Prognosis and conditional nomogram of cervical spine fracture in patients with severe spinal cord injury: a multicenter retrospective study.

INTRODUCTION: Cervical spine fractures with severe spinal cord injury (SCI) are common following cervical spine trauma and are associated with a high mortality rate. Understanding the mortality patterns of patients with cervical spine fractures and severe SCI can offer valuable evidence to surgeons and family members who are required to make critical healthcare decisions. The authors aimed to evaluate the instantaneous death risk and conditional survival (CS) of such patients and developed conditional nomograms to account for different periods of survivors and predict the survival rates. METHODS: Their instantaneous death risks were calculated using the hazard function, and the Kaplan-Meier method was used to evaluate the survival rates. Cox regression was used to choose the variables for the construction of the nomograms. The area under the receiver operating characteristic curve and calibration plots were used to validate the performance of the nomograms. RESULTS: The authors finally included 450 patients with cervical spine fractures and severe SCI using propensity score matching. The instantaneous death risk was the highest during the first 12 months after injury. Surgical treatment can help decrease the instantaneous death risk quickly, especially in early-term surgery. The 5-year CS increased constantly from 73.3% at baseline to 88.0% after 2 years of survival. Conditional nomograms were constructed at baseline and in those who survived for 6 and 12 months. The area under the receiver operating characteristic curve and calibration curves indicated that the nomograms had a good performance. CONCLUSION: Their results improve our understanding of the instantaneous death risk of patients in different periods following injury. CS demonstrated the exact survival rate among medium-term and long-term survivors. Conditional nomograms are suitable for different survival periods in predicting the probability of survival. Conditional nomograms help in understanding the prognosis and improve the shared decision-making approaches.

Bioactive graphene oxide-functionalized self-expandable hydrophilic and osteogenic nanocomposite for orthopaedic applications.

Polymethyl methacrylate (PMMA) bone cement (PBC) is commonly used in orthopaedic surgery. However, polymerization volumetric shrinkage, exothermic injury, and low bioactivity prevent PBC from being an ideal material. The developed expandable P(MMA-AA-St) well overcomes the volumetric shrinkage of PBC. However, its biomechanical properties are unsatisfactory. Herein, graphene oxide (GO), a hydrophilic material with favourable biomechanics and osteogenic capability, was added to P(MMA-AA-St) to optimize its biomechanics and bioactivity. The GO-modified self-expandable P(MMA-AA-St)-GO nanocomposite (PGBCs) exhibited outstanding compressive strength (>70 â€‹MPa), water absorption, and volume expansion, as well as a longer handling time and a reduced setting temperature. The cytocompatibility of PGBCs was superior to that of PBC, as demonstrated by CCK-8 assay, live-dead cell staining, and flow cytometry. In addition, better osteoblast attachment was observed, which could be attributed to the effects of GO. The improved level of osteogenic gene and protein expression further illustrated the improved cell-material interactions between osteoblasts and PGBCs. The results of an in vivo study performed by filling bone defects in the femoral condyles of rabbits with PGBCs demonstrated promising intraoperative handling properties and convenient implantation. Blood testing and histological staining demonstrated satisfactory in vivo biosafety. Furthermore, bone morphological and microarchitecture analyses using bone tissue staining and micro-CT scanning revealed better bone-PGBCs contact and osteogenic capability. The results of this study indicate that GO modification improved the physiochemical properties, cytocompatibility, and osteogenic capability of P(MMA-AA-St) and overcame the drawbacks of PBC, allowing its material derivatives to serve as effective implantable biomaterials.

Closing-opening wedge osteotomy for the treatment of congenital kyphosis in children.

