Does spinopelvic alignment affect femoral head cartilage and the proximal femoral physis in slipped capital femoral epiphysis? A finite element analysis.

BACKGROUND: Slipped capital femoral epiphysis is a prevalent pediatric hip disorder. Recent studies suggest the spine's sagittal profile may influence the proximal femoral growth plate's slippage, an aspect not extensively explored. This study utilizes finite element analysis to investigate how various spinopelvic alignments affect shear stress and growth plate slip. METHODS: A finite element model was developed from CT scans of a healthy adult male lumbar spine, pelvis, and femurs. The model was subjected to various sagittal alignments through reorientation. Simulations of two-leg stance, one-leg stance, walking heel strike, ascending stairs heel strike, and descending stairs heel strike were conducted. Parameters measured included hip joint contact area, stress, and maximum growth plate Tresca (shear) stress. FINDINGS: Posterior pelvic tilt cases indicated larger shear stresses compared to the anterior pelvic tilt variants except in two leg stance. Two leg stance resulted in decreases in the posterior tilted pelvi variants hip contact and growth plate Tresca stress compared to anterior tilted pelvi, however a combination of posterior pelvic tilt and high pelvic incidence indicated larger shear stresses on the growth plate. One leg stance and heal strike resulted in higher shear stress on the growth plate in posterior pelvic tilt variants compared to anterior pelvic tilt, with a combination of posterior pelvic tilt and high pelvic incidence resulting in the largest shear. INTERPRETATION: Our findings suggest that posterior pelvic tilt and high pelvic incidence may lead to increased shear stress at the growth plate. Activities performed in patients with these alignments may predispose to biomechanical loading that shears the growth plate, potentially leading to slip.

Addition of a Second Calcaneal Pin for Spanning Ankle External Fixation.

Spanning ankle external fixation is a commonly used technique for the treatment of fractures of the lower extremity. Traditionally, a single pin is placed in the safe zone of the calcaneus to provide a point of traction for fracture reduction and stabilization. Complications include infection and pin loosening with subsequent loss of fracture reduction. We aim to highlight the benefits and techniques of adding a second calcaneal pin to reduce the likelihood of infection, pin loosening, and possible loss of fracture reduction. Using the standard medial-to-lateral placement technique, two centrally threaded Schanz pins were placed within the safe zone of the calcaneus approximately 2 cm apart and were connected by clamps and a short carbon fiber rod. The remainder of the external fixation apparatus is assembled using a standard technique after obtaining fracture reduction. There is an increased incidence of infection and pin loosening with decreased bone quality and a longer duration within an external fixator. The addition of a second calcaneal pin can be used to reduce the incidence of pin loosening and associated sequela, especially in patients with decreased bone quality, thus improving outcomes for patients undergoing spanning ankle external fixation.

A systematic review of the operative techniques for treating cubitus varus deformity in children.

A systematic review of the operative techniques for treating cubitus varus deformity in children was performed using research databases including PubMed and Embase. Outcome measurements included mean angular correction of the humerus-elbow-wrist angle, complications, revisions and outcome scores. A total of 45 papers and 911 patients were included. Lateral closing wedge osteotomy (LCWO) (427 patients) was the most common procedure and 5.56% of these patients experienced lateral condylar prominence. This technique had the highest revision rate at 3%. The step-cut osteotomy (111 patients) yielded zero postoperative infections or loss of motion. Distraction osteogenesis (92 patients) was the least common technique. Superficial pin tract infections occurred in 18% of patients and 88.04% of patients reported excellent results, the highest of any technique in this study. The infection rate of dome osteotomy (151 patients) was 9.45% and 4.72% of patients experienced loss of motion. 3D osteotomy (130 patients) had no infections, 87.78% of patients reported excellent outcomes, and 2.22% of patients reported poor outcomes, the lowest of all techniques. For unidimensional correction, LCWO provides a technically simple procedure and reasonable outcomes. Step-cut osteotomy has less lateral condylar prominence but is more complicated than LCWO. Distraction osteogenesis is a minimally invasive alternative to LCWO and step-cut osteotomy, but it has more superficial infections and can be bothersome to patients. For a multidimensional correction, 3D osteotomy is superior to dome osteotomy due to its lower infection rate and higher rate of functionally excellent outcomes.

