Biomechanical Comparison of Anterior Cervical Plate Fixation Versus Integrated Fixation Cage for Anterior Cervical Discectomy and Fusion.

STUDY DESIGN: Cadaveric, biomechanic study. OBJECTIVE: To compare the range of motion profiles of the cervical spine following one-level anterior cervical discectomy and fusion (ACDF) constructs instrumented with either an interbody cage and anterior plate or integrated fixation cage in a cadaveric model. SUMMARY OF BACKGROUND DATA: While anterior plates with interbody cages are the most common construct of fixation in ACDF, newer integrated cage-plate devices seek to provide similar stability with a decreased implant profile. However, differences in postoperative cervical range of motion between the 2 constructs remain unclear. METHODS: Six cadaveric spines were segmented into 2 functional spine units (FSUs): C2-C5 and C6-T2. Each FSU was nondestructively bent in flexion-extension (FE), right-left lateral bending (LB), and right-left axial rotation (AR) at a rate of 0.5°/s under a constant axial load until a limit of 2-Nm was reached to evaluate baseline range of motion (ROM). Matched pairs were then randomly assigned to undergo instrumentation with either the standard anterior cage and plate (CP) or the integrated fixation cage (IF). Following instrumentation, ROM was then remeasured as previously described. RESULTS: For CP fixation, ROM increased by 61.2±31.7% for FE, 36.3±20.4% for LB, and 31.7±19.1% for AR. For IF fixation, ROM increased by 64.2±15.5% for FE, 56.7±39.8% for LB, and 94.5±65.1% for AR. There was no significant difference in motion between each group across FE, LB, and AR. CONCLUSION: This biomechanical study demonstrated increased motion in both the CP and IF groups relative to the intact, un-instrumented state. However, our model showed no differences in ROM between CP and IF constructs in any direction of motion. These results suggest that either method of instrumentation is a suitable option for ACDF with respect to constructing stiffness at time zero.

Cerebral Cavernous Malformations Patient Perception Analysis via Social Media.

BACKGROUND: The rise of social media has allowed for individuals and patients to connect with each other and influence patient behavior. This study aimed to improve our understanding of the patients' experience with cerebral cavernous malformations (CCM) via social media. METHODS: Instagram and Twitter were searched using terms of ("cavernoma," "cavernous malformations," "cavernous angioma," or "cav mal"). Public Instagram posts tagged with "#cavernoma" and "@cavernoma" identified 327 posts that directly included a patient's own experience. Twitter posts that included "#cavernoma" and "@cavernoma" were searched, yielding 75 after eliminating those that did not pertain to the patient's own experience. The posts and tweets were coded for relevant themes related to their experience with the disease. RESULTS: Overall, more patients are using Instagram (n = 327) over Twitter (n = 84) to share their personal experience with CCM with a trend for male patients to use Twitter more compared to females with a female predominance in Instagram. A total of 277 of 327 (84.7%) Instagram posts and 67 of 84 (89.3%) Twitter posts were made after the patient's surgery. The most common theme on Instagram was focused on the postoperative rehabilitation process and mobility support (52.0 and 24.5%, respectively). Other common themes present on Twitter and Instagram were recounting symptoms and complications and life satisfaction (26.0 and 24.2%, respectively). Cavernoma patients prior to surgery were more likely to discuss on Instagram their symptoms (p = 0.001), fear of bleeding (p < 0.001), and mental health (p = 0.014). Postoperatively, cavernoma patients were more likely to discuss disability than they were preoperatively (p = 0.001). CONCLUSION: Social media platforms offer a communication tool for patients with CCM patients to share their experience with other patients and the general public and portrays their personal experience with CCM. These platforms allow for physicians to better understand the patient experience following cavernoma surgery.

p-Chloropropynyl Phenylalanine, a Versatile Non-Canonical Amino Acid for Co-Translational Peptide Macrocyclization and Side Chain Diversification.

