ERK signaling promotes resistance to TRK kinase inhibition in NTRK fusion-driven glioma mouse models.

Pediatric-type high-grade gliomas frequently harbor gene fusions involving receptor tyrosine kinase genes, including neurotrophic tyrosine kinase receptor (NTRK) fusions. Clinically, these tumors show high initial response rates to tyrosine kinase inhibition but ultimately recur due to the accumulation of additional resistance-conferring mutations. Here, we developed a series of genetically engineered mouse models of treatment-naïve and -experienced NTRK1/2/3 fusion-driven gliomas. Both the TRK kinase domain and the N-terminal fusion partners influenced tumor histology and aggressiveness. Treatment with TRK kinase inhibitors significantly extended survival of NTRK fusion-driven glioma mice in a fusion- and inhibitor-dependent manner, but tumors ultimately recurred due to the presence of treatment-resistant persister cells. Finally, we show that ERK activation promotes resistance to TRK kinase inhibition and identify MEK inhibition as a potential combination therapy. These models will be invaluable tools for preclinical testing of novel inhibitors and to study the cellular responses of NTRK fusion-driven gliomas to therapy.

Immediate Unprotected Weightbearing vs 2 Weeks Nonweightbearing After Open Reduction Internal Fixation of Ankle Fractures.

BACKGROUND: Postoperative care protocols for ankle fracture surgery remain controversial with variability among care providers. This prospective controlled trial compared 12-week postoperative outcomes for immediate unprotected weightbearing (IMWB) vs nonweightbearing (NWB) for 2 weeks in a splint followed by weightbearing as tolerated (WBAT) in a boot after surgical fixation of selected low-energy ankle fractures without superior articular involvement. METHODS: Eighty-seven patients undergoing surgical fixation of ankle fractures at a single level 1 trauma center were recruited according to specific criteria and enrolled by presentation date. The first 43 eligible patients were allocated to the control group, with NWB in a splint for 2 weeks followed by WBAT in a walker boot. The next 44 patients recruited were allocated to the IMWB group. The primary outcome was the Olerud-Molander score (OMAS). Secondary outcome measures included the Euroquol-5D (EQ5D) score and Work Productivity and Activity Impairment: Specific Health Problem (WPAI:SHP) scores, ankle range of motion (ROM), wound complications, time to return to work, radiograph measurements, and fracture reduction loss. In this perioperative-focused study, we collected data on patients until 12 weeks postoperation. RESULTS: The IMWB group had 5 superficial wound complications vs 1 in the control group. At 12 weeks, we found no difference in OMAS, EQ5D, WPAI:SHP scores, ROM, time to return to work, or radiographic measurements. CONCLUSION: In this short-term and relatively small prospective trial, we found more wound complications among patients treated with immediate unprotected weightbearing compared with patients treated with 2 weeks of NWB followed by protected weightbearing. Given the low incidence and small sample size, we do not know if these observed findings are generalizable. However, we also found no difference in functional outcomes at 12 weeks postoperation between these 2 groups. In light of that, we do not recommend IMWB after open reduction internal fixation of low-energy ankle fractures with plate and/or screw fixation. LEVEL OF EVIDENCE: Level II, prospective controlled trial.

COVID-19 and the transition to virtual teaching sessions in an orthopaedic surgery training program: a survey of resident perspectives.

BACKGROUND: COVID-19 has had a tremendous impact on medical education. Due to concerns of the virus spreading through gatherings of health professionals, in-person conferences and rounds were largely cancelled. The purpose of this study is the evaluate the implementation of an online educational curriculum by a major Canadian orthopaedic surgery residency program in response to COVID-19. METHODS: A survey was distributed to residents of a major Canadian orthopaedic surgery residency program from July 10th to October 24th, 2020. The survey aimed to assess residents' response to this change and to examine the effect that the transition has had on their participation, engagement, and overall educational experience. RESULTS: Altogether, 25 of 28 (89%) residents responded. Respondents generally felt the quality of education was superior (72%), their level of engagement improved (64%), and they were able to acquire more knowledge (68%) with the virtual format. Furthermore, 88% felt there was a greater diversity of topics, and 96% felt there was an increased variety of presenters. Overall, 76% of respondents felt that virtual seminars better met their personal learning objectives. Advantages reported were increased accessibility, greater convenience, and a wider breadth of teaching faculty. Disadvantages included that the virtual sessions felt less personal and lacked dynamic feedback to the presenter. CONCLUSIONS: Results of this survey reveal generally positive attitudes of orthopaedic surgery residents about the transition to virtual learning in the setting of an ongoing pandemic. This early evaluation and feedback provides valuable guidance on how to grow this novel curriculum and bring the frontier of virtual teaching to orthopaedic education long-term.

