Objective: Primary leiomyosarcoma of bone (PLB) is a rare type of malignant bone tumor considered as a variant of the spindle cell sarcomas (SCS). The objective of this study was to analyze the clinicopathologic and the prognostic factors of patients with PLB treated at a single institution. Methods: We retrospectively reviewed the records of 22 patients with pathologically confirmed PLB. The data collected were: age, sex, tumor size and location, grade and stage of the disease and histopathologic features. Mean age was 45.5 years (range, 17 to 73 y). Location was: upper limb (27.3%), lower limb (68.2%) and pelvis (4.5%). Patients had high grade in 90.9% of the reports. Margins were negative in 77.3% of the cases. Histological reports describe spindly sarcomatous cells arranged in fascicles with increased vascular formation without osteoid or chondroid matrix production. On immunohistochemistry, smooth muscle actin and desmin where positive in all cases. Results: Mean follow-up time was 73.5 months (range, 5.3 to 331.1 m). We found 22.7% of local recurrence (LR). Distant metastasis (DM) was reported in 9 (40.9%) patients. Lung metastasis was the only DM affected site. Overall survival (OS) rate in 5 years was 59.1%. Predictors of OS were LR and DM. Conclusions: PLB is an extremely rare malignant bone tumor that has a higher rate of DM and similar OS prognosis compared with other bone sarcomas. Level of Evidence IV, Case Series.

Objective: To evaluate the effects of the self-management program PARQVE in patients with severe knee osteoarthritis (KOA). Methods: Prospective randomized controlled clinical trial with 65 grade IV Kelgren & Lawrence (K&L) KOA patients who were allocated into groups: Control (CG) and Intervention (IG). Both groups received usual care. IG also participated in two days of multi-professional interventions about OA (causes and treatment) and received the program’s DVD and book. Standing X-rays were obtained at inclusion and Ahlback’s classification was registered. Western Ontario and McMaster Universities Index (WOMAC), Numerical Rating Scale (NRS), Lequesne, weight, and body mass index (BMI) were obtained at inclusion, and after 6, 12 and 24 months. Results: Groups were similar at baseline, despite higher WOMAC stiffness scores and a greater number of Ahlback’s grade 4 and 5 in the IG. Only the IG improved WOMAC and total functions (p<0.001) during the study period above 12%, but did not reach the minimal clinically important difference of 20%. Best results were in one year. Non-significant improvements were observed without changes in body composition (P>0.05). Conclusions: Patients with severe KOA have mild to moderate function and quality of life improvement due to self-management program (PARQVE). Level of Evidence I; Therapeutic Studies; Prospective Randomized Controlled Trial.

Objective: To compare postoperative radiographic outcomes of Schatzker type V and VI tibial plateau fractures treated with double-plate or single lateral locked plate. Methods: Sixty-three patients operated from December 2011 to February 2016 were selected, 47 from the double-plate group and 16 from the single lateral locked plate group. Minimum follow-up for all patients was 6 months. Fracture reduction evaluation was based on radiographic parameters: joint reduction, sagittal alignment, coronal alignment, and condylar width. Results: Radiographic evaluation showed no statistical difference in the immediate or late postoperative periods. Conclusion: Despite the reduced sample, this study is aligned with current results published in the medical literature. The severity of Schatzker type V and VI tibial plateau fractures can be minimized by the correct indication for the implant regarding fracture morphology. Level of Evidence III, Retrospective comparative study.

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3824 The factor SDF-1 (stromal derived factor-1) was identified as an important chemoattractant factor produced by bone marrow cells. SDF-1 acts on its receptor CXCR4 and plays primordial function in migration, retention and development of hematopoietic progenitors in bone marrow. CXCR4 is expressed in leukemic cells and enables them to access marrow niches that normally are restricted to quiescent stem cells, thereby ensuring its protection from cell death resulting in a worse prognosis. In addition, it may induce activity of metalloproteinases (MMPs), which are enzymes that digest the extracellular matrix, making tumor cells more infiltrating. Moreover, higher levels of TIMP-2, an inhibitor of metalloproteinase 2 (MMP2), correlates with better prognosis in solid tumors. Recently, CXCR7 was identified as another SDF-1-binding receptor and the involvement of CXCR7 with tumor progression is well established in non-hematopoietic malignancies. Since it is well established that CD34 + progenitor cells from patients with myelodysplastic syndromes (MDS) are not attracted by gradient of SDF-1 despite of having CXCR4 normal expression, we addressed if MDS cells have an abnormal localization of CXCR4 or association with CXCR7. P39 and U937 cell line were used as a model of MDS and AML, respectively. Western blot analysis showed similar expression levels of CXCR4 and CXCR7 in both cell lines however we found, by confocal microscopy and flow cytometry, that CXCR4 was localized in the cytoplasm) of P39 cells while it was was in the membrane of U937 cells. Since the protein quinase C (PKC z) is related to the SDF-1/CXCR4 signaling by increasing CXCR4 expression and its membrane availability, we overexpressed HA-tagged PKCz in P39 cells.This procedure resulted in translocation of CXCR4 to the membrane of P39 cells but did not change the CXCR7 subcellular localization. Transwell chemotaxis assay showed that P39 cells overexpressing PKCz displayed higher chemotactic ability upon SDF-1 treatment compared with control P39 (35 fold increase pcDNA3-PKCz-HA vs pcDNA3-HA transfected P39 cells, p=0.0032; x2 test), suggesting that PKCz restored the chemotactic capacity of P39 cells. RNA expression of CXCR7 and TIMP-2 was analyzed by Real-time PCR (normalized by GAPDH and HPRT) in bone marrow samples from 50 MDS (FAB= 22 RA, 8 RARS, 20 RAEB), 29 acute myeloid leukemia (AML) patients and 11 healthy donors. CXCR7 mRNA expression did not differ significantly comparing all groups: controls, MDS (low or high risk) and AML whereas the expression of TIMP- 2 mRNA was significantly decreased in high risk MDS (p=0.0033) and AML (p=0.0003), (Mann-Whitney test) compared with normal controls. Taken together, our results suggest that a defect in the PKC ζ/CXCR4 pathway is involved with the unresponsiveness of MDS cells to SDF-1 and TIMP-2 downregulation could play a role in worse prognosis of myeloid malignancies. The role of CXCR7 is still undefined in myeloid malignancies. Disclosures: No relevant conflicts of interest to declare.