Humeral shaft fractures

Management of humeral shaft fractures has historically been largely conservative. A significant body of literature, dating back to the 1970s, has shown that functional bracing may achieve greater than 90 % union rates and acceptable functional outcomes. More recently, however, with the advent of new surgical techniques and implant options, less tolerance for acceptable deformity and functional deficits, and less patience with conservative management, many treating orthopaedic surgeons are increasingly likely to consider surgical intervention. This article reviews the current recommendations for treatment of humeral shaft fractures, including both nonoperative and operative intervention. It also discusses the current thinking and operative trends in humeral shaft fracture fixation.     

Kinetics of T-cell receptor binding to peptide/I-Ek complexes: correlation of the dissociation rate with T-cell responsiveness.

Recognition by T-cell antigen receptors (TCRs) of processed peptides bound to major histocompatibility complex (MHC) molecules is required for the initiation of most T-lymphocyte responses. Despite the availability of soluble forms of TCRs and MHC heterodimers, this interaction has proven difficult to study directly due to the very low affinity. We report here on the kinetics of TCR binding to peptide/MHC complexes in a cell-free system using surface plasmon resonance. The apparent association rates for the interactions of related peptide/MHC complexes to one such TCR are relatively slow (900-3000 M-1.s-1) and dissociation rates are very fast (0.3-0.06 s-1) with t1/2 of 2-12 s at 25 degrees C. The calculated affinity of the engineered soluble molecules compares well with previously reported competition data for native TCRs or competition data reported here for native peptide/MHC complexes, indicating that these soluble heterodimers bind in the same manner as the original molecules expressed on cells. We also find that the peptide variants which give weaker T-cell stimulatory responses have similar affinities but distinctly faster dissociation rates compared with the original peptide (when loaded onto the MHC molecule) and that this later property may be responsible for their lower activity. This has implications for both downstream signaling events and models of TCR-peptide antagonists.     

Ferumoxytol Does Not Impact Standardized Uptake Values on PET/MR Scans

Purpose

Tumor response assessments on positron emission tomography (PET)/magnetic resonance imaging (MRI) scans require correct quantification of radiotracer uptake in tumors and normal organs. Historically, MRI scans have been enhanced with gadolinium (Gd)-based contrast agents, which are now controversial due to brain deposition. Recently, ferumoxytol nanoparticles have been identified as an alternative to Gd-based contrast agents because they provide strong tissue enhancement on MR images but are not deposited in the brain. However, it is not known if the strong T1- and T2-contrast obtained with iron oxide nanoparticles such as ferumoxytol could affect MR-based attenuation correction of PET data. The purpose of our study was to investigate if ferumoxytol administration prior to a 2-deoxy-2-[¹⁸F]fluoro-d-glucose [¹⁸F]FDG PET/MR scan would change standardized uptake values (SUV) of normal organs.

Procedures

Thirty pediatric patients (6–18 years) with malignant tumors underwent [¹⁸F]FDG-PET/MR scans (dose 3 MBq/kg). Fifteen patients received an intravenous ferumoxytol injection (5 mg Fe/kg) prior to the [¹⁸F]FDG-PET/MR scans (group 1). Fifteen additional age- and sex-matched patients received unenhanced [¹⁸F]FDG-PET/MR scans (group 2). For attenuation correction of PET data, we used a Dixon-based gradient echo sequence (TR 4.2 ms, TE 1.1, 2.3 ms, FA 5), which accounted for soft tissue, lung, fat, and background air. We used a mixed linear effects model to compare the tissue MRI enhancement, quantified as the signal-to-noise ratio (SNR), as well as tissue radiotracer signal, quantified as SUVmean and SUVmax, between group 1 and group 2. Alpha was assumed at 0.05.

Results

The MRI enhancement of the blood and solid extra-cerebral organs, quantified as SNR, was significantly higher on ferumoxytol-enhanced MRI scans compared to unenhanced scans (p?<?0.001). However, SUVmean and SUVmax values, corrected based on the patients’ body weight or body surface area, were not significantly different between the two groups (p?>?0.05).

Conclusion

Ferumoxytol administration prior to a [¹⁸F]FDG PET/MR scan did not change standardized uptake values (SUV) of solid extra-cerebral organs. This is important, because it allows injection of ferumoxytol contrast prior to a PET/MRI procedure and, thereby, significantly accelerates image acquisition times.