Comparison of pedicle screw fixation with or without cement augmentation for treating single-segment isthmic spondylolisthesis in the osteoporotic spine.

The present study examined the necessity of cement-augmented pedicle screw fixation in osteoporotic patients with single-segment isthmic spondylolisthesis.Fifty-nine cases were reviewed retrospectively. Thirty-three cases were in the polymethylmethacrylate-augmented pedicle screw (PMMA-PS) group, and the other 26 cases were in the conventional pedicle screw (CPS) group. Evaluation data included operation time, intraoperative blood loss, hospitalization cost, hospitalization days, rates of fusion, screw loosening, bone cement leakage, visual analogue scale (VAS) scores, Oswestry disability index (ODI), lumbar lordosis (LL), pelvic tilt (PT) and sacral slope (SS).The operation time and blood loss in the CPS group decreased significantly compared to those in the PMMA-PS group. The average hospitalization cost of the PMMA-PS group was significantly higher than that of the CPS group. There was no significant difference in the average hospital stay between the 2 groups. The initial and last follow-up postoperative VAS and ODI scores improved significantly in the two groups. There were no significant differences in VAS and ODI between the 2 groups at each time point. The last postoperative spine-pelvic parameters were significantly improved compared with those preoperatively. In the PMMA-PS group, the fusion rate was 100%. The fusion rate was 96.15% in the CPS group. No significant difference was found between the two groups for the fusion rate. Nine patients in the PMMA-PS group had bone cement leakage. There was no screw loosening in the PMMA-PS group. There were 2 cases of screw loosening in the CPS group. There were no significant differences in screw loosening, postoperative adjacent segment fractures, postoperative infection or postoperative revision between the 2 groups. The use of PMMA-PS on a regular basis is not recommended in posterior lumbar interbody fusion for the treatment of single-segment isthmic spondylolisthesis with osteoporosis.

Long-term efficacy and safety of bone cement-augmented pedicle screw fixation for stage III Kümmell disease.

This study aimed to evaluate the efficacy and safety of bone cement-augmented pedicle screw fixation for stage III Kümmell disease. Twenty-five patients with stage III Kümmell disease who received bone cement-augmented pedicle screw fixation at the First Affiliated Hospital of Guangzhou University of Chinese Medicine between June 2009 and December 2015 were enrolled. All patients were females with a history of osteoporosis. The vertebral Cobb angle (V-Cobb angle), the fixed segment Cobb Angle (S-Cobb angle), pelvic parameters, visual Analogue Scale (VAS) score, and Oswestry Disability Index (ODI) were assessed preoperatively, postoperatively and at the final follow-up. Complications, loosening rate, operation time, and intraoperative bleeding were recorded. The average lumbar vertebral density T-value was - 3.68 ± 0.71 SD, and the average age was 71.84 ± 5.39. The V-Cobb angle, S-Cobb angle, and Sagittal Vertical Axis (SVA) were significantly smaller postoperatively compared to the preoperative values. The VAS and ODI at 1 month after surgery were 3.60 ± 1.00 and 36.04 ± 6.12%, respectively, which were both significantly lower than before surgery (VAS: 8.56 ± 1.04, ODI: 77.80 ± 6.57%). Bone cement-augmented pedicle screw fixation is a safe and effective treatment for stage III Kümmell disease. It can effectively correct kyphosis, restore and maintain sagittal balance, and maintain spinal stability.

Selective cement augmentation of cranial and caudal pedicle screws provides comparable stability to augmentation on all segments in the osteoporotic spine: a finite element analysis.