BACKGROUND: To evaluate the safety and effectiveness of posterior closed-open wedge osteotomy for treatment of congenital kyphosis in children. METHODS: Imaging and clinical data from January 2010 to December 2019 of posterior closed-open wedge osteotomy of congenital kyphosis with at least 2-year follow up was analyzed retrospectively. Perioperative indicators such as operation time, osteotomy site, osteotomy method and occurrence of complications, and imaging indicators were observed. The 3D printed models were used to measure the expanded distance of anterior edge vertebra and closed length of spinal canal line. The clinical effect was evaluated through SRS-22 questionnaires. RESULTS: There were 15 CK patients in this study. The osteotomy segments and details are as follows: 1 case each for T6-9 and L2, 2 cases at T11, 3 cases at T12, and 6 cases at L1. The average operation time was 314 min, the average blood loss was 970 mL, the average fusion range was 6.3 segments, and the average time of follow up was 70.5 months. The Cobb angle of local kyphosis was corrected from 65.6 ± 18.8° to 11.3 ± 7.1°(p < .001). The range of kyphosis correction was 40-90°, and average correction rate was 83.2% (67.7-95.7%). The correction was stable in follow-up, and the kyphotic angle was 11.0 ± 7.6 (p = .68). The preoperative SVA was 31.5 ± 21.8 mm, and the postoperative recovery was 18.0 ± 15.5, while the last follow-up was 9.1 ± 7.9. The p values were 0.02 and 0.07 respectively. By using 3D printed models, the expanded distance of anterior edge vertebra and closed length of spinal canal line were 14.5 ± 7.5 mm and 24.5 ± 8.0 mm respectively. Self-image and satisfaction in SRS-22 improved significantly. There was no recurrence of deformity and junctional kyphosis. CONCLUSIONS: The posterior closing-opening wedge osteotom for treatment of congenital kyphosis in children is satisfactory, if selected appropriately. During the longitudinal follow-up, the patients could achieve solid fusion and the correction could be well maintained.Evidence of Confidence: IVa.

Radical treatment of severe open fractures of extremities by orthoplastic surgery: a 10-year retrospective study.

OBJECTIVE: This study aimed to retrospectively analyze clinical data of a series of patients with severe open fractures of extremities (Gustilo IIIb or IIIc), who achieved a satisfactory outcome through radical orthoplastic surgery, so as to provide a reference for determining the treatment of severe open fractures of extremities. METHODS: The clinical data of 41 consecutive patients with severe open fracture (Gustilo IIIb or IIIc) of the limb, who underwent successful surgical debridement, fixation, and soft tissue reconstruction in one stage between January 2008 and January 2019, were retrospectively reviewed. Postoperative indicators, including infection rate and union time, were acquired by a regular follow-up and analyzed. RESULTS: The mean (±SD) age of the patients was 38 ± 16 years. A total of 90 open fractures and severe soft tissue damages were analyzed. The soft tissue cover was achieved within 72 h. The overall rate of infection was 14.6% (6/41). Sex and the Mangled Extremity Severity Score were associated with infection. The median union time of 40 patients (one amputation) was 32 weeks. CONCLUSION: The overall rate of infection exhibited a lower tendency in this study compared with previous studies on high-grade open fractures following a two-stage orthopedic approach. The consequence of infection rate and union time was similar to that in previous studies. These results indicated that the single-stage radical orthoplastic treatment was an effective and reliable option for reconstructing severe open fractures.

Biomechanical comparison of four types of instrumentation constructs for revision surgery in lumbar adjacent segment disease: A finite element study.

BACKGROUND: Different constructs are applied in revision surgery (RS) for adjacent segment disease (ASD) aiming to further decompress and fixate the affected segment(s) in two ways: replacing or preserving the primary implants. This study aimed to compare the biomechanical properties of four constructs with different configurations. METHODS: An T12-L5 finite element (FE) model was constructed and validated. Primary surgery was performed at L4-L5 and instrumented from L3 to L5. Thereafter, RS was undertook by decompressing L2-L3 and fixated with implant-replacing construct A, or implant-preserving construct B, C or D. Range of motion (ROM) and intervertebral disc pressure (IDP) were compared. Maximum von Mises stress on the rods between Construct A and B was evaluated. RESULTS: An obvious reduction of ROM was observed when the FE model was instrumented with four constructs respectively. The overall changing characteristics of ROM were approximately identical among four constructs. The changing characteristic of IDP among four constructs was similar. The degree of IDP reduction of Construct B was comparable to Construct A, while that of Construct C was comparable to Construct D. Maximum von Mises stress on the rods between Construct A and B indicated that no stress concentration was recorded at the locking part of the connector rod. CONCLUSIONS: The biomechanics of implant-preserving constructs were comparable to the traditional implant-replacing construct. The location of side-by-side connector could not affect the stability of Construct C and D. Construct B might be an optimal choice in RS for less dissection, less complication and more convenience in manipulation.

Wandering rod: form lumbar spine into left pleural cavity with nerve irritated symptoms.

Spinal instrumented rod migrating from the surgical site to another remote site in the body is rare. Some cases result in organ or blood vessel injury. Most reported cases were asymptomatic until the finally injuries were generated. We report a unique case of spinal implant failure in which the rod moved from lumbar spine into chest 13 years post lumbar instrumentation. The migrated rod caused no damage to the organs in the pleural cavity but did cause an atypical pleural irritation syndrome which seemed to correlate with the mechanical irritation caused by the rod. These atypical symptoms of rod migration have not been reported previously.