Early Definitive Fixation of Talus Fractures Is Safe: A Retrospective Review.

BACKGROUND: Talus fractures are often result of high energy mechanisms and can lead to devastating complications. Treatment is often operative; however, the appropriate timing of this has been debated. The purpose of this study is to determine the efficacy and safety of the early treatment of talus fractures. METHODS: Patients aged 18 years or older who underwent definitive operative stabilization of their talus fracture at a single urban level 1 trauma center were retrospectively reviewed. Patients were split into 2 groups based on their time to definitive fixation: ≤ or >24 hours. Pertinent demographic, surgical, and follow-up data were collected and analyzed. RESULTS: A total of 108 fractures were treated with 65 in the ≤24 hours fixation group and 43 in the >24 hours fixation group. Fractures involving the talar neck were the most commonly treated fracture pattern followed by the body and the head. There was no difference between the 2 groups in length to full weight bearing, union, or time to union. Open fracture was found to be the only significant risk factor for nonunion in both groups. There was no significant difference in infection or arthrodesis rates between the 2 groups. CONCLUSION: Definitive treatment of talus fractures within 24 hours from presentation is both safe and effective with equal outcomes and without increased complications when compared with those injuries that undergo delayed or staged definitive fixation. LEVEL OF EVIDENCE: Level III.

A PEEK into carbon fiber: A practical guide for high performance composite polymeric implants for orthopaedic oncology.

Introduction: The use of carbon fiber implants in orthopaedic oncology has increased within recent years. The most widely used type of polymer is carbon fiber polyether ether ketone (CF-PEEK). Its radiolucency enables targeted radiotherapy and artifact-free tumor surveillance, which provides major advantages over metallic hardware. We aim to summarize the unique benefits within orthopaedic oncology, clinical pitfalls, and recent advancements. Methods: Four representative patient cases from a single tertiary academic medical center were treated with carbon fiber implants (n = 2 nails, n = 2 plates) from 2021 to 2022. Results: There were no adverse events noted during intraoperative implantation or postoperative follow up. All patients reported improvements in pain and no difficulties in ambulation. There were no instances of catastrophic failure or implant loosening. Conclusion: CF implants offer a diverse array of advantages regarding its radiolucency, low scatter density, and bioinert profile. Nonetheless, further research is required to understand the long-term surgical outcomes and robustness of CF implants. Multi institutional trials could address important aspects of durability and stability over extended periods, feasibility and ease-of-use for different anatomical sites and bone quality, as well as cost-effectiveness in post-operative imaging, healthcare resource utilization, and revision rates. Providing orthopaedic surgeons with valuable insight will enable thorough clinically supported, informed decision making regarding optimal use of implants.

A Polymorphism in the Epstein-Barr Virus EBER2 Noncoding RNA Drives In Vivo Expansion of Latently Infected B Cells.

The oncogenic gammaherpesviruses, including human Epstein-Barr virus (EBV), human Kaposi's sarcoma-associated herpesvirus (KSHV), and murine gammaherpesvirus 68 (MHV68, γHV68, MuHV-4), are associated with numerous malignancies, including B cell lymphomas and nasopharyngeal carcinoma. These viruses employ numerous molecular strategies to colonize the host, including the expression of noncoding RNAs (ncRNAs). As the first viral ncRNAs identified, EBV-encoded RNA 1 and 2 (EBER1 and EBER2, respectively) have been investigated extensively for decades; however, their specific in vivo functions remain largely unknown. In work here, we used chimeric MHV68 viruses in an in vivo complementation system to test whether EBV EBER2 contributes to acute and/or chronic phases of infection. Expression of EBER2 derived from EBV strain B95-8 resulted in a significant expansion of latently infected B cells in vivo, which was accompanied by a decrease in virus-infected plasma cells. EBV strains typically carry one of two variants of EBER2, which differ primarily by a 5-nucleotide core polymorphism identified initially in the EBV strain M81. Strikingly, mutation of the 5 nucleotides that define this core polymorphism resulted in the loss of the infected B cell expansion and restored plasma cell infection. This work reveals that the B95-8 variant of EBER2 promotes the expansion of the latently infected B cell pool in vivo and may do so in part through inhibition of terminal differentiation. These findings provide new insight into mechanisms by which viral ncRNAs promote in vivo colonization and further and provide further evidence of the inherent tumorigenic risks associated with gammaherpesvirus manipulation of B cell differentiation. IMPORTANCE The oncogenic gammaherpesviruses, including human Epstein-Barr virus (EBV), human Kaposi's sarcoma-associated herpesvirus (KSHV), and murine gammaherpesvirus 68, employ numerous strategies to colonize the host, including expression of noncoding RNAs (ncRNAs). As the first viral ncRNAs ever identified, EBV-encoded RNA 1 and 2 (EBER1 and EBER2) have been investigated extensively for decades; however, their specific in vivo functions remain largely unknown. Work here reveals that an EBV EBER2 variant highly associated with B cell lymphoma promoted a significantly increased expansion of the infected B cell pool in vivo, which coincided with altered B cell differentiation. Mutation of the 5 nucleotides that define this EBER2 variant resulted in the loss of B cell expansion and normal B cell differentiation. These findings provide new insight into the mechanisms by which EBV manipulates B cells in vivo to retain infected cells in the high-risk B cell differentiation pathway where they are poised for tumorigenesis.

