Arthroscopic Decompression of a Malunited Infrafoveal Femoral Head Fracture: A Case Report.

CASE: A patient presented with a traumatic posterior wall fracture and small femoral head fracture. He initially underwent open reduction and internal fixation to treat the posterior wall fracture. The femoral head fracture was left alone because of its small size and lack of joint incongruity. At 1 year postoperatively, the patient reported pain due to malunion of the femoral head fragment, which was treated arthroscopically. Treatment resulted in significant pain relief sustained at the 6-year follow-up. CONCLUSION: Symptomatic femoral head fractures malunited to the femoral neck are rare complications. Arthroscopy may offer a viable treatment approach for select patients with this condition.

Potency of a tau fibrillization inhibitor is influenced by its aggregation state.

Tau fibrillization is a potential therapeutic target for Alzheimer's and other neurodegenerative diseases. Several small-molecule inhibitors of tau aggregation have been developed for this purpose. One of them, 3,3'-bis(beta-hydroxyethyl)-9-ethyl-5,5'-dimethoxythiacarbocyanine iodide (N744), is a cationic thiacarbocyanine dye that inhibits recombinant tau filament formation when present at submicromolar concentrations. To prepare dosing regimens for testing N744 activity in biological models, its full concentration-effect relationship in the range 0.01-60muM was examined in vitro by electron microscopy and laser light scattering methods. Results revealed that N744 concentration dependence was biphasic, with fibrillization inhibitory activity appearing at submicromolar concentration, but with relief of inhibition and increases in fibrillization apparent above 10muM. Therefore, fibrillization was inhibited 50% only over a narrow concentration range, which was further reduced by filament stabilizing modifications such as tau pseudophosphorylation. N744 inhibitory activity also was paralleled by changes in its aggregation state, with dimer predominating at inhibitory concentrations and large dye aggregates appearing at high concentrations. Ligand dimerization was promoted by the presence of tau protein, which lowered the equilibrium dissociation constant for dimerization more than an order of magnitude relative to controls. The results suggest that ligand aggregation may play an important role in both inhibitory and disinhibitory phases of the concentration-effect curve, and may lead to complex dose-response relationships in model systems.