Implant Preservation versus Implant Replacement in Revision Surgery for Adjacent Segment Disease After Thoracolumbar Instrumentation: A Retrospective Study of 43 Patients.

OBJECTIVE: To evaluate the mechanical properties of a new connector rod aiming to preserve implants in revision surgery (RS) for adjacent segment disease, a problematic complication of instrumented spinal fusion, and to assess its clinical applicability. METHODS: The mechanical properties of the connector-rod construct (implant preservation) and traditional rod construct (implant replacement) were evaluated and compared. Forty-three patients underwent RS for adjacent segment disease in the thoracolumbar spine with implant preservation or replacement, and radiological and clinical outcomes were assessed. RESULTS: Mechanical properties in group A were comparable to those in group B. Total mean time from prior surgery to RS was 6.86 ± 1.08 years. Surgical time and blood loss values of group A were 40.14% and 29.29% statistically significantly smaller than values of group B. In group B, 12% (3/25) of patients developed surgical site infections. In both groups, the visual analog scale leg score decreased significantly after RS. Early postoperative (at 1-month and 3-month follow-up) Oswestry Disability Index and visual analog scale back scores of group A were significantly lower than those of group B; the difference in the visual analog scale back score between groups was significant until the 6-month follow-up. No implant failures occurred, and spinal fusion was achieved in all cases. CONCLUSIONS: The connector rod is considered safe and can reduce the surgical time, blood loss, risk of complications, and medical costs. Better early postoperative clinical outcomes can be achieved with the rod owing to less surgical trauma.

Impairment of type H vessels by NOX2-mediated endothelial oxidative stress: critical mechanisms and therapeutic targets for bone fragility in streptozotocin-induced type 1 diabetic mice.

Rationale: Mechanisms underlying the compromised bone formation in type 1 diabetes mellitus (T1DM), which causes bone fragility and frequent fractures, remain poorly understood. Recent advances in organ-specific vascular endothelial cells (ECs) identify type H blood vessel injury in the bone, which actively direct osteogenesis, as a possible player. Methods: T1DM was induced in mice by streptozotocin (STZ) injection in two severity degrees. Bony endothelium, the coupling of angiogenesis and osteogenesis, and bone mass quality were evaluated. Insulin, antioxidants, and NADPH oxidase (NOX) inhibitors were administered to diabetic animals to investigate possible mechanisms and design therapeutic strategies. Results: T1DM in mice led to the holistic abnormality of the vascular system in the bone, especially type H vessels, resulting in the uncoupling of angiogenesis and osteogenesis and inhibition of bone formation. The severity of osteopathy was positively related to glycemic levels. These pathological changes were attenuated by early-started, but not late-started, insulin therapy. ECs in diabetic bones showed significantly higher levels of reactive oxygen species (ROS) and NOX 1 and 2. Impairments of bone vessels and bone mass were effectively ameliorated by treatment with anti-oxidants or NOX2 inhibitors, but not by a NOX1/4 inhibitor. GSK2795039 (GSK), a NOX2 inhibitor, significantly supplemented the insulin effect on the diabetic bone. Conclusions: Diabetic osteopathy could be a chronic microvascular complication of T1DM. The impairment of type H vessels by NOX2-mediated endothelial oxidative stress might be an important contributor that can serve as a therapeutic target for T1DM-induced osteopathy.

Effects of Revision Rod Position on Spinal Construct Stability in Lumbar Revision Surgery: A Finite Element Study.