Macrocyclization has proven to be a beneficial strategy to improve upon some of the disadvantages of peptides as therapeutics. Nevertheless, many peptide cyclization strategies are not compatible with in vitro display technologies like mRNA display. Here we describe the novel amino acid p-chloropropynyl phenylalanine (pCPF). pCPF is a substrate for a mutant phenylalanyl-tRNA synthetase and its introduction into peptides via in vitro translation leads to spontaneous peptide macrocyclization in the presence of peptides containing cysteine. Macrocyclization occurs efficiently with a wide variety of ring sizes. Moreover, pCPF can be reacted with thiols after charging onto tRNA, enabling the testing of diverse ncAAs in translation. The versatility of pCPF should facilitate downstream studies of translation and enable the creation of novel macrocyclic peptide libraries.

Viral-specific T cells for Cytomegalovirus retinitis following hematopoietic stem cell transplantation: A success story.

Cytomegalovirus retinitis (CMVR) following hematopoietic stem cell transplantation (HCT) for a primary immunodeficiency is a rare but highly morbid condition with potential irreversible consequences despite optimal antiviral pharmacotherapy. Viral-specific T cells (VSTs) pose a promising and safe approach eradicating intractable viral disease. We describe the case of a 21-month-old male with Wiskott-Aldrich syndrome (WAS) and CMVR post HCT with sustained long-term virologic and clinical response after CMV-specific T-cell therapy. This case highlights the need to consider VST as an adjunct upfront strategy in refractory CMVR and for routine ophthalmologic screening and surveillance in high-risk patients post HCT.

Biomechanical Analysis of Multilevel Posterior Cervical Spinal Fusion Constructs.

STUDY DESIGN: Controlled Laboratory Study. OBJECTIVE: To compare multilevel posterior cervical fusion (PCF) constructs stopping at C7, T1, and T2 under cyclic load to determine the range of motion (ROM) between the lowest instrumented level and lowest instrumented-adjacent level (LIV-1). SUMMARY OF BACKGROUND DATA: PCF is a mainstay of treatment for various cervical spine conditions. The transition between the flexible cervical spine and rigid thoracic spine can lead to construct failure at the cervicothoracic junction. There is little evidence to determine the most appropriate level at which to stop a multilevel PCF. METHODS: Fifteen human cadaveric cervicothoracic spines were randomly assigned to 1 of 3 treatment groups: PCF stopping at C7, T1, or T2. Specimens were tested in their native state, following a simulated PCF, and after cyclic loading. Specimens were loaded in flexion-extension), lateral bending, and axial rotation. Three-dimensional kinematics were recorded to evaluate ROM. RESULTS: The C7 group had greater flexion-extension motion than the T1 and T2 groups following instrumentation (10.17±0.83 degree vs. 2.77±1.66 degree and 1.06±0.55 degree, P <0.001), and after cyclic loading (10.42±2.30 degree vs. 2.47±0.64 degree and 1.99±1.23 degree, P <0.001). There was no significant difference between the T1 and T2 groups. The C7 group had greater lateral bending ROM than both thoracic groups after instrumentation (8.81±3.44 degree vs. 3.51±2.52 degree, P =0.013 and 1.99±1.99 degree, P =0.003) and after cyclic loading. The C7 group had greater axial rotation motion than the thoracic groups (4.46±2.27 degree vs. 1.26±0.69 degree, P =0.010; and 0.73±0.74 degree, P =0.003) following cyclic loading. CONCLUSION: Motion at the cervicothoracic junction is significantly greater when a multilevel PCF stops at C7 rather than T1 or T2. This is likely attributable to the transition from a flexible cervical spine to a rigid thoracic spine. Although this does not account for in vivo fusion, surgeons should consider extending multilevel PCF constructs to T1 when feasible. LEVEL OF EVIDENCE: Not applicable.

Biomechanical Comparison of Anatomic Restoration of the Ulnar Footprint vs Traditional Ulnar Tunnels in Ulnar Collateral Ligament Reconstruction.

