Higher Cumulative Dose of Opioids and Other Sedatives are Associated with Extubation Failure in Norwood Patients.

BACKGROUND: The primary purpose of this study is to evaluate the relationship between sedation usage and extubation failure, and to control for the effects of hemodynamic, oximetric indices, clinical characteristics, ventilatory settings pre- and post-extubation, and echocardiographic (echo) findings in neonates with hypoplastic left heart syndrome (HLHS) post-Norwood procedure. METHODS: Single-center, retrospective analysis of Norwood patients during their first extubation post-surgery from January 2015 to July 2021. Extubation failure was defined as reintubation within 48 h of extubation. Demographics, clinical characteristics, ventilatory settings, echo findings (right ventricular function, tricuspid regurgitation), and cumulative dose of sedation medications before extubation were compared between patients with successful or failed extubation. RESULTS: The analysis included 130 patients who underwent the Norwood procedure with 121 (93%) successful and 9 (7%) failed extubations. Univariate analyses showed that vocal cord anomaly (p = 0.05), lower end-tidal CO2 (p < 0.01), lower pulse-to-respiratory quotient (p = 0.02), and ketamine administration (p = 0.04) were associated with extubation failure. The use of opioids, benzodiazepines, dexmedetomidine, and ketamine are mutually correlated in this cohort. On multivariable analysis, the vocal cord anomaly (OR = 7.31, 95% CI 1.25-42.78, p = 0.027), pre-extubation end-tidal CO2 (OR = 0.80, 95% CI 0.65-0.97, p = 0.025), and higher cumulative dose of opioids (OR = 10.16, 95% CI 1.25-82.43, p = 0.030) were independently associated with extubation failure while also controlling for post-extubation respiratory support (CPAP/BiPAP/HFNC vs NC), intubation length, and echo results. CONCLUSION: Higher cumulative opioid doses were associated with a greater incidence of extubation failure in infants post-Norwood procedure. Therefore, patients with higher cumulative doses of opioids should be more closely evaluated for extubation readiness in this population. Low end-tidal CO2 and low pulse-to-respiratory quotient were also associated with failed extubation. Consideration of the pulse-to-respiratory quotient in the extubation readiness assessment can be beneficial in the Norwood population.

Missed Visits Predict Recurrence in Idiopathic Clubfoot.

BACKGROUND: Congenital talipes equinovarus, also known as "clubfoot," is a common congenital deformity. While reported relapse rates vary widely, relapse continues to be a common problem faced in the treatment of this condition. The objective of this study is to assess relationships between demographic/socioeconomic factors, follow-up, and rates of relapse in our population of clubfoot patients. METHODS: Retrospective chart review was conducted for patients undergoing treatment for idiopathic clubfoot from February 2012 to December 2022 at a tertiary children's hospital. Records were analyzed for follow-up adherence and recurrence in the Ponseti method, in addition to patient demographic and socioeconomic factors. Statistical analysis was performed to evaluate associations between recurrence, missed clinical visits, and demographic/socioeconomic factors of interest. RESULTS: Ninety-five patients were included in the study [74.7% male (N=71) and 25.2% female (N=24)]. A total of 64.2% (N=61) of patients developed recurrence during their treatment. Recurrence rates differed significantly by reported bracing noncompliance >1 month (35/46 vs. 26/49, P =0.019), having missed 1 or more clinical visits (38/61 vs. 8/34, P < 0.001), Medicaid or equivalent insurance type (41/56 vs. 20/39, P =0.028), non-white race (47/66 vs. 14/29, P =0.032, higher Social Deprivation Index score (56.13 vs. 41.06, P =0.019). Significant variables were analyzed using a multivariate logistic regression analysis (MVLR). After MVLR, having 1 or more missed clinical visits (OR 4.462, 95% CI: 1.549-12.856) remained significantly associated with increased rates of recurrence. Primary language preference and distance to the hospital were not associated with recurrence. CONCLUSIONS: Higher SDI scores, non-white race, Medicaid insurance, and missed clinical follow-up visits were all associated with increased rates of recurrence for clubfoot patients. Using an MVLR model, missed clinical follow-up visits remained independently associated with increased recurrence rates. LEVEL OF EVIDENCE: Level 2-retrospective, prognostic study.

