Hierarchical antibiotic delivery system based on calcium phosphate cement/montmorillonite-gentamicin sulfate with drug release pathways.

Antibiotic-loaded calcium phosphate cement (CPC) has emerged as a promising biomaterial for drug delivery in orthopedics. However, there are problems such as the burst release of antibiotics, low cumulative release ratio, inappropriate release cycle, inferior mechanical strength, and poor anti-collapse properties. In this research, montmorillonite-gentamicin (MMT-GS) was fabricated by solution intercalation method and served as the drug release pathways in CPC to avoid burst release of GS, achieving promoted cumulative release ratios and a release cycle matched the time of inflammatory response. The results indicated that the highest cumulative release ratio and release concentration of GS in CPC/MMT-GS was 94.1 ± 2.8 % and 1183.05 µg/mL, and the release cycle was up to 504 h. In addition, the hierarchical GS delivery system was divided into three stages, and the kinetics followed the Korsmeyer-Peppas model, the zero-order model, and the diffusion-dissolution model, respectively. Meanwhile, the compressive strength of CPC/MMT-GS was up to 51.33 ± 3.62 MPa. Antibacterial results demonstrated that CPC/MMT-GS exhibited excellent in vitro long-lasting antibacterial properties to E. coli and S. aureus. Furthermore, CPC/MMT-GS promoted osteoblast proliferation and exhibited excellent in vivo histocompatibility. Therefore, CPC/MMT-GS has favorable application prospects in the treatment of bone defects with bacterial infections and inflammatory reactions.

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.

Can a Nomogram Predict Survival After Treatment for an Ankylosing Spondylitis Cervical Fracture in a Patient With Neurologic Impairment? A National, Multicenter Study.

BACKGROUND: Ankylosing spondylitis-related cervical spine fracture with neurologic impairment (ASCF-NI) is a rare but often lethal injury. Factors independently associated with survival after treatment remain poorly defined, and identifying patients who are likely to survive the injury remains challenging. QUESTIONS/PURPOSES: (1) What factors are independently associated with survival after treatment among patients with ASCF-NI? (2) Can a nomogram be developed that is sufficiently simple for clinicians to use that can identify patients who are the most likely to survive after injury? METHODS: This retrospective study was conducted based on a multi-institutional group of patients admitted and treated at one of 29 tertiary hospitals in China between March 1, 2003, and July 31, 2019. A total of 363 patients with a mean age of 53 ± 12 years were eventually included, 343 of whom were male. According to the National Household Registration Management System, 17% (61 of 363) died within 5 years of injury. Patients were treated using nonsurgical treatment or surgery, including procedures using the anterior approach, posterior approach, or combined anterior and posterior approaches. Indications for surgery included three-column injury, unstable fracture displacement, neurologic impairment or continuous progress, and intervertebral disc incarceration. By contrast, patients generally received nonsurgical treatment when they had a relatively stable fracture or medical conditions that did not tolerate surgery. Demographic, clinical, and treatment data were collected. The primary study goal was to identify which factors are independently associated with death within 5 years of injury, and the secondary goal was the development of a clinically applicable nomogram. We developed a multivariable Cox hazards regression model, and independent risk factors were defined by backward stepwise selection with the Akaike information criterion. We used these factors to create a nomogram using a multivariate Cox proportional hazards regression analysis. RESULTS: After controlling for potentially confounding variables, we found the following factors were independently associated with a lower likelihood of survival after injury: lower fracture site, more-severe peri-injury complications, poorer American Spinal Injury Association (ASIA) Impairment Scale, and treatment methods. We found that a C5 to C7 or T1 fracture (ref: C1 to C4 and 5; hazard ratio 1.7 [95% confidence interval 0.9 to 3.5]; p = 0.12), moderate peri-injury complications (ref: absence of or mild complications; HR 6.0 [95% CI 2.3 to 16.0]; p < 0.001), severe peri-injury complications (ref: absence of or mild complications; HR 30.0 [95% CI 11.5 to 78.3]; p < 0.001), ASIA Grade A (ref: ASIA Grade D; HR 2.8 [95% CI 1.1 to 7.0]; p = 0.03), anterior approach (ref: nonsurgical treatment; HR 0.5 [95% CI 0.2 to 1.0]; p = 0.04), posterior approach (ref: nonsurgical treatment; HR 0.4 [95% CI 0.2 to 0.8]; p = 0.006), and combined anterior and posterior approach (ref: nonsurgical treatment; HR 0.4 [95% CI 0.2 to 0.9]; p = 0.02) were associated with survival. Based on these factors, a nomogram was developed to predict the survival of patients with ASCF-NI after treatment. Tests revealed that the developed nomogram had good performance (C statistic of 0.91). CONCLUSION: The nomogram developed in this study will allow us to classify patients with different mortality risk levels into groups. This, coupled with the factors we identified, was independently associated with survival, and can be used to guide more appropriate treatment and care strategies for patients with ASCF-NI. LEVEL OF EVIDENCE: Level III, therapeutic study.

