Achieving High Accuracy in Predicting the Probability of Periprosthetic Joint Infection From Synovial Fluid in Patients Undergoing Hip or Knee Arthroplasty: The Development and Validation of a Multivariable Machine Learning Algorithm.

Background and objective The current periprosthetic joint infection (PJI) diagnostic guidelines require clinicians to interpret and integrate multiple criteria into a complex scoring system. Also, PJI classifications are often inconclusive, failing to provide a clinical diagnosis. Machine learning (ML) models could be leveraged to reduce reliance on these complex systems and thereby reduce diagnostic uncertainty. This study aimed to develop an ML algorithm using synovial fluid (SF) test results to establish a PJI probability score. Methods We used a large clinical laboratory's dataset of SF samples, aspirated from patients with hip or knee arthroplasty as part of a PJI evaluation. Patient age and SF biomarkers [white blood cell count, neutrophil percentage (%PMN), red blood cell count, absorbance at 280 nm wavelength, C-reactive protein (CRP), alpha-defensin (AD), neutrophil elastase, and microbial antigen (MID) tests] were used for model development. Data preprocessing, principal component analysis, and unsupervised clustering (K-means) revealed four clusters of samples that naturally aggregated based on biomarker results. Analysis of the characteristics of each of these four clusters revealed three clusters (n=13,133) with samples having biomarker results typical of a PJI-negative classification and one cluster (n=4,032) with samples having biomarker results typical of a PJI-positive classification. A decision tree model, trained and tested independently of external diagnostic rules, was then developed to match the classification determined by the unsupervised clustering. The performance of the model was assessed versus a modified 2018 International Consensus Meeting (ICM) criteria, in both the test cohort and an independent unlabeled validation set of 5,601 samples. The SHAP (SHapley Additive exPlanations) method was used to explore feature importance. Results The ML model showed an area under the curve of 0.993, with a sensitivity of 98.8%, specificity of 97.3%, positive predictive value (PPV) of 92.9%, and negative predictive value (NPV) of 99.8% in predicting the modified 2018 ICM diagnosis among test set samples. The model maintained its diagnostic accuracy in the validation cohort, yielding 99.1% sensitivity, 97.1% specificity, 91.9% PPV, and 99.9% NPV. The model's inconclusive rate (diagnostic probability between 20-80%) in the validation cohort was only 1.3%, lower than that observed with the modified 2018 ICM PJI classification (7.4%; p<0.001). The SHAP analysis found that AD was the most important feature in the model, exhibiting dominance among >95% of "infected" and "not infected" diagnoses. Other important features were the sum of the MID test panel, %PMN, and SF-CRP. Conclusions Although defined methods and tools for diagnosis of PJI using multiple biomarker criteria are available, they are not consistently applied or widely implemented. There is a need for algorithmic interpretation of these biomarkers to enable consistent interpretation of the results to drive treatment decisions. The new model, using clinical parameters measured from a patient's SF sample, renders a preoperative probability score for PJI which performs well compared to a modified 2018 ICM definition. Taken together with other clinical signs, this model has the potential to increase the accuracy of clinical evaluations and reduce the rate of inconclusive classification, thereby enabling more appropriate and expedited downstream treatment decisions.

Supercooling of the A phase of 3He.

Because of the extreme purity, lack of disorder, and complex order parameter, the first-order superfluid 3He A-B transition is the leading model system for first order transitions in the early universe. Here we report on the path dependence of the supercooling of the A phase over a wide range of pressures below 29.3 bar at nearly zero magnetic field. The A phase can be cooled significantly below the thermodynamic A-B transition temperature. While the extent of supercooling is highly reproducible, it depends strongly upon the cooling trajectory: The metastability of the A phase is enhanced by transiting through regions where the A phase is more stable. We provide evidence that some of the additional supercooling is due to the elimination of B phase nucleation precursors formed upon passage through the superfluid transition. A greater understanding of the physics is essential before 3He can be exploited to model transitions in the early universe.

Thermal transport of helium-3 in a strongly confining channel.