BACKGROUND: Cement-augmented pedicle screw instrumentation (CAPSI) has been proven to significantly increase the biomechanical stability in the osteoporotic lumbar spine. However, besides the merits, it is responsible for the inevitable cement leakage growing with more instrumented segments and volumes involved. This study aimed to compare the biomechanical performance of pedicle screws augmented on all segments with those augmented only on the cranial and caudal vertebrae selectively. METHODS: The finite element model of L3-S1 was modeled with the CT data of a healthy volunteer, the solid/fenestrated pedicle screws from micro-CT scans of physical screws, and bone cement from the CT scans of a postoperative patient with CAPSI. Three different augmented strategies for pedicle screws were taken into consideration: augmentation at each pedicle trajectory (Model A), selective augmentation at the cranial and caudal pedicle trajectories (Model B), and pedicle trajectories without augmentation (Model C). A total of six surgical models were constructed: Models A, B, and C were subdivided into double segmental fusion from L4 to S1 (Models A1, B1, and C1) and multi-segment fusion from L3 to S1 (Models A2, B2, and C2). The Range of motion (ROM), stress on the cage, and stress on the fixed segments were compared among the six models. RESULTS: The ROM at the fusion segments decreased in all instrumentation models. The ROMs of Model B and Model A are similar in each direction, while that of Model C is significantly larger. The differences in the ROMs between Model A and Model B were noted to be less than 0.1°. Compared with Models A1 and A2, the peak Von Mise stress on the cage-endplate interface and pedicle screws were slightly higher in Models B1 and B2. In contrast, the stress of Models C1 and C2 increased significantly. The compressive stress was concentrated in the screw head, the cranial and caudal screws, and rods. CONCLUSIONS: The selective augmentation of pedicle screws is capable of providing reliable stability in short-segment posterior fixation (2- or 3-level). It could be a potential optimal procedure to minimize the associated complications of CAPSI.

Biomechanical evaluation of four different posterior instrumentation techniques for single-level transforaminal lumbar interbody fusion: a finite element analysis.

This study aims to investigate the fixation strength of unilateral cortical bone trajectory screw fixation (UCBT) and UCBT with contralateral translaminar facet screw fixation (UCBT-TFS) by repeating the verification of three finite element models. Three healthy female models of the lumbosacral spine were constructed. For each of them, four transforaminal lumbar interbody fusion (TLIF) models with the following instruments were created: bilateral traditional trajectory pedicle screw fixation (TT), bilateral cortical bone trajectory screw fixation (CBT), UCBT, and UCBT-TFS. A 150-N compressive load with 10 N/m moments was applied to simulate flexion, extension, lateral bending, and axial rotation. The range of motion (ROM), the stress of the cages, and the stress of the posterior fixations were compared. TT and UCBT-TFS had a similar low ROM compared to the intact models, and CBT showed a higher ROM in lateral bending. UCBT resulted in the highest ROM under all loading conditions, especially in lateral bending (116% and 170% greater than TT in left bending and right bending). UCBT induced a significant increase in the peak stress of cages and instruments, followed by CBT and UCBT-TFS, and the lowest mean values were observed for TT. Among the four different fixation techniques, TT offered the highest fixation strength and lowest implant stress, followed by UCBT-TFS and CBT, while UCBT was the least stable and resulted in increased stress of the screws and cages. UCBT-TFS improved biomechanical stability and appeared to be a less invasive alternative in well-selected patients with single-level TLIF.

Influence of cement-augmented pedicle screws with different volumes of polymethylmethacrylate in osteoporotic lumbar vertebrae over the adjacent segments: a 3D finite element analysis.