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.

Black phosphorous-based biomaterials for bone defect regeneration: a systematic review and meta-analysis.

Critical-sized bone defects are always difficult to treat, and they are associated with a significant burden of disease in clinical practice. In recent decades, due to the fast development of biomaterials and tissue engineering, many bioinspired materials have been developed to treat large bone defects. Due to the excellent osteoblastic ability of black phosphorous (BP), many BP-based biomaterials have been developed to treat bone defects. Therefore, there are abundant studies as well as a tremendous amount of research data. It is urgent to conduct evidence-based research to translate these research data and results into validated scientific evidence. Therefore, in our present study, a qualitative systematic review and a quantitative meta-analysis were performed. Eighteen studies were included in a systematic review, while twelve studies were included in the meta-analysis. Our results showed that the overall quality of experimental methods and reports of biomaterials studies was still low, which needs to be improved in future studies. Besides, we also proved the excellent osteoblastic ability of BP-based biomaterials. But we did not find a significant effect of near-infrared (NIR) laser in BP-based biomaterials for treating bone defects. However, the quality of the evidence presented by included studies was very low. Therefore, to accelerate the clinical translation of BP-based biomaterials, it is urgent to improve the quality of the study method and reporting in future animal studies. More evidence-based studies should be conducted to enhance the quality and clinical translation of BP-based biomaterials.

Instantaneous death risk, conditional survival and optimal surgery timing in cervical fracture patients with ankylosing spondylitis: A national multicentre retrospective study.

Background: The mortality rate in patients with ankylosing spondylitis (AS) and cervical fracture is relatively high. Objectives: This study aimed to investigate the instantaneous death risk and conditional survival (CS) in patients with AS and cervical fracture. We also studied the relationship between surgical timing and the incidence of complications. Methods: This national multicentre retrospective study included 459 patients with AS and cervical fractures between 2003 and 2019. The hazard function was used to determine the risk of instantaneous death. The five-year CS was calculated to show the dynamic changes in prognosis. Results: The instantaneous death risk was relatively high in the first 6 months and gradually decreased over time in patients with AS and cervical fracture. For patients who did not undergo surgery, the instantaneous risk of death was relatively high in the first 15 months and gradually decreased over time. For patients with American Spinal Injury Association impairment scale (ASIA) A and B, the 5-year CS was 55.3% at baseline, and improved steadily to 88.4% at 2 years. Odds ratios (ORs) for pneumonia, electrolyte disturbance, respiratory insufficiency, and phlebothrombosis decreased as the surgery timing increased. Conclusion: Deaths occurred mainly in the first 6 months after injury and gradually decreased over time. Our study highlights the need for continued surveillance and care in patients with AS with cervical fractures and provides useful survival estimates for both surgeons and patients. We also observed that early surgery can significantly increase functional recovery, and decrease the incidence of complications and rehospitalisation.

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.

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.

Sequential release of double drug (graded distribution) loaded gelatin microspheres/PMMA bone cement.

Drugs are loaded into PMMA bone cement to reduce the risk of infection in freshly implanted prostheses or to promote the differentiation and growth of osteoblasts. However, the same method of loading of drugs in the bone cement cannot simultaneously achieve an effective antibacterial response and long-term treatment outcomes for osteoporosis based on a patient's clinical needs. In the present study, gentamicin sulfate (GS)/alendronate (ALN)-dual-loaded gelatin modified PMMA bone cement (GAPBC) was fabricated to provide rapid and continuous antibiotic release and long-term anti-osteoporotic therapy. Specifically, the gelatin microspheres were loaded with the drugs using separate methodologies, namely, ALN was loaded during fabrication of the gelatin microspheres after which GS was absorbed onto the gelatin from solution. The results demonstrate that sequential release of the GS and ALN was achieved, GS release playing a major role over the first 24 hours and ALN release dominant after 3 weeks of immersion in PBS, resulting from the graded distribution within the gelatin microspheres, and the final drug release ratio of GS (73.6%) and ALN (68.5%) from the modified bone cement was significantly higher than from PMMA bone cement. Therefore, GAPBC represents a potential drug carrier for future clinical applications.