Effect of 3d/4p Mixing on 1s2p Resonant Inelastic X-ray Scattering: Electronic Structure of Oxo-Bridged Iron Dimers.

1s2p resonant inelastic X-ray scattering (1s2p RIXS) has proven successful in the determination of the differential orbital covalency (DOC, the amount of metal vs ligand character in each d molecular orbital) of highly covalent centrosymmetric iron environments including heme models and enzymes. However, many reactive intermediates have noncentrosymmetric environments, e.g., the presence of strong metal-oxo bonds, which results in the mixing of metal 4p character into the 3d orbitals. This leads to significant intensity enhancement in the metal K-pre-edge and as shown here, the associated 1s2p RIXS features, which impact their insight into electronic structure. Binuclear oxo bridged high spin Fe(III) complexes are used to determine the effects of 4p mixing on 1s2p RIXS spectra. In addition to developing the analysis of 4p mixing on K-edge XAS and 1s2p RIXS data, this study explains the selective nature of the 4p mixing that also enhances the analysis of L-edge XAS intensity in terms of DOC. These 1s2p RIXS biferric model studies enable new structural insight from related data on peroxo bridged biferric enzyme intermediates. The dimeric nature of the oxo bridged Fe(III) complexes further results in ligand-to-ligand interactions between the Fe(III) sites and angle dependent features just above the pre-edge that reflect the superexchange pathway of the oxo bridge. Finally, we present a methodology that enables DOC to be obtained when L-edge XAS is inaccessible and only 1s2p RIXS experiments can be performed as in many metalloenzyme intermediates in solution.

PERICARDIAL MESOTHELIOMA AND ASSOCIATED PERICARDIAL EFFUSION IN A TIGER RAT SNAKE (SPILOTES PULLATUS) TREATED WITH PERICARDIOCENTESIS.

A 1.5 kg, male, wild-caught tiger rat snake (Spilotes pullatus) presented with an externally visible distension of the body wall at the level of the heart. Ultrasound examination showed marked pericardial effusion. Pericardial fluid showed no bacterial or fungal growth, few leukocytes, and few suspected reactive mesothelial or neoplastic cells. Therapeutic pericardiocentesis was successfully performed, removing most of the fluid from the pericardial sac. The snake had mild lethargy and weakness immediately after the procedure but returned to normal behavior within 2 wk. Repeat pericardiocentesis was performed 6 mo after the initial presentation when moderate refilling of the pericardial sac was seen. The snake died 4 days after the second procedure with acute hemorrhage. Pericardial mesothelioma was diagnosed by histopathology after postmortem examination. This report provides the first documented case of mesothelioma in a tiger rat snake and the first description of the disease in colubrids.

Three-dimensional printing in orthopaedic surgery: a scoping review.

Three-dimensional printing (3DP) has become more frequently used in surgical specialties in recent years. These uses include pre-operative planning, patient-specific instrumentation (PSI), and patient-specific implant production.The purpose of this review was to understand the current uses of 3DP in orthopaedic surgery, the geographical and temporal trends of its use, and its impact on peri-operative outcomesOne-hundred and eight studies (N = 2328) were included, published between 2012 and 2018, with over half based in China.The most commonly used material was titanium.Three-dimensional printing was most commonly reported in trauma (N = 41) and oncology (N = 22). Pre-operative planning was the most common use of 3DP (N = 63), followed by final implants (N = 32) and PSI (N = 22).Take-home message: Overall, 3DP is becoming more common in orthopaedic surgery, with wide range of uses, particularly in complex cases. 3DP may also confer some important peri-operative benefits. Cite this article: EFORT Open Rev 2020;5:430-441. DOI: 10.1302/2058-5241.5.190024.

Heterotopic Ossification following Total Elbow Arthroplasty in a Patient with Parkinson's Disease: Case Report and Literature Review.