BACKGROUND: Current techniques for ulnar collateral ligament (UCL) reconstruction do not reproduce the anatomic ulnar footprint of the UCL. The purpose of this study was to describe a novel UCL reconstruction technique that utilizes proximal-to-distal ulnar bone tunnels to better re-create the anatomy of the UCL and to compare the biomechanical profile at time zero among this technique, the native UCL, and the traditional docking technique. HYPOTHESIS: The biomechanical profile of the anatomic technique is similar to the native UCL and traditional docking technique. STUDY DESIGN: Controlled laboratory study. METHODS: Ten matched cadaveric elbows were potted with the forearm in neutral rotation. The palmaris longus tendon graft was harvested, and bones were sectioned 14 cm proximal and distal to the elbow joint. Specimen testing included (1) native UCL testing performed at 90° of flexion with 0.5 N·m of valgus moment preload, (2) cyclic loading from 0.5 to 5 N·m of valgus moment for 1000 cycles at 1 Hz, and (3) load to failure at 0.2 mm/s. Elbows then underwent UCL reconstruction with 1 elbow of each pair receiving the classic docking technique using either anatomic (proximal to distal) or traditional (anterior to posterior) tunnel locations. Specimen testing was then repeated as described. RESULTS: There were no differences in maximum load at failure between the anatomic and traditional tunnel location techniques (mean ± SD, 34.90 ± 10.65 vs 37.28 ± 14.26 N·m; P = .644) or when including the native UCL (45.83 ± 17.03 N·m; P = .099). Additionally, there were no differences in valgus angle after 1000 cycles across the anatomic technique (4.58°± 1.47°), traditional technique (4.08°± 1.28°), and native UCL (4.07°± 1.99°). The anatomic group and the native UCL had similar valgus angles at failure (24.13°± 5.86° vs 20.13°± 5.70°; P = .083), while the traditional group had a higher valgus angle at failure when compared with the native UCL (24.88°± 6.18° vs 19.44°± 5.86°; P = .015). CONCLUSION: In this cadaveric model, UCL reconstruction with the docking technique utilizing proximal-to-distal ulnar tunnels better restored the ulnar footprint while providing valgus stability comparable with reconstruction with the docking technique using traditional anterior-to-posterior ulnar tunnel locations. These results suggest that utilization of the anatomic tunnel location in UCL reconstruction has similar biomechanical properties to the traditional method at the time of initial fixation (ie, not accounting for healing after reconstruction in vivo) while keeping the ulnar tunnels farther from the ulnar nerve. Further studies are warranted to determine if an anatomically based UCL reconstruction results in differing outcomes than traditional reconstruction techniques. CLINICAL RELEVANCE: Current UCL reconstruction techniques do not accurately re-create the ulnar UCL footprint. The UCL is a dynamic constraint to valgus loads at the elbow, and a more anatomic reconstruction may afford more natural joint kinematics. This more anatomic technique performs similarly to the traditional docking technique at time zero, and the results of this study may offer a starting point for future in vivo studies.

Intramedullary Unicortical Button and All-Suture Anchors Provide Similar Maximum Strength for Onlay Distal Biceps Tendon Repair.

PURPOSE: To evaluate the biomechanical profile of onlay distal biceps repair with an intramedullary unicortical button versus all-suture anchors under cyclic loading and maximal load to failure. METHODS: Twenty paired fresh-frozen human cadaveric elbows were randomized to onlay distal biceps repair with either a single intramedullary button or with two 1.35-mm all-suture anchors. A 1.3-mm high tensile strength tape was used in a Krackow stitch to suture the tendons in both groups. Specimens and repair constructs were loaded for 3,000 cycles and then loaded to failure. Maximum load to failure, mode of failure, and construct elongation were recorded. RESULTS: Mean (± standard deviation) maximum load to failure for the unicortical intramedullary button and all-suture anchor repairs were 503.23 ± 141.77 N and 537.33 ± 262.13 N (P = .696), respectively. Mean maximum displacement after 3,000 cycles (± standard deviation) was 4.17 ± 2.05 mm in the button group and 2.06 ± 1.05 mm in the suture anchor group (P = .014). Mode of failure in the button group was suture tape rupture in 7 specimens, failure at the tendon-suture interface in 2 specimens, and button pullout in 1 specimen. Anchor pullout was the mode of failure in all suture anchor specimens. There were no tendon ruptures or radial tuberosity fractures in either group. CONCLUSIONS: This study demonstrates that onlay distal biceps repair with 2 all-suture anchors has similar maximum strength to repair with an intramedullary button and that both are viable options for fixation. CLINICAL RELEVANCE: All-suture anchors and unicortical intramedullary button have similar maximum strength at time zero. Both constructs provide suitable fixation for onlay distal biceps repair.

