Background and Objectives:Ewing sarcoma is a primary malignancy affecting both bone and soft tissue. Following preoperative chemotherapy and surgical resection, histologic response (tumor necrosis) is correlated with patient survival. The most prognostic cutoff for tumor necrosis continues to be debated. The objective of this study was to explore several cutoffs and determine their prognostic value in a contemporary cohort of Ewing sarcoma patients. Methods:The National Cancer Database was used to identify 564 patients with osseous and soft tissue tumors in the Ewing sarcoma family from 2010 to 2015. All patients had documented preoperative chemotherapy, surgical resection, and vital status. Survival was stratified by tumor necrosis using Kaplan Meier analysis. 356 patients with osseous tumors were included in multivariate logistic and cox regression analyses to identify predictors of histologic response and survival, respectively. Results:In a combined soft tissue and osseous tumor cohort, there was a significant difference (p = 0.01, log-rank test) in overall survival between patients with 100% necrosis and patients with less than 100% necrosis. This was observed over the 5-year study period. Other cutoffs were not statistically different. In patients with osseous tumors, less than 100% necrosis was negatively associated with survival (HR 3.48 [95% CI 1.19-10.13]; p< 0.05), with only skip metastasis having a stronger negative association (HR 4.31 [95% CI 1.22-15.29]; p< 0.05). Male sex (OR 0.50 [95% CI 0.28-0.90]; p<0.05), tumors located in the axial skeleton (OR 0.30 [95% CI 0.12- 0.77]; p<0.05), and positive surgical margins (OR 0.28 [95% CI 0.08-0.95]; p<0.05) were negatively associated with 100% necrosis. Conclusion and Implications:A cutoff of 100% tumor necrosis was associated with improved survival in Ewing sarcoma. This association was strong relative to other commonly used prognostic factors in osseous cases and is a valuable tool to counsel patients and guide future clinical trials.

Appropriate classification of fusion-driven bone and soft tissue neoplasms continues to evolve, often relying on the careful integration of morphologic findings with immunohistochemical, molecular, and clinical data. Herein, we present 3 cases of a morphologically distinct myxoid mesenchymal neoplasm with myogenic differentiation and novel CRTC1::MRTFB (formerly MKL2) gene fusion. Three tumors occurred in 1 male and 2 female patients with a median age of 72 years (range: 28-78). Tumors involved the left iliac bone, the right thigh, and the left perianal region with a median size of 4.0 cm (4.0-7.6 cm). Although 1 tumor presented as an incidental finding, the other 2 tumors were noted, given their persistent growth. At the time of the last follow-up, 1 patient was alive with unresected disease at 6 months, 1 patient was alive without evidence of disease at 12 months after surgery, and 1 patient died of disease 24 months after diagnosis. On histologic sections, the tumors showed multinodular growth and were composed of variably cellular spindle to round-shaped cells with distinct brightly eosinophilic cytoplasm embedded within a myxoid stroma. One tumor showed overt smooth muscle differentiation. Cytologic atypia and mitotic activity ranged from minimal (2 cases) to high (1 case). By immunohistochemistry, the neoplastic cells expressed focal smooth muscle actin, h-caldesmon, and desmin in all tested cases. Skeletal muscle markers were negative. Next-generation sequencing detected nearly identical CRTC1::MRTFB gene fusions in all cases. We suggest that myxoid mesenchymal tumors with myogenic differentiation harboring a CRTC1::MRTFB fusion may represent a previously unrecognized, distinctive entity that involves soft tissue and bone. Continued identification of these novel myxoid neoplasms with myogenic differentiation will be important in determining appropriate classification, understanding biologic potential, and creating treatment paradigms.

Background/Objective: Cachexia is a systemic wasting syndrome characterized by skeletal muscle mass loss and is estimated to affect 80% of lung cancer patients. Previous studies haveshown that metastatic bone disease may have a role in inducing cachexia, which is mediated bycytokines such as IL-6, TNF-α, and TGF-β. To develop therapies for cachexia, a better understanding of the impact of metastatic bone disease and these cytokines on cachexia is needed. Methods: Patients diagnosed with lung cancer were identified from an institutional database and were designated to one of three cohorts: local disease (n=63), osseous metastatic disease(n=39), and extraosseous metastatic disease (n=39). Body mass index (BMI) at diagnosis and follow up were collected. Change in BMI per year was calculated and the Kruskal-Wallis Test was used to compare groups. In a parallel study, ELISA was performed for IL-6, TNF-α, and TGF-β on supernatant collected after 48 hours from the cell lines BEAS-2B (normal lung epithelia), H1299 (lung cancer), and A549 (lung cancer). These groups were compared using a one-way ANOVA. Results: Median change in BMI was not statistically different (P=.79) among any cohort. The cytokine level varied by cell line. H1299 had significantly increased levels of TGF-β as compared to BEAS-2B (P=.004). A549 had elevated, but not a statistically significant differentlevel of IL-6 as compared to BEAS-2B (P=.17). TNF-α was not present in any cell line. Conclusion:BMI was not associated with disease state with the numbers available. The parallel study showed cell line specific elevation of TGF-β and IL-6 in lung cancer compared to noncancerous tissues. Together, these findings are inconclusive but support continued investigation into the pathogenesis of cachexia in lung cancer. Future studies will employ imaging-based body composition measurements in these disease cohorts and explore int eractions between tumor, bone, and muscle in vitro.