Revision surgery (RS) is a necessary surgical intervention in clinical practice to treat spinal instrumentation-related symptomatic complications. Three constructs with different configurations have been applied in RS. One distinguishing characteristic of these configurations is that the revision rods connecting previous segments and revision segments are placed alongside, outside, or inside the previous rods at the level of facetectomy. Whether the position of the revision rod could generate mechanical disparities in revision constructs is unknown. The objective of this study was to assess the influence of the revision rod position on the construct after RS. A validated spinal finite element (FE) model was developed to simulate RS after previous instrumented fusion using a modified dual-rod construct (DRCm), satellite-rod construct (SRC), and cortical bone trajectory construct (CBTC). Thereafter, maximum von Mises stress (VMS) on the annulus fibrosus and cages and the ligament force of the interspinous ligament, supraspinous ligament, and ligamentum flavum under a pure moment load and a follower load in six directions were applied to assess the influence of the revision rod position on the revision construct. An approximately identical overall reducing tendency of VMS was observed among the three constructs. The changing tendency of the maximum VMS on the cages placed at L4-L5 was nearly equal among the three constructs. However, the changing tendency of the maximum VMS on the cage placed at L2-L3 was notable, especially in the CBTC under right bending and left axial rotation. The overall changing tendency of the ligament force in the DRCm, SRC, and CBTC was also approximately equal, while the ligament force of the CBTC was found to be significantly greater than that of the DRCm and SRC at L1-L2. The results indicated that the stiffness associated with the CBTC might be lower than that associated with the DRCm and SRC in RS. The results of the present study indicated that the DRCm, SRC, and CBTC could provide sufficient stabilization in RS. The CBTC was a less rigid construct. Rather than the revision rod position, the method of constructing spinal instrumentation played a role in influencing the biomechanics of revision.

Cangrelor alleviates pulmonary fibrosis by inhibiting GPR17-mediated inflammation in mice.

Pulmonary fibrosis is a progressive and intractable lung disease. Macrophages play a critical role in the progression of pulmonary fibrosis. Cangrelor, an anti-platelet agent, is also a non-selective Gprotein-coupled receptor 17 (GPR17) antagonist. GPR17 mediates microglial inflammation in the chronic phase of cerebral ischemia and regulates allergic pulmonary inflammation. In this study, we observed the effects of cangrelor on bleomycin (BLM)-induced macrophage cellular inflammation and BLM-induced pulmonary fibrosis in C57BL/6J mice. We found that BLM significantly increased GPR17 expression, the mRNA synthesis and release of inflammatory cytokines including TNF-α, IL-6 and TGF-ß1 in murine RAW 264.7 macrophage cells. Knockdown of GPR17 attenuated the BLM-induced inflammatory responses. Cangrelor (2.5 µM-10 µM) significantly alleviated BLM-induced inflammatory response in RAW 264.7 macrophage cells in concentration-dependent manner. In BLM-induced fibrotic mouse lungs, GPR17 expression and GPR17-positive macrophages were increased. Cangrelor (2.5 mg/kg-10 mg/kg) alleviated pulmonary fibrosis in dose-dependent manner. Cangrelor not only reduced the number of GPR17-positive macrophages, but also decreased BLM-induced mRNA synthesis and release of inflammatory cytokine. As such, we concluded that cangrelor alleviates BLM-induced pulmonary fibrosis by suppressing GPR17-mediated inflammation. Cangrelor could be a potential therapeutic drug for pulmonary fibrosis.

Adiponectin improves the osteointegration of titanium implant under diabetic conditions by reversing mitochondrial dysfunction via the AMPK pathway in vivo and in vitro.

Diabetes-induced reactive oxygen species (ROS) overproduction would result in compromised osteointegration of titanium implant (TI) and high rate of implant failure, yet the underlying mechanisms remain elusive. Adiponectin (APN) is a fat-derived adipocytokine with strong antioxidant, mitochondrial-protective and anti-diabetic efficacies. We hypothesized that mitochondrial dysfunction under diabetes may account for the oxidative stress in osteoblasts and titanium-bone interface (TBI) instability, which could be ameliorated by APN. To test this hypothesis, we incubated primary rat osteoblasts on TI and tested the cellular behaviors when subjected to normal milieu (NM), diabetic milieu (DM), DM+APN, DM+AICAR (AMPK activator) and DM+APN+Compound C (AMPK inhibitor). In vivo, APN or APN+Compound C were administered to diabetic db/db mice with TI implanted in their femurs. Results showed that diabetes induced structural damage, dysfunction and content decrease of mitochondria in osteoblasts, which led to ROS overproduction, dysfunction and apoptosis of osteoblasts accompanied by the inhibition of AMPK signaling. APN alleviated the mitochondrial damage by activating AMPK, thus reversing osteoblast impairment and improving the osteointegration of TI evidenced by Micro-CT and histological analysis. Furthermore, AICAR showed beneficial effects similar to APN treatment, while the protective effects of APN were abolished when AMPK activation was blocked by Compound C. This study clarifies mitochondrial dysfunction as a crucial mechanism in the impaired bone healing and implant loosening in diabetes, and provides APN as a novel promising active component for biomaterial-engineering to improve clinical performance of TI in diabetic patients. STATEMENT OF SIGNIFICANCE: The loosening rate of titanium implants in diabetic patients is high. The underlying mechanisms remain elusive and, with the rapid increase of diabetic morbility, efficacious strategies to mitigate this problem have become increasingly important. Our study showed that the mitochondrial impairment and the consequent oxidative stress in osteoblasts at the titanium-bone interface (TBI) play a critical role in the diabetes-induced poor bone repair and implant destabilization, which could become therapeutic targets. Furthermore, adiponectin, a cytokine, promotes the bio-functional recovery of osteoblasts and bone regeneration at the TBI in diabetes. This provides APN as a novel bioactive component used in material-engineering to promote the osteointegration of implants, which could reduce implant failure, especially for diabetic patients.