Characterization of neuromas in peripheral nerves and their effects on heterotopic bone formation.

The formation of neuromas involves expansion of the cellular components of peripheral nerves. The onset of these disorganized tumors involves activation of sensory nerves and neuroinflammation. Particularly problematic in neuroma is arborization of axons leading to extreme, neuropathic pain. The most common sites for neuroma are the ends of transected nerves following injury; however, this rodent model does not reliably result in neuroma formation. In this study, we established a rodent model of neuroma in which the sciatic nerve was loosely ligated with two chromic gut sutures. This model formed neuromas reliably (∼95%), presumably through activation of the neural inflammatory cascade. Resulting neuromas had a disorganized structure and a significant number of replicating cells. Quantification of changes in perineurial and Schwann cells showed a significant increase in these populations. Immunohistochemical analysis showed the presence of ß-tubulin 3 in the rapidly expanding nerve and a decrease in neurofilament heavy chain compared to the normal nerve, suggesting the axons forming a disorganized structure. Measurement of the permeability of the blood-nerve barrier shows that it opened almost immediately and remained open as long as 10 days. Studies using an antagonist of the ß3-adrenergic receptor (L-748,337) or cromolyn showed a significant reduction in tumor size and cell expansion as determined by flow cytometry, with an improvement in the animal's gait detected using a Catwalk system. Previous studies in our laboratory have shown that heterotopic ossification is also a result of the activation of neuroinflammation. Since heterotopic ossification and neuroma often occur together in amputees, they were induced in the same limbs of the study animals. More heterotopic bone was formed in animals with neuromas as compared to those without. These data collectively suggest that perturbation of early neuroinflammation with compounds such as L-748,337 and cromolyn may reduce formation of neuromas.

Biomechanical Comparison of Bicortical, Unicortical, and Unicortical Far-Cortex-Abutting Screw Fixations in Plated Comminuted Midshaft Clavicle Fractures.

PURPOSE: The objective of this study was to assess the biomechanical properties of bicortical locking screws, unicortical locking screws, and unicortical far-cortex-abutting locking screw fixation in a cadaver model of comminuted midshaft clavicle fractures stabilized with a locking plate placed on the superior surface of the clavicle. METHODS: Nine pairs of adult fresh-frozen cadaver clavicles were allocated into 3 groups for either bicortical, unicortical, or unicortical far-cortex-abutting locking plate fixation. After a 1-cm osteotomy to simulate a comminuted fracture and instrumentation with an 8-hole locking plate placed on the superior surface of the clavicle, the specimens were mounted in a custom dual-gimbal fixture in a materials-testing system and tested in axial compression, torsional, and torsional load to failure. RESULTS: Axial stiffness and axial osteotomy site stiffness did not demonstrate differences between constructs. In cyclical torsion, both the bicortical and the unicortical far-cortex-abutting constructs were significantly stiffer than the unicortical construct. For torsional failure stiffness, both the bicortical and the unicortical far-cortex-abutting constructs were significantly stiffer than the unicortical construct. There was no difference between bicortical and unicortical far-cortex-abutting for torsional failure stiffness. The bicortical construct exhibited significantly higher peak failure torque compared with the unicortical construct. CONCLUSIONS: Unicortical far-cortex-abutting locking screw fixation provides comparable mechanical properties under axial and torsional loads to bicortical fixation, without penetrating the far cortex. CLINICAL RELEVANCE: Unicortical far-cortex-abutting locking screw fixation obviates far cortex penetration, and thereby protects nearby anatomical structures, may ease symptomatic implant removal, alleviates refracture risk, and eases conversion to bicortical fixation in the case of revision surgery.

A dedicated research program increases the quantity and quality of orthopaedic resident publications.