Background Many cancers metastasize to bone and may lead to pathologic fracture or impending pathologic fracture. Prophylactically stabilizing bones before fracture has been shown to be more cost-effective with improved outcomes. Many studies have examined risk factors for pathological fracture, with radiographic and functional pain data serving as predominant indicators for surgery. Conditions associated with poor bone health and increased risk of fracture in the non-oncologic population, including diabetes mellitus, chronic obstructive pulmonary disease (COPD), cardiovascular disease, renal disease, smoking, corticosteroid use, and osteoporosis, have not been studied in the context of metastatic disease. Characterization of these factors could help providers identify candidates for prophylactic stabilization thereby reducing the number of completed pathological fractures. Methods 298 patients over the age of 40 with metastatic bone disease of the femur treated between 2010-2021 were retrospectively identified. Patients without complete medical documentation or with non-metastatic diagnoses were excluded. 186 patients met inclusion and exclusion criteria, including 74 patients who presented with pathological femur fracture and 112 patients who presented for prophylactic stabilization. Patient demographics and comorbidities including diabetes mellitus, COPD, cardiovascular disease, renal disease, osteoporosis, active tobacco or corticosteroid use, and use of anti-resorptive therapy were collected. Descriptive statistics were compiled, with univariable analysis by Mann-Whitney or chisquared testing. Multiple logistic regression was then performed to identify the most significant patient variables for presenting with completed fracture. Results On univariable analysis, patients with COPD were more likely to present with pathologic fracture (19/32 [59%] compared to 55/154 [36%], p = 0.02). A trend emerged for patients with an increasing number of comorbidities (28/55 [51%] for 2+ comorbidities compared to 18/61 [29%] with zero comorbidities, p = 0.06). On multivariable analysis, patients with two or more comorbidities (OR: 2.49; p=0.02) were more likely to present with a femur fracture. Conclusion This analysis suggests that those with an increasing number of comorbidities may be at increased risk for pathologic fracture. This study raises the possibility that patient factors and/ or comorbidities alter bone strength and/or pain experiences and may guide orthopaedic oncologists weighing prophylactic stabilization of femur lesions. Level of Evidence: III.

BACKGROUND:The histologic response of osteosarcoma to chemotherapy is commonly cited as a prognostic factor and typically graded as the percent necrosis of the tumor at the time of surgical resection. Few studies, to our knowledge, have examined the relationship of tumor necrosis relative to other factors. Existing studies are limited by prolonged enrollment periods or analysis of patient subsets without the strongest predictor of mortality: metastasis at diagnosis. Additionally, the definitive threshold value for a good histologic response is commonly set at more than 90% tumor necrosis with little evidence; some authors advocate other values. QUESTION/PURPOSES:(1) Are there alternative cutoff values for a good response to chemotherapy in a large, national cohort of contemporarily treated patients with osteosarcoma? (2) How does the association of histologic response to survival in osteosarcoma compare with other clinicopathologic factors? (3) What patient and clinical factors are associated with the histologic response? METHODS:We identified 2006 patients with osteosarcoma diagnosed between 2010 and 2015 in the National Cancer Database (NCDB), a registry that includes 70% of all new cancers diagnosed in the United States with 90% follow-up. Patients were excluded for missing documentation of percent tumor necrosis (21% [425 of 2006]) or if definitive resection was not performed (< 1% [1 of 2006]). A total of 1580 patients were included in the analysis, with a mean follow-up duration of 37 ± 22 months. A Kaplan-Meier survival analysis, stratified by the percent tumor necrosis after chemotherapy, was performed for the 5-year period. Other covariates examined were sex, race, socioeconomic score composite, insurance type, Charlson/Deyo score, distance from the hospital, and location (metropolitan, urban, or rural). Clinical and sociodemographic data including patient-identified race from the patient's medical record is input into the NCDB by certified registrars. The NCDB only allows coding of one primary race for each patient; thus, most of our patients were grouped as White or Black race and the remaining were grouped as Other for our analysis. A multiple Cox regression analysis was performed to evaluate the effect of percent necrosis compared with other demographic, clinicopathologic, and treatment effects on survival. Finally, a multiple logistic regression analysis was performed to assess demographic and clinicopathologic characteristics associated with percent necrosis. RESULTS:Five-year overall survival for patients with histologic gradings of 90% to 94% necrosis (70% [95% confidence interval (CI) 60.6% to 79.7%) and 95% to 100% necrosis (74% [95% CI 68% to 80.3%) was not different between groups (p = 0.47). A comparison of histologic responses below 90% necrosis found no difference in survival between patients with decreasing histologic response (p > 0.05). Necrosis of less than 90% was associated with worse survival (HR 2.00 [95% CI 1.58 to 2.52]; p < 0.001 compared with more than 90% necrosis), and factors most associated with poor survival were metastasis (HR 2.85 [95% CI 2.27 to 3.59]; p < 0.001) and skip metastasis at the time of diagnosis (HR 2.52 [95% CI 1.64 to 3.88]; p < 0.001). On multivariate analysis, adjusting for demographic, clinicopathologic, and treatment factors, social determinants of health were negatively associated with percent necrosis of 90% or more, including uninsured status (OR 0.46 [95% CI 0.23 to 0.92]; p = 0.02 compared with private insurance) and lower socioeconomic status composite (OR for the lowest first and second quartiles were 0.63 [95% CI 0.44 to 0.90]; p = 0.01 and 0.70 [95% CI 0.50 to 0.96]; p = 0.03, respectively). Race other than White or Black (OR 0.61 [95% CI 0.40 to 0.94]; p = 0.02 compared with White race) was also negatively associated with percent necrosis of more than 90% after controlling for available covariates. CONCLUSION:This study suggests that a cutoff of 90% necrosis provides the best prognostic value for patients with osteosarcoma undergoing chemotherapy. Other threshold values did not show different survival benefits. Sociodemographic factors were associated with histologic response less than 90%. These associations must be carefully understood not as cause and effect but likely demonstrating the effects of health disparities and access to care. Although we controlled for multiple variables in our analysis, broad variables such as race may have been associated with histologic response due to unaccounted confounders. Medical providers should be aware of these associations to ensure equitable access and delivery of care because access to care may be responsible for these associations. Future studies should examine potential drivers of this observation, such as a delay in presentation or deviation from standard of care practices. LEVEL OF EVIDENCE:Level III, therapeutic study.

