Imaging Depiction of Hypoxic Pulmonary Vasoconstriction Using Dual-Energy CT.

In this article, we aim to highlight the utility of dual-energy computed tomography (DECT) in demonstrating imaging changes due to hypoxic pulmonary vasoconstriction (HPV). DECT allows detailed image reconstructions that have been shown to better characterize cardiothoracic pathologies, as compared to conventional CT techniques. DECT simultaneously detects two different X-ray energies, which enables generation of iodine density maps, virtual monoenergetic images, and effective atomic number maps (Zeff), among others. DECT has been shown to have utility in the assessment of benign versus malignant pulmonary nodules, pulmonary embolism, myocardial perfusion defects, and other conditions. Herein, we describe four cases of indeterminate pulmonary pathology when imaged with conventional CT in which subsequent use of DECT-derived image reconstructions demonstrated HPV as the underlying pathophysiological mechanism. The goal of this article is to understand the imaging appearance of HPV on DECT and discuss how HPV may mimic other causes of perfusion defects.

Clinical Implementation of an Artificial Intelligence Tool in the Detection and Management of Pneumothoraces in Patients With COVID-19.

In this report, we present a series involving critically ill patients with known coronavirus disease (COVID-19) infection where a portable X-ray machine equipped with artificial intelligence (AI) software aided in the urgent radiographic diagnosis of pneumothorax. These cases demonstrate how real-world clinical employment of AI tools capable of analyzing and prioritizing studies in the radiologist's worklist can potentially lead to earlier detection of emergent findings like pneumothorax. The use of AI tools in this manner has the potential to both improve radiology workflow and add significant clinical value in managing critically ill patient populations, such as those with severe COVID-19 infection.

Deep cerebellar stimulation enhances cognitive recovery after prefrontal traumatic brain injury in rodent.

Functional outcome following traumatic brain injury (TBI) varies greatly, with approximately half of those who survive suffering long-term motor and cognitive deficits despite contemporary rehabilitation efforts. We have previously shown that deep brain stimulation (DBS) of the lateral cerebellar nucleus (LCN) enhances rehabilitation of motor deficits that result from brain injury. The objective of the present study was to evaluate the efficacy of LCN DBS on recovery from rodent TBI that uniquely models the injury location, chronicity and resultant cognitive symptoms observed in most human TBI patients. We used controlled cortical impact (CCI) to produce an injury that targeted the medial prefrontal cortex (mPFC-CCI) bilaterally, resulting in cognitive deficits. Unilateral LCN DBS electrode implantation was performed 6 weeks post-injury. Electrical stimulation started at week eight post-injury and continued for an additional 4 weeks. Cognition was evaluated using baited Y-maze, novel object recognition task and Barnes maze. Post-mortem analyses, including Western Blot and immunohistochemistry, were conducted to elucidate the cellular and molecular mechanisms of recovery. We found that mPFC-CCI produced significant cognitive deficits compared to pre-injury and naïve animals. Moreover, LCN DBS treatment significantly enhanced the long-term memory process and executive functions of applying strategy. Analyses of post-mortem tissues showed significantly greater expression of CaMKIIα, BDNF and p75NTR across perilesional cortex and higher expression of postsynaptic formations in LCN DBS-treated animals compared to untreated. Overall, these data suggest that LCN DBS is an effective treatment of cognitive deficits that result from TBI, possibly by activation of ascending, glutamatergic projections to thalamus and subsequent upregulation of thalamocortical activity that engages neuroplastic mechanisms for facilitation of functional re-organization. These results support a role for cerebellar output neuromodulation as a novel therapeutic approach to enhance rehabilitation for patients with chronic, post-TBI cognitive deficits that are unresponsive to traditional rehabilitative efforts.

Randomized, Prospective Study of the Order of Preoperative Preparation Solutions for Patients Undergoing Foot and Ankle Orthopedic Surgery.