BACKGROUND: Polymethylmethacrylate (PMMA) is commonly used for cement-augmented pedicle screw instrumentation (CAPSI) to improve the fixation stability and reduce the risk of screw loosening in the osteoporotic thoracolumbar spine. Biomechanical researches have shown that various dose of cement (1-3 ml) can be injected to enhance screw stability. To date, there have been no studies on the relationship between adjacent segment degeneration and the volume of PMMA. This study aimed to explore the influence of CAPSI with different volumes of PMMA in osteoporotic lumbar vertebrae over adjacent segments by using finite element analysis. METHODS: Seven different finite element models were reconstructed and simulated under different loading conditions, including (1) an intact model, (2) three single-level CAPSI models with different volumes of PMMA (1, 1.73, and 2.5 ml), and (3) three double-level CAPSI models with different volumes of PMMA (1, 1.73, and 2.5 ml). To improve the accuracy of the finite element analysis, the models of the injectable pedicle screw and bone cement were created by using a three-dimensional scanning machine and the CAPSI patient's CT data, respectively. The range of motion (ROM), the stress of intervertebral discs, and the stress of facet in the adjacent segment were comparatively analyzed among the different models. RESULTS: The ROMs of the different segments were compared with experimental data, with good agreement under the different load conditions (21.3°, 13.55°, 13.99°, and 6.11° in flexion, extension, bending, and rotation at L3-S1 level, respectively). Compared with the intact model, the ROM, disc stresses, and facet stress in adjacent segments were found to be higher in the six operative models. Otherwise, with a larger volume of PMMA injected, the ROM, disc stresses, and facet stress slightly increased at the adjacent segment. However, the differences were insignificant with the biggest difference less than 3.8%. CONCLUSIONS: CAPSI could increase the incidence of disk degeneration in the adjacent segment, while within a certain range, different volumes of PMMA provided an approximate impact over the adjacent segment degeneration.

Pedicle Screw Fixation in Single-Level, Double-Level, or Multilevel Posterior Lumbar Fusion for Osteoporotic Spine: A Retrospective Study with a Minimum 2-Year Follow-Up.

BACKGROUND: Pedicle screw loosening is a common postoperative complication for osteoporotic patients, and several studies have identified the important role of fusion length in internal fixation failure, but the relationship between the number of fusion segments and the potential risks remains unclear. This study aimed to investigate the rate and risk factors of screw loosening in osteoporotic patients with different levels of degenerative lumbar disease. METHODS: The total cohort of 217 patients was divided into 3 groups according to the different fusion levels: single-level (group A; 100 cases), double-level (group B; 73 cases), and multilevel group (group C; 44 cases). Patient baseline demographic characteristics and assessments with a visual analog scale (VAS) and the Oswestry Disability Index (ODI) before operation and at the last follow-up were compared among the 3 groups. RESULTS: Compared with preoperative values, VAS and ODI scores at the last follow-up were significantly improved in all 3 groups. Operative time, blood loss, length of hospital stay, screw loosening rate, fusion rate, and VAS and ODI scores at the last follow-up obviously increased with the increasing number of fusion segments (group C> group B> group A). Of note, all the screw loosening was observed in cranial and caudal vertebra. Furthermore, multivariate logistic regression analysis identified lumbosacral fixation, larger pelvic incidence (PI)-lumbar lordosis (LL) difference (PT-LL), and greater postoperative pelvic tilt (PT) as independent predictors of screw loosening. However, sex, bone mineral density, body mass index, LL, sacral slope, PI, the change in LL, and preoperative PT were not relevant to screw loosening (P > 0.05). CONCLUSIONS: Owing to the high rate of screw loosening in cranial and caudal vertebra, osteoporotic patients with double-level or multilevel pedicle screw fixation benefited less than those with single-level pedicle screw fixation. Larger PI-LL, larger PT, and lumbosacral fixation are other risk factors for screw loosening. An instrument with stronger holding strength at cranial and caudal pedicle screws is recommended for those high-risk patients.

Effect and potential risks of using multilevel cement-augmented pedicle screw fixation in osteoporotic spine with lumbar degenerative disease.

