Richard Stern

Outcome of orthopedic implant infections due to different staphylococci

BACKGROUNDnComparisons of different staphylococci in orthopedic implant infections have rarely been reported. In this study we assessed total joint arthroplasty infections and other orthopedic implant infections due to methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA), and coagulase-negative staphylococci (CoNS).nnnMETHODSnThis was a retrospective study performed at the Geneva University Hospitals for the period January 1996 to June 2008.nnnRESULTSnThere were 44 infections due to MRSA, 58 due to MSSA, and 61 due to CoNS. Overall cure was achieved in 57% (25/44) of MRSA infections, 72% (42/58) of MSSA infections, and 82% (50/61) of CoNS infections, after a minimum follow-up of 1 year. In the subgroup of arthroplasty infections only, cure was achieved in 39% (7/18) of MRSA, 60% (15/25) of MSSA, and 77% (30/39) of CoNS episodes. In multivariate analysis, arthroplasty (odds ratio (OR) 0.2, 95% confidence interval (95% CI) 0.1-0.6) and MRSA infections (OR 0.3, 95% CI 0.1-0.9) were inversely associated with overall cure for all implants. CoNS infection (OR 3.0, 95% CI 1.2-8.0) and the insertion of a new implant (OR 4.5, 95% CI 1.6-13.1) were associated with higher cure results. Methicillin resistance, immunosuppression, sex, age, duration of antibiotic therapy, one-stage revision, rifampin use, and total number of surgical interventions did not influence cure. MRSA-infected patients had more post-infection sequelae than patients with MSSA or CoNS (Chi-square test 13/44 vs. 93/119, OR 3.4, 95% CI 1.3-8.9, p=0.004).nnnCONCLUSIONSnIn orthopedic implant infections, S. aureus is more virulent than CoNS. MRSA has the worst outcome and CoNS the best.

Low incidence of haematogenous seeding to total hip and knee prostheses in patients with remote infections

OBJECTIVESnThe exposure of joint prostheses to remote infections is unknown. We wanted to estimate (a) the exposure of arthroplasty patients to severe remote infections, and (b) the incidence of arthroplasty infections associated with remote infections.nnnMETHODSnProspective cohort study of all elective hip and knee arthroplasties performed between March 1996 and September 2008, with retrospective documentation of remote infections in hospitalized patients.nnnRESULTSnA total of 6101 elective total joint arthroplasties, consisting of 4002 hip replacements (66%) and 2099 knee replacements (34%), were included. The mean follow-up was 70 months. During the study period, the cohort patients experienced 553 remote infections after a median delay of 33 months post-arthroplasty. There were 71 prosthetic infections detected, 7 (total incidence 7/6101, 0.1%) of which were secondary to a remote infection. The ratio of infections associated with remote infections to potential exposure was 1:79. Among hip arthroplasty patients the incidence rate was 1.4 infections associated with remote infections per 10,000 patient-years of follow-up. Infections associated with remote infections occurred later than surgical site infections, (46 months vs. 19 months post-surgery, respectively; mean difference 27 months, 95% CI 8-45 months).nnnCONCLUSIONSnArthroplasty infections associated with remote infections were rare, and occurred like their potential exposure mostly more than 24 months post-arthroplasty.

Physical Activity Before and After Primary Total Hip Arthroplasty: A Registry-Based Study

Detailed assessment of activity before and after total hip arthroplasty (THA) including a long‐term followup period is lacking. Our objectives were to evaluate patient activity levels prior to disease onset, prior to THA, and at 5 and 10 years after surgery, and to determine the predictors of high activity 5 years after surgery.

Low incidence of severe respiratory syncytial virus infections in lung transplant recipients despite the absence of specific therapy.