BACKGROUND: Programs seek to expose trainees to research during residency. However, little is known in any formal sense regarding how to do this effectively, or whether these efforts result in more or better-quality research output. QUESTIONS/PURPOSES: The objective of our study was to evaluate a dedicated resident research program in terms of the quantity and quality of resident research peer-reviewed publications. Specifically we asked: (1) Did residents mentored through a dedicated resident research program have more peer-reviewed publications in higher-impact journals with higher citation rates compared with residents who pursued research projects under a less structured approach? (2) Did this effect continue after graduation? METHODS: In 2006, our department of orthopaedic surgery established a dedicated resident research program, which consisted of a new research policy and a research committee to monitor quality and compliance with this policy. Peer-reviewed publications (determined from PubMed) of residents who graduated 6 years before establishing the dedicated resident research program were compared with publications from an equal period of the research-program-directed residents. The data were assessed using descriptive statistics and regression analysis. Twenty-four residents graduated from 2001 to 2006 (before implementation of the dedicated resident research program); 27 graduated from 2007 to 2012 (after implementation of the dedicated resident research program). There were 74 eligible publications as defined by the study inclusion and exclusion criteria. RESULTS: Residents who trained after implementation of the dedicated resident research program published more papers during residency than did residents who trained before the program was implemented (1.15 versus 0.79 publications per resident; 95% CI [0.05,0.93]; p = 0.047) and the journal impact factor was greater in the group that had the research program (1.25 versus 0.55 per resident; 95% CI [0.2,1.18]; p = 0.005). There were no differences between postresidency publications by trainees who graduated with versus without the research program in the number of publications, citations, and average journal impact factor per resident. A regression analysis showed no difference in citation rates of the residents' published papers before and since implementation of the research program. CONCLUSIONS: Currently in the United States, there are no standard policies or requirements that dictate how research should be incorporated in orthopaedic surgery residency training programs. The results of our study suggest that implementation of a dedicated resident research program improves the quantity and to some extent quality of orthopaedic resident research publications, but this effect did not persist after graduation.

Osteoblasts Have a Neural Origin in Heterotopic Ossification.

BACKGROUND: Heterotopic ossification (HO) is the process of bone formation at a nonskeletal site. Recently, we showed that the earliest steps occur in sensory nerves. We now extend these studies by identifying unique osteogenic progenitors within the endoneurial compartment of sensory nerves. QUESTIONS/PURPOSES: We asked: (1) What is the nature of the osteoprogenitor in the endoneurium of peripheral nerves? (2) How do osteoprogenitors travel from the nerve to the site of new bone formation? METHODS: HO was induced by intramuscular injection of Ad5BMP-2-transduced cells in mice. Osteoprogenitors were identified through immunohistochemistry and then quantified and further characterized by fluorescence-activated cell sorting and immunocytochemistry. The kinetics of the appearance of markers of extravasation was determined by quantitative reverse transcription-polymerase chain reaction. In each experiment mice were injected with bone morphogenetic protein-2 (BMP-2)-producing cells (experimental) or with cells transduced with empty vector or, in some cases, a group receiving no injection (control). RESULTS: Induction of HO leads to the expression, within 24 hours, of osteoblast-specific transcription factors in cells in the endoneurium followed by their coordinate disappearance from the nerve at 48 hours. They reappear in blood also at 48 hours after induction. During vessel entrance they begin to express the tight junction molecule, claudin 5. The cells expressing both the osteoblast-specific transcription factor, osterix, as well as claudin 5, then disappear from circulation at approximately 3 to 4 days by extravasation into the site of new bone formation. These endoneurial osteoprogenitors express neural markers PDGFRα, musashi-1, and the low-affinity nerve growth factor receptor p75(NTR) as well as the endothelial marker Tie-2. In a key experiment, cells that were obtained from mice that were injected with cells transduced with an empty vector, at 2 days after injection, contained 0.83% (SD, 0.07; 95% confidence interval [CI], 0.59-1.05) cells expressing claudin 5. However, cells that were obtained from mice 2 days after injection of BMP-2-producing cells contained 4.5% cells expressing claudin 5 (SD, 0.72%; 95% CI, 2.01-6.94; p < 0.0015). Further analysis revealed that all of the cells expressing claudin 5 were found to be positive for osteoblast-specific markers, whereas cells not expressing claudin 5 were negative for these same markers. CONCLUSIONS: The findings suggest that the endoneurial progenitors are the major osteogenic precursors that are used for HO. They exit the nerve through the endoneurial vessels, flow through vessels to the site of new bone formation, and then extravasate out of the vessels into this site. CLINICAL RELEVANCE: The biogenesis of osteoblasts in HO is very different than expected and shows that HO is, at least in part, a neurological disorder. This could result in a major shift in orthopaedic methodologies to prevent or treat this disease. The fact that nerves are intimately involved in the process may also provide clues that will lead to an explanation of the clinical fact that HO often occurs as a result of traumatic brain injury.