Putative roles as oncogene or tumour suppressor of the Mid-clustered microRNAs in Gallid alphaherpesvirus 2 (GaHV2) induced Marek's disease lymphomagenesis.

In the last decade, numerous microRNAs (miRNAs) have been identified in diverse virus families, particularly in herpesviruses. Gallid alphaherpesvirus 2 (GaHV2) is a representative oncogenic alphaherpesvirus that induces rapid-onset T-cell lymphomas in its natural hosts, namely Marek's disease (MD). In the GaHV2 genome there are 26 mature miRNAs derived from 14 precursors assembled into three clusters, namely the Meq-cluster, Mid-cluster and LAT-cluster. Several GaHV2 miRNAs, especially those in the Meq-cluster (e.g. miR-M4-5p), have been demonstrated to be critical in MD pathogenesis and/or tumorigenesis. Interestingly the downstream Mid-cluster is regulated and transcribed by the same promoter as the Meq-cluster in the latent phase of the infection, but the role of these Mid-clustered miRNAs in GaHV2 biology remains unclear. We have generated the deletion mutants of the Mid-cluster and of its associated individual miRNAs in GX0101 virus, a very virulent GaHV2 strain, and demonstrated that the Mid-clustered miRNAs are not essential for virus replication. Using GaHV2-infected chickens as an animal model, we found that, compared with parental GX0101 virus, the individual deletion of miR-M31 decreased the mortality and gross tumour incidence of infected chickens while the deletion individually of miR-M1 or miR-M11 unexpectedly increased viral pathogenicity or oncogenicity, similarly to the deletion of the entire Mid-cluster region. More importantly, our data further confirm that miR-M11-5p, the miR-M11-derived mature miRNA, targets the viral oncogene meq and suppresses its expression in GaHV2 infection. We report here that members of the Mid-clustered miRNAs, miR-M31-3p and miR-M11-5p, potentially act either as oncogene or tumour suppressor in MD lymphomagenesis.

Effects of Hindlimb Unweighting on MBP and GDNF Expression and Morphology in Rat Dorsal Root Ganglia Neurons.

With the development of technology and space exploration, studies on long-duration space flights have shown that microgravity induces damage to multiple organs, including the dorsal root ganglia (DRG). However, very little is known about the effects of long-term microgravity on DRG neurons. This study investigated the effects of microgravity on lumbar 5 (L5) DRG neurons in rats using the hindlimb unweighting (HU) model. Male (M) and female (F) Sprague-Dawley rats were randomly divided into M- and F-control (CON) groups and M- and F-HU groups, respectively (n = 10). At the end of HU treatment for 4 weeks, morphological changes were detected. Myelin basic protein (MBP) and degenerated myelin basic protein (dgen-MBP) expressions were analyzed by immunofluorescence and western blot assays. Glial cell line-derived neurotrophic factor (GDNF) protein and mRNA expressions were also analyzed by immunohistochemistry, western blot, and RT-PCR analysis, respectively. Compared with the corresponding CON groups, the HU groups exhibited slightly loose junctions between DRG neurons, some separated ganglion cells and satellite cells, and lightly stained Nissl bodies that were of smaller size and had a scattered distribution. High levels of dgen-MBP and low MBP expressions were appeared and GDNF expressions were significantly decreased in both HU groups. Changes were more pronounced in the F-HU group than in the M-HU group. In conclusion, HU treatment induced damage of L5 DRG neurons, which was correlated with decreased total MBP protein expression, increased dgen-MBP expression, and reduced GDNF protein and mRNA expression. Importantly, these changes were more severe in F-HU rats compared with M-HU rats.

Surgical Treatment of Dystrophic Spinal Curves Caused by Neurofibromatosis Type 1: A Retrospective Study of 26 Patients.