Establishment of clinically annotated, molecularly characterized, patient-derived xenografts (PDXs) from treatment-naïve and pretreated patients provides a platform to test precision genomics-guided therapies. An integrated multi-OMICS pipeline was developed to identify cancer-associated pathways and evaluate stability of molecular signatures in a panel of pediatric and AYA PDXs following serial passaging in mice. Original solid tumor samples and their corresponding PDXs were evaluated by whole-genome sequencing, RNA-seq, immunoblotting, pathway enrichment analyses, and the drug–gene interaction database to identify as well as cross-validate actionable targets in patients with sarcomas or Wilms tumors. While some divergence between original tumor and the respective PDX was evident, majority of alterations were not functionally impactful, and oncogenic pathway activation was maintained following serial passaging. CDK4/6 and BETs were prioritized as biomarkers of therapeutic response in osteosarcoma PDXs with pertinent molecular signatures. Inhibition of CDK4/6 or BETs decreased osteosarcoma PDX growth (two-way ANOVA, p < 0.05) confirming mechanistic involvement in growth. Linking patient treatment history with molecular and efficacy data in PDX will provide a strong rationale for targeted therapy and improve our understanding of which therapy is most beneficial in patients at diagnosis and in those already exposed to therapy.

BACKGROUND:Patients with incidentally found musculoskeletal lesions are regularly referred to orthopaedic oncology. Most orthopaedic oncologists understand that many incidental findings are nonaggressive and can be managed nonoperatively. However, the prevalence of clinically important lesions (defined as those indicated for biopsy or treatment, and those found to be malignant) remains unknown. Missing clinically important lesions can result in harm to patients, but needless surveillance may exacerbate patient anxiety about their diagnosis and accrue low-value costs to the payor. QUESTIONS/PURPOSES:(1) What percentage of patients with incidentally discovered osseous lesions referred to orthopaedic oncology had lesions that were clinically important, defined as those receiving biopsy or treatment or those found to be malignant? (2) Using standardized Medicare reimbursements as a surrogate for payor expense, what is the value of reimbursements accruing to the hospital system for the imaging of incidentally found osseous lesions performed during the initial workup period and during the surveillance period, if indicated? METHODS:This was a retrospective study of patients referred to orthopaedic oncology for incidentally found osseous lesions at two large academic hospital systems. Medical records were queried for the word "incidental," and matches were confirmed by manual review. Patients evaluated at Indiana University Health between January 1, 2014, and December 31, 2020, and those evaluated at University Hospitals between January 1, 2017, and December 31, 2020, were included. All patients were evaluated and treated by the two senior authors of this study and no others were included. Our search identified 625 patients. Sixteen percent (97 of 625) of patients were excluded because their lesions were not incidentally found, and 12% (78 of 625) were excluded because the incidental findings were not bone lesions. Another 4% (24 of 625) were excluded because they had received workup or treatment by an outside orthopaedic oncologist, and 2% (10 of 625) were excluded for missing information. A total of 416 patients were available for preliminary analysis. Among these patients, 33% (136 of 416) were indicated for surveillance. The primary indication for surveillance included lesions with a benign appearance on imaging and low clinical suspicion of malignancy or fracture. A total of 33% (45 of 136) of these patients had less than 12 months of follow-up and were excluded from further analysis. No minimum follow-up criteria were applied to patients not indicated for surveillance because this would artificially inflate our estimated rate of clinically important findings. A total of 371 patients were included in the final study group. Notes from all clinical encounters with orthopaedic and nonorthopaedic providers were screened for our endpoints (biopsy, treatment, or malignancy). Indications for biopsy included lesions with aggressive features, lesions with nonspecific imaging characteristics and a clinical picture concerning for malignancy, and lesion changes seen on imaging during the surveillance period. Indications for treatment included lesions with increased risk of fracture or deformity, certain malignancies, and pathologic fracture. Diagnoses were determined using biopsy results if available or the documented opinion of the consulting orthopaedic oncologist. Imaging reimbursements were obtained from the Medicare Physician Fee Schedule for 2022. Because imaging charges vary across institutions and reimbursements vary across payors, this method was chosen to enhance the comparability of our findings across multiple health systems and studies. RESULTS:Seven percent (26 of 371) of incidental findings were determined to be clinically important, as previously defined. Five percent (20 of 371) of lesions underwent tissue biopsy, and 2% (eight of 371) received surgical intervention. Fewer than 2% (six of 371) of lesions were malignant. Serial imaging changed the treatment of 1% (two of 136) of the patients, corresponding to a rate of one in 47 person-years. Median reimbursements to work up the incidental findings analyzed was USD 219 (interquartile range USD 0 to 404), with a range of USD 0 to 890. Among patients indicated for surveillance, the median annual reimbursement was USD 78 (IQR USD 0 to 389), with a range of USD 0 to 2706. CONCLUSION:The prevalence of clinically important findings among patients referred to orthopaedic oncology for incidentally found osseous lesions is modest. The likelihood of surveillance resulting in a change of management was low, but the median reimbursements associated with following these lesions was also low. We conclude that after appropriate risk stratification by orthopaedic oncology, incidental lesions are rarely clinically important, and judicious follow-up with serial imaging can be performed without incurring high costs. LEVEL OF EVIDENCE:Level III, therapeutic study.

