The "sliver sign": a specific radiographic sign of acute lateral patellar dislocation.

OBJECTIVE: The objective of this work is to assess the prevalence of the sliver sign, defined as an intraarticular linear or curvilinear ossific density, in association with knee effusion in patients with acute knee trauma, as a predictor of recent lateral patellar dislocation (LPD). MATERIALS AND METHODS: A retrospective radiology database search for the term 'patellar dislocation' on MRI knee exams performed at our institution over a 7-year period identified 216 studies. Of these, 142 exams met true positive gold standard diagnostic criteria for LPD. Imaging findings of both the retrospectively identified radiographs and subsequent MRI were recorded. Accuracy of radiographic interpretation was also analyzed. RESULTS: After review by an experienced musculoskeletal radiologist, 27 patients (19%) with LPD had knee radiographs demonstrating intraarticular osseous fragments. The majority of these patients had fragments (22/27, 81%) that were linear or curvilinear in configuration. A smaller subset of patients had fragments (5/27, 19%) that were rounded or oblong, felt to most likely represent sequelae of chronic dislocation. The fragments were identified on the patellar view only in eight of 27 patients (30%). These fragments were often initially misinterpreted, with the diagnosis explicitly stated in the report in 2/27 cases (7%). More often, the fractures were described vaguely (13/27, 48%), interpreted incorrectly (6/27, 22%), or missed (6/27, 22%). All 27 patients had moderate or large knee joint effusions. CONCLUSIONS: In the setting of acute knee trauma, knee radiographs demonstrating a joint effusion and an intraarticular sliver-like osseous fragment correlate with recent lateral patellar dislocation. The routine trauma knee radiographic series does not include a patellar view but probably should, especially in young patients.

BRCA1-induced apoptosis involves inactivation of ERK1/2 activities.

Mutation in the BRCA1 gene is associated with an increased risk of breast and ovarian cancer. Recent studies have shown that the BRCA1 gene product may be important in mediating responses to DNA damage and genomic instability. Previous studies have indicated that overexpression of BRCA1 can induce apoptosis or cell cycle arrest at the G(2)/M border in various cell types. Although the activation of JNK kinase has been implicated in BRCA1-induced apoptosis, the role of other members of the mitogen-activated protein kinase family in mediating the cellular response to BRCA1 has not yet been examined. In this study, we monitored the activities of three members of the MAPK family (ERK1/2, JNK, p38) in MCF-7 breast cancer cells and U2OS osteosarcoma cells after their exposure to a recombinant adenovirus expressing wild type BRCA1 (Ad.BRCA1). Overexpression of BRCA1 in MCF-7 cells resulted in arrest at the G(2)/M border; however, BRCA1 expression in U2OS cells induced apoptosis. Although BRCA1 induced JNK activation in both cell lines, there were marked differences in ERK1/2 activation in response to BRCA1 expression in these two cell lines. BRCA1-induced apoptosis in U2OS cells was associated with no activation of ERK1/2. In contrast, BRCA1 expression in MCF-7 cells resulted in the activation of both ERK1/2 and JNK. To directly assess the role of ERK1/2 in determining the cellular response to BRCA1, we used dominant negative mutants of MEK1 as well as MEK1/2 inhibitor PD98059. Our results indicate that inhibition of ERK1/2 activation resulted in increased apoptosis after BRCA1 expression in MCF-7 cells. Furthermore, BRCA1-induced apoptosis involved activation of JNK, induction of Fas-L/Fas interaction, and activation of caspases 8 and 9. The studies presented in this report indicate that the response to BRCA1 expression is determined by the regulation of both the JNK and ERK1/2 signaling pathways in cells.