Biomechanical comparison of bicortical locking versus unicortical far-cortex-abutting locking screw-plate fixation for comminuted radial shaft fractures.

PURPOSE: To provide comparative biomechanical evaluation of bicortical locking versus unicortical-abutting locking screw-plate fixation in a comminuted radius fracture model. METHODS: A validated synthetic substitute of the adult human radius with a 1.5-cm-long segmental mid-diaphyseal defect was used in the study to simulate a comminuted fracture. Stabilization was achieved with an 8-hole locking plate and either bicortical screws or unicortical-abutting screws. The specimens were tested using nondestructive cyclical loading in 4-point bending, axial compression, and torsion to determine stiffness and displacement and subsequently in 4-point bending to assess load to failure. RESULTS: There were no statistically significant differences between bicortical versus unicortical-abutting locking screw fixation in nondestructive 4-point bending, axial compression, and torsion. Both locking screw constructs also demonstrated comparable 4-point bending loads to failure. CONCLUSION: The biomechanical equivalence between bicortical locking versus unicortical-abutting locking screw-plate fixation suggests that adequate locking plate fixation can be achieved without perforation of the far cortex. The abutment of the screw tip within the far cortex enhances the unicortical screw positional stability and thereby effectively opposes the displacement of the screw when subjected to bending or axial or rotational loads. CLINICAL RELEVANCE: Unicortical-abutting screws potentially offer several clinical advantages. They eliminate the need for drilling through the far cortex and thereby a risk of adjacent neurovascular injury or soft tissue structure compromise. They eliminate the issues associated with symptomatic screw prominence. They can decrease risk of refracture after screw-plate removal. In case of revision plating, they permit conversion to bicortical locking screws through the same near-cortex screw holes, which eliminates the need for a longer or repositioned plate.

Adding corticosteroids to intra-operative periarticular injections in total knee arthroplasty: A systematic review.

BACKGROUND: Adding corticosteroids to intraoperative periarticular injections (PAIs) have become a current trend in total knee arthroplasty (TKA). Periarticular corticosteroid injections (PACSIs) intend to improve postoperative pain and function. However, preoperative corticosteroid injections for symptomatic arthritis increase the rates of prosthetic joint infection (PJI) when given months prior to TKA. The aim of this systematic review was to determine whether the addition of corticosteroids to PAIs during TKA improves patient outcomes and whether such practice increases the risk of PJI? METHODS: A systematic review of the current literature following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines screened 1025 abstracts. Thirteen studies meeting specific eligibility criteria were included for further analysis. RESULTS: Among the studies comparing the PACSIs versus nonsteroidal PAIs, 36% showed a significant reduction in postoperative pain scores, 20% showed significant improvement in range of motion (ROM), and 16% showed a significant reduction in total morphine equivalence (TME). While 100% of the studies comparing PACSI to saline or no injections showed significant improvement in pain, ROM and TME. In total, there were 3 infections in 576 TKA cases receiving PACSIs and 2 infections in 534 cases not receiving a PACSI. However, studies were not powered specifically to assess for infection. CONCLUSIONS: The addition of corticosteroids to intraoperative PAIs do not demonstrate a significant benefit in the majority of studies, and tend to not have an effect on PJI risk; however, studies were not specifically powered to assess PJI risk.

Unbiased metastatic niche-labeling identifies estrogen receptor-positive macrophages as a barrier of T cell infiltration during bone colonization.