BACKGROUND: Surgical site infection is routinely cited as the most common complication following orthopedic foot and ankle surgery. Our institution uses 4% chlorhexidine gluconate followed by 70% isopropyl alcohol to reduce skin bacterial loads prior to surgery. These solutions have potential synergistic qualities to prevent a postoperative infection. The purpose of this study was to determine if the order of these solutions has a significant effect on the residual bacterial pathogens load following operative site preparation for foot and ankle surgery, as evidenced by positive culture swabs. METHODS: A total of 95 consecutive patients, undergoing surgery of the foot and ankle with a single surgeon, were prospectively randomized to 1 of 2 operative preparation groups: isopropyl alcohol (IPA) group, whose operative site preparation consisted of a 4% chlorhexidine application followed by alcohol rinse (49 patients), and chlorhexidine gluconate (CHG) group, which had 46 patients undergo operative site preparation using alcohol followed by chlorhexidine. A total of 4 aerobic culture specimens were obtained from the third web space of the operative foot on each patient: (1) prior to operative site preparation, (2) after the prep was completed, (3) after completion of the procedure, and (4) after the incision was closed. Each patient was then followed for 6 months postoperatively to monitor the operative site. Medical comorbidities were also analyzed. RESULTS: The average time for IPA procedures was 52 minutes vs 54 for CHG (ns). There was no difference between groups with respect to diabetes, tobacco use, obesity, race, or immunosuppression. Both groups had 100% bacterial growth from specimens obtained prior to operative site preparation (P > .05). For all postpreparation swabs, 19.0% (28/147) of the IPA cultures were positive compared to 10.9% (15/138) from the CHG group cultures (P = .07). The amount of patients with positive culture results favored the CHG group at each collection point: 6.5% (3/46) versus 25% (12/49) after draping (P = .02); 15% (7/46) versus 33% (16/49) after completion of the surgery (P = .05); and 20% (9/46) versus 35% (17/49) after skin closure (P = .07). One operative site infection was seen in the first 30 days following surgery for each treatment group, each treated with oral antibiotics. No additional skin or wound complications were encountered during the 6-month study follow-up. CONCLUSION: Postoperative infection rates following foot and ankle orthopedic surgery was low. Both chlorhexidine and isopropyl alcohol solutions were effective methods in reducing operative site bacterial colonization when combined. In this study, applying isopropyl alcohol solution followed by the chlorhexidine solution was more effective in reducing positive bacterial cultures taken after operative site preparation. No difference in clinical wound infection rate was seen. LEVEL OF EVIDENCE: Level I, prospective randomized study.

Risk factors for failure of a single surgical debridement in adults with acute septic arthritis.

BACKGROUND: Acute septic arthritis in a native joint may require more than one surgical debridement to eradicate the infection. Our objectives were to determine the prevalence of failure of a single surgical debridement for acute septic arthritis, to identify risk factors for failure of a single debridement, and to develop a prognostic probability algorithm to predict failure of a single surgical debridement for acute septic arthritis in adults. METHODS: We collected initial laboratory and medical comorbidity data of 128 adults (132 native joints) with acute septic arthritis who underwent at least one surgical debridement at our institution between 2000 and 2011. Univariate and logistic regression analyses were used to identify potential risk factors for failure of a single surgical debridement. Stepwise variable selection was used to develop a prediction model and identify probabilities of failure of a single surgical debridement. RESULTS: Of the 128 patients (132 affected joints) who underwent surgical debridement for acute septic arthritis, forty-nine (38%) of the patients (fifty joints) experienced failure of a single debridement and required at least two debridements (range, two to four debridements). Staphylococcus aureus was the most common bacterial isolate (in sixty, or 45%, of the 132 joints). Logistic regression analysis identified five independent clinical predictors for failure of a single surgical debridement: a history of inflammatory arthropathy (odds ratio [OR], 7.3; 95% confidence interval [CI], 2.4 to 22.6; p < 0.001), the involvement of a large joint (knee, shoulder, or hip) (OR, 7.0; 95% CI, 1.2 to 37.5; p = 0.02), a synovial-fluid nucleated cell count of >85.0 x 10(9) cells/L (OR, 4.7; 95% CI, 1.8 to 17.7; p = 0.002), S. aureus as the bacterial isolate (OR, 4.6; 95% CI, 1.8 to 11.9; p = 0.002), and a history of diabetes (OR, 2.6; 95% CI, 1.1 to 6.2; p = 0.04). CONCLUSIONS: Most (62%) of the septic joints were managed effectively with a single surgical debridement. Adults with a history of inflammatory arthropathy, involvement of a large joint, a synovial-fluid nucleated cell count of >85.0 x 10(9) cells/L, an infection with S. aureus, or a history of diabetes had a higher risk of failure of a single surgical debridement for acute septic arthritis and requiring additional surgical debridement(s).