BACKGROUND: The increase of augmented level and bone cement dose are accompanied by the rising incidence of cement leakage (CL) of cement-augmented pedicle screw instrumentation (CAPSI). But the effect and potential risks of the application of CAPSI to osteoporotic lumbar degenerative disease (LDD) have not been studied in the case of multilevel fixation. This study aimed to investigate the effectiveness and potential complications of using multilevel CAPSI for patients with osteoporotic LDD. METHODS: A total of 93 patients with multilevel LDD were divided into the CAPSI group (46 subjects) and the conventional pedicle screw (CPS) group (47 subjects), including 75 cases for three levels and 18 cases for four levels. Relevant data were compared between two groups, including baseline data, clinical results, and complications. RESULTS: In the CAPSI group, a total of 336 augmented screws was placed bilaterally. The CL was observed in 116 screws (34.52%). Three cemented screws (0.89%) were found loosened during the follow-up and the overall fusion rate was 93.47%. For perioperative complications, two patients (4.35%) experienced pulmonary cement embolism (PCE), one patient augmented vertebral fracture, and three patients (6.52%) wound infection. And in the CPS group, thirty-three screws (8.46%) suffered loosening in cranial and caudal vertebra with a fusion rate of 91.49%. The operation time and hospital stay of CAPSI group were longer than the CPS group, but CAPSI group has a lower screw loosening percentage (P<0. 05). And in terms of blood loss, perioperative complications, fusion rate, and VAS and ODI scores at the follow-up times, there were no significant differences between the two groups. CONCLUSIONS: Patients with osteoporotic LDD underwent multilevel CPS fixation have a higher rate of screw loosening in the cranial and caudal vertebra. The application of cemented pedicle screws for multilevel LDD can achieve better stability and less screw loosening, but it also accompanied by longer operating time, higher incidence of CL, PCE and wound infections. Selective cement augmentation of cranial and caudal pedicle screws may be a worthy strategy to decrease the complications.

Stability Evaluation of Oblique Lumbar Interbody Fusion Constructs with Various Fixation Options: A Finite Element Analysis Based on Three-Dimensional Scanning Models.

BACKGROUND: Little is known about the biomechanical performance of various fixation constructs after oblique lumbar interbody fusion (OLIF). This study aimed to explore the stability of various fixation options for OLIF by using finite element analysis based on three-dimensional scanning models. METHODS: Six validated finite element models of the L3-L5 segment were reconstructed via computed tomography images, including (1) intact model, (2) stand-alone model with no instrument, (3) lateral rod-screw model, (4) lateral rod-screw plus contralateral translaminar facet screw (LRS-CTLFS) model, (5) unilateral pedicle screw model, and (6) bilateral pedicle screw (BPS) model. Models of the OLIF cage and pedicle screw were created with three-dimensional scanning to improve the accuracy of finite element analysis. Range of motion, stress of the cage, and stress of fixation were evaluated in the different models. RESULTS: Range of motion increased from least to greatest as follows: BPS, LRS-CTLFS, unilateral pedicle screw, lateral rod-screw, stand-alone. Differences in range of motion between BPS and LRS-CTLFS were not significant for all loading cases. Compared with the other 3 models, the stress of the cage was found to be lower in BPS and LRS-CTLFS under all loading conditions, especially in BPS. Stress exerted on the fixation was the greatest in LRS-CTLFS, and the stress experienced by the translaminar facet screw was concentrated in part of the facet joint. CONCLUSIONS: The BPS model provided the best biomechanical stability for OLIF; the stand-alone model could not provide sufficient stability. The LRS-CTLFS procedure increases the approximate stability and reduces stress at the cage-endplate interface; however, it causes an increase in screw stress.

Risk Factor Analysis of the Incidence of Subsequent Adjacent Vertebral Fracture After Lumbar Spinal Fusion Surgery with Instrumentation.

