Finite element study on whether posterior upper wall fracture is a risk factor for the failure of short-segment pedicle screw fixation in the treatment of L1 burst fracture.

PURPOSE: To establish the finite element model of T12 and L2 (T12-L2) pedicle screw fixation for severe L1 burst fracture, and quantitatively simulate and analyze the screw stress and vertebral displacement in different degrees of L1 posterior upper wall fracture (PUWF), and evaluate whether PUWF degree is a risk factor for fixation failure. METHODS: The data of 6 healthy volunteers were used to establish a finite element model of T12-L2 pedicle screw fixation for type A severe burst fractures. The stress and displacement of the conventional and Schanz pedicle screws for the different degrees of PUWF (including the anterior upper wall of the vertebral canal and the bipedicle) were evaluated. RESULTS: The maximum stress and L1 displacement of conventional and Schanz pedicle screws were positively correlated with the severity of the PUWF (P<0.05). During anterior flexion, the maximum stress of conventional pedicle screws for 70% type I were 538.3±59.75MPa and the maximum stress of Schanz pedicle screws for 90% type Ⅱ, 90% type Ⅲ and 70% type IV fractures were close to the fatigue threshold. The maximum stress during anterior flexion were significantly higher than those during posterior extension, bending and rotation (P<0.05). CONCLUSION: The posterior upper wall fracture of vertebral body (VB) of type A burst fracture is not an independent risk factor for the failure of short-segment pedicle screw fixation (SSPSF). Anterior flexion of type A fractures combined with severe PUWF of VB was a risk factor for the failure of SSPSF.

Primary multiple angiosarcoma of vertebra: A case report.

RATIONALE: Angiosarcoma is a rare malignant tumors. The objective of this study is to report a patient who suffered from a progressive low back pain and left lower extremities radiation pain for about 8 months, After diagnoses, this was identified as an extremely rare case of primary multiple angiosarcoma of vertebra. PATIENT CONCERNS: A 54-year-old man with a history of 2-year hypertension and 8-year diabetes, both of which were well controlled by drug management. Lately, he suffered from a progressive low back pain and left lower extremities radiation pain for about 8 months. DIAGNOSES: Magnetic resonance imaging of lumbar showed a clear pathological fracture and primary multiple angiosarcoma of all vertebra. Postoperative pathology and High-throughput sequencing confirmed the diagnosis of primary multiple angiosarcoma of vertebra. INTERVENTIONS: The patient underwent minimally invasive pedicle screw fixation combined with bone cement augmentation for the purpose of stabilizing the damaged vertebrae. Following operation, he received both radiotherapy and chemotherapy for a period of time. OUTCOMES: The operation has achieved positive results in relieving pain and stabilizing the spine. No wound problem or operative complications occurred after operation. The patient reported an obvious remission of low back pain and was only capable to perform restricted physiological activities. A long-term palliative radiotherapy and chemotherapy were performed after operation. Unfortunately, the patient died 18 months later. CONCLUSION: This article emphasizes primary multiple angiosarcoma of vertebra. Despite being rare, it should be part of the differential when the patient manifested back pain and radiculopathy. We recommended the minimally invasive pedicle screw fixation for angiosarcoma of vertebra. Osteoplasty by bone cement augmentation was also an ideal choice for surgical treatment. It also advocates the use of specific targeted radiotherapy drugs based on gene analysis of tumors.

Finite element analysis comparing short-segment instrumentation with conventional pedicle screws and the Schanz pedicle screw in lumbar 1 fractures.

Previous finite element studies of thoracolumbar fractures were mostly based on simulation analysis of one single object, which was difficult to objectively evaluate the differences between conventional pedicle screws and Schanz pedicle screws. The aim of this study was to evaluate the stress of screw and injured vertebrae displacement using the finite element model of conventional pedicle screw and Schanz pedicle screw instrumentation for the treatment of lumbar 1 fractures. Data of eight healthy volunteers were used to simulate the finite element model. The instrumentation models were divided into four groups: moderate fracture conventional (MC), moderate fracture Schanz (MS), unstable/severe fracture conventional (UC), and unstable/severe fracture Schanz (US) pedicle screw groups. The maximum screw stress and lumbar 1 displacement/micro-motion in each group increased with the increase of torque and/or load. Under the same fracture, maximum von Mises stress of conventional pedicle screw (MC/UC) was larger than Schanz pedicle screw (MS/US) (P < 0.05) and lumbar 1 displacement/micro-motion of Schanz pedicle screw (MS/US) was larger than conventional pedicle screw (MC/UC) (P < 0.05). Under the same screws, the maximum von Mises stress and displacement/micro-motion of unstable fracture (UC/US) were larger than moderate fracture (MC/MS) (P < 0.05). Posterior short-segment instrumentation with Schanz pedicle screws were recommended for unstable fractures. The compression displacement/micro-motion of bony defect during flexion may lead to the postoperative re-collapse of injured vertebrae.

Modified Posterior Short-Segment Pedicle Screw Instrumentation for Lumbar Burst Fractures with Incomplete Neurological Deficit.