The investigation of transport properties in normal liquid helium-3 and its topological superfluid phases provides insights into related phenomena in electron fluids, topological materials, and putative topological superconductors. It relies on the measurement of mass, heat, and spin currents, due to system neutrality. Of particular interest is transport in strongly confining channels of height approaching the superfluid coherence length, to enhance the relative contribution of surface excitations, and suppress hydrodynamic counterflow. Here we report on the thermal conduction of helium-3 in a 1.1 µm high channel. In the normal state we observe a diffusive thermal conductivity that is approximately temperature independent, consistent with interference of bulk and boundary scattering. In the superfluid, the thermal conductivity is only weakly temperature dependent, requiring detailed theoretical analysis. An anomalous thermal response is detected in the superfluid which we propose arises from the emission of a flux of surface excitations from the channel.

Magnetic properties of (Fe1-xMnx)2AlB2 and the impact of substitution on the magnetocaloric effect.

In this work, we investigate the magnetic structures of (Fe1-xMnx)2AlB2 solid-solution quaternaries in the x=0 to 1 range using x-ray and neutron diffraction, magnetization measurements, and mean-field theory calculations. While Fe2AlB2 and Mn2AlB2 are known to be ferromagnetic (FM) and antiferromagnetic (AFM), respectively, herein we focused on the magnetic structure of their solid solutions, which is not well understood. The FM ground state of Fe2AlB2 becomes a canted AFM at x≈0.2, with a monotonically diminishing FM component until x≈0.5. The FM transition temperature (TC) decreases linearly with increasing x. These changes in magnetic moments and structures are reflected in anomalous expansions of the lattice parameters, indicating a magnetoelastic coupling. Lastly, the magnetocaloric properties of the solid solutions were explored. For x=0.2 the isothermal entropy change is smaller by 30% than it is for Fe2AlB2, while the relative cooling power is larger by 6%, due to broadening of the temperature range of the transition.

Parinaud syndrome: Any clinicoradiological correlation?

INTRODUCTION: The significance of MRI findings of patients with Parinaud syndrome (PS) with respect to clinical characteristics is poorly defined. Over the past decades, all patients with PS undergo magnetic resonance imaging which allows a better identification of the lesion localization. We compared the neuro-ophthalmological findings of patients with PS caused by intrinsic (intra-axial) vs extrinsic (pineal gland tumor) brainstem lesions. METHODS: Medical records of patients with PS evaluated between 2000 and 2016 were retrospectively reviewed. RESULTS: Twenty-six patients with PS were included. Eight patients had pineal gland tumors and hydrocephalus. Two patients had hydrocephalus due to aqueduct stenosis and fourth ventricle tumor. Sixteen patients suffered from an intrinsic brainstem lesion and seven associated with hydrocephalus. The neuro-ophthalmological findings did not differ between patients with extrinsic and intrinsic brainstem lesions. No correlation was found between the grade of hydrocephalus and number of clinical findings except for more findings in low-grade hydrocephalus in intrinsic (40%) vs extrinsic (0%) lesions (P=.003). Patients with moderate brainstem lesions and hydrocephalus had more clinical findings (65%) than patients with the same grade of brainstem involvement without hydrocephalus (29%) (P=.03). The resolution rate of ophthalmological findings was comparable in all groups of patients. CONCLUSIONS: Our results did not show differences in neuro-ophthalmological findings between intra- and extra-axial lesions causing PS. However, the presence of hydrocephalus was an important factor influencing clinical findings. The prognosis of PS was less favorable than generally reported.

Antibiotic impregnated cement spacer for salvage of diabetic osteomyelitis.