OBJECTIVE: This study aimed to evaluate the risk factors for adjacent vertebral compression fractures after lumbar spinal fusion with instrumentation. METHODS: A total of 669 patients who received lumbar instrumented spinal fusion between January 2012 and December 2015 were divided into 2 groups according to whether the adjacent vertebral body was fractured. The covariates recorded were age, sex, bone mineral density, and the number of fixed segments. The anatomic variables were pelvic incidence angle (PI), preoperative lumbar lordosis angle (Pre-LL), postoperative lumbar lordosis angle (Post-LL), Pre-LL minus Post-LL (Loss of LL), postoperative pelvic tilt (Post-PT), postoperative sacral slope, Pre-PI-LL mismatch (Pre-PI minus Pre-LL), and Post-PI-LL mismatch (Post-PI minus Post-LL). A 1-way analysis of variance (ANOVA) was performed with the aforementioned parameters, and binary logistic regression analysis was used to determine the relative risk factors. RESULTS: The 669 patients were followed-up for a mean of 2.7 ± 1.1 years (range, 2-4 years). Twenty-seven patients demonstrated fractures in the adjacent vertebral body after surgery. Analysis by 1-way ANOVA demonstrated that age, PI, Pre-LL, Post-LL, Loss of LL, Post-PI-LL mismatch, Post-PT, and osteoporosis were potential risk factors (all parameters, P < 0.001). Furthermore, binary logistic regression analysis showed that a large Loss of LL, osteoporosis, and old age were also risk factors for adjacent vertebral compression fractures. CONCLUSIONS: A greater Loss of LL, osteoporosis, and advanced age may be risk factors for fractures in the adjacent vertebral body of the fixed segment after lumbar fusion fixation.

Novel Surgical Strategy for Treating Osteoporotic Vertebral Fractures with Cord Compression.

OBJECTIVES: Treatment for osteoporotic vertebral fracture (OVF) with cord compression is challenging and it usually requires surgical interventions to decompress nerves and restore spinal sequences. To describe a novel surgical strategy for treating OVFs with cord compression. METHODS: This is a single-center retrospective analysis. The inclusion criteria were Frankel grade C-E, single level T10 -L2 . Between January 2008 and December 2016, a total of 56 OVF patients (47 females and nine males, with an average age of 72 years (66-88 years), comprising of eight grade C, 23 grade D, and 25 grade E patients) were enrolled. The treatment algorithm included preoperative evaluation by MRI, extension CT, and radiography to classify the OVFs as type 1.1 (reducible, stable; n = 13), type1.2 (reducible, unstable; n = 16), type 2 (irreducible; n = 19) or type 2M (modifier; n = 8). Vertebroplasty (VP)/kyphoplasty (KP) was applied in type 1.1. VP/KP with posterior fixation and posterolateral fusion was applied in type 1.2. And additional laminectomy/osteotomy was used in type 2, except in a modifier group (2M) where same procedure as applied for type 1.2 was used. VAS, ODI, Cobb angle, Frankel functional grade, and complications were recorded. RESULTS: Thirteen cases were classified as type 1.1, 16 cases as type 1.2, 19 cases as type 2, and eight cases as type 2M. The follow-up period was 38.9 months (range, 24-108 months). All patients were followed-up in at least 24 months, in which time four patients died, two patients were lost at the last follow-up, and 50 patients completed the full study. The total VAS and ODI improved from 8 (7, 9) and 75.5% (67.2%, 80.0%) preoperatively to 2 (1, 3) and 31% (24.0%, 37.0%) on conclusion, respectively (P < 0.01). The local kyphotic angle was corrected from 22.3° (17.1°, 33. 8°) preoperatively to 10.4° (6.4°, 15.3°) on conclusion (P < 0.01). Twenty-three patients had achieved neurological recovery on conclusion (42E, 8D, P < 0.01). Asymptotic cement leakage was observed in 17/56 cases (30.4%), 6/56 in the affected vertebra (10.7%), and 24/330 in the screw trajectory (7.3%). At 2 years postoperatively, 11 new VFs had occurred in nine patients (16.1%), including VFs in nine adjacent segments that all occurred within 1 year after surgery. No cement migration or implant failure was noted. CONCLUSION: The novel surgical strategy for treating OVFs with cord compression consists of the most tailored and least invasive treatment for each patient. The positive mid- and long-term clinical and radiological outcomes observed could represent a step forward in devising the proposed algorithm.

Augmented pedicle trajectory applied on the osteoporotic spine with lumbar degenerative disease: mid-term outcome.