Epstein-Barr virus EBER1 and murine gammaherpesvirus TMER4 share conserved in vivo function to promote B cell egress and dissemination.

The oncogenic gammaherpesviruses, including human Epstein-Barr virus (EBV), human Kaposi's sarcoma-associated herpesvirus (KSHV), and murine gammaherpesvirus 68 (MHV68, γHV68, MuHV-4) establish life-long latency in circulating B cells. The precise determinants that mediate in vivo gammaherpesvirus latency and tumorigenesis remain unclear. The EBV-encoded RNAs (EBERs) are among the first noncoding RNAs ever identified and have been the subject of decades of studies; however, their biological roles during in vivo infection remain unknown. Herein, we use a series of refined virus mutants to define the active isoform of MHV68 noncoding RNA TMER4 and demonstrate that EBV EBER1 functionally conserves this activity in vivo to promote egress of infected B cells from lymph nodes into peripheral circulation.

Identification of murine gammaherpesvirus 68 miRNA-mRNA hybrids reveals miRNA target conservation among gammaherpesviruses including host translation and protein modification machinery.

Gammaherpesviruses, including the human pathogens Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV), establish lifelong latent infection in B cells and are associated with a variety of tumors. In addition to protein coding genes, these viruses encode numerous microRNAs (miRNAs) within their genomes. While putative host targets of EBV and KSHV miRNAs have been previously identified, the specific functions of these miRNAs during in vivo infection are largely unknown. Murine gammaherpesvirus 68 (MHV68) is a natural pathogen of rodents that is genetically related to both EBV and KSHV, and thus serves as an excellent model for the study of EBV and KSHV genetic elements such as miRNAs in the context of infection and disease. However, the specific targets of MHV68 miRNAs remain completely unknown. Using a technique known as qCLASH (quick crosslinking, ligation, and sequencing of hybrids), we have now identified thousands of Ago-associated, direct miRNA-mRNA interactions during lytic infection, latent infection and reactivation from latency. Validating this approach, detailed molecular analyses of specific interactions demonstrated repression of numerous host mRNA targets of MHV68 miRNAs, including Arid1a, Ctsl, Ifitm3 and Phc3. Notably, of the 1,505 MHV68 miRNA-host mRNA targets identified in B cells, 86% were shared with either EBV or KSHV, and 64% were shared among all three viruses, demonstrating significant conservation of gammaherpesvirus miRNA targeting. Pathway analysis of MHV68 miRNA targets further revealed enrichment of cellular pathways involved in protein synthesis and protein modification, including eIF2 Signaling, mTOR signaling and protein ubiquitination, pathways also enriched for targets of EBV and KSHV miRNAs. These findings provide substantial new information about specific targets of MHV68 miRNAs and shed important light on likely conserved functions of gammaherpesvirus miRNAs.

Genome-wide Transcript Structure Resolution Reveals Abundant Alternate Isoform Usage from Murine Gammaherpesvirus 68.