Passive immunization with anti-glucosaminidase monoclonal antibodies protects mice from implant-associated osteomyelitis by mediating opsonophagocytosis of Staphylococcus aureus megaclusters.

Towards the development of a methicillin-resistant Staphylococcus aureus (MRSA) vaccine we evaluated a neutralizing anti-glucosaminidase (Gmd) monoclonal antibody (1C11) in a murine model of implant-associated osteomyelitis, and compared its effects on LAC USA300 MRSA versus a placebo and a Gmd-deficient isogenic strain (ΔGmd). 1C11 significantly reduced infection severity, as determined by bioluminescent imaging of bacteria, micro-CT assessment of osteolysis, and histomorphometry of abscess numbers (p < 0.05). Histology also revealed infiltrating macrophages, and the complete lack of staphylococcal abscess communities (SAC), in marrow abscesses of 1C11 treated mice. In vitro, 1C11 had no direct effects on proliferation, but electron microscopy demonstrated that 1C11 treatment phenocopies ΔGmd defects in binary fission. Moreover, addition of 1C11 to MRSA cultures induced the formation of large bacterial aggregates (megaclusters) that sedimented out of solution, which was not observed in ΔGmd cultures or 1C11 treated cultures of a protein A-deficient strain (ΔSpa), suggesting that the combined effects of Gmd inhibition and antibody-mediated agglutination are required. Finally, we demonstrated that macrophage opsonophagocytosis of MRSA and megaclusters is significantly increased by 1C11 (p < 0.01). Collectively, these results suggest that the primary mechanism of anti-Gmd humoral immunity against MRSA osteomyelitis is macrophage invasion of Staphylococcal abscess communities (SAC) and opsonophagocytosis of megaclusters. .

Anti-glucosaminidase IgG in sera as a biomarker of host immunity against Staphylococcus aureus in orthopaedic surgery patients.

BACKGROUND: Staphylococcus aureus infections remain a major complication of orthopaedic surgery. Although serum C-reactive protein is useful for diagnosis, there are no specific tests for host immunity that can assess a patient's risk for serious infection. On the basis of the identification of glucosaminidase as a potentially protective antigen in animal models, we tested the hypotheses that anti-glucosaminidase IgG (immunoglobulin G) levels vary in sera of mice and orthopaedic patients with Staphylococcus aureus infections and that physical and neutralizing titers correlate. METHODS: In vitro ELISAs (enzyme-linked immunosorbent assays) were developed to quantify binding (physical) and enzyme-neutralizing (functional) anti-glucosaminidase IgG titers. The assays were validated with use of sera from naive, Staphylococcus aureus-challenged, and glucosaminidase-immunized mice. The physical, functional, and isotype titers of anti-glucosaminidase IgG were measured in sera from twenty-four patients with a confirmed Staphylococcus aureus infection following orthopaedic surgery and in sera from twenty noninfected patients. The specificity of the anti-glucosaminidase assay was evaluated by means of linear regression and receiver-operator characteristic curve analysis. RESULTS: In mice, the analytic range of the physical titer assay for anti-glucosaminidase IgG was determined to be 1 ng/mL to 1 µg/mL, and physical titers correlated with functional titers (p < 0.002). Although all patients had measurable anti-glucosaminidase IgG, the physical titers in the infected patients were significantly higher by a factor of two compared with those in the healthy controls (p = 0.015). The physical titers were significantly correlated with the functional titers (p < 0.0001). Receiver-operator characteristic curve analysis demonstrated a diagnostic specificity of 0.72 (p = 0.014) for the assay. The anti-glucosaminidase titer in almost every patient was dominated by the IgG1 isotype. CONCLUSIONS: Humoral immunity against glucosaminidase varied in mammals with Staphylococcus aureus osteomyelitis. Anti-glucosaminidase titers in sera were a potential biomarker of infection and have the potential to assess the quality of host immunity against Staphylococcus aureus. CLINICAL RELEVANCE: Staphylococcus aureus infections can be challenging to diagnose, and there is no diagnostic test for host immunity. We demonstrated a cost-effective assay for determining the anti-glucosaminidase titer, which can be readily combined with conventional serology to improve diagnosis and to assess host immunity against Staphylococcus aureus.