PURPOSE: To compare the safety and efficiency of cement-augmented pedicle screw with traditional pedicle screw technique applied on the patients in the osteoporotic spine with lumbar degenerative diseases. METHODS: Fifty-six patients followed up at least 2 years were enrolled in our institute with retrospectively reviewed from January 2009 to June 2014, diagnosed as lumbar spondylolisthesis, or lumbar stenosis, with T score ≤- 2.5 SD of BMD, and received less than three-segment PLIF or TLIF. All patients were divided into 2 groups: 28 (2 males, 26 females) in polymethylmethacrylate-augmented pedicle screw group (PSA) group, the other 28 (3 males, 25 females) in traditional pedicle screw group (TPS). Surgical data including the operation time, intra-operative blood loss, hospitalization day and surgical complications were recorded, as well as the radiological parameters measured from the postoperative X-rays and CT scans containing the rates of fusion, screw loosening, and cage subsidence incidence. In addition, the visual analog scores (VAS) and Oswestry Disability Index (ODI) were evaluated preoperatively and postoperatively. RESULTS: The average follow-up period was 34.32 months (ranging from 24 months to 51 months). Compared with PSA group, operation time and average hospital stay in the TPS group decreased significantly (P < 0.05). While no statistical difference for blood loss between 2 groups (P > 0.05). At 2 years postoperation, from CT-scans, 2/172 screws loosening and 1/56 segment non-union occurred in PSA group, with significantly lower incidence than those in TPS group (8/152 screws loosening and 6/50 segments non-union occurred, P < 0.05). Regarding the cage subsidence, 24 segments found height loss (5.30 ± 1.92 mm) in PSA group without difference compared with that of 19 segments (4.78 ± 1.37 mm) in TPS group (P > 0.05). Besides, the number and the location of cages and the leakage of the cement were found out little related with the subsidence in the PSA group (P > 0.05). After surgeries, VAS and ODI at 1 month, 6 months, 12 months, and last follow-up improved significantly in two groups (P < 0.05). There were no significant differences in VAS and ODI preoperatively and postoperatively between 2 groups (P > 0.05). In addition, eight patients with asymptomatic trajectory PMMA leakages were detected. CONCLUSION: Cement-augmented pedicle screw technique is effective and safe in the osteoporotic spine with lumbar degenerative diseases, with better fusion rates and less screw loosening incidence. There is no difference in the fusion rate and loosening rate between the two groups in the single segment patients; however, there are better fusion rate and lower pedicle screw loosening rate of the PSA group in the double or multiple group patients.

The cement leakage in cement-augmented pedicle screw instrumentation in degenerative lumbosacral diseases: a retrospective analysis of 202 cases and 950 augmented pedicle screws.

PURPOSE: To evaluate the incidence, type and risk factors of cement leakage (CL) with cement-augmented pedicle screw instrumentation (CAPSI) in degenerative lumbosacral disease. METHODS: Two hundred and two patients using a total of 950 cement-augmented screws were enrolled. CL was classified into three types: type S: leakage via segmental veins; type B: leakage via basivertebral veins; and type I: leakage via pedicle screw instrumentation to paravertebral soft tissue. The age, gender, operation stage (primary or later stage), body mass index, bone mineral density, the number and type of augmented screw, the position of the tip of screw (lateral or internal part of vertebral body), the position of screw (left or right side), the volume of bone cement, location of the augmented vertebra (lumbar or sacrum), the type of CL and complications were recorded. Binary logistic regression correlation was used to analyze risk factors of veins leakage (type S and type B). RESULTS: The CL was observed in 165 patients (81.68%) and 335 screws (35.26%), leakage types of S, B and I were seen in 255 (76.12%), 77 (22.99%), and 30 (8.96%) of screws, respectively. Besides, double or multiple routes of leakage were seen in 27 screws. Number of augmented screw was a risk factor for vein leakage (OR 0.58; 95% CI 0.44-0.77; P = 0.000). Furthermore, the doses of cement (OR 0.79; 95% CI 0.61-0.99; P = 0.038) and the position of screw (OR 0.39; 95% CI 0.29-0.53; P = 0.000) were identified as risk factors for type S, and the doses of bone cement (OR 0.37; 95% CI 0.25-0.54; P = 0.000) and the position of the tip of screw (OR 0.07; 95% CI 0.04-0.13; P = 0.000) were risk factors for type B. CONCLUSIONS: CAPSI bears a high risk of asymptomatic CL, with a higher rate of leakage into segmental veins and basivertebral veins. As is known, more augmented screws and larger doses of cement are risk factors for veins leakage (type S and type B), while the tip of screw approaching to the midline of the vertebral body is another risk factor to type B. Thus, the CL could be reduced by the amelioration of operative techniques and procedures. These slides can be retrieved under Electronic Supplementary Material.

