Biomechanical evaluation of an experimental internal ring fixator (RingFix) for stabilization of pelvic ring injuries on an osteoporotic bone model.

During the last decades, effective pain reduction and early mobilization were identified as the central priorities in therapy of insufficiency fractures of the pelvis. For operative treatment minimally-invasive stabilization techniques are favored. While there is consensus on the significance of sufficient dorsal stabilization the role of additional fixation of the anterior fracture component stays under discussion. Within the present study we developed an internal ring fixator system (RingFix) with the question whether an in-itself-closed construct can improve stability of the entire ring structure. RingFix was evaluated on an osteoporotic bone model with a standardized FFP IIIc fracture within an established biomechanical setup regarding its primary stabilization potential. Further, it was compared to transiliac-transsacral screw fixation with and without stabilization of the anterior fracture component. The transiliac-transsacral fixation with separate screw fixation of the anterior fracture showed significantly higher stability than the RingFix and the transiliac-transsacral screw fixation without anterior stabilization. Our results show that stabilization of the anterior fracture component relevantly improves the stability of the entire ring construct. As a bridging stabilizer, RingFix shows biomechanical advantages over an isolated dorsal fracture fixation, but inferior results than direct stabilization of the single fracture components.

Do we need to fix the anterior fracture component in insufficiency fractures of the pelvis? A biomechanical comparison on an FFP type IIIc fracture in an osteoporotic pelvic bone model.

There is a growing understanding of the specific characteristics of insufficiency fractures of the pelvis and of general requirements for the treatment of affected patients with focus on early mobilization and effective pain reduction as the main goals of therapy. While there is consensus on the significance of achieving stability of the dorsal pelvic ring structures there is still an open discussion about the potential benefits of additional stabilization of an anterior fracture component. Within a biomechanical test setup, two established methods of dorsal fracture fixation were tested under axial loading (25-1200 N; 1000 test cycles) on an explicit osteoporotic bone model (n = 32) with a standardized FFP type IIIc fracture with and without additional fixation of the anterior fracture component. Dorsal fixation was performed with and long and a short 7.3 mm cannulated screw in S1 in one group (n = 16), and a trans sacral bar with an additional short 7.3 mm cannulated screw in S1 in the other group (n = 16). Half of the samples received a 7.3 mm cannulated retrograde transpubic screw for anterior fixation. The fixation with the trans sacral bar and the additional anterior screw fixation showed the highest rate of stability (p = 0.0014), followed by the double SI-screw fixation with stabilization of the anterior fracture (p = 0.0002). During testing, we observed the occurrence of new sacral fractures contralateral to the initial fracture in 22/32 samples. The results let us assume that stabilization of an additional anterior fracture component relevantly improves the stability of the entire ring construct and might prevent failure of the dorsal stabilization or further fracture progression.

Directed ortho metalation approach to C-7-substituted indoles. Suzuki-Miyaura cross coupling and the synthesis of pyrrolophenanthridone alkaloids.

[reaction: see text] Although the indole N-phosphinoyl derivative 4 undergoes n-BuLi deprotonation/electrophile quench to afford C-7-substituted products, its deprotection requires harsh conditions. On the other hand, the N-amide 12, upon sequential or one-pot C-2 metalation, silylation, C-7 metalation, and electrophile treatment, furnishes indoles 7 in good overall yields. In combination with the Suzuki-Miyaura protocol, C-7 aryl (heteroaryl)-substituted indoles 14 and 16 are obtained, including hippadine and pratosine, members of the pyrrolophenanthridone alkaloid family.

A general study of [(eta5-Cp')2Ti(eta2-Me3SiC2SiMe3)]-catalyzed hydroamination of terminal alkynes: regioselective formation of Markovnikov and anti-Markovnikov products and mechanistic explanation (Cp'=C5H5, C5H4Et, C5Me5).

A general study of the regioselective hydroamination of terminal alkynes in the presence of [(eta5-Cp)2Ti(eta2-Me3SiC2SiMe3)] (1), [(eta5-CpEt)2Ti(eta2-Me3SiC2SiMe3)] (CpEt=ethylcyclopentadienyl) (2), and [(eta5-Cp*)2Ti(eta2-Me3SiC2SiMe3)] (Cp*=pentamethylcyclopentadienyl) (3) is presented. While aliphatic amines give mainly the anti-Markovnikov products, anilines and aryl hydrazines yield the Markovnikov isomer as main products. Interestingly, using aliphatic amines such as n-butylamine and benzylamine the different catalysts lead to a significant change in the observed regioselectivity. Here, for the first time a highly selective switch from the Markovnikov to the anti-Markovnikov product is observed simply by changing the catalyst. Detailed theoretical calculations for the reaction of propyne with different substituted anilines and tert-butylamine in the presence of [(eta5-C5H5)Ti(=NR)(NHR)] (R=4-C6H4X; X=H, F, Cl, CH3, 2,6-dimethylphenyl) reveal that the experimentally observed regioselectivity is determined by the relative stability of the corresponding pi-complexes 10. While electrostatic stabilization favors the Markovnikov performance for aniline, the steric repulsive destabilization disfavors the Markovnikov performance for tert-butylamine.