Introduction. Heterotopic ossification (HO) usually develops following surgery or trauma. Risk factors for HO following elbow fractures include delay to surgery (>7 days), floating fractures, and elbow subluxation. Systemic risk factors for HO include male sex; concurrent cranial, neurological, or abdominal injury; high-energy trauma; previous development of HO; and contralateral fracture. To date, no studies have reported on Parkinson's disease (PD) as a risk factor for the development of HO. Case Presentation. A 68-year-old female with PD (treated with levodopa-carbidopa) sustained a right closed (OTA type A3) distal humerus fracture and was treated with a total elbow arthroplasty. Postoperatively, development of significant near-ankylosing HO was observed and contributed to significant restriction of elbow motion with activities of daily living. After HO maturation, the osseous growth was excised, and the area irradiated. The patient regained excellent elbow motion with no recurrence of HO. Discussion. A literature review revealed six cases of HO development in PD patients following arthroplasty. Patients with PD have higher serum concentrations of interleukins (IL) and tumor necrosis factor- (TNF-) α. These factors stimulate BMP-2 production which may promote osteogenesis. Levodopa-carbidopa may also influence HO through stimulation of growth hormone and IGF-1. Conclusion. Parkinsonism may promote heterotopic bone growth through the release of osteoinductive factors. HO development may also be mediated by levodopa-carbidopa therapy. Future research should highlight the link between HO and PD and identify if prophylaxis is warranted in PD patients undergoing arthroplasty.

Evaluation of a concerted vs. sequential oxygen activation mechanism in α-ketoglutarate-dependent nonheme ferrous enzymes.

Determining the requirements for efficient oxygen (O2) activation is key to understanding how enzymes maintain efficacy and mitigate unproductive, often detrimental reactivity. For the α-ketoglutarate (αKG)-dependent nonheme iron enzymes, both a concerted mechanism (both cofactor and substrate binding prior to reaction with O2) and a sequential mechanism (cofactor binding and reaction with O2 precede substrate binding) have been proposed. Deacetoxycephalosporin C synthase (DAOCS) is an αKG-dependent nonheme iron enzyme for which both of these mechanisms have been invoked to generate an intermediate that catalyzes oxidative ring expansion of penicillin substrates in cephalosporin biosynthesis. Spectroscopy shows that, in contrast to other αKG-dependent enzymes (which are six coordinate when only αKG is bound to the FeII), αKG binding to FeII-DAOCS results in ∼45% five-coordinate sites that selectively react with O2 relative to the remaining six-coordinate sites. However, this reaction produces an FeIII species that does not catalyze productive ring expansion. Alternatively, simultaneous αKG and substrate binding to FeII-DAOCS produces five-coordinate sites that rapidly react with O2 to form an FeIV=O intermediate that then reacts with substrate to produce cephalosporin product. These results demonstrate that the concerted mechanism is operative in DAOCS and by extension, other nonheme iron enzymes.

Phase I Pharmacokinetic Study of Niraparib in Chinese Patients with Epithelial Ovarian Cancer.

LESSONS LEARNED: Pharmacokinetics characteristics of niraparib in Chinese patients were similar to those in white patients. Niraparib could be well tolerated by Chinese patients, and adverse events were manageable in this study. Population pharmacokinetics analysis indicated that baseline body weight had a modest impact on pharmacokinetics parameters of niraparib; however, it was not considered clinically important. BACKGROUND: This randomized, open-label, single-arm, phase I study was designed to investigate the pharmacokinetics (PK) and safety of niraparib in Chinese patients with epithelial ovarian cancer. METHODS: Eligible patients were randomized in a 1:1:1 ratio to receive 100, 200, or 300 mg of niraparib once daily. PK parameters were analyzed after single and multiple dose administrations. RESULTS: Thirty-six Chinese patients were enrolled in total. Niraparib was rapidly absorbed after administration, and median time-to-peak (Tmax ) was 3 hours. The long terminal elimination half-life (T1/2 ∼ 35 hours) supports once-daily dosing regimen. The exposure to niraparib showed linear and dose-proportional pharmacokinetics, whereas other PK parameters such as Tmax , T1/2 , and accumulation ratio were dose independent. Population PK analysis indicated that there was no effect of race on niraparib PK parameters, whereas baseline body weight had a modest impact on niraparib exposure. Grade 3/4 treatment-emergent adverse events (TEAEs; reported in ≥10% of patients) included platelet count decreased (a total of five patients who were all from the 300-mg group) and neutrophil count decreased. The TEAEs were manageable after dose modification. CONCLUSION: The PK profile of niraparib in Chinese patients is consistent with that in white patients. Niraparib is safe and well tolerated in Chinese patients with ovarian cancer.