The Effect and Safety of Polymethylmethacrylate-Augmented Sacral Pedicle Screws Applied in Osteoporotic Spine with Lumbosacral Degenerative Disease: A 2-Year Follow-up of 25 Patients.

BACKGROUND: A high rate of instrumentation failure is frequently seen in osteoporotic spines, especially at the sacral segment because of the great shear stress. Several techniques of sacral pedicle screw placement, such as bicortical and tricortical fixation, have been developed; however, the problems of loosening and pulling out of the screws are still a concern. Recently, the polymethylmethacrylate (PMMA)-augmented pedicle screws have been shown to strengthen the purchase in osteoporotic spine, but there are few reports on the effect of S1 pedicle screw with PMMA augmentation. METHODS: Seventy-five patients receiving cement-augmented pedicle screws at lumbosacral vertebra were enrolled and divided into 3 groups by different patterns of S1 pedicle screw placement: S1 pedicle screw with PMMA augmentation (group A, 25 patients), S1 bicortical pedicle screw fixation (group B, 25 patients), and S1 tricortical pedicle screw fixation (group C, 25 patients). The Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) scores were assessed preoperatively and at the last follow-up. Besides, the complications, loosening rate, and fusion rate were recorded. RESULTS: The VAS and ODI scores at the last follow-up were significantly improved in the 3 groups compared with preoperative results. Better pain relief and functional improvement at the last follow-up was seen in group A compared with the other 2 groups; however, no significant difference was detected between groups B and C. Although the lowest screws loosening rates and the highest fusion rate were found in group A, no significant difference among these 3 groups. Furthermore, longer fusion segments and larger postoperative pelvic incidence-lumbar lordosis (PL-LL) were found as risks related to S1 screw loosening without cement augmentation. CONCLUSIONS: The S1 pedicle screws with PMMA augmentation achieved better stability with less screw loosening in the osteoporotic spine with lumbosacral degenerative diseases compared with bicortical/tricortical fixation at S1. This procedure is especially recommended for patients with long segment fixation and large postoperative PI-LL, but there is also a risk of bone cement leakage and a learning curve.

[Establish mouse osteoblast -osteoclast cell co-culture system in a Transwell chamber].

OBJECTIVE: To establish osteoblast-osteoclast cell co-culture system in a Transwell chamber, and detect cell viability of osteoblasts and osteoclasts in system. METHODS: Osteoblast MC3T3-E1 and mouse monocytes RAW264.7 were cultivated in vitro. RANKL-induced mouse RAW264.7 monocytes differentiated into mature osteoclasts, osteoblast-osteoclast cell co-culture system was established in Transwell chamber. Cell activity of osteoblasts and osteoclasts were detected by CCK-8 experimenting, Alizarin Red staining, TRAP staining. The expression of OPG, ALP, RANKL, TGF-b1 gene and RANKL protein in osteoblast MC3T3-E1 were detected by PCR, Western-Blot methods. Also, the expression of RANK, NF-κB in gene and protein level in osteoclast were measured through the same method respectively. RESULTS: The co-culture system of Mouse MC3T3-E1 cells and RAW264.7 cell were established in Transwell chamber. Co-culture system affected cell division activities of osteoblasts and osteoclasts. Differentiation of osteoblasts were increased, while differentiation of osteoclast division were slight decreased under microscope observation. OPG (0.65±0.08) and ALP (0.16±0.01) gene expression of co-culture system were less than single culture OPG(1.00±0.08) and ALP (1.01±0.16); TGF-b1(4.42±0.21) and RANKL(4.12±1.04) of osteoblasts in co-culture system were higher than TGF-b1(1.00±0.10) and RANKL(1.00±0.09) under single culture. However, gene expression of RANK(0.63±0.06) and NF-κB(0.64±0.08) in co-culture system were decreased than RANK(1.00±0.08) and NF-κB(1.00±0.09), in single culture, and had significant differences. Similarly, protein expression of OPG(0.43±0.05) and NF-κB(0.59±0.05) of co-culture system were less than OPG(0.84±0.06) and NF-κB(1.13±0.03) of single culture. While RANKL protein expression (0.54±0.03)of co-culture system was more than single culture RANKL(0.31±0.03), and had statistically differences, which was in agreement of the trend of gene expression change. CONCLUSIONS: Co-culture system of mouse MC3T3-E1 cells and RAW264.7 cell was viable in Transwell chamber, and the activity of osteoblasts is higher than osteoclasts in co-culture system.