Microenvironment niches determine cellular fates of metastatic cancer cells. However, robust and unbiased approaches to identify niche components and their molecular profiles are lacking. We established Sortase A-Based Microenvironment Niche Tagging (SAMENT), which selectively labels cells encountered by cancer cells during metastatic colonization. SAMENT was applied to multiple cancer models colonizing the same organ and the same cancer to different organs. Common metastatic niche features include macrophage enrichment and T cell depletion. Macrophage niches are phenotypically diverse between different organs. In bone, macrophages express the estrogen receptor alpha (ERα) and exhibit active ERα signaling in male and female hosts. Conditional knockout of Esr1 in macrophages significantly retarded bone colonization by allowing T cell infiltration. ERα expression was also discovered in human bone metastases of both genders. Collectively, we identified a unique population of ERα+ macrophages in the metastatic niche and functionally tied ERα signaling in macrophages to T cell exclusion during metastatic colonization. HIGHLIGHTS: SAMENT is a robust metastatic niche-labeling approach amenable to single-cell omics.Metastatic niches are typically enriched with macrophages and depleted of T cells.Direct interaction with cancer cells induces ERα expression in niche macrophages. Knockout of Esr1 in macrophages allows T cell infiltration and retards bone colonization.

Statistical validity and clinical merits of a new civilian gunshot injury classification.

BACKGROUND: Despite the high prevalence of civilian gunshot injuries (GSIs) in the United States, no universally accepted classification currently exists. Recently, two of us (ZG, RWL) proposed a GSI classification based on energy transferred, vital structure damage, wound characteristics, fracture, and degree of contamination. This classification has not been validated in a clinical setting. QUESTIONS/PURPOSES: We determined the feasibility, internal consistency, and predictive accuracy of this classification. METHODS: We reviewed the medical records of 216 patients with 264 GSIs treated at a Level I trauma center. Feasibility was determined by the investigators' ability to retrospectively complete the classification system based on patient information routinely collected in medical records. Internal consistency was determined using Cronbach's coefficient alpha. Predictive accuracy was constructed and interpreted in a receiver operating characteristic (ROC) curve using all the classification components to predict GSI severity. The clinical management/outcome (deceased, hospitalization versus nonadmission, and surgical versus nonsurgical treatment) was used as a proxy measure of GSI severity. RESULTS: We were able to apply the classification to 82% of charts we reviewed. The classification components appeared to be internally consistent (Cronbach's alpha was 0.69 and was increased to 0.78 after exclusion of contamination). Each component was associated with clinical management. GSI classified as high energy, worse vital structure, and high contamination had higher rates of surgery (84%, 84%, and 100%, respectively). The area under the ROC curve was 0.80, suggesting the classification can accurately describe GSI severity. CONCLUSIONS: Our results suggest this new civilian GSI classification is statistically valid and has clinical merits warranting further investigation in the setting of a prospective trial.

Bone Metastasis Initiation Is Coupled with Bone Remodeling through Osteogenic Differentiation of NG2+ Cells.

The bone microenvironment is dynamic and undergoes remodeling in normal and pathologic conditions. Whether such remodeling affects disseminated tumor cells (DTC) and bone metastasis remains poorly understood. Here, we demonstrated that pathologic fractures increase metastatic colonization around the injury. NG2+ cells are a common participant in bone metastasis initiation and bone remodeling in both homeostatic and fractured conditions. NG2+ bone mesenchymal stem/stromal cells (BMSC) often colocalize with DTCs in the perivascular niche. Both DTCs and NG2+ BMSCs are recruited to remodeling sites. Ablation of NG2+ lineage impaired bone remodeling and concurrently diminished metastatic colonization. In cocultures, NG2+ BMSCs, especially when undergoing osteodifferentiation, enhanced cancer cell proliferation and migration. Knockout of N-cadherin in NG2+ cells abolished these effects in vitro and phenocopied NG2+ lineage depletion in vivo. These findings uncover dual roles of NG2+ cells in metastasis and remodeling and indicate that osteodifferentiation of BMSCs promotes metastasis initiation via N-cadherin-mediated cell-cell interaction. SIGNIFICANCE: The bone colonization of cancer cells occurs in an environment that undergoes constant remodeling. Our study provides mechanistic insights into how bone homeostasis and pathologic repair lead to the outgrowth of disseminated cancer cells, thereby opening new directions for further etiologic and epidemiologic studies of tumor recurrences. This article is highlighted in the In This Issue feature, p. 247.