Thermosensitive injectable decellularized nucleus pulposus hydrogel as an ideal biomaterial for nucleus pulposus regeneration.

Extracellular matrix loss is one of the early manifestations of intervertebral disc degeneration. Stem cell-based tissue engineering creates an appropriate microenvironment for long term cell survival, promising for NP regeneration. We created a decellularized nucleus pulposus hydrogel (DNPH) from fresh bovine nucleus pulposus. Decellularization removed NP cells effectively, while highly preserving their structures and major biochemical components, such as glycosaminoglycan and collagen II. DNPH could be gelled as a uniform grid structure in situ at 37°C for 30 min. Adding adipose marrow-derived mesenchymal stem cells into the hydrogel for three-dimensional culture resulted in good bioactivity and biocompatibility in vitro. Meanwhile, NP-related gene expression significantly increased without the addition of exogenous biological factors. In summary, the thermosensitive and injectable hydrogel, which has low toxicity and inducible differentiation, could serve as a bio-scaffold, bio-carrier, and three-dimensional culture system. Therefore, DNPH has an outstanding potential for intervertebral disc regeneration.

[Short-term effectiveness of Kirschner wire elastic fixation in treatment of Doyle type â and â ¡ mallet finger].

Objective: To evaluate the short-term effectiveness of Kirschner wire (K-wire) elastic fixation in the treatment of Doyle type Ⅰ and Ⅱ mallet finger. Methods: Between July 2016 and March 2017, 18 patients with Doyle type Ⅰ and Ⅱ mallet finger were treated. There were 12 males and 6 males, with an average age of 45 years (range, 16-61 years). The index finger was involved in 2 cases, the middle finger in 3 cases, the ring finger in 10 cases, and the little finger in 3 cases. The interval from injury to operation ranged from 2 hours to 45 days (median, 5.5 hours). There were 8 patients of closed wound and 10 patients of open wound. Fourteen patients were simply extensor tendon rupture and 4 were extensor tendon rupture complicated with avulsion fracture. The distal interphalangeal joints (DIPJ) of injured fingers were elastically fixed with the K-wire at mild dorsal extend position. The K-wire was removed after 6 weeks, and the functional training started. Results: The operation time was 34-53 minutes (mean, 38.9 minutes). Patients were followed up 3-8 months (mean, 5 months). All incisions healed primarily and no K-wire loosening or infection happened during the period of fixation. All mallet fingers were corrected. The range of motion (ROM) in terms of active flexion of injured DIPJ was (75.83±11.15)° at 6 weeks after operation, showing significant difference when compared with the normal DIPJ of contralateral finger [(85.28±6.06)°] ( t=3.158, P=0.003). The ROM in terms of active flexion was (82.67±6.78)° in 15 patients who were followed up at 8 months after operation, showing no significant difference when compared with the normal DIPJ of contralateral finger [(86.00±5.73)°] ( t=1.454, P=0.157). After the removal of K-wire at 6 weeks, visual analogue scale (VAS) score of active flexion and of passive flexion to maximum angle were 1.78±0.88 and 3.06±1.06, respectively. According to the total active motion criteria, the effectiveness was rated as excellent in 10 cases, good in 5 cases, moderate in 2 cases, and poor in 1 case, and the excellent and good rate was 83.33%. The patients' satisfaction were accessed by Likert scale, which were 3-5 (mean, 4.2). Conclusion: K-wire elastic fixation in the treatment of Doyle typeⅠand Ⅱ mallet finger can repair the extensor effectively, correct the mallet finger deformity, and also be benefit for the flexion-extension function restoration of DIPJ.

Osteogenic actions of metoprolol in an ovariectomized rat model of menopause.