Arming oHSV with ULBP3 drives abscopal immunity in lymphocyte-depleted glioblastoma.

Oncolytic viruses induce local tumor destruction and inflammation. Whether virotherapy can also overcome immunosuppression in noninfected tumor areas is under debate. To address this question, we have explored immunologic effects of oncolytic herpes simplex viruses (oHSVs) in a genetically engineered mouse model of isocitrate dehydrogenase (IDH) wild-type glioblastoma, the most common and most malignant primary brain tumor in adults. Our model recapitulates the genomics, the diffuse infiltrative growth pattern, and the extensive macrophage-dominant immunosuppression of human glioblastoma. Infection with an oHSV that was armed with a UL16-binding protein 3 (ULBP3) expression cassette inhibited distant tumor growth in the absence of viral spreading (abscopal effect) and yielded accumulation of activated macrophages and T cells. There was also abscopal synergism of oHSVULBP3 with anti-programmed cell death 1 (anti-PD-1) against distant, uninfected tumor areas; albeit consistent with clinical trials in patients with glioblastoma, monotherapy with anti-PD-1 was ineffective in our model. Arming oHSV with ULBP3 led to upregulation of antigen processing and presentation gene sets in myeloid cells. The cognate ULBP3 receptor NKG2D, however, is not present on myeloid cells, suggesting a noncanonical mechanism of action of ULBP3. Overall, the myeloid-dominant, anti-PD-1-sensitive abscopal effect of oHSVULBP3 warrants further investigation in patients with IDH wild-type glioblastoma.

Resonant inelastic X-ray scattering determination of the electronic structure of oxyhemoglobin and its model complex.

Hemoglobin and myoglobin are oxygen-binding proteins with S = 0 heme {FeO2}8 active sites. The electronic structure of these sites has been the subject of much debate. This study utilizes Fe K-edge X-ray absorption spectroscopy (XAS) and 1s2p resonant inelastic X-ray scattering (RIXS) to study oxyhemoglobin and a related heme {FeO2}8 model compound, [(pfp)Fe(1-MeIm)(O2)] (pfp = meso-tetra(α,α,α,α-o-pivalamido-phenyl)porphyrin, or TpivPP, 1-MeIm = 1-methylimidazole) (pfpO2), which was previously analyzed using L-edge XAS. The K-edge XAS and RIXS data of pfpO2 and oxyhemoglobin are compared with the data for low-spin FeII and FeIII [Fe(tpp)(Im)2]0/+ (tpp = tetra-phenyl porphyrin) compounds, which serve as heme references. The X-ray data show that pfpO2 is similar to FeII, while oxyhemoglobin is qualitatively similar to FeIII, but with significant quantitative differences. Density-functional theory (DFT) calculations show that the difference between pfpO2 and oxyhemoglobin is due to a distal histidine H bond to O2 and the less hydrophobic environment in the protein, which lead to more backbonding into the O2 A valence bond configuration interaction multiplet model is used to analyze the RIXS data and show that pfpO2 is dominantly FeII with 6-8% FeIII character, while oxyhemoglobin has a very mixed wave function that has 50-77% FeIII character and a partially polarized Fe-O2 π-bond.

Mechanism of selective benzene hydroxylation catalyzed by iron-containing zeolites.