Acute and severe trabecular bone loss in a rat model of critical illness myopathy.

Prolonged mechanical ventilation for critically ill patients with respiratory distress can result in severe muscle wasting with preferential loss of myosin. Systemic inflammation triggered by lung mechanical injury likely contributes to this myopathy, although the exact mechanisms are unknown. In this study, we hypothesized that muscle wasting following mechanical ventilation is accompanied by bone loss. The objective was to determine the rate, nature, and extent of bone loss in the femora of rats ventilated up to 10 days and to relate the bone changes to muscle deterioration. We have developed a rat model of ventilator-induced muscle wasting and established its feasibility and clinical validity. This model involves pharmacologic paralysis, parenteral nutrition, and continuous mechanical ventilation. We assessed the hindlimb muscle and bone of rats ventilated for 0, 2, 5, 8, and 10 days. Routine histology, microCT, and biomechanical evaluations were performed. Hindlimb muscles developed changes consistent with myopathy, whereas the femurs demonstrated a progressive decline in trabecular bone volume, mineral density, and microarchitecture beginning Day 8 of mechanical ventilation. Biomechanical testing showed a reduction in flexural strength and stiffness on Day 10. The bone changes correlated with the loss of muscle mass and myosin. These results demonstrate that mechanical ventilation leads to progressive trabecular bone loss parallel to muscle deterioration. The results of our study suggest that mechanically ventilated patients may be at risk of compromised bone integrity and muscle weakness, predisposing to post-ventilator falls and fractures, thereby warranting interventions to prevent progressive bone and muscle decline.

The Legal, Ethical, and Scientific Considerations for Returning Explanted Orthopaedic Hardware to the Patient.

ABSTRACT: Orthopaedic hardware explantation is a multifaceted topic with complex legal, ethical, and scientific aspects that require thorough exploration. Issues of device ownership, explant-induced disease propagation, and potential device resale pose legal risks to providers and health-care institutions. Ethically, implant removal highlights the potential that performing procedures at the request of the patient will incentivize patient compliance and strengthen the patient-surgeon relationship. However, the return of explanted hardware to patients could hinder scientific study and innovation, ultimately limiting advancement in risk reduction and patient outcomes. Continued research into these topics remains paramount to ensure that clinicians and institutions deliver optimal patient care while abiding with legal and ethical imperatives. This article addresses the legal, ethical, and scientific issues that are pertinent to returning an explanted orthopaedic implant to the patient and the potential ramifications of such practice.

Optimization and Characterization of a Bone Culture Model to Study Prostate Cancer Bone Metastasis.

Nearly 90% of patients with advanced prostate cancer manifest bone metastases. Distinct from the osteolytic metastasis mostly observed in other cancer types, prostate cancer bone metastasis is typically more osteoblastic, which is relatively understudied due to the lack of reliable and efficient models to resemble the indolent cellular growth and complexity of metastatic progression. In our previous studies, we developed bone-in-culture array (BICA) to primarily model the osteoblast-involved, pre-osteolytic stage of breast cancer bone metastasis. Given that the progression of prostate cancer bone metastasis is largely osteoblastic, it is reasonable to speculate that the original BICA model can be adjusted to investigate prostate cancer bone metastases. In this study, we refined BICA by reducing the surgical labor and improving its reproducibility and capacity. The optimized BICA can successfully recapitulate important features of prostate cancer bone metastasis such as the osteoblastic phenotype, indolent growth, cancer-niche interactions, and response to hormones. Our efforts address the long-standing need for reliable and efficient models to study prostate cancer bone metastasis.

Inflammatory stimuli alter bone marrow composition and compromise bone health in the malnourished host.