The gammaherpesviruses, including Epstein-Barr virus (EBV), Kaposi's sarcoma-associated herpesvirus (KSHV), and murine gammaherpesvirus 68 (MHV68, MuHV-4, γHV68), are etiologic agents of a wide range of lymphomas and non-hematological malignancies. These viruses possess large and highly dense dsDNA genomes that feature >80 bidirectionally positioned open reading frames (ORFs). The abundance of overlapping transcripts and extensive splicing throughout these genomes have until now prohibited high throughput-based resolution of transcript structures. Here, we integrate the capabilities of long-read sequencing with the accuracy of short-read platforms to globally resolve MHV68 transcript structures using the transcript resolution through integration of multi-platform data (TRIMD) pipeline. This approach reveals highly complex features, including: (1) pervasive overlapping transcript structures; (2) transcripts containing intra-gene or trans-gene splices that yield chimeric ORFs; (3) antisense and intergenic transcripts containing ORFs; and (4) noncoding transcripts. This work sheds light on the underappreciated complexity of gammaherpesvirus transcription and provides an extensively revised annotation of the MHV68 transcriptome.

The Development and Reliability of 4 Clinical Neurocognitive Single-Leg Hop Tests: Implications for Return to Activity Decision-Making.

Context: Functional tests are limited primarily by measuring only physical performance. However, athletes often multitask, and deal with complex visual-spatial processing while being engaged in physical activity. Objective: To present the development and reliability of 4 new neurocognitive single-leg hop tests that provide more ecological validity to test sport activity demands than previous functional return to sport testing. Design: Cross-sectional. Setting: Gymnasium. Participants: Twenty-two healthy participants (9 males and 13 females; 20.9 [2.5] y, 171.2 [11.7] cm, 70.3 [11.0] kg) were recruited. Interventions: Maximum distance (physical performance) and reaction time (cognitive performance) were measured for 3 of the neurocognitive hop tests all testing a different aspect of neurocognition (single-leg central-reaction hop-reaction time to 1 central stimulus, single-leg peripheral-reaction crossover hop-reaction time between 2 peripheral stimuli, and single-leg memory triple hop-reaction to memorized stimulus with distractor stimuli). Fastest time (physical performance) and reaction time (cognitive performance) were measured for the fourth neurocognitive hop test (single-leg pursuit 6m hop-requiring visual field tracking [pursuit] and spatial navigation). Main Outcome Measures: Intraclass correlation coefficients were calculated to assess reliability of the 4 new hop tests. Additionally, Bland-Altman plots and 1-sample t tests were conducted for each single-leg neurocognitive hop to evaluate any systematic changes. Results: Intraclass correlation coefficients based on day 1 and day 2 scores ranged from .87 to .98 for both legs for physical and cognitive performance. The Bland-Altman plots and 1-sample t tests (P > .05) indicated that all 4 single-leg neurocognitive hop tests did not change systematically. Conclusions: These data provide evidence that a neurocognitive component can be added to the traditional single-leg hop tests to provide a more ecologically valid test that incorporates the integration of physical and cognitive function for return to sport. The test-retest reliability of the 4 new neurocognitive hop tests is highly reliable and does not change systematically.

PI3K-Akt signaling pathway upregulates hepatitis C virus RNA translation through the activation of SREBPs.

Hepatitis C virus (HCV) activates PI3K-Akt signaling to enhance entry and replication. Here, we found that this pathway also increased HCV translation. Knocking down the three Akt isoforms significantly decreased, whereas ectopic expression increased HCV translation. HCV translation upregulation by Akt required their kinase activities because Akt kinase-dead mutants downregulated HCV translation; and was dependent on PI3K activity since it was sensitive to PI3K inhibitor wortmannin. The viral 3'UTR was not involved in translation upregulation by Akt. HCV NS5A increased Akt phosphorylation/activity and HCV translation in the absence of the viral 3'UTR. Sterol regulatory element-binding proteins (SREBPs) were the downstream effectors of the PI3K-Akt pathway in regulating HCV translation because Akt1 and Akt2 activated both SREBP-1 and SREBP-2, whereas Akt3 upregulated SREBP-1. Knocking down SREBPs significantly decreased, while ectopic expression of SREBPs increased HCV translation. Taken together, we showed that the PI3K-Akt signaling pathway positively regulates HCV translation through SREBPs.

Arginine 112 is involved in HCV translation modulation by NS5A domain I.