In-hospital postoperative radiographs for instrumented single-level degenerative spinal fusions: utility after intraoperative fluoroscopy.

BACKGROUND CONTEXT: There is a paucity of literature examining the clinical yield of in-hospital postoperative radiographs for patients who have had instrumented single-level spinal fusions with intraoperative fluoroscopic guidance. Many spinal surgeons consider postoperative standing radiographs to be the appropriate standard of care, even in patients who have an uneventful postoperative course. PURPOSE: To evaluate the additional clinical yield and cost-effectiveness of in-hospital postoperative standing radiographs for patients undergoing instrumented single-level cervical and lumbar fusions in which intraoperative fluoroscopy is used. Are postoperative standing radiographs necessary before hospital discharge? STUDY DESIGN: Retrospective review of 100 consecutive degenerative spinal surgical cases in which intraoperative fluoroscopic imaging was compared with immediate postoperative radiographs using a vertebral grid mapping technique. METHODS: A retrospective review of 100 consecutive patients who had an instrumented single-level cervical (30) or lumbar (70) fusion for a degenerative spinal condition performed by the same surgeon using intraoperative fluoroscopy. All patients had a documented uneventful postoperative hospitalization without evidence of new postoperative neurologic finding. All patients had both anteroposterior (AP) and lateral intraoperative fluoroscopic images and same-hospitalization standing AP and lateral radiographic images, which were performed within 72 hours postoperatively. Intraoperative and postoperative images were compared by two observers independently using a vertebral grid mapping technique to locate screw position and control magnification differences. Study parameters included screw tip position grids, interbody graft position, segmental sagittal plane alignment, spondylolisthesis grade, and hospital charges for patient imaging and interpretation. RESULTS: Early instrumentation failure and/or screw position change was not observed in any patient. Seventy-four patients demonstrated a grid match for all screw tip positions on both true AP and lateral radiographs. Twenty-six patients had either a postoperative AP or lateral radiograph that was clinically malrotated and precluded comparison with the intraoperative true fluoroscopic images. Segmental sagittal alignment difference between intraoperative fluoroscopic and postoperative radiographic sagittal images averaged only 1.2° (range, 0-9) and was not statistically significant (paired Student t test, p=.88). Significant difference between intraoperative and immediate postoperative interbody graft position and spondylolisthesis grade was not demonstrated in any patient. Patient hospital billing charges for postoperative AP and lateral radiographic imaging with interpretation averaged $600. CONCLUSIONS: In patients who have a single-level instrumented fusion and a documented uneventful postoperative course, in-hospital postoperative standing AP and lateral radiographs do not appear to provide additional clinically relevant information when intraoperative fluoroscopy is properly used. Fluoroscopy also demonstrated more consistent accuracy and a potential for significant cost savings.