Meta-Analysis of Neoadjuvant Immunotherapy for Patients with Resectable Non-Small Cell Lung Cancer.

PURPOSE: Immunotherapy has created a paradigm shift in the treatment of metastatic non-small cell lung cancer (NSCLC), overcoming the therapeutic plateau previously achieved by systemic chemotherapy. There is growing interest in the utility of immunotherapy for patients with resectable NSCLC in the neoadjuvant setting. The present systematic review and meta-analysis aim to provide an overview of the existing evidence, with a focus on pathological and radiological response, perioperative clinical outcomes, and long-term survival. METHODS: A systematic review was conducted using electronic databases from their dates of inception to August 2021. Pooled data on pathological response, radiological response, and perioperative outcomes were meta-analyzed where possible. RESULTS: Eighteen publications from sixteen studies were identified, involving 548 enrolled patients who underwent neoadjuvant immunotherapy, of whom 507 underwent surgery. Pathologically, 52% achieved a major pathological response, 24% a complete pathological response, and 20% reported a complete pathological response of both the primary lesion as well as the sampled lymph nodes. Radiologically, 84% of patients had stable disease or partial response. Mortality within 30 days was 0.6%, and morbidities were reported according to grade and frequency. CONCLUSION: The present meta-analysis demonstrated that neoadjuvant immunotherapy was feasible and safe based on perioperative clinical data and completion rates of surgery within their intended timeframe. The pathological response after neoadjuvant immunotherapy was superior to historical data for patients who were treated with neoadjuvant chemotherapy alone, whilst surgical and treatment-related adverse events were comparable. The limitations of the study included the heterogenous treatment regimens, lack of long-term follow-up, variations in the reporting of potential prognostic factors, and potential publication bias.

A Biomechanical Comparison of High-Tensile Strength Tape Versus High-Tensile Strength Suture for Tendon Fixation Under Cyclic Loading.

PURPOSE: To compare the biomechanical properties of high-tensile strength tape and high-tensile strength suture across 2 selected stitch techniques, the Krackow and whip stitch, in securing tendinous tissue during 5,000 cycles of nondestructive loading followed by a load to failure. METHODS: Fourteen matched pairs each of cadaveric Achilles, quadriceps, and patellar tendons (n = 84) were randomly assigned to either Krackow or whip stitch and sutured with either 2-mm high-tensile strength tape or No. 2 high-tensile strength suture. Specimens were preloaded to 20 N, cyclically loaded from 20 to 200 N for 5,000 cycles at 2 Hz, and then loaded to failure at 200 mm/min. Linear mixed models evaluated the effects of suture material and stitch technique on cyclic normalized tendon-suture elongation, total normalized tendon-suture elongation at 5,000 cycles, and maximum load at failure. RESULTS: Across all suture constructs, normalized elongation was greater during the initial 10 cycles, compared with all subsequent cycling intervals (all P < .001). There was less total normalized elongation (ß = -0.239; P = .007) and greater maximum load at failure in tape (ß = 163.71; P = .014) when used in the Krackow stitch compared with the whip stitch. CONCLUSIONS: Our findings indicate that tape used in the Krackow stitch maintains the most favorable fixation strength after enduring cyclic loading, with greater maximum load at failure. In addition, overall normalized elongation during long-term cyclic loading was predominately affected by the stitch technique used, regardless of the suture material; however, tape allowed less normalized elongation during the initial loading cycles, especially when placed in the whip stitch. CLINICAL RELEVANCE: Understanding the potential short- and long-term outcomes of suture material and stitch technique on securing tendinous tissue under repetitive stresses can help inform clinicians on optimal tendon fixation techniques for early postoperative activities.

An Investigation of a Novel Tendon Transfer Surgery for High Median-Ulnar Nerve Palsy in a Chicken Model.