OBJECTIVE: Osteoporosis and hypertension are age-related chronic diseases with increased morbidity rates among postmenopausal women. Clinical epidemiological investigations have demonstrated that hypertensive patients treated with ß1-selective ß-blockers have a higher bone mineral density (BMD) and lower fracture risk. Nevertheless, no fundamental studies have examined the relationships between ß1-selective ß-blockers and these effects. The present study explored the effects and mechanisms of metoprolol in the in vitro treatment of osteoblasts and the in vivo treatment of ovariectomy-induced osteoporosis in rats. METHODS: Primary osteoblasts were obtained by digestion of the cranial bones of 24-hour-old Sprague-Dawley rats. After metoprolol treatment, cell proliferation and differentiation capacities were assessed at the corresponding time points. In addition, 3-month-old female Sprague-Dawley rats (200-220 g) were divided into a sham-operated group (n = 8) and three ovariectomized (OVX) (bilateral removal of ovaries) groups as follows: vehicle (OVX; n = 8), low-dose metoprolol (L-M, oral, 120 mg/kg/d; n = 8), and high-dose metoprolol (H-M, oral, 240 mg/kg/d; n = 8). After 12 weeks of metoprolol treatment, BMD, microarchitecture, and biomechanical properties were evaluated. RESULTS: The results indicated that the treatments with 0.01 to 0.1 µM metoprolol increased osteoblast proliferation, alkaline phosphatase activity, and calcium mineralization, and promoted the expression of osteogenic genes. The in vivo study indicated that administration of metoprolol to OVX rats resulted in maintenance of the BMDs of the L4 vertebrae. Moreover, amelioration of trabecular microarchitecture deterioration and preservation of bone biomechanical properties were detected in the trabecular bones of the OVX rats. CONCLUSIONS: Our findings indicate that metoprolol prevents estrogen deficiency-induced bone loss by increasing the number and enhancing the biological functions of osteoblasts, implying its potential use as an alternative treatment for postmenopausal osteoporosis in hypertensive patients.

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.

[RESEARCH PROGRESS OF FENESTRATED PEDICLE SCREW].

OBJECTIVE: To review the research background, biomechanical characteristics, and clinical application of fenestrated pedicle screw (FPS). METHODS: The recent literature about the study and application of FPS was reviewed, analyzed, and summarized. RESULTS: Compared with the technique of conventional pedicle screw augmentation, FPS can be augmented with polymethyl methacrylate (PMMA) through inner central pore and side holes. Hence, the augmentation process of FPS is more convenient during operation. The biomechanics of PMMA augmented FPS is strong enough for instrumentation in osteoporotic vertebra body and the way of FPS PMMA augmentation can reduce the risk of PMMA leakage. CONCLUSIONS: FPS is an innovation in the technology of spinal instrumentation, which is expected to improve the clinical outcome of PMMA augmented pedicle screw in osteoporotic vertebra body fixation.

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.

Systemic treatment with telmisartan improves femur fracture healing in mice.

Recent clinical studies indicated that angiotensin receptor blockers (ARBs) would decrease the risk of bone fractures in the elderly populations. There is little known about the role of the ARBs in the process of fracture healing. The purpose of the present study was to verify the hypothesis that systemic treatment with telmisartan has the ability to promote fracture healing. In this study, femur fractures were produced in 96 mature male BALB/c mice. Animals were treated with the ARBs telmisartan or vehicle. Fracture healing was analysed after 2, 5 and 10 weeks postoperatively using X-ray, biomechanical testing, histomorphometry, immunohistochemistry and micro-computed tomography (micro-CT). Radiological analysis showed the diameter of the callus in the telmisartan treated animals was significantly increased when compared with that of vehicle treated controls after two weeks of fracture healing. The radiologically observed promotion of callus formation was confirmed by histomorphometric analyses, which revealed a significantly increased amount of bone formation when compared with vehicle-treated controls. Biomechanical testing further showed a significantly greater peak torque at failure, and a higher torsional stiffness in telmisartan-treated animals compared with controls. There was an increased fraction of PCNA-positive cells and VEGF-positive cells in telmisartan-treated group compared with vehicle-treated controls. From the three-dimensional reconstruction of the bony callus, telmisartan-treated group significantly increased the values of BV/TV by 21.7% and CsAr by 26.0% compared to the vehicle-treated controls at 5 weeks post-fracture. In summary, we demonstrate in the current study that telmisartan could promote fracture healing in a mice model via increasing mechanical strength and improving microstructure. The most mechanism is probably by an increase of cell proliferation and neovascularization associated with a decreased VEGF expression in hypertrophic chondrocytes.