Epithelioid and spindle cell sarcomas with NR1D1::MAML1/2 gene fusions are rare and emerging entities. Only six cases of NR1D1-rearranged mesenchymal tumors have previously been reported in the literature; they are often characterized by an epithelioid morphology, at least focal pseudogland formation, prominent cytoplasmic vacuoles, and focal to diffuse immunohistochemical expression of keratin. We herein report the first case of an NR1D1::MAML1 epithelioid and spindle cell sarcoma with dual immunohistochemical expression of ERG and FOSB, mimicking a pseudomyogenic hemangioendothelioma (PHE) on core biopsy. The sarcoma arose in the left forearm of a 64-year-old man. Initial biopsy showed a mesenchymal neoplasm composed of epithelioid and spindle cells dispersed in myxoid stroma with scattered stromal neutrophils. The morphologic features, combined with the dual immunohistochemical expression of ERG and FOSB, initially mimicked PHE, representing an important potential diagnostic pitfall. The patient subsequently underwent a radical resection, which showed a much more diffuse epithelioid appearance with nested architecture and pseudogland formation. Next-generation sequencing was performed on the resection specimen, which revealed an NR1D1::MAML1 gene fusion, confirming the final diagnosis. Given the fully malignant potential of this tumor, knowledge and recognition of this rare entity are essential to ensure proper management, prevent misdiagnosis, and further characterize the clinical course of this emerging entity. Comprehensive molecular testing can help to identify these rare tumors and exclude the possibility of epithelioid mimics, including PHE.

Bony union is a primary predictor of outcome after surgical fixation of long bone fractures. Murine models offer many advantages in assessing bony healing due to their low costs and small size. However, current fracture recovery investigations in mice frequently rely on animal sacrifice and costly analyses. The modified Radiographic Union Score for Tibia fractures (mRUST) scoring system is a validated metric for evaluating bony healing in humans utilizing plain radiographs, which are relatively inexpensive and do not require animal sacrifice. However, its use has not been well established in murine models. The aim of this study was to characterize the longitudinal course of mRUST and compare mRUST to other conventional murine fracture analyses. 158 mice underwent surgically created midshaft femur fractures. Mice were evaluated after fracture creation and at 7, 10, 14, 17, 21, 24, 28, 35, and 42 days post-injury. mRUST scoring of plain radiographs was performed by three orthopaedic surgeons in a randomized, blinded fashion. Interrater correlations were calculated. Micro-computed tomography (μCT) was analyzed for tissue mineral density (TMD), total callus volume (TV), bone volume (BV), trabecular thickness, trabecular number, and trabecular separation. Histomorphometry measures of total callus area, cartilage area, fibrous tissue area, and bone area were performed in a blinded fashion. Ultimate torque, stiffness, toughness, and twist to failure were calculated from torque-twist curves. A sigmoidal log-logistic curve fit was generated for mRUST scores over time which shows mRUST scores of 4 to 6 at 7 days post-injury that improve to plateaus of 14 to 16 by 24 days post-injury. mRUST interrater correlations at each timepoint ranged from 0.51 to 0.86, indicating substantial agreement. mRUST scores correlated well with biomechanical, histomorphometry, and μCT parameters, such as ultimate torque (r=0.46, p<0.0001), manual stiffness (r=0.51, p<0.0001), bone percentage based on histomorphometry (r=0.86, p<0.0001), cartilage percentage (r=-0.87, p<0.0001), tissue mineral density (r=0.83, p<0.0001), BV/TV based on μCT (r=0.65, p<0.0001), and trabecular thickness (r=0.78, p<0.0001), among others. These data demonstrate that mRUST is reliable, trends temporally, and correlates to standard measures of murine fracture healing. Compared to other measures, mRUST is more cost-effective and non-terminal. The mRUST log-logistic curve could be used to characterize differences in fracture healing trajectory between experimental groups, enabling high-throughput analysis.