Inflammation has a role in the pathogenesis of childhood malnutrition. We investigated the effect of malnutrition and inflammatory challenge on bone marrow composition and bone health. We studied an established murine model of moderate acute malnutrition at baseline and after acute inflammatory challenge with bacterial lipopolysaccharide (LPS), a surrogate of Gram-negative bacterial sepsis, or Leishmania donovani, the cause of visceral leishmaniasis. Both of these infections cause significant morbidity and mortality in malnourished children. Of the 2 stimuli, LPS caused more pronounced bone marrow changes that were amplified in malnourished mice. LPS challenge led to increased inflammatory cytokine expression (Il1b, Il6, and Tnf), inflammasome activation, and inflammatory monocyte accumulation in the bone marrow of malnourished mice. Depletion of inflammatory monocytes in Csfr1-LysMcre-DT malnourished mice significantly reduced the inflammasome activation and IL1-ß production after LPS challenge. The inflammatory challenge also led to increased expansion of mesenchymal stem cells (MSCs), bone marrow adiposity, and expression of genes (Pparg, Adipoq, and Srbp1) associated with adipogenesis in malnourished mice. This suggests that inflammatory challenge promotes differentiation of BM MSCs toward the adipocyte lineage rather than toward bone-forming osteoblasts in the malnourished host. Concurrent with this reduced osteoblastic potential there was an increase in bone-resorbing osteoclasts, enhanced osteoclast activity, upregulation of inflammatory genes, and IL-1B involved in osteoclast differentiation and activation. The resulting weakened bone formation and increased bone resorption would contribute to the bone fragility associated with malnutrition. Lastly, we evaluated the effect of replacing lipid rich in omega-6 fatty acids (corn oil) with lipid-rich in omega-3 fatty acids (fish oil) in the nutrient-deficient diet. LPS-challenged malnourished mice that received dietary fish oil showed decreased expression of inflammatory cytokines and Rankl and reduced osteoclast differentiation and activation in the bone marrow. This work demonstrates that the negative effect of inflammatory challenge on bone marrow is amplified in the malnourished host. Increasing dietary intake of omega-3 fatty acids may be a means to reduce inflammation and improve bone health in malnourished children.

A Population of M2 Macrophages Associated With Bone Formation.

We previously identified transient brown adipocyte-like cells associated with heterotopic ossification (HO). These ancillary cells support new vessel synthesis essential to bone formation. Recent studies have shown that the M2 macrophage contributes to tissue regeneration in a similar way. To further define the phenotype of these brown adipocyte-like cells they were isolated and characterized by single-cell RNAseq (scRNAseq). Analysis of the transcriptome and the presence of surface markers specific for macrophages suggest that these cells are M2 macrophages. To validate these findings, clodronate liposomes were delivered to the tissues during HO, and the results showed both a significant reduction in these macrophages as well as bone formation. These cells were isolated and shown in culture to polarize towards either M1 or M2 similar to other macrophages. To confirm that these are M2 macrophages, mice received lipopolysacheride (LPS), which induces proinflammation and M1 macrophages. The results showed a significant decrease in this specific population and bone formation, suggesting an essential role for M2 macrophages in the production of bone. To determine if these macrophages are specific to HO, we isolated these cells using fluorescence-activated cell sorting (FACS) from a bone defect model and subjected them to scRNAseq. Surprisingly, the macrophage populations overlapped between the two groups (HO-derived versus callus) suggesting that they may be essential ancillary cells for bone formation in general and not selective to HO. Of further note, their unique metabolism and lipogenic properties suggest the potential for unique cross talk between these cells and the newly forming bone.

Osteofibrous dysplasia and adamantinoma: A summary of diagnostic challenges and surgical techniques.

Osteofibrous dysplasia is an indolent benign fibro-osseous tumor, while adamantinoma is a locally aggressive biphasic malignancy with epithelial and fibro-osseous components. Predominantly arising in the tibial diaphysis of children and young adults, both tumors are resistant to chemotherapy and radiation. Wide surgical resection is regarded as the mainstay of therapy for adamantinoma, and limb-salvage reconstructive procedures can achieve good functional outcomes, albeit with non-negligible rates of complications. This review discusses emerging advances in the pathogenesis, histogenesis, and diagnosis of these entities and presents advantages and limitations of the most common surgical techniques used for their management.

