Hemiarthroplasty for the treatment of distal humerus fractures: short-term clinical results.

Total elbow arthroplasty is the current gold standard of treatment for unreconstructable distal humerus fractures; however, longevity of the implant remains a concern in younger, more active patients. Distal humerus hemiarthroplasty offers an alternative and may allow for more durable results. The authors retrospectively evaluated the short-term clinical outcomes of 10 patients who underwent elbow hemiarthroplasty for distal humerus fractures. This short-term review suggests that distal humerus hemiarthroplasty may be an effective treatment for certain distal humerus fractures. Additional studies must be conducted to further define the role of elbow hemiarthroplasty for the treatment of complex fractures of the distal humerus.

Osteoblastoma: a 30-year study of 99 cases.

BACKGROUND AND OBJECTIVES: Osteoblastoma is a rare, bone-forming neoplasm accounting for 1% of primary bone tumors. It arises in young patients and develops in long bones and posterior elements of the spine. Osteoblastoma is characterized by interconnecting trabeculae of woven bone and rimmed by prominent osteoblasts. In the current study we characterize osteoblastoma by its demographic and anatomic prevalence. We looked at rates of recurrence as related to treatment. METHODS: We performed a review of our institution's Orthopaedic Oncology tumor registry and identified 99 verified cases of osteoblastoma treated between 1974 and 2006. Data related to demographic, anatomic, surgical treatment and follow-up information were analyzed. RESULTS: The cohort included 69 males and 30 females with an average age of 24 +/- 14 years. The most common sites of occurrence were the vertebral column (28 patients) and the humerus (21 patients). The tumors were treated with en bloc surgical resection or curettage with allograft or autograft. Local recurrence rate was 24% and most followed curettage and packing. No patient died of disease. CONCLUSIONS: Osteoblastoma frequently affects the long bones and the spine. The recurrence rate following curettage is relatively high and can be minimized by resective surgery, in select cases.

Osteogenic differentiation is inhibited and angiogenic expression is enhanced in MC3T3-E1 cells cultured on three-dimensional scaffolds.

Osteogenic differentiation of osteoprogenitor cells in three-dimensional (3D) in vitro culture remains poorly understood. Using quantitative real-time RT-PCR techniques, we examined mRNA expression of alkaline phosphatase, osteocalcin, and vascular endothelial growth factor (VEGF) in murine preosteoblastic MC3T3-E1 cells cultured for 48 h and 14 days on conventional two-dimensional (2D) poly(l-lactide-co-glycolide) (PLGA) films and 3D PLGA scaffolds. Differences in VEGF secretion and function between 2D and 3D culture systems were examined using Western blots and an in vitro Matrigel-based angiogenesis assay. Expression of both alkaline phosphatase and osteocalcin in cells cultured on 3D scaffolds was significantly downregulated relative to 2D controls in 48 h and 14 day cultures. In contrast, elevated levels of VEGF expression in 3D culture were noted at every time point in short- and long-term culture. VEGF protein secretion in 3D cultures was triple the amount of secretion observed in 2D controls. Conditioned medium from 3D cultures induced an enhanced level of angiogenic activity, as evidenced by increases in branch points observed in in vitro angiogenesis assays. These results collectively indicate that MC3T3-E1 cells commit to osteogenic differentiation at a slower rate when cultured on 3D PLGA scaffolds and that VEGF is preferentially expressed by these cells when they are cultured in three dimensions.

Osteopontin is a negative regulator of proliferation and differentiation in MC3T3-E1 pre-osteoblastic cells.

Osteopontin (OPN) is an important mediator of bone remodeling. However, the role of OPN in the process of bone formation is not fully understood. In previous studies, we have shown that MC3T3-E1 pre-osteoblastic cells at higher passage number exhibited weakened osteogenic capacity and elevated OPN mRNA expression. In this work, we investigated the role of OPN on proliferation and differentiation of low-passage MC3T3-E1 cells by studying stable cell lines overexpressing either OPN mRNA or its antisense RNA. Overexpression was verified by both Northern and Western blot analyses. Overexpression of OPN markedly inhibited proliferation as determined by daily cell counts, while overexpression of antisense RNA stimulated cellular proliferation. We also examined the effect of OPN level on BMP-2-induced alkaline phosphatase activity. Overexpression of OPN inhibited BMP-2 responsiveness while overexpression of antisense RNA enhanced the effect of BMP-2 on alkaline phosphatase activity. Increased OPN expression also caused decreases in expression of osteocalcin and bone sialoproteins while a reduction of OPN level caused the opposite. Furthermore, endogenous OPN expression in response to BMP-2 exhibited a biphasic pattern, that is, it was initially inhibited and then enhanced by the treatment of BMP-2, indicating that OPN might function as a negative feedback regulator for osteoblastic differentiation. Finally, overexpression of OPN inhibited mineral deposition. In contrast, overexpression of antisense RNA enhanced mineral deposition. These results indicate that OPN is a negative regulator of proliferation and differentiation in MC3T3-E1 cells.