BACKGROUND: Florid infection and osteomyelitis of the forefoot in patients with diabetic neuropathy often requires minor amputation, with risk of subsequent reulceration, reamputation, and patient dissatisfaction. We investigated use of an antibiotic-impregnated cement spacer (ACS) to release antibiotic locally to resolve residual infection and to fill the cavity created by debridement. METHODS: We report 23 cases of osteomyelitis and associated severe infection of forefoot joints in 20 consecutive patients, age 60.3 +/- 13.4 years. Antibiotic-impregnated cement, extensive meticulous debridement, and ACS placement to fill the gap were employed in all cases. Deep cultures were taken routinely. Fixation with Kirschner wires was used as necessary. Mean followup was 21.2 +/- 10.2 months. A successful result was resolution of infection and wound healing to full skin closure without amputation. RESULTS: Of 23 cases, 21 (91.3%) healed and two required toe amputation. ACS was left permanently in 10 patients, removed with arthrodesis in six, and removed without arthrodesis in five. One patient recovered but subsequently underwent transtibial amputation due to infection of a different site. CONCLUSION: Severe infection associated with osteomyelitis of the foot in diabetic patients was successfully treated with extensive debridement and use of ACS, which filled the void created by debridement. Amputation was avoided in most patients. This procedure allowed extensive debridement through filling large voids with ACS, with prolonged antibiotic release.

Evidence for a high-temperature disorder-induced mobility in solid 4He.

We have carried out torsional oscillator experiments on solid 4He at temperatures between 1.3 K and 1.9 K. We discovered phenomena similar to those observed at temperatures below 0.2 K, which currently are under debate regarding their interpretation in terms of supersolidity. These phenomena include a partial decoupling of the solid helium mass from the oscillator, a change of the dissipation, and a velocity dependence of the decoupled mass. These were all observed both in the bcc and hcp phases of solid 4He. The onset of this behavior is coincidental with the creation of crystalline disorder but does not depend strongly on the crystalline symmetry or on the temperature.

HIV and venous thrombotic events.

HIV has been widely recognised as a prothrombotic condition, with the first case reports having appeared more than 20 years ago. However, surprisingly little evidence is available regarding the mechanisms by which this disease leads to thrombosis. There is little doubt that the relationship is both multifactorial and complex. This review aims to look at the available data and provide a concise summary of the present level of knowledge.

Secure communication in fiber optic systems via transmission of broad-band optical noise.

We propose a new scheme for data encryption in the physical layer. Our scheme is based on the distribution of a broadband optical noise-like signal between Alice and Bob. The broadband signal is used for the establishment of a secret key that can be used for the secure transmission of information by using the one-time-pad method. We characterize the proposed scheme and study its applicability to the existing fiber-optics communications infrastructure.

A 10-year audit of burns at Kalafong Hospital.

Kalafong Hospital is a secondary hospital situated to the west of Pretoria. It serves as the regional burns centre for Gauteng province north of the Jukskei river. It mainly serves a poor population. This is a retrospective review of a 10-year period, looking at both numbers and the aetiology of burns treated by this unit. Only adult cases--patients over the age of 12--were assessed. Over this period, a total number of 1046 patients were admitted and treated by this unit, consisting of 634 males and 406 females. The period covered, includes a period when the government has been expending massive amounts of funds to electrify townships and rural areas. Despite this, however, the majority of burn wounds are still caused by open flames and paraffin stoves.

Two modifications of the Weil osteotomy: analysis on sawbone models.

Second metatarsal osteotomies (30 degrees angle to shaft) were performed in 40 sawbones with: 1. head shifted proximally 5 mm; 2. head shifted proximally 10 mm; 3. 5-mm slice resected and head shifted proximally 5 mm; or 4. 5-mm dorsally based wedge resected and head shifted proximally 5 mm. Bone slice resection resulted in shortening (16.4+/-1.7 mm) and mild plantar displacement of the head (3.5+/-0.8 mm). Bone wedge excision resulted in moderate shortening (7.8+/-0.9 mm) and essentially no plantar displacement of the head (0.8+/-1.4 mm).

Arthrodesis of the first metatarsophalangeal joint: a biomechanical study comparing memory compression staples, cannulated screws, and a dorsal plate.