A direct, catalytic conversion of benzene to phenol would have wide-reaching economic impacts. Fe zeolites exhibit a remarkable combination of high activity and selectivity in this conversion, leading to their past implementation at the pilot plant level. There were, however, issues related to catalyst deactivation for this process. Mechanistic insight could resolve these issues, and also provide a blueprint for achieving high performance in selective oxidation catalysis. Recently, we demonstrated that the active site of selective hydrocarbon oxidation in Fe zeolites, named α-O, is an unusually reactive Fe(IV)=O species. Here, we apply advanced spectroscopic techniques to determine that the reaction of this Fe(IV)=O intermediate with benzene in fact regenerates the reduced Fe(II) active site, enabling catalytic turnover. At the same time, a small fraction of Fe(III)-phenolate poisoned active sites form, defining a mechanism for catalyst deactivation. Density-functional theory calculations provide further insight into the experimentally defined mechanism. The extreme reactivity of α-O significantly tunes down (eliminates) the rate-limiting barrier for aromatic hydroxylation, leading to a diffusion-limited reaction coordinate. This favors hydroxylation of the rapidly diffusing benzene substrate over the slowly diffusing (but more reactive) oxygenated product, thereby enhancing selectivity. This defines a mechanism to simultaneously attain high activity (conversion) and selectivity, enabling the efficient oxidative upgrading of inert hydrocarbon substrates.

Predatory Publishing in Orthopaedic Research.

BACKGROUND: The open-access model has changed the landscape of academic publishing over the last 20 years. An unfortunate consequence has been the advent of predatory publishing, which exploits the open-access model for monetary gain by collecting publishing fees from authors under the pretense of being a legitimate publication while providing little-to-no peer review. This study aims to investigate the predatory publishing phenomenon in orthopaedic literature. METHODS: We searched Beall's List of Predatory Journals and Publishers and another list of predatory journals for journal titles that are possibly related to orthopaedics. We then searched their web sites for the following information: total number of articles published, journal country of origin, author country of origin, article processing charge (APC), quoted review time, and location of the listed headquarters. We also reported the article quality of a random sample of these journals. We consulted InCites Journal Citation Reports to determine the number of nonpredatory orthopaedic publications that are indexed, and we manually searched a random sample of these legitimate journals for Beall's criteria. Additionally, we searched the Directory of Open Access Journals (DOAJ) and PubMed databases for any possible predatory journal titles. RESULTS: We found 104 suspected predatory publishers, representing 225 possible predatory journals. One journal was indexed in the DOAJ, and 20 were indexed in PubMed. Review time was not identified for 56.2% of the journals, and 36.5% quoted a review time of <1 month. Nearly half of the listed addresses of the publishers were either unsearchable or led to residential or empty lots. Eighty-two legitimate journals were identified. The median APC was $420 for predatory journals and $2,900 for legitimate journals. We found that a random sample of the legitimate journals published studies with higher reporting standards, but a few also contained 1 criterion that is found on Beall's list. CONCLUSIONS: This study highlights the scope of orthopaedic predatory publishing. Possibly predatory journals outnumber legitimate orthopaedic journals. Orthopaedic surgeons should be aware of the suspected predatory journals and consult available online tools to identify them because distinguishing them from legitimate journals can be a challenge.

A mononuclear nonheme {FeNO}6 complex: synthesis and structural and spectroscopic characterization.

While the synthesis and characterization of {FeNO}7,8,9 complexes have been well documented in heme and nonheme iron models, {FeNO}6 complexes have been less clearly understood. Herein, we report the synthesis and structural and spectroscopic characterization of mononuclear nonheme {FeNO}6 and iron(iii)-nitrito complexes bearing a tetraamido macrocyclic ligand (TAML), such as [(TAML)FeIII(NO)]- and [(TAML)FeIII(NO2)]2-, respectively. First, direct addition of NO(g) to [FeIII(TAML)]- results in the formation of [(TAML)FeIII(NO)]-, which is sensitive to moisture and air. The spectroscopic data of [(TAML)FeIII(NO)]-, such as 1H nuclear magnetic resonance and X-ray absorption spectroscopies, combined with computational study suggest the neutral nature of nitric oxide with a diamagnetic Fe center (S = 0). We also provide alternative pathways for the generation of [(TAML)FeIII(NO)]-, such as the iron-nitrite reduction triggered by protonation in the presence of ferrocene, which acts as an electron donor, and the photochemical iron-nitrite reduction. To the best of our knowledge, the present study reports the first photochemical nitrite reduction in nonheme iron models.

Structural characterization of a non-heme iron active site in zeolites that hydroxylates methane.