Background Most cancer centers prefer preoperative radiation therapy (preRT) over postoperative therapy to treat soft-tissue sarcoma (STS) to limit long-term fibrosis, joint stiffness, and edema. Surgery is often delayed after preRT to allow for tissue recovery and to reduce wound complications. However, the association between the time interval between preRT and surgery and survival is unknown. Questions/purposes (1) What factors are associated with the preRT-surgery interval in patients with STS? (2) Is the preRT-surgery interval associated with overall survival? Methods The National Cancer Database, a nationwide registry that includes 70% of all new cancers in the United States with 90% follow-up, was reviewed to identify 6378 patients who underwent preRT and surgical resection for a localized extremity or pelvic STS from 2004 to 2014. Patients were excluded if they had lymphatic or metastatic disease at diagnosis (23%; n = 1438), underwent neoadjuvant chemotherapy (24%; 1531), were missing vital status (8%; 487), had chemosensitive histologies (9%; 603), underwent radiation other than external beam (1%; 92), were missing preRT-surgery interval (1%; 45), or had a preRT-surgery interval greater than 120 days (< 1%; 6). A total of 2176 patients were included for analysis, with a mean preRT-surgery interval of 35 +/- 16 days. A multiple linear regression model was generated to assess demographic, clinicopathologic, and treatment characteristics associated with the preRT-surgery interval. A Kaplan-Meier survival analysis was then conducted, stratified by the preRT-surgery interval, to assess survival over 10 years. Finally, a multivariate Cox regression analysis model was constructed to further evaluate the association between the preRT-surgery interval and overall survival, adjusted for demographic, clinicopathologic, and treatment characteristics. Results A longer preRT-surgery interval was associated with higher age (beta = 0.002 per year [95% CI 0.0 to 0.004]; p = 0.026), tumor location in the pelvis (compared with the lower extremity; beta = 0.15 [95% CI 0.082 to 0.22]; p < 0.001), and malignant peripheral nerve sheath tumor subtype (compared with undifferentiated pleomorphic sarcoma; beta = 0.17 [95% CI 0.044 to 0.29]; p = 0.008). A shorter preRT-surgery interval was associated with higher facility volume (beta = -0.002 per case [95% CI -0.003 to -0.002]; p = 0.026) and higher tumor stage (compared with Stage I; beta = -0.066 [95% CI -0.13 to -0.006]; p = 0.03 for Stage II; beta = -0.12 [95% CI -0.17 to -0.065]; p < 0.001 for Stage III). The 5-year overall survival rates were similar across all preRT-surgery interval groups: less than 3 weeks (66% [95% CI 60 to 72]), 3 to 4 weeks (65% [95% CI 60 to 71]), 4 to 5 weeks (65% [95% CI 60 to 71]), 5 to 6 weeks (66% [95% CI 60 to 72]), 6 to 7 weeks (63% [95% CI 54 to 72]), 7 to 9 weeks (66% [95% CI 58 to 74]), and more than 9 weeks (59% [95% CI 48 to 69]). Over 10 years, no difference in overall survival was observed when stratified by the preRT-surgery interval (p = 0.74). After controlling for potentially confounding variables, including age, sex, Charlson/Deyo comorbidity score, histology, tumor size, stage and surgery type, the preRT-surgery interval was not associated with survival (hazard ratio = 1 per day [95% CI 1 to 1]; p = 0.88). Conclusion With the numbers available, this study demonstrates that a delay in surgery up to 120 days after radiation is not associated with poorer survival. Therefore, clinicians may be able to delay surgery to minimize the risks of wound complications and modifiable comorbidities without affecting overall survival. Level of Evidence Level III, therapeutic study.