Arthrodesis of the first metatarsophalangeal joint of 21 matched pairs of cadaver toes was performed in order to compare the strength of three methods of internal fixation: 1. two crossed cannulated screws, 2. a dorsal plate with an oblique 0.062 K-wire, and 3. two compression staples with an oblique 0.062 K-wire. Biomechanical testing with plantar force was carried out, and gapping across the fusion site was measured. Stiffness, load to 1-mm displacement, and force to failure was determined for each specimen. Both the plate and screw constructs were statistically stronger in force to failure and initial stiffness than the compression construct. Compression staples have an advantage in their ease of insertion and theoretical continuous compressive force across an arthrodesis site, but should be supplemented with a cast or other external immobilization until union is achieved.

Distal arteriovenous fistula to maintain patency of the venous drainage of a latissimus dorsi flap following subclavian vein repair.

Successful reconstructive surgery with muscle flaps depends on adequate arterial supply and undisturbed venous drainage. Combining such surgery with reconstructive vascular surgery of a large-caliber vein that is responsible for the venous drainage of the flap poses an additional challenge--the repaired vein's susceptibility to thrombosis. Every attempt must be made to prevent venous outflow obstruction following muscle flap surgery. Data from the vascular surgery literature demonstrate a low success rate for subclavian vein repair. The success rate with venous reconstructive surgery has been greater when a distal arteriovenous fistula accompanied the repair. The present case described the use of a temporary distal cephalic-brachial arteriovenous fistula to maintain the patency of the venous drainage of a pedicled latissimus dorsi muscle flap, following subclavian vein repair, for one-stage coverage of a large chest wall defect.

The value of the occipitomental (Waters') view in diagnosis of sinusitis: a comparative study with computed tomography.

AIM: Sinus X-rays are still frequently used in the evaluation of paranasal sinusitis. Many radiology departments nowadays provide the referring doctors with a single Waters' projection. Our purpose was to evaluate the diagnostic accuracy of a single Waters' view vs high resolution computed tomography (CT) in the diagnosis of paranasal sinusitis. SUBJECTS AND METHODS: A total of 134 patients with suspected paranasal sinusitis underwent a Waters' view X-ray and high resolution CT on the same day. The radiographs were evaluated independently by nine experienced radiologists, who observed each sinus separately. Sensitivity, specificity, accuracy, positive and negative predictive values were calculated for each sinus and for each observer, using the CT findings as a 'gold standard'. RESULTS: The weighted mean sensitivity for diagnosis of any abnormality in the maxillary sinus was 67.7%, specificity 87.6%, accuracy 78.6%, positive predictive value 82.5% and negative predictive value 76.9%. For this sinus the variation between observers was small, however, the sensitivity for diagnosis of any disease in the frontal and ethmoid sinuses varied widely between observers (range 1.9-54.0% and 0-58.9%, respectively). The sensitivity for the sphenoid sinus was very low (range 0-3.8%), even in radiographs which seemed to demonstrate it well. CONCLUSION: The Waters' view has its limits in the diagnosis of sinusitis of the maxillary sinuses and its contribution for diagnosing lesions in the remaining sinuses is very poor. Whenever access to CT is available, a low dose high-resolution CT study of the paranasal sinuses is highly recommended.Konen, E. (2000). Clinical Radiology55, 856-860.

Statistical determination of the length dependence of high-order polarization mode dispersion.

We describe a method of characterizing high-order polarization mode dispersion (PMD). Using a new expansion to approximate the Jones matrix of a polarization-dispersive medium, we study the length dependence of high-order PMD to the fourth order. A simple rule for the asymptotic behavior of PMD for short and long fibers is found. It is also shown that, in long fibers (~1000 km), at 40 Gbits/s the third- and fourth-order PMD may become comparable to the second-order PMD.

Interlocking stents for improving stent fixation at graft-venous anastomosis.

To lower the risk of stent migration in a graft-venous anastomosis stenosis following failed percutaneous transluminal angioplasty, two Strecker stents of different caliber were placed in partly overlapping fashion across the stenosis. In contrast to other methods, stent "floating" on the venous side was eliminated by using a stent with a caliber matching the tapering postanastomotic vein and anchoring it to both the venous wall and the second stent. Using this method we believe we accomplished better fixation of the stent placed mostly in the venous side of the anastomosis, thus lowering its risk of migration. At 6 months follow-up the stents are in place and the anastomosis is patent.