Iron-containing zeolites exhibit unprecedented reactivity in the low-temperature hydroxylation of methane to form methanol. Reactivity occurs at a mononuclear ferrous active site, α-Fe(II), that is activated by N2O to form the reactive intermediate α-O. This has been defined as an Fe(IV)=O species. Using nuclear resonance vibrational spectroscopy coupled to X-ray absorption spectroscopy, we probe the bonding interaction between the iron center, its zeolite lattice-derived ligands, and the reactive oxygen. α-O is found to contain an unusually strong Fe(IV)=O bond resulting from a constrained coordination geometry enforced by the zeolite lattice. Density functional theory calculations clarify how the experimentally determined geometric structure of the active site leads to an electronic structure that is highly activated to perform H-atom abstraction.

Oxidation of Naphthalene with a Manganese(IV) Bis(hydroxo) Complex in the Presence of Acid.

Naphthalene oxidation with metal-oxygen intermediates is a difficult reaction in environmental and biological chemistry. Herein, we report that a MnIV bis(hydroxo) complex, which was fully characterized by various physicochemical methods, such as ESI-MS, UV/Vis, and EPR analysis, X-ray diffraction, and XAS, can be employed for the oxidation of naphthalene in the presence of acid to afford 1,4-naphthoquinone. Redox titration of the MnIV bis(hydroxo) complex gave a one-electron reduction potential of 1.09 V, which is the most positive potential for all reported nonheme MnIV bis(hydroxo) species as well as MnIV oxo analogues. Kinetic studies, including kinetic isotope effect analysis, suggest that the naphthalene oxidation occurs through a rate-determining electron transfer process.

Surgical simulation training in orthopedics: current insights.

BACKGROUND: While the knowledge required of residents training in orthopedic surgery continues to increase, various factors, including reductions in work hours, have resulted in decreased clinical learning opportunities. Recent work suggests residents graduate from their training programs without sufficient exposure to key procedures. In response, simulation is increasingly being incorporated into training programs to supplement clinical learning. This paper reviews the literature to explore whether skills learned in simulation-based settings results in improved clinical performance in orthopedic surgery trainees. MATERIALS AND METHODS: A scoping review of the literature was conducted to identify papers discussing simulation training in orthopedic surgery. We focused on exploring whether skills learned in simulation transferred effectively to a clinical setting. Experimental studies, systematic reviews, and narrative reviews were included. RESULTS: A total of 15 studies were included, with 11 review papers and four experimental studies. The review articles reported little evidence regarding the transfer of skills from simulation to the clinical setting, strong evidence that simulator models discriminate among different levels of experience, varied outcome measures among studies, and a need to define competent performance in both simulated and clinical settings. Furthermore, while three out of the four experimental studies demonstrated transfer between the simulated and clinical environments, methodological study design issues were identified. CONCLUSION: Our review identifies weak evidence as to whether skills learned in simulation transfer effectively to clinical practice for orthopedic surgery trainees. Given the increased reliance on simulation, there is an immediate need for comprehensive studies that focus on skill transfer, which will allow simulation to be incorporated effectively into orthopedic surgery training programs.

Cement Waste During Primary Total Knee Arthroplasty and its Effect on Cost Savings: An Institutional Analysis.

Purpose Healthcare costs are increasingly garnering more media attention and there is increasing focus on improving efficiencies in daily practice. Orthopedic surgery is also subject to these fiscal pressures, particularly in arthroplasty surgeries, secondary to high volumes with costly equipment. Total knee arthroplasties (TKA) are one of the most common surgical procedures, with over 64,000 annual cases in Canada. Even marginal cost reductions per procedure can be compounded over the large volume to result in considerable savings. This study's purpose is to investigate and quantify the cost of wasted intraoperative cement used in primary TKA. Methods Residual amounts of wasted bone cement were collected and measured following uncomplicated primary TKAs performed by the senior authors in a high-volume arthroplasty centre between January and June 2017. Stryker Simplex® with Tobramycin Bone Cement was the specific institutional cement used. Results One hundred and two primary total knee arthroplasties were investigated. The results revealed that an average 91.2 g of surgical cement was wasted per case, with less than 30 g retained in the bone-implant interface (26.8 g). Institutional costs per package of cement is $120.62, amounting to $2.04 per gram of cement. This represents a value of $186.25 CAD per case. Conclusion On average, each primary TKA procedure wastes 91.2 g of bone cement per case. The value of this wasted cement is $186.25 CAD per TKA. When extrapolated to the most recent recorded numbers of TKAs done in Canada, that figure nears $12 million. The results of this study are important, as they reveal a potential source to target for both waste reduction and cost control.