[Posterior spinal canal decompression with screw fixation and reconstruction of three vertebral column for thoracolumbar burst fractures complicated with nerve injury].

OBJECTIVE: To explore the feasibility and clinical effect of posterior spinal canal decompression with pedicle screw fixation and reconstruction of anterior and middle vertebral column for thoracolumbar burst fractures complicated with nerve injury. METHODS: A total of 36 patients with thoracolumbar burst fractures treated from March 2011 to April 2016 were enrolled in the retrospective study. There were 20 males and 16 females, aged from 21 to 52 years old with an average of 37.6 years. All the fractures were located on a single segment, 8 cases of T1111, 10 cases of T12, 12 cases of L1, 6 cases of L2. According to thoracolumbar injury classification and severity score(TLICS) system, the score was 7 to 9 points, with an average of 7.4 points. According to the America Spine Injury Association(ASIA) grade, 4 cases were type A, 10 cases were type B, 14 cases were type C, 8 cases were type D. All the patients underwent posterior spinal canal decompression with pedicle screw fixation and reconstruction of anterior and middle vertebral column. The recovery of nerve function was evaluated by ASIA grading. The correction of kyphosis(Cobb angle), the volume change of injuried spinal canal, the change of anterior border height of injury vertebra which can be observed by X-rays;the internal fixation loosening and breakage and all the information of bone fusion were recorded. RESULTS: All the operations were successful, the mean operative time and intraoperative blood loss were(2.8±0.3) h (2.1 to 3.5 h) and (880±120) ml(550 to 1 350 ml), respectively. All the incisions got primary healing. All the patients were followed up for 12 to 28 months with an average of 18.4 months. All the patients obtained satisfactory bone fusion. No pseudoarticulation formation was found, and there was no loosening, breakage of pedicle screws or displacement of titanium mesh. Neurological function was improved in different degree, except in one patient with grade A and another one with grade B. According to the ASIA grade, there were 1 case of type A, 1 case of type B, 7 cases of type C, 10 cases of type D and 17 cases of type E, postoperatively. At 3 days after operative, the anterior border height of injury vertebra, Cobb angle and the volume changes of injury spinal canal were obviously improved(P<0.05), and there was no significant difference between postoperative at 3 days and final follow-up(P>0.05). CONCLUSIONS: Spinal canal decompression with screw fixation and reconstruction of anterior and middle vertebral column through posterior midline approach is a safe and effective method in the treatment of thoracolumbar burst fractures with nerve injury, it is worthy to be popularized. It can complete the spinal canal decompression of 360 degree, reduction of fractures and reconstruction of vertebral three-column at the same time through a single posterior approach. The advantages includes less trauma, perfect decompression, good stability and etc.

A theoretical rationale for why azetidine has a faster rate of formation than oxetane in TC(6-4) photoproducts.

The mechanism of formation of azetidine and oxetane in (6-4) photoproducts between thymine and imine-type cytosine is studied using the MPWB1K and B3LYP functionals together with the 6-31G(d,p) and 6-311++G(d,p) basis sets, in vacuum and bulk solvent. The photoinduced cycloaddition displays favorable energy barriers in the triplet excited state for formation of both azetidine and oxetane. The stepwise cycloaddition in the triplet excited state involves the initial formation of a diradical followed by ring closure via singlet-triplet interaction. The distinguishing feature in the formation of azetidine compared to that of oxetane is an intermediate H3' back-transfer to N3', which is a low-barrier exothermic reaction, and thus shifts the energy balance toward azetidine formation.

A triplet mechanism for the formation of thymine-thymine (6-4) dimers in UV-irradiated DNA.

The reaction pathway for the photochemical formation of thymine-thymine (6-4) dimers in DNA is explored using hybrid density functional theory techniques in gas and in bulk solvent. It is concluded that the photo-induced cycloaddition displays favorable energy barriers in the triplet excited state. The stepwise cycloaddition in the triplet excited state involves the initial formation of a diradical followed by ring closure via singlet-triplet interaction. The key geometric features and electron spin densities are also discussed. The difference in barriers of H3' transfer for the lowest-lying triplet and singlet states shows that the singlet oxetane intermediate could catch the second photon to accelerate the rate of proton transfer, leading to formation of the Dewar structure. The present results provide a rationale for the formation of thymine-thymine (6-4) dimers in the triplet excited states.