Dystrophic scoliosis in neurofibromatosis type 1 (NF-1) is difficult to treat. The purpose of this study was to review the clinical and radiological outcome of surgical treatment of dystrophic spinal curves in NF-1, for analyzing its efficacy, safety, and possible complications.This retrospective study consisted of 26 NF-1 patients with spinal deformities treated between 2003 and 2012 in our department. Preoperative X-ray, 3D-CT, and MRI were performed to evaluate the deformities of dystrophic scoliosis accurately. All patients were treated with posterior instrumented fusion alone using screws and hooks. According to the anatomical development situation of each patient's pedicles and the transverse processes, we chose different fixations and different fixed segments. The clinical and radiological outcomes of surgical correction were evaluated postoperatively.The average preoperative kyphosis was 43° (range 15-86°). The postoperative kyphosis had an average of 20° (range 10-39°) yielding 53% correction. At final follow-up, there was an average of 4.6% correction loss. The preoperative scoliosis Cobb angle had an average of 47° (range 35-96°). The postoperative scoliosis Cobb angle had an average of 21° (range 10-37°) yielding 55% correction. At final follow-up, there was an average of 6.6% correction loss. The apical vertebral body rotation was corrected by an average of 48%. At final follow-up, the score of the SRS-30 questionnaire ranged from 97 to 135 with an average of 109.In conclusion, the deformities of dystrophic scoliosis can be accurately determine through preoperative radiolographic evaluation, which plays an important role in guiding the correction of scoliosis program development. The results of this study demonstrate that satisfactory therapeutic effects can be achieved in the dystrophic scoliosis patients by preoperative meticulous surgical plans, intraoperative careful manipulation, and hybrid instrumentation.

Augmented PMMA distribution: improvement of mechanical property and reduction of leakage rate of a fenestrated pedicle screw with diameter-tapered perforations.

OBJECTIVE This study investigated the optimum injection volume of polymethylmethacrylate (PMMA) to augment a novel fenestrated pedicle screw (FPS) with diameter-tapered perforations in the osteoporotic vertebral body, and how the distribution characteristics of PMMA affect the biomechanical performance of this screw. METHODS Two types of FPSs were designed (FPS-A, composed of 6 perforations with an equal diameter of 1.2 mm; and FPS-B, composed of 6 perforations each with a tapered diameter of 1.5 mm, 1.2 mm, and 0.9 mm from tip to head. Each of 28 human cadaveric osteoporotic vertebrae were randomly assigned to 1 of 7 groups: FPS-A1.0: FPS-A+1.0 ml PMMA; FPS-A1.5: FPS-A+1.5 ml PMMA; FPS-A2.0: FPS-A+2.0 ml PMMA; FPS-B1.0: FPS-B+1.0 ml PMMA; FPS-B1.5: FPS-B+1.5 ml PMMA; FPS-B2.0: FPS-B+2.0 ml PMMA; and conventional pedicle screws (CPSs) without PMMA. After the augmentation, 3D CT was performed to assess the cement distribution characteristics and the cement leakage rate. Axial pullout tests were performed to compare the maximum pullout force thereafter. RESULTS The CT construction images showed that PMMA bone cement formed a conical mass around FPS-A and a cylindrical mass around FPS-B. When the injection volume was increased from 1.0 ml to 2.0 ml, the distribution region of the PMMA cement was enlarged, the PMMA was distributed more posteriorly, and the risk of leakage was increased. When the injection volume reached 2.0 ml, the risk of cement leakage was lower for screws having diameter-tapered perforations. The pullout strengths of the augmented FPS-A groups and FPS-B groups were higher than that of the CPS group (p < 0.0001). All FPS-B groups had a higher pullout strength than the FPS-A groups. CONCLUSIONS The diameter of the perforations affects the distribution of PMMA cement. The diameter-tapered design enabled PMMA to form larger bone-PMMA interfaces and achieve a relatively higher pullout strength, although statistical significance was not reached. Study results indicated 1.5-ml of PMMA was a conservative volume for PMMA augmentation; more cement injection would significantly increase the risk of cement leakage.

Local Treatment of Osteoporotic Sheep Vertebral Body With Calcium Sulfate for Decreasing the Potential Fracture Risk: Microstructural and Biomechanical Evaluations.