n n Backgroundn Respiratory syncytial virus (RSV) infections in lung transplant recipients (LTRs) have been associated with significant morbidity and mortality. Immunoglobulins, ribavirin, and palivizumab are suggested treatments for both pre-emptive and therapeutic purposes. However, in the absence of randomized, placebo-controlled trials, efficacy is controversial and there is toxicity as well as cost concerns.n n n Methodsn We retrospectively reviewed cases of lower respiratory tract RSV infections in adult LTRs. Diagnosis was based on clinical history, combined with a positive polymerase chain reaction (PCR) and/or viral cultures of bronchoalveolar lavage (BAL) specimens.n n n Resultsn Ten symptomatic patients were identified (7 men and 3 women, age range 28 to 64 years). All were hospitalized for community-acquired respiratory tract infections. Two patients had a concomitant acute Grade A3 graft rejection, and 1 patient had a concomitant bacterial pneumonia. Eight patients did not receive a specific anti-RSV treatment because of clinical stability and/or improvement at the time of RSV diagnosis. Only 2 patients (1 with Grade A3 allograft rejection and 1 requiring mechanical ventilation) received ribavirin and palivizumab. All patients recovered without complications and with no persistent RSV infection. However, bronchiolitis obliterans (BOS) staging worsened in 6 patients during the mean follow-up of 45 months.n n n Conclusionsn Our data suggest that mild RSV infections in LTRs might evolve favorably in the absence of specific anti-viral therapy. However, this observation needs confirmation in a large clinical trial specifically investigating the development of BOS in untreated vs treated patients.n n

Treatment challenges associated with bone echinococcosis

OBJECTIVESnIn this literature review, we concentrate on epidemiology and therapy of osseous echinococcosis, with an emphasis on the recurrence risk.nnnMETHODSnLiterature review 1930-2012.nnnRESULTSnWe retrieved 200 publications based upon single case reports or case series, mostly from resource-poor settings. Among the 721 rural patients (22% females; median age 37 years), 60% of all reported cases were from the Mediterranean region and almost all patients were immune competent. Echinococcus granulosus was identified as the most frequent species. Most infections involved a single bone (602/721; 83%) and often the spine (321 cases; 45%). In eight cases (8/702; 1%), a secondary bacterial surgical site infection was reported. Surgical intervention was performed in 702 cases (97%), with single intervention in 687 episodes (95%). Complete excision of the lesion was possible in only 117 episodes (16%). Albendazole was by far the most frequently used agent in monotherapy with various dosages, while mebendazole in monotherapy was less frequent (32 cases). The median duration of antihelminthic therapy was 6 months (range 0.7-144 months). There were 124 recurrences (17%) after a median delay of 2 years (range 0.4-17 years). In multivariate analysis, the presence of visceral organ involvement increased the odds of recurrence by 5.4 (95% CI 3.1-9.4), whereas the number of surgical interventions, the duration of antihelminthic therapy or the use of hypertonic saline did not influence recurrence.nnnCONCLUSIONSnBone echinococcosis is a rare parasitic disease. While treatment modalities vary considerably, combined surgical and medical approaches are the standard of care with a 17% risk of recurrence.

Remission rate of implant-related infections following revision surgery after fractures.

PurposeIn contrast to a large amount of epidemiological data regarding the incidence of implant infections after fracture management, surprisingly few have been published concerning the success of their treatment.MethodsThis was a single-centre cohort study at Geneva University Hospitals from 2000 to 2012 investigating the remission rates of orthopaedic implant infections after fracture repair and associated variables.ResultsA total of 139 episodes were included: There were 51 women (37xa0%) and 28 immunosuppressed (20xa0%) patients with a median age and American Society of Anaesthesiologists (ASA) score of 51xa0years and 2 points, respectively. The infected implants were plates (nu2009=u200975, 54xa0%), nails (24, 17xa0%), wires (20), screws (10), cerclage cables or wires (3), hip screws (4) or material for spondylodesis (3). A pathogen was identified in 135 (97xa0%) cases, including Staphylococcus aureus (73, 52xa0%), coagulase-negative staphylococci (20), streptococci (7) and 19 Gram-negative rods. All patients underwent antibiotic treatment, and 128 (92xa0%) remained in remission at a median follow-up time of 2.6xa0years (range one to 13xa0years). In multivariate logistic regression analysis, the plate infections were significantly associated with lower remission rates [65/75, 87xa0%, odds ratio (OR) 0.1, 95xa0% confidence interval (CI) 0.01–0.90]. No associations were found for gender, age, immune status, ASA score, additional surgical interventions (OR 0.4, 95xa0% CI 0.1–4.1) or duration of antibiotic treatment (OR 1.0, 95xa0% CI 0.98–1.01).ConclusionsAmong all infected and removed orthopaedic implants, plates were associated with slightly lower remission rates, while the overall treatment success exceeded 90xa0%. The duration of antibiotic therapy did not alter the outcome.