BACKGROUNDBenign bone tumors are common incidental findings in the pediatric population during radiographic evaluation. Counseling these patients requires reassurance and raises questions about the natural history of these tumors over time. The purpose of this study was to estimate the prevalence and observe the behavior of benign childhood bone tumors in an asymptomatic population.METHODSA historical, longitudinal radiographic collection of healthy children was reviewed, which included comprehensive left-sided radiographs of the extremities at yearly intervals. In this study, 262 subjects with 25,555 radiographs were screened for benign bone tumors at a median age of 8 years (range, 0 to 18 years). All potential tumors were reviewed by a multidisciplinary panel, which confirmed the radiographic diagnosis of each lesion, the age at which the lesion first appeared, and the age at which it had resolved. Prevalence rates were calculated using the number of distinct subjects available for each radiographic location and age.RESULTSThirty-five tumors were identified in 33 subjects, including 19 nonossifying fibromas, 8 enostoses, 6 osteochondromas, and 2 enchondromas. The prevalence rate for all tumors combined increased with age and was 18.9% overall. The overall prevalence rates for specific tumor types were 7.5% for nonossifying fibromas, 5.2% for enostoses, 4.5% for osteochondromas, and 1.8% for enchondromas. Nonossifying fibromas demonstrated a bimodal distribution of prevalence, with a peak at 5 years (10.8%) and another after skeletal maturity (13.3%). The median age at the first appearance for all tumors combined was 9 years (range, 2 to 15 years), but varied by tumor type. Nonossifying fibromas often resolved (7 [37%] of 19), with further resolution possible beyond the last available radiograph. Enostoses, osteochondromas, and enchondromas persisted until the last available radiographs in all subjects.CONCLUSIONSThe prevalence of benign childhood bone tumors of the extremities was 18.9% in a historical asymptomatic population. Longitudinal radiographs allowed observation of the timing of the first appearance and the potential for resolution for each tumor type. These findings provide unique evidence to answer many commonly encountered questions when counseling patients and their families on benign bone tumors.LEVEL OF EVIDENCEPrognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Background. Scientific meetings provide a forum to disseminate new research and advance patient care. The American Academy of Orthopaedic Surgeons (AAOS), Connective Tissue Oncology Society (CTOS), and Musculoskeletal Tumor Society (MSTS) annual meetings are examples of such gatherings in the field of musculoskeletal oncology. After a review of select MSTS abstracts from 1991 to 1999 revealed a 41% publication rate in scientific journals, previous authors cautioned meeting attendees that the majority of abstracts may not survive rigorous peer review and may not be scientifically valid. Since two decades have passed, this study reexamined publication rates and characteristics in a contemporary and expanded cohort of oncology abstracts presented at the AAOS, CTOS, and MSTS annual meetings. Methods. 1408 podium and poster abstracts from the AAOS (oncology-focused from 2013 to 2015), CTOS (2012 to 2014), and MSTS (2012 to 2014) annual meetings were reviewed to allow for a four-year publication window. Searches were performed with PubMed and Google Scholar databases to identify full-text publications using abstract keywords. Characteristics of each abstract and resulting publication were collected. Statistical analysis was performed using the chi-square and Kruskal-Wallis tests for time-independent comparisons, and the log-rank test after reverse Kaplan-Meier analysis for time-dependent comparisons. Results. Abstract publication rates overall were higher for podium presentations (67%, 280 of 415) compared to poster presentations (53%, 530 of 993; p<0.001). When both abstract types were combined, differences between meetings did not meet statistical significance (AAOS: 65%, 106 of 162; CTOS: 57%, 521 of 909; MSTS: 54%, 183 of 337, p=0.06). Abstracts from AAOS meetings were more often published prior to the first day of the meeting (AAOS: 24%, 25 of 106; CTOS: 10%, 52 of 521; MSTS: 14%, 25 of 183; p<0.01). After excluding previously published abstracts, AAOS abstracts had the shortest time to publication (median: 10.8 months, interquartile range (IQR): 4.4 to 18.8 months), compared to those from CTOS (16.0 months, 8.4 to 25.9 months, p<0.01) and MSTS (15 months, 7.9 to 25.0 months, p<0.01) meetings. CTOS abstracts were published in higher impact journals (median: 3.7, IQR: 2.9 to 5.9), compared to those from AAOS (2.9, 1.9 to 3.2, p<0.01) and MSTS (3.1, 2.3 to 3.1, p<0.01) meetings. Finally, 7.7% (62 of 810) of published abstracts were presented at more than one meeting. Conclusions. Publication rates in this study were higher than previous reports in musculoskeletal oncology and comparable or better than recent reports for other orthopedic meetings. Comparisons across the AAOS, CTOS, and MSTS annual meetings highlight notable differences but suggest similarity overall in the quality of evidence presented with little overlap between meetings. Taken together, this study points to progress in the review processes used by the program committees, reaffirms the importance of critical appraisal when considering abstract findings, and supports the continued organization of multiple scientific meetings in musculoskeletal oncology.

Long bone fractures are one of the most common and costly medical conditions encountered after trauma. Characterization of the biology of fracture healing and development of potential medical interventions generally involves animal models of fracture healing using varying genetic or treatment groups, then analyzing relative repair success via the synthesis of diverse assessment methodologies. Murine models are some of the most widely used given their low cost, wide variety of genetic variants, and rapid breeding and maturation. This review addresses key concerns regarding fracture repair investigations in mice and may serve as a guide in conducting and interpreting such studies. Specifically, this review details the procedures, highlights relevant parameters, and discusses special considerations for the selection and integration of the major modalities used for quantifying fracture repair in such studies, including X-ray, microcomputed tomography, histomorphometric, biomechanical, gene expression and biomarker analyses.