HCV NS5A has three domains, which have multiple roles in the viral life cycle. We previously found that NS5A is able to down-regulate HCV RNA translation through a mechanism requiring the polyU/UC region within the viral 3'UTR to which NS5A binds. In this study, we further investigated the role of domain I in modulating viral translation. Using a series of deletion and substitution mutants, we identified a number of positively charged residues that played a role in this modulatory effect, most prominently R112. The R112A mutation negated the ability of domain I and full-length NS5A to modulate viral translation. Additionally, the R112A mutation impeded domain I binding to the polyU/UC RNA, suggesting a mechanism for this down-regulatory effect. Finally, the R112A mutation rendered HCV replication deficient. These results collectively point to a crucial role for the R112 residue of NS5A in the modulation of HCV life cycle by NS5A.

K312 and E446 are involved in HCV RNA translation modulation by NS5A domains II and III.

HCV NS5A plays a critical role in the HCV life cycle. We previously demonstrated that NS5A down-regulates viral translation through a mechanism requiring the polyU/UC region of the viral 3'UTR and that each of the three domains is capable of carrying out this function individually. In this study, we mapped the regions and amino acid residues within domains II and III involved in the modulation of viral translation. Using a series of deletion and amino acid substitution mutants, we found that K312 and E446 play important roles in the modulation of viral translation by NS5A domains II and III, respectively. In the context of full-length NS5A, mutations of K312 and E446 alone or in combination again abrogate translation down-regulation. In a transient replication assay using HCV subgenomic replicons, the K312A mutation alone does not affect HCV replication throughout a 96-h time course. While the E446A mutation can increase HCV replication at early time points (4-24 h), the K312A and E446A double mutation can enhance viral replication at 24-96 h, suggesting both residues are involved. Our results shed more light on the functions of NS5A.

Downregulation of viral RNA translation by hepatitis C virus non-structural protein NS5A requires the poly(U/UC) sequence in the 3' UTR.

Hepatitis C virus (HCV) non-structural protein 5A (NS5A) is essential for viral replication; however, its effect on HCV RNA translation remains controversial partially due to the use of reporters lacking the 3' UTR, where NS5A binds to the poly(U/UC) sequence. We investigated the role of NS5A in HCV translation using a monocistronic RNA containing a Renilla luciferase gene flanked by the HCV UTRs. We found that NS5A downregulated viral RNA translation in a dose-dependent manner. This downregulation required both the 5' and 3' UTRs of HCV because substitution of either sequence with the 5' and 3' UTRs of enterovirus 71 or a cap structure at the 5' end eliminated the effects of NS5A on translation. Translation of the HCV genomic RNA was also downregulated by NS5A. The inhibition of HCV translation by NS5A required the poly(U/UC) sequence in the 3' UTR as NS5A did not affect translation when it was deleted. In addition, we showed that, whilst the amphipathic α-helix of NS5A has no effect on viral translation, the three domains of NS5A can inhibit translation independently, also dependent on the presence of the poly(U/UC) sequence in the 3' UTR. These results suggested that NS5A downregulated HCV RNA translation through a mechanism involving the poly(U/UC) sequence in the 3' UTR.

Hepatitis C viral protein translation: mechanisms and implications in developing antivirals.

Hepatitis C viral protein translation occurs in a cap-independent manner through the use of an internal ribosomal entry site (IRES) present within the viral 5'-untranslated region. The IRES is composed of highly conserved structural domains that directly recruit the 40S ribosomal subunit to the viral genomic RNA. This frees the virus from relying on a large number of translation initiation factors that are required for cap-dependent translation, conferring a selective advantage to the virus especially in times when the availability of such factors is low. Although the mechanism of translation initiation on the Hepatitis C virus (HCV) IRES is well established, modulation of the HCV IRES activity by both cellular and viral factors is not well understood. As the IRES is essential in the HCV life cycle and as such remains well conserved in an otherwise highly heterogenic virus, the process of HCV protein translation represents an attractive target in the development of novel antivirals. This review will focus on the mechanisms of HCV protein translation and how this process is postulated to be modulated by cis-acting viral factors, as well as trans-acting viral and cellular factors. Numerous therapeutic approaches investigated in targeting HCV protein translation for the development of novel antivirals will also be discussed.