STUDY DESIGN: In this study, calcium sulfate (CS) was injected through pedicle into the osteoporotic vertebral body in vivo in sheep, and micro-computed tomography analysis, histologic observation, and biomechanical test were performed. OBJECTIVE: To investigate the improvement on microstructure and biomechanical performance of lumbar vertebrae augmented with CS in osteoporotic sheep. SUMMARY OF BACKGROUND DATA: The present treatments for osteoporosis relies on systemic medications intended to increase the bone mineral density (BMD). Although effective, these time-consuming medications provide little protection from fracture in the "early period" after initiation of therapy. In this regard, the strategy of local treatment is to target specific areas of the skeletal system that are prone to osteoporotic fractures. However, there is little or no research focused on local treatment of osteoporotic vertebrae with CS. METHODS: Eight female sheep were induced to osteoporosis with bilateral ovariectomy and methylprednisolone administration for 12 months. After successful establishment of an osteoporotic model, lumbar vertebrae (L1-L4) in every sheep were randomly divided into 2 groups: CS group and control group (2 vertebrae in each group in every sheep). CS was injected into the vertebral body transpedicularly in the CS group and no treatments were performed in the control group. Three months later, all sheep were killed and all L1-L4 vertebrae were harvested. Thereafter, microstructure and biomechanical performance of the cancellous bone of the vertebral body were assessed through micro-computed tomography analysis, histologic observation, and biomechanical test, respectively. RESULTS: After a 12-month induction with ovariectomy and methylprednisolone administration, the mean BMD of the sheep lumbar vertebrae significantly decreased (>25%) compared with the value before induction, which demonstrated successful establishment of osteoporosis. Three months after injection of CS, CS was completely degraded without any remains in bone tissue and the quality of bone tissue (amount and density of the bone tissue) in the CS group was significantly higher than that in the control group. The ultimate load, stiffness, and energy absorption in the CS group were all significantly higher than those in the control group. CONCLUSIONS: The preliminary data suggest that local injection of CS can significantly improve the amount, density, and biomechanical performance of the bone trabeculae in osteoporotic vertebra. The local injection of CS could also be used as a new method to improve the physical microstructure and augment the mechanical properties in "high-risk" vertebral bodies, decreasing the potential fracture risk of patients with osteoporosis. The strict inclusion and exclusion criteria should be performed before treatment.

Time Related Changes of Mineral and Collagen and Their Roles in Cortical Bone Mechanics of Ovariectomized Rabbits.

As cortical bone has a hierarchical structure, the macroscopic bone strength may be affected by the alterations of mineral crystal and collagen, which are main components of cortical bone. Limited studies focused on the time related alterations of these two components in osteoporosis, and their contributions to bone mechanics at tissue level and whole-bone level. Therefore, the purpose of this study was to elucidate the time related changes of mineral and collagen in cortical bone of ovariectomized (OVX) rabbits, and to relate these changes to cortical bone nanomechanics and macromechanics. 40 Rabbits (7-month-old) were randomly allocated into two groups (OVX and sham). OVX group received bilateral ovariectomy operation. Sham group received sham-OVX operation. Cortical bone quality of five rabbits in each group were assessed by DXA, µCT, nanoindentation, Fourier transform infrared (FTIR) spectroscopy and biomechanical tests (3-point bending of femoral midshaft) at pre-OVX, 4, 6, and 8 weeks after OVX. As time increased from pre-OVX to 8 weeks, the mineral to matrix ratio decreased with time, while both collagen crosslink ratio and crystallinity increased with time in OVX group. Elastic modulus and hardness measured by nanoindentation, whole-bone strength measured by biomechanical tests all decreased in OVX group with time. Bone material properties measured by FTIR correlated well with nano or whole-bone level mechanics. However, bone mineral density (BMD), structure, tissue-level and whole-bone mechanical properties did not change with age in sham group. Our study demonstrated that OVX could affect the tissue-level mechanics and bone strength of cortical bone. And this influence was attributed to the time related alterations of mineral and collagen properties, which may help us to design earlier interventions and more effective treatment strategies on osteoporosis.

A novel total cervical prosthesis for single-level cervical subtotal corpectomy: radiologic and histomorphometric analysis in a caprine model.