PURPOSE: The state-of-the-art tendon transfer surgery for high median-ulnar nerve palsy involves directly suturing four finger flexor tendons to one wrist extensor muscle. This couples finger flexion limiting the patient's ability to grasp objects. Therefore, we propose a new approach to attach a novel passive implant to the extensor digitorum longus tendon in order to create a differential mechanism in situ. The implant is expected to enable the fingers to adapt to an object's shape during grasping. Chickens have been used as a model in tendon research, but studies have primarily focused on the digital flexor tendon mechanism. Thus, the aim of this study was to explore the feasibility of the chicken model for extensor tendon research and to validate the surgical technique for a new approach to tendon transfer surgery. MATERIALS AND METHODS: Twenty-nine chickens were randomly divided into three groups: implant (n = 12), sham (n = 10), and control (n = 7). Postoperative healing and complications were documented. RESULTS: Surgery was successful in all chickens. All animals healed appropriately by Day 16 postoperatively. Chickens in the implant group experienced significantly more intermittent toe-knuckling gait than the sham group (p = 0.001). CONCLUSIONS: The described surgical technique allowed for successful application of a novel implantable passive mechanism in a live chicken model. In combination with previous work, findings from the present study further validated a novel tendon-transfer surgery for high median-ulnar nerve palsy. Based on the degree of intermittent abnormal gait experienced by the implant group, refinement to the implant design is warranted in future studies.

Oncogenic KRAS Regulates Amino Acid Homeostasis and Asparagine Biosynthesis via ATF4 and Alters Sensitivity to L-Asparaginase.

KRAS is a regulator of the nutrient stress response in non-small-cell lung cancer (NSCLC). Induction of the ATF4 pathway during nutrient depletion requires AKT and NRF2 downstream of KRAS. The tumor suppressor KEAP1 strongly influences the outcome of activation of this pathway during nutrient stress; loss of KEAP1 in KRAS mutant cells leads to apoptosis. Through ATF4 regulation, KRAS alters amino acid uptake and asparagine biosynthesis. The ATF4 target asparagine synthetase (ASNS) contributes to apoptotic suppression, protein biosynthesis, and mTORC1 activation. Inhibition of AKT suppressed ASNS expression and, combined with depletion of extracellular asparagine, decreased tumor growth. Therefore, KRAS is important for the cellular response to nutrient stress, and ASNS represents a promising therapeutic target in KRAS mutant NSCLC.

Nutrients differentially regulate nucleobindin-2/nesfatin-1 in vitro in cultured stomach ghrelinoma (MGN3-1) cells and in vivo in male mice.

Nesfatin-1 is secreted, meal-responsive anorexigenic peptide encoded in the precursor nucleobindin-2 [NUCB2]. Circulating nesfatin-1 increases post-prandially, but the dietary components that modulate NUCB2/nesfatin-1 remain unknown. We hypothesized that carbohydrate, fat and protein differentially regulate tissue specific expression of nesfatin-1. NUCB2, prohormone convertases and nesfatin-1 were detected in mouse stomach ghrelinoma [MGN3-1] cells. NUCB2 mRNA and protein were also detected in mouse liver, and small and large intestines. MGN3-1 cells were treated with glucose, fatty acids or amino acids. Male C57BL/6 mice were chronically fed high fat, high carbohydrate and high protein diets for 17 weeks. Quantitative PCR and nesfatin-1 assays were used to determine nesfatin-1 at mRNA and protein levels. Glucose stimulated NUCB2 mRNA expression in MGN3-1 cells. L-Tryptophan also increased NUCB2 mRNA expression and ghrelin mRNA expression, and nesfatin-1 secretion. Oleic acid inhibited NUCB2 mRNA expression, while ghrelin mRNA expression and secretion was enhanced. NUCB2 mRNA expression was significantly lower in the liver of mice fed a high protein diet compared to mice fed other diets. Chronic intake of high fat diet caused a significant reduction in NUCB2 mRNA in the stomach, while high protein and high fat diet caused similar suppression of NUCB2 mRNA in the large intestine. No differences in serum nesfatin-1 levels were found in mice at 7 a.m, at the commencement of the light phase. High carbohydrate diet fed mice showed significantly elevated nesfatin-1 levels at 1 p.m. Serum nesfatin-1 was significantly lower in mice fed high fat, protein or carbohydrate compared to the controls at 7 p.m, just prior to the dark phase. Mice that received a bolus of high fat had significantly elevated nesfatin-1/NUCB2 at all time points tested post-gavage, compared to control mice and mice fed other diets. Our results for the first time indicate that nesfatin-1 is modulated by nutrients.