Phonon engineering in proximity enhanced superconductor heterostructures.

In this research, we tailor the phonon density of states (DOS) in thin superconducting films to suppress quasiparticle losses. We examine a model system of a proximity-enhanced three-layered Al/Nb/Al heterostructure and show that the local quantized phonon spectrum of the ultrathin Al cladding layers in the heterostructure has a pronounced effect on the superconducting resonator's quality factors. Instead of a monotonic increase of quality factors with decreasing temperatures, we observe the quality factor reaches a maximum at 1.2 K in 5/50/5 nm Al/Nb/Al microstrip resonators, because of a quantized phonon ladder. The phonon DOS may be engineered to enhance the performance of quantum devices.

[Analysis of clinical characteristics of 20 patients with pyogenic spondylitis].

OBJECTIVE: To investigate the diagnostic value of clinical manifestation, laboratory examination and imaging changes for pyogenic spondylitis and to summarize the clinical characteristics of patients with pyogenic spondylitis. METHODS: The clinical data, of 20 patients with pyogenic spondylitis were diagnosed by histopathological examination from March 2012 to March 2015, were retrospectively analyzed. There were 9 males and 11 females, aged from 43 to 72 years old with an average of 58.9 years. Included 3 cases of cervical vertebrae, 7 cases of thoracic vertebrae, 10 cases of lumbar vertebrae. Patients of blood analysis, erythrocyte sedimentation rate(ESR), C reactive protein(CRP), X rays, CT and MRI were performed before treatment. Visual analogue scale (VAS) was used to evaluate the pain of patients suffering from vertebral pain. RESULTS: All the patients had suffered from vertebral pain before treatment. VAS was 9 points in 4 cases, 8 points in 6 cases, 7 points in 1 case, 3 points in 6 cases, and 2 points in 3 cases. Among them, 7 patients complicated with neurological symptoms, 11 with aggravating night pain, 10 with fever. WBC and Neutrophil count (NEU) of 5 cases were increased and other 15 cases were normal;CRP of 19 cases were increased and 1 case was normal;ESR of all 20 cases were increased. X rays showed the intervertebral space narrowing in all 20 cases, 13 cases complicated with destruction of vertebral body; CT showed the lesions of vertebral body in the 20 cases and complicated with destruction, sclerosis of sclerotin; MRI showed that the lesions of the vertebral body in the T1 image had uneven medium low signal, in the T2 image of the 16 cases had uneven high signal and 2 cases had uniform and high signal, 2 cases had main high signal compliated with mixed signal. Thirteen patients underwent surgical treatment and 7 patients received conservative treatment, and the patients left hospital while VAS had significantly improved after treatment. CONCLUSIONS: Pyogenic spondylitis is easy to be misdiagnosed or missed in clinic. It can be combined with the clinical manifestations, laboratory examination and imaging characteristics in order to make a definite diagnosis for purulent spondylitis in early.