STUDY DESIGN: A novel total cervical prosthesis (TCP) for single-level cervical subtotal corpectomy was assessed in a caprine animal model. OBJECTIVES: To investigate the radiologic and histomorphometric characteristics of a novel TCP for single-level cervical subtotal corpectomy. SUMMARY OF BACKGROUND: Cervical disk replacement has emerged as a promising alternative to arthrodesis in the management of cervical disk herniation. However, they are designed for anterior cervical discectomy, and not suitable for cervical subtotal corpectomy. To solve this problem, our group has developed a novel TCP for single-level cervical subtotal corpectomy. MATERIALS AND METHODS: There were 12 adult Shannxi goats (2 y old) used in this study. The goats were divided into 2 groups based on postoperative survival periods of 3 (n=6) and 6 (n=6) months after surgery. Using an anterior surgical approach, a standard anterior C3 vertebra subtotal corpectomy and decompression of the spinal canal were performed, followed by implantation of the TCP device. Then all the goats were killed and underwent radiographic and histologic observations. RESULTS: The TCP implant procedures were successfully completed in all 12 goats without incidence of vascular or infectious complications. The range of motion of C2-C3 and C3-C4 segments were preserved in both of the groups. Three-dimensional images of specimens interface indicated confluent interdigitization of trabeculae at the prosthetic endplate-bone interface, without evidence of significant radiolucent lines or gaps. Histomorphometric analysis showed that there were a large number of fibrous tissue and a small amount of cartilage cells between the prostheses and bone in the 3 months' group. In the 6 months' group, part of fibrous tissue has changed into the cartilage tissue. CONCLUSIONS: Our data show that this prosthesis can maintain the stability of the cervical spine and retain the activity of the cervical spine in vivo. The findings in this study provide a foundation for ongoing clinical investigations using the TCP.

Effect of bone material properties on effective region in screw-bone model: an experimental and finite element study.

BACKGROUND: There have been numerous studies conducted to investigate the pullout force of pedicle screws in bone with different material properties. However, fewer studies have investigated the region of effect (RoE), stress distribution and contour pattern of the cancellous bone surrounding the pedicle screw. METHODS: Screw pullout experiments were performed from two different foams and the corresponding reaction force was documented for the validation of a computational pedicle screw-foam model based on finite element (FE) methods. After validation, pullout simulations were performed on screw-bone models, with different bone material properties to model three different age groups (<50, 50-75 and >75 years old). At maximum pullout force, the stress distribution and average magnitude of Von Mises stress were documented in the cancellous bone along the distance beyond the outer perimeter pedicle screw. The radius and volume of the RoE were predicted based on the stress distribution. RESULTS: The screw pullout strengths and the load-displacement curves were comparable between the numerical simulation and experimental tests. The stress distribution of the simulated screw-bone vertebral unit showed that the radius and volume of the RoE varied with the bone material properties. The radii were 4.73 mm, 5.06 mm and 5.4 mm for bone properties of ages >75, 75 > ages >50 and ages <50 years old, respectively, and the corresponding volumes of the RoE were 6.67 mm3, 7.35 mm3 and 8.07 mm3, respectively. CONCLUSIONS: This study demonstrated that there existed a circular effective region surrounding the pedicle screw for stabilization and that this region was sensitive to the bone material characteristics of cancellous bone. The proper amount of injection cement for augmentation could be estimated based on the RoE in the treatment of osteoporosis patients to avoid leakage in spine surgery.

Surgical results of developmental dysplasia of the hip in older children based on using three-dimensional computed tomography.

BACKGROUND: The surgical management of developmental dysplasia of the hip (DDH) in older children has been the subject of controversy. The purpose of this study was to evaluate the outcome in patients with neglected DDH who underwent individual procedures based on using three-dimensional computed tomography. METHODS: Forty-seven patients (59 hips) were treated using Pemberton osteotomy or Dega plus Pemberton osteotomy. Subtrochanteric transverse femoral shortening and derotation osteotomy were performed for all patients. The average age at the time of surgery was 10.5 y for group 1 (bilateral dislocation, 24 hips) and 11.2 y for group 2 (unilateral dislocation, 35 hips). Mean follow-up was 5.3 y for group 1 and 5.8 y for group 2. RESULTS: At the end of follow-up, 13 hips (54.2%) were rated excellent, eight hips (33.3%) were good, and three hips (12.5%) were fair in group 1. In group 2, 20 hips (57.1%) were rated excellent, 10 hips (28.6%) were good, and five hips (14.3%) were fair. There were five patients who had a limb length discrepancy of approximately 1.5 cm in group 2. Six hips in group 1 and seven hips in group 2 had osteonecrosis of varying severity. CONCLUSIONS: We believe that preoperation three-dimensional computed tomography evaluation, personalized operation plans, and experience with the surgical procedure are the main reasons for the satisfactory therapeutic effects achieved in this study in older children with DDH.