Degree of glutathione deficiency and redox imbalance depend on subtype of mitochondrial disease and clinical status.

Mitochondrial disorders are associated with decreased energy production and redox imbalance. Glutathione plays a central role in redox signaling and protecting cells from oxidative damage. In order to understand the consequences of mitochondrial dysfunction on in vivo redox status, and to determine how this varies by mitochondrial disease subtype and clinical severity, we used a sensitive tandem mass spectrometry assay to precisely quantify whole blood reduced (GSH) and oxidized (GSSG) glutathione levels in a large cohort of mitochondrial disorder patients. Glutathione redox potential was calculated using the Nernst equation. Compared to healthy controls (n = 59), mitochondrial disease patients (n = 58) as a group showed significant redox imbalance (redox potential -251 mV ± 9.7, p<0.0001) with an increased level of oxidation by ∼ 9 mV compared to controls (-260 mV ± 6.4). Underlying this abnormality were significantly lower whole blood GSH levels (p = 0.0008) and GSH/GSSG ratio (p = 0.0002), and significantly higher GSSG levels (p<0.0001) in mitochondrial disease patients compared to controls. Redox potential was significantly more oxidized in all mitochondrial disease subgroups including Leigh syndrome (n = 15), electron transport chain abnormalities (n = 10), mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (n = 8), mtDNA deletion syndrome (n = 7), mtDNA depletion syndrome (n = 7), and miscellaneous other mitochondrial disorders (n = 11). Patients hospitalized in metabolic crisis (n = 7) showed the greatest degree of redox imbalance at -242 mV ± 7. Peripheral whole blood GSH and GSSG levels are promising biomarkers of mitochondrial dysfunction, and may give insights into the contribution of oxidative stress to the pathophysiology of the various mitochondrial disorders. In particular, evaluation of redox potential may be useful in monitoring of clinical status or response to redox-modulating therapies in clinical trials.

A new LC-MS/MS method for the clinical determination of reduced and oxidized glutathione from whole blood.

Reduced levels of glutathione (γ-glutamylcysteinylglycine, GSH) and the ratio of GSH to glutathione disulfide (GSSG) can serve as important indicators of oxidative stress and disease risk. Measured concentrations of GSH and GSSG vary widely between laboratories, largely due to the instability of GSH during sample handling and variables arising from different analytical methods. We have developed a simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for measuring whole blood GSH and GSSG that minimizes preanalytic and analytic variability, reliably eliminates interference from ion suppression, and can easily be implemented in clinical laboratories. Samples were deproteinized with sulfosalicylic acid (SSA) and derivatized with N-ethylmaleimide (NEM) in a single preparative step, and the resulting supernatants combined with stable-isotope internal standards (GSH-(13)C, (15)N-NEM and GSSG-(13)C,(15)N), subjected to chromatographic separation using a Hypercarb column, and analyzed by MS/MS in the positive-ion mode. Results showed excellent linearity for both GSH and GSSG over the ranges of physiologic normal, with inter- and intra-assay CV's of 3.1-4.3% and accuracy between 95% and 101%. The lower limits of detection (LLOD) were 0.4µM for GSH and 0.1µM for GSSG and the lower limits of quantitation (LLOQ) were 1.5µM for GSH and 0.1µM for GSSG. Derivatized samples are stable for at least 3 years when stored at -80°C, and underivatized samples for at least 24h at either 4°C or room temperature. Reference intervals were determined for 59 control samples, and were (mean±SD): GSH 900±140µM; GSSG 1.17±0.43µM; GSH/GSSG 880±370.

A new technique for Charcot's foot reconstruction.

External fixation was used to reduce or arrest progressive degeneration in 28 patients with Charcot's foot dislocations. Adjunctive procedures included tendo Achilles lengthening and application of an external bone stimulator. Advantages of using external fixation are that surgeries are usually performed percutaneously and that most patients are weightbearing in 10 to 14 days. There was no incidence of pin tract infection or further foot collapse, with the longest follow-up period being 24 months. The authors propose that use of external fixation with bone stimulation may be an effective alternative method of treating the Charcot foot.