A replicating stem-like cell that contributes to bone morphogenetic protein 2-induced heterotopic bone formation.

Bone morphogenetic protein 2 (BMP2)-induced heterotopic bone formation (HBF) starts synchronously from zero upon BMP2 induction, which is advantageous for lineage tracking. The studies reported here in GLAST-CreErt2 :tdTomato red (TR)floxSTOPflox mice during BMP2-induced HBF show 78.8 ± 11.6% of chondrocytes and 86.5 ± 1.9% of osteoblasts are TR+ after approximately 1 week. Clustering after single-cell RNAseq resulted in nine cell types, and analysis revealed one as a highly replicating stem-like cell (RSC). Pseudotiming suggested that the RSC transitions to a mesenchymal stem-like cell that simultaneously expresses multiple osteoblast and chondrocyte transcripts (chondro-osseous progenitor [COP]). RSCs and COPs were isolated using flow cytometry for unique surface markers. Isolated RSCs (GLAST-TR+ Hmmr+ Cd200- ) and COPs (GLAST-TR+ Cd200+ Hmmr- ) were injected into the muscle of mice undergoing HBF. Approximately 9% of the cells in heterotopic bone (HB) in mice receiving RSCs were GLAST-TR+ , compared with less than 0.5% of the cells in mice receiving COPs, suggesting that RSCs are many times more potent than COPs. Analysis of donor-derived TR+ RSCs isolated from the engrafted HB showed approximately 50% were COPs and 45% were other cells, presumably mature bone cells, confirming the early nature of the RSCs. We next isolated RSCs from these mice (approximately 300) and injected them into a second animal, with similar findings upon analysis of HBF. Unlike other methodology, single cell RNAseq has the ability to detect rare cell populations such as RSCs. The fact that RSCs can be injected into mice and differentiate suggests their potential utility for tissue regeneration.

The bone microenvironment increases phenotypic plasticity of ER+ breast cancer cells.

Estrogen receptor-positive (ER+) breast cancer exhibits a strong bone tropism in metastasis. How the bone microenvironment (BME) impacts ER signaling and endocrine therapy remains poorly understood. Here, we discover that the osteogenic niche transiently and reversibly reduces ER expression and activities specifically in bone micrometastases (BMMs), leading to endocrine resistance. As BMMs progress, the ER reduction and endocrine resistance may partially recover in cancer cells away from the osteogenic niche, creating phenotypic heterogeneity in macrometastases. Using multiple approaches, including an evolving barcoding strategy, we demonstrated that this process is independent of clonal selection, and represents an EZH2-mediated epigenomic reprogramming. EZH2 drives ER+ BMMs toward a basal and stem-like state. EZH2 inhibition reverses endocrine resistance. These data exemplify how epigenomic adaptation to BME promotes phenotypic plasticity of metastatic seeds, fosters intra-metastatic heterogeneity, and alters therapeutic responses. Our study provides insights into the clinical enigma of ER+ metastatic recurrences despite endocrine therapies.

Clearing the cervical spine in the blunt trauma patient.

The goal of cervical spine clearance is to establish that injuries are not present. Patients are classified into four groups: asymptomatic, temporarily nonassessable secondary to distracting injuries or intoxication, symptomatic, and obtunded. Level I evidence supports that the asymptomatic patient can be cleared on clinical grounds and does not require imaging. The temporarily nonassessable patient may have short-term mental status changes (eg, intoxication, painful distracting injuries) and can be evaluated by two methods. When there is urgency, the evaluation is similar to that for the obtunded patient. Alternatively, the patient can be reevaluated within 24 to 48 hours, after return of mentation or following treatment of painful injuries. The patient then can be assessed as the asymptomatic patient is. The symptomatic patient requires advanced imaging. The obtunded patient should undergo, at minimum, a multidetector CT scan. Two methods are advocated. One uses only multidetector CT; a normal result is sufficient to clear the obtunded patient. The alternative method is obtaining a magnetic resonance image subsequent to a negative multidetector CT scan. Because at present information is insufficient to determine whether MRI is indicated, this is an area of controversy.