Background/Objective: Long bone fractures are an expensive and frequent cause of disability in humans. Research seeking to accelerate and improve the healing process is more essential than ever. Animal models, mice especially, provide an inexpensive and reproducible model of in vivo fracture healing. However, many measures of murine fracture healing outcomes are either expensive or destructive, limiting their ability to be translated to clinical studies. We seek to determine how these measures such as biomechanics, µCT, and histology correlate to the relatively new, inexpensive, and non-destructive method of mRUST scoring in a mouse model. Methods: One hundred and thirty-five, 12-week old male C57BL6/J mice were divided into nine groups of 15 mice. Mice underwent a surgically created, femoral fracture. At biweekly timepoints, anteroposterior and lateral radiographs were taken, and 15 mice were sacrificed at each time point (7, 10, 14, 17, 21, 24, 28, 35, and 42 days post-surgery) for biomechanical, µCT, and histological analyses. The modified Radiographic Union Scale for Tibial fractures (mRUST scoring) provides a score based on the visualization of a callus and fracture line in four cortices on the radiographs. Data analysis will be performed to determine the degree of correlation between mRUST scoring and other fracture healing outcomes. Results/Conclusion: Data collection in this experiment is still forthcoming. Upon successful completion of this project, we will have established numerical correlations between mRUST scoring and other fracture healing outcomes, such as biomechanics, µCT microarchitecture, and histology. These correlations will provide a powerful tool in future mouse fracture healing studies, as data on the state and strength of fracture repair could be determined by simple radiograph. Scientific/Clinical Policy Impact and Implications: This study will both provide future murine fracture studies with an inexpensive and non-destructive method of assessment that is more directly translatable to human fracture studies.

Epigenetic deregulation is an emerging hallmark of cancer that enables tumor cells to escape surveillance by tumor suppressors and ultimately progress. The structure of the epigenome consists of covalent modifications of chromatin components, including acetylation by histone acetyltransferases (HATs) and deacetylation by histone deacetylases (HDACs). Targeting these enzymes with inhibitors to restore epigenetic homeostasis has been explored for many cancers. Osteosarcoma, an aggressive bone malignancy that primarily affects children and young adults, is notable for widespread genetic and epigenetic instability. This may explain why therapy directed at unique molecular pathways has failed to substantially improve outcomes in osteosarcoma over the past four decades. In this review, we discuss the potential of targeting the cancer epigenome, with a focus on histone deacetylase inhibitors (HDACi) for osteosarcoma. We additionally highlight the safety and tolerance of HDACi, combination chemotherapy with HDACi, and the ongoing challenges in the development of these agents.

Purpose The classic fracture model, described by Bonnarens and Einhorn in 1984, enlists a blunt guillotine to generate a closed fracture in a pre-stabilized rodent femur. However, in less experienced hands, this technique yields considerable variability in fracture pattern and requires highly-specialized equipment. This study describes a reproducible and low-cost model of mouse fracture healing using an open femoral osteotomy. Methods Femur fractures were produced in skeletally mature male and female mice using an open femoral osteotomy after intramedullary stabilization. Mice were recovered for up to 28 days prior to analysis with microradiographs, histomorphometry, a novel μCT methodology, and biomechanical torsion testing at weekly intervals. Results Eight mice were excluded due to complications (8/193, 4.1%), including unacceptable fracture pattern (2/193, 1.0%). Microradiographs showed progression of the fracture site to mineralized callus by 14 days and remodelling 28 days after surgery. Histomorphometry from 14 to 28 days revealed decreased cartilage area and maintained bone area. μCT analysis demonstrated a reduction in mineral surface from 14 to 28 days, stable mineral volume, decreased strut number, and increased strut thickness. Torsion testing at 21 days showed that fractured femurs had 61% of the ultimate torque, 63% of the stiffness, and similar twist to failure when compared to unfractured contralateral femurs. Conclusions The fracture model described herein, an open femoral osteotomy, demonstrated healing comparable to that reported using closed techniques. This simple model could be used in future research with improved reliability and reduced costs compared to the current options.

Background/Objective: Long bone fractures are of the most common and costly medical traumas humans experience. Adequate characterization of the fracture healing process and development of potential medical interventions generally involves fracture induction operations on animal models of varying treatment or genetic groups, then analyzing relative repair success via synthesis of diverse assessment methodologies. This review discusses the procedures, relevant parameters, special considerations, and key correlations of these major methodologies of fracture repair quantification. Methods: A literature review was conducted for articles discussing the procedures or identifying correlations between each of the major fracture healing assessment methodologies. Results: These methodologies include biomechanical testing, which provides the most direct quantification of skeletal functionality; micro-computed tomography, which enables high resolution visualization of fracture callus architecture; histology which helps elucidate the intricate processes underlying fracture repair; and x-ray which offers a non-invasive and clinically relevant view of fracture repair progress. Each of these methodologies measure parameters directly correlating to restored functionality of fractured bone. Conclusion: When appropriately integrated, synthesis of relevant parameters from each methodology of fracture repair assessment enables a comprehensive understanding of varying fracture healing outcomes and associated causalities. Scientific/Clinical Policy Impact and Implications: This review may guide the interpretation and planning of fracture healing studies utilizing murine models.