Case-based fracture image retrieval.

PurposeCase-based fracture image retrieval can assist surgeons in decisions regarding new cases by supplying visually similar past cases. This tool may guide fracture fixation and management through comparison of long-term outcomes in similar cases.MethodsA fracture image database collected over 10xa0years at the orthopedic service of the University Hospitals of Geneva was used. This database contains 2,690 fracture cases associated with 43 classes (based on the AO/OTA classification). A case-based retrieval engine was developed and evaluated using retrieval precision as a performance metric. Only cases in the same class as the query case are considered as relevant. The scale-invariant feature transform (SIFT) is used for image analysis. Performance evaluation was computed in terms of mean average precision (MAP) and early precision (P10, P30). Retrieval results produced with the GNU image finding tool (GIFT) were used as a baseline.Two sampling strategies were evaluated. One used a dense 40xa0×xa040 pixel grid sampling, and the second one used the standard SIFT features. Based on dense pixel grid sampling, three unsupervised feature selection strategies were introduced to further improve retrieval performance. With dense pixel grid sampling, the image is divided into 1,600 (40xa0×xa040) square blocks. The goal is to emphasize the salient regions (blocks) and ignore irrelevant regions. Regions are considered as important when a high variance of the visual features is found. The first strategy is to calculate the variance of all descriptors on the global database. The second strategy is to calculate the variance of all descriptors for each case. A third strategy is to perform a thumbnail image clustering in a first step and then to calculate the variance for each cluster. Finally, a fusion between a SIFT-based system and GIFT is performed.ResultsA first comparison on the selection of sampling strategies using SIFT features shows that dense sampling using a pixel grid (MAP = 0.18) outperformed the SIFT detector-based sampling approach (MAP = 0.10). In a second step, three unsupervised feature selection strategies were evaluated. A grid parameter search is applied to optimize parameters for feature selection and clustering. Results show that using half of the regions (700 or 800) obtains the best performance for all three strategies. Increasing the number of clusters in clustering can also improve the retrieval performance. The SIFT descriptor variance in each case gave the best indication of saliency for the regions (MAP = 0.23), better than the other two strategies (MAP = 0.20 and 0.21). Combining GIFT (MAP = 0.23) and the best SIFT strategy (MAP = 0.23) produced significantly better results (MAP = 0.27) than each system alone.ConclusionsA case-based fracture retrieval engine was developed and is available for online demonstration. SIFT is used to extract local features, and three feature selection strategies were introduced and evaluated. A baseline using the GIFT system was used to evaluate the salient point-based approaches. Without supervised learning, SIFT-based systems with optimized parameters slightly outperformed the GIFT system. A fusion of the two approaches shows that the information contained in the two approaches is complementary. Supervised learning on the feature space is foreseen as the next step of this study.

Multiscale salient point-based retrieval of fracture cases

Fractures are common injuries, some complicated fractures may require a surgical intervention. When such an operation is planned it can be beneficial to have access to similar past cases including follow ups to compare, which method might be the most adapted one in a particular situation. At the orthopaedic service of the University hospitals of Geneva a database of past cases including pre- and post-operative images and case descriptions has been created over the past years with the goal to support clinical decision making. Images play an important role in the decision making process and the judgment of a fracture, but visual image content is currently not directly accessible for search. At the moment, search is mainly via a classification system of the fractures or in the patient record itself only by patient ID. In this paper we propose a solution that combines visual information from several images in a case to calculate similarity between cases and allow thus an access to visually similar cases. Such a system can complement the text- or classification-based search that has been used so far. In a preliminary study, we used pixel-grid-based salient-point features to build a first prototype of case-based visual retrieval of fracture cases. Cases belonging to different fracture classes were beforehand often confused due to the similar bone structures in the various images. In this article, a multi-scale approach is used in order to perform similarity measures at both large and small scales. When compared to the first prototype, the introduction of scale and spatial information allowed improving the performance of the system. Cases containing similar bone structures but with dissimilar fractures are generally ranked lower whereas more relevant cases are returned. The system can thus be expected to perform sufficiently well for use in clinical practice and particularly for teaching.