acnes isolates biobanked in cryovials frozen at −80°C were subcultured on anaerobic blood agar, DNA extracted by freeze-thawing and bead-milling, and typed according to the 9 gene MLST scheme proposed by Lomholt HB. and al. Results. Over the 5-year period, 39 cases of PJI positive with P. acnes were diagnosed in our center. Three to ten intraoperative samples were sent for microbiological analysis per surgery. Overall, 113 P. acnes isolates were grown from 210 samples. On average, four samples were positive out of six. In 34/39 cases, all isolates belonged to the same ST. In 5 cases, multiples STs were found among the P.acnes isolates. In 3/39 cases (7.7%), a single ST was found to be microbiologically significant, with a single isolate of the alternate ST. In 2/39 cases (5.1%), we found that each isolate belonged to a different ST. Conclusions. P. acnes PJI were found to be polyclonal by MLST in 12.8% of cases in our experience, with more than 5% of cases not fulfilling the requirements for microbiological significance. The criteria for microbiological significance do not necessarily apply to commensal agents with no antimicrobial susceptibility pattern variation such as P. acnes

Introduction. Acetabular bone deficiency, especially proximal and lateral deficiency, is a difficult technical problem during primary total hip arthroplasty (THA) in developmental hip dysplasia (DDH). We report a configuration-based acetabular classification, a modification of the Crowe's classification, of DDH, including a definition of shallow acetabuli. We also report a new reconstruction method using a medial reduced cemented socket andadditional bulk bone in conjunction with impaction morselized bone grafting (Ad-BBG method). We aimed to evaluate usefulness of the classification and the method's clinical/radiographic outcomes. Methods. One hundred thirty one hips of 330 THAs for DDH (40%) were defined shallow. The Ad-BBG methodwas performed on 102 hips (78% shallow hips). For the 24 remaining hips, THA was performed using the conventional interposition bulk bone grafting (Ip-BBG) (8 hips)or without bone grafting by using rigid lateral osteophyte (16 hips). Japanese Orthopaedic Association (JOA) scores and the Merle d'Aubigne and Postel (M&P) scores were used in follow-up; radiographs were analyzed retrospectively. The criteria used for determining loosening were migration or a total radiolucent zone between the prosthesis/bone cement and host bone. The follow-up period was 9.2 ± 2.6 (range, 5.0–14.0) years. Operative Technique. Theresected femoral head was sectioned at 1–2-cm thickness, and a suitable size of the bulk bone graft was placed on the lateral iliac cortex and fixed by polylactate absorbable screws. Autogenous impaction morselized bone grafting, with or without hydroxyapatite granules, was performed along with the implantation of medial reduced cemented prosthetic hip socket. The same surgical team performed all surgical procedures. Results. Acetabular component was revised in only one case with a shallow and Crowe Type IV acetabulum. The mean JOA and M&P scores improved from preoperative 39.3 and 6.8 points to postoperative 93.9 and 17.2 points, respectively. Within 2 years postoperatively, most Ad-BBGs cases showed successful bone remodeling and bone graft reorientation on radiographs. Conclusions. We had good results of acetabular reconstruction in primary THA using the medial reduced cemented socket and bone grafting methods including the Ad-BBG technique in conjunction with impaction morselized bone grafting for shallow dysplastic hip. Osteointegration and good clinical outcomes were achieved in most cases. However, long-term outcomes should be subject of further investigation. Summary. Reconstruction methods for shallow dysplastic hip using medial reduced cemented socket and additional bulk bone grafting in conjunction with impaction morselized bone grafting are presented

Introduction

The successful performance of ceramic on ceramic bearings in today's THA can mainly be addressed to the excellent tribological behaviour and the minimal wear of ceramic bearings. The clearance between head and shell plays a major role in this functionality of artificial hip joints. Knowledge about the deformation behaviour of the shell during implantation but also under daily loads is essential to be able to define a minimum clearance of the system. The aim of this work is to establish a tool for determining maximum ceramic shell deformation in order to predict minimum necessary clearance between heads and monolithic ceramic shells.