PURPOSE: We have introduced a method of modified posterior short-segment pedicle screw fixation and evaluated its clinical effects in treating lumbar burst fractures with incomplete neurological deficits. METHODS: The data from 22 patients with lumbar burst fracture and incomplete neurological deficits who had undergone modified posterior short-segment instrumentation with Schanz screw fixation from January 2012 to February 2018 in our clinic were evaluated in the present retrospective study. All Schanz screws were implanted in an oblique downward direction into the vertebrae above and below the injured vertebra (insertion depth, 90%-100%). The implants were removed ∼1 year after surgery. Neurological function, back pain, anterior and posterior body height ratio, kyphosis angle, percentage of canal compromise, fracture severity, and treatment-related complications were evaluated. RESULTS: Technical success was achieved in all 22 patients. No infection, instrument loosening or failure, or breakage was observed. Statistically significant improvements with regard to the anterior body height (P < 0.05) and posterior body height (P < 0.05) ratios, kyphosis angle, and percentage of canal compromise (P < 0.05) were observed at 1 week postoperatively or the final follow-up visit. No correction loss had occurred at the final follow-up examination. Postoperatively, all patients with neurological deficits had functional improvement equivalent to ≥1 grade on the American Spinal Injury Association impairment scale and fracture union. Back pain was greatly improved postoperatively. CONCLUSIONS: Short-segment Schanz screw fixation implanted in an oblique downward direction seems to be a promising method for lumbar burst fractures with incomplete neurological deficits because it provided good clinical and radiographic outcomes.

Biomechanical effects of USS fixation with different screw insertion depths on the vertebrae stiffness and screw stress for the treatment of the L1 fracture.

OBJECTIVE: To evaluate the biomechanical effects of internal fixation with different screw insertion depths on vertebrae stiffness and screw stress for L1 fracture. METHODS: The established L1 fracture was fixed with 10 different depths of screw insertion: 10-100% screw-path length (SPL). Loading on the T12 endplate was simulated. RESULTS: Screws inserted to 60-100% depths has a higher axial displacement of screw against injured vertebrae and maximum stress of screws compared to those of screws inserted to 30-50% depths and 10-20% (P< 0.05). No significant difference was noted among 60-100% SPL groups. Under single loading condition, the incidence rate of maximum stress of each screw ranged from 16.7-50.0%. Chi-square test showed superior screw has a higher incidence rate of maximum stress than inferior screw (P< 0.05). CONCLUSIONS: Screws inserted to 60% depth or more can achieve effective strength to withstand the postoperative height correction loss of the L1 vertebrae fracture. However, continuous prolonged depth of screw insertion did not significantly increase the effective strength of the screw against injured vertebrae and maximum equivalent stress of screws. The incidence rate of the maximum stress of each screw in correlated with position of screw insertion but not associated with the screw insertion depth.

Metformin increases sensitivity of osteosarcoma stem cells to cisplatin by inhibiting expression of PKM2.

Multiple drug resistance is reported to be a major obstacle in treatment of osteosarcoma (OS). Research has demonstrated that small subsets of cells called cancer stem cells (CSCs) are responsible for multiple drug resistance. CSCs are potential targets for reversing chemoresistance. In the present study, we compared cisplatin sensitivity between OS stem cells and OS non-stem cells. We confirmed that OS stem cells showed significant cisplatin-resistance compared with the OS non-CSCs. Mechanically, we proved that overexpression of the pyruvate kinase isoenzyme M2 (PKM2) was responsible for the resistance to cisplatin in OS stem cells. As a potential strategy, we found that co-treatment with metformin significantly decreased the half maximal inhibitory concentration (IC50) of cisplatin to HOS OS stem cells by downregulating the expression of PKM2. PKM2 downregulation resulted in, metformin inhibited glucose uptake, lactate production and ATP production in HOS CSCs. Therefore, metformin impaired the resistance of HOS CSCs to cisplatin and promoted cisplatin-induced apoptosis. In addition, antitumor effects of other chemotherapeutic drugs such as doxorubicin and 5-fluorouracil were proved to be enhanced by metformin on OS stem cells.

Association between the vitamin D receptor gene polymorphism and osteoporosis.

The influence of the vitamin D receptor (VDR) gene for the risk of osteoporosis remains to be elucidated. The aim of the present study was to understand the distribution of various single-nucleotide polymorphisms (SNPs) within the VDR gene and its association with the risk of osteoporosis. In total, 378 subjects without a genetic relationship were recruited to the study between January 2013 and July 2015. The subjects were divided into three groups, which were the normal (n=234), osteoporosis (n=65) and osteoporosis with osteoporotic fracture (n=79) groups. Three pertinent SNPs of the VDR gene rs17879735 (ApaI, Allele A/a, SNP C>A) were examined with polymerase chain reaction-restriction fragment length polymorphism. The bone mineral density (BMD) of the lumbar spine (L2-L4), femoral neck, Ward's and Tro was measured using dual-energy X-ray absorptiometry. The distributions of genotype frequencies aa, AA and Aa were 48.68, 42.86 and 8.46%, separately. Following analysis of each site, BMD, body mass index (BMI) and age, BMD for each site was negatively correlated with age (P<0.01) and positively correlated with BMI (P<0.01). Correction analysis revealed that there were significant differences in the Ward's triangle BMD among each genotype (P<0.05), in which the aa genotype exhibited the lower BMD (P<0.05). No significant difference was identified among the different genotypes in the occurrence of osteoporosis with osteoporotic fracture (P>0.05). In conclusion, these indicated that the VDR gene ApaI polymorphisms had an important role in the osteoporosis risk.