Modified triangular posterior osteosynthesis of unstable sacrum fracture.

We report preliminary results for unstable sacral fractures treated with a modified posterior triangular osteosynthesis. Seven patients were admitted to our trauma center with an unstable sacral fracture. The average age was 31 years (22-41). There were four vertical shear lesions of the pelvis and three transverse fracture of the upper sacrum. The vertical shear injuries were initially treated with an anterior external fixator inserted at the time of admission. Definitive surgery was performed at a mean time of 9 days after trauma. The operation consisted in a posterior fixation combining a vertebropelvic distraction osteosynthesis with pedicle screws and a rod system, whereby the transverse fixation was obtained using a 6 mm rod as a cross-link between the two main rods. Late displacement of the posterior pelvis or fracture was measured on X-ray films according to the criteria of Henderson. The patients were followed-up for a minimum time of 12 months. Four patients who presented with a pre-operative perineal neurological impairment made a complete recovery. No iatrogenic nerve injury was reported. One case of deep infection was managed successfully with surgical debridement and local antibiotics. All patients complained of symptoms related to the prominence of the iliac screws. The metalwork was removed in all cases after healing of the fracture, at a mean time of 4.3 months after surgery. No loss of reduction of fracture was seen at final radiological follow-up. The preliminary results are promising. The fixation is sufficiently stable to allow an immediate progressive weight-bearing, and safe nursing care in polytrauma cases. The only problem seems to be related to prominent heads of the distal screws

Chiroptical properties of chiral substituted polyfluorenes

Liquid-crystalline polyfluorene (PF) homopolymers substituted with chiral alkyl side chains were synthesized, and their chiroptical properties in the solid state were investigated by means of circular dichroism (CD), circularly polarized photoluminescence (CPPL), and circularly polarized electroluminescence (CPEL) measurements. Polarization-selective scattering of light is shown to cause artifacts in the circularly polarized absorption and emission spectra in the wavelength range near or above the absorption edge, and a measurement scheme to avoid these is presented. For all derivatives, significant chiroptical effects appeared only after the solid layers have been annealed at elevated temperatures, preferably into the liquid-crystalline state of the polymer. The largest anisotropy factors were measured for a polyfluorene substituted with chiral (R)-2-ethylhexyl side chains, yielding absolute values of up to 0.28 for CPPL and up to 0.25 for CPEL. These are among the highest ever reported for a chiral conjugated polymer. Anisotropy factors for CD, CPEL, and CPPL were consistently found to follow an "odd-even effect" concerning the position of the chiral center in the alkyl side chain. If the chiral center is placed close to the polymer backbone, the CD is dominated by one peak with its maximum close to the maximum of the pi-pi* absorption band. This indicates that the chiroptical. properties are most probably caused by intrachain effects rather than by pure interchain exciton coupling. This interpretation is supported by the results of time-dependent Hartree-Fock calculations for the isolated fluorene dimer and trimer. In both cases, the anisotropy factor depends strongly on the torsion angle between neighboring fluorene units. For the trimer, a maximum anisotropy factor of 0.25, close to the maximum values determined experimentally, is predicted for a torsion angle of ca. 105degrees. Both experimental and theoretical results indicate that the chiroptical properties of these chiral substituted polyfluorenes are mainly caused by a helical conformation of the conjugated polymer backbone