The primary conclusions of our 2014 contribution to this series were as follows: Multiple receptor tyrosine kinases (RTKs) likely contribute to aggressive phenotypes in osteosarcoma and, therefore, inhibition of multiple RTKs is likely necessary for successful clinical outcomes. Inhibition of multiple RTKs may also be useful to overcome resistance to inhibitors of individual RTKs as well as resistance to conventional chemotherapies. Different combinations of RTKs are likely important in individual patients. AXL, EPHB2, FGFR2, IGF1R, and RET were identified as promising therapeutic targets by our in vitro phosphoproteomic/siRNA screen of 42 RTKs in the highly metastatic LM7 and 143B human osteosarcoma cell lines. This chapter is intended to provide an update on these topics as well as the large number of osteosarcoma clinical studies of inhibitors of multiple tyrosine kinases (multi-TKIs) that were recently published.

OBJECTIVES:A total of 30% to 40% of soft tissue sarcoma (STS) patients develop major wound complications (MWCs) after preoperative radiation (preRT). The optimal preRT-surgery interval and its association with MWCs is unknown. This study investigated whether a longer preRT-surgery interval is associated with fewer MWCs compared with historical controls.METHODS:All patients treated by a single surgeon after preRT with limb-sparing wide resection for extremity and trunk STS were retrospectively reviewed from 2004 to 2014. The primary outcome was MWCs defined as a secondary operation, invasive procedure, wound packing, or readmission for wound care. Secondary outcomes of local recurrence and survival were followed and independent variables were analyzed for an association with MWCs.RESULTS:Fifty-four patients were included with a median follow-up of 32 months and age of 61 years. The majority of tumors were deep (91%), large (median size of 11 cm), high grade (78%) and within the lower extremity (78%). The median preRT-surgery interval was 43 days and 80% of patients received surgery 35 to 49 days after radiation. MWCs were observed in 15% of patients and 88% occurred within 40 days. Predictors for MWCs on multivariate analysis were peripheral vascular disease (P=0.03), location in the medial compartment of the thigh (P=0.03), and neurovascular involvement (P=0.03).CONCLUSIONS:This study presents a cohort of STS patients with an extended preRT-surgery interval of ~6 weeks. MWCs in this population occurred at a lower rate than historical controls. Overall these findings support the exploration of a longer interval to reduce MWCs and their associated morbidity.

Update This article was updated on December 18, 2019, because a new reference was added post-publication. This new reference (Niemeier TE, Leddy LR, Chapin RW, Smith TM. Metachronous Aneurysmal Bone Cysts in a Fourteen-Year-Old Girl: A Case Report and Review of the Literature. JBJS Case Connect. 2013 Jun 12;3[2 Suppl 8]:1-7) has been inserted as reference 26, and the original references 26 and 29 through 35 have been renumbered accordingly. Additionally, Table I and several passages in the text have been updated to reflect the addition of the new reference. Specifically, in Table I, the study by Niemeier et al. has been inserted as the fifth row between the “Amer et al.” and “Current case” rows. On page 3, the text that had read “To our knowledge, there are only 4 published cases of metachronous, polyostotic ABCs in 4 male patients 25–28 . The longest documented interval between clinical presentation of the first and second lesions is 15 years 25 , whereas the shortest interval is 15 months 26 .” now reads “To our knowledge, there are only 5 published cases of metachronous, polyostotic ABCs in 4 male patients and 1 female patient 25–29 . The longest documented interval between clinical presentation of the first and second lesions is 15 years 25 , whereas the shortest interval is 3 months 26 .” On page 7, the passage that had read “However, to our knowledge, there are only 4 published cases of metachronous, polyostotic ABCs, and all patients were males 25–28 . The current case demonstrates that females may also develop polyostotic disease. None of the 4 previously reported cases of metachronous, polyostotic ABCs demonstrated a previous history of malignancy 25–28 .” now reads “However, to our knowledge, there are only 5 published cases of metachronous, polyostotic ABCs with only 1 case describing lesions in a female patient 25–29 . This is the second case demonstrating that females may also develop polyostotic disease. None of the 5 previously reported cases of metachronous, polyostotic ABCs demonstrated a previous history of malignancy 25–29 .” Also on page 7, the sentence that had read “Metachronous ABCs are rare and have been reported to present anywhere from 15 months to 15 years after diagnosis of the initial lesion 25,26 .” now reads “Metachronous ABCs are rare and have been reported to present anywhere from 3 months to 15 years after diagnosis of the initial lesion 25–29 .” An erratum has been published: JBJS Case Connect. 2019 Dec 24;9(4):e0263ER. Case: We present a case involving an adolescent female who developed metachronous, polyostotic aneurysmal bone cysts (ABCs) of the left hemipelvis and left proximal tibia within a 16-month interval. At age 12 years, the left periacetabular ABC was initially treated with selective arterial embolization and percutaneous sclerotherapy, followed by intralesional curettage and bone grafting. At age 14 years, the left proximal tibia ABC was treated with intralesional curettage, bone grafting, and prophylactic internal fixation. She showed no evidence of recurrence of either lesion after 32 and 12 months, respectively. Conclusions: Metachronous, polyostotic ABCs may occur in females. Metachronous lesions may present years after the initial ABC; therefore, additional imaging to rule out polyostotic disease is not indicated in the routine management of a solitary ABC. Patients with multiple ABCs should be managed by following the standard approach for treatment of each lesion.