Yuntong Zhang

Biomechanical comparison of different stabilization constructs for unstable posterior wall fractures of acetabulum. A cadaveric study.

Purpose Operative treatment of unstable posterior wall fractures of acetabulum has been widely recommended. This laboratory study was undertaken to evaluate static fixation strength of three common fixation constructs: interfragmentary screws alone, in combination with conventional reconstruction plate, or locking reconstruction plate. Methods Six formalin-preserved cadaveric pelvises were used for this investigation. A posterior wall fracture was created along an arc of 40–90 degree about the acetabular rim. Three groups of different fixation constructs (two interfragmentary screws alone; two interfragmentary screws and a conventional reconstruction plate; two interfragmentary screws and a locking reconstruction) were compared. Pelvises were axial loaded with six cycles of 1500 N. Dislocation of superior and inferior fracture site was analysed with a multidirectional ultrasonic measuring system. Results: No statistically significant difference was found at each of the superior and inferior fracture sites between the three types of fixation. In each group, the vector dislocation at superior fracture site was significantly larger than inferior one. Conclusions All those three described fixation constructs can provide sufficient stability for posterior acetabular fractures and allow early mobilization under experimental conditions. Higher posterior acetabular fracture line, transecting the weight-bearing surface, may indicate a substantial increase in instability, and need more stable pattern of fixation.

Deletion of mammalian sterile 20-like kinase 1 attenuates neuronal loss and improves locomotor function in a mouse model of spinal cord trauma

Neuronal cell death following spinal cord injury (SCI) is an important contributor to neurological deficits. The purpose of our work was to delineate the function of mammalian sterile 20-like kinase 1 (Mst1), a pro-apoptotic kinase and key mediator of apoptotic signaling, in the pathogenesis of an experimental mouse model of SCI. Male mice received a mid-thoracic spinal contusion injury, and it was found that phosphorylation of Mst1 at the injured site was enhanced significantly following SCI. Furthermore, when compared to the wild-type controls, Mst1-deficient mice displayed improved locomotor function by increased Basso mouse scale score. Deletion of Mst1 in mice attenuated loss of motor neurons and suppressed microglial and glial activation following SCI. Deletion of Mst1 in mice reduced apoptosis via suppressing cytochrome c release and caspase-3 activation following SCI. Deletion of Mst1 attenuated mitochondrial dysfunction and increased ATP formation following SCI. Deletion of Mst1 in mice inhibited local inflammation following SCI, evidenced by reduced activities of myeloperoxidase and protein levels of TNF-α, IL-1β, and IL-6. In conclusion, the present study demonstrated that deletion of Mst1 attenuated neuronal loss and improved locomotor function in a mouse model of SCI, via preserving mitochondrial function, attenuating mitochondria-mediated apoptotic pathway, and suppressing inflammation, at least in part.

Degradability, biocompatibility, and osteogenesis of biocomposite scaffolds containing nano magnesium phosphate and wheat protein both in vitro and in vivo for bone regeneration.

In this study, bioactive scaffold of nano magnesium phosphate (nMP)/wheat protein (WP) composite (MWC) was fabricated. The results revealed that the MWC scaffolds had interconnected not only macropores (sized 400–600 μm) but also micropores (sized 10–20 μm) on the walls of macropores. The MWC scaffolds containing 40 w% nMP had an appropriate degradability in phosphate-buffered saline and produced a weak alkaline microenvironment. In cell culture experiments, the results revealed that the MWC scaffolds significantly promoted the MC3T3-E1 cell proliferation, differentiation, and growth into the scaffolds. The results of synchrotron radiation microcomputed tomography and analysis of the histological sections of the in vivo implantation revealed that the MWC scaffolds evidently improved the new bone formation and bone defects repair as compared with WP scaffolds. Moreover, it was found that newly formed bone tissue continued to increase with the gradual reduction of materials residual in the MWC scaffolds. Furthermore, the immunohistochemical analysis further offered the evidence of the stimulatory effects of MWC scaffolds on osteogenic-related cell differentiation and new bone regeneration. The results indicated that MWC scaffolds with good biocompability and degradability could promote osteogenesis in vivo, which would have potential for bone tissue repair.

O-Acrylamidomethyl-2-hydroxypropyltrimethyl ammonium chloride chitosan and silk modified mesoporous bioactive glass scaffolds with excellent mechanical properties, bioactivity and long-lasting antibacterial activity

Mesoporous bioactive glass (MBG) is a promising scaffold in bone tissue engineering because its large specific surface area facilitates bioactive behavior and allows mesopores to be loaded with osteogenic agents for promoting the formation of new bone. In the present study, a biocompatible MBG-based scaffold for bone regeneration applications with long-lasting antibacterial activity were fabricated via surface modification with O-acrylamidomethyl-2-hydroxypropyltrimethyl ammonium chloride chitosan (NMA-HACC) and silk. The NMA-HACC–silk (NHS) modified MBG scaffolds were prepared by evaporation-induced self-assembly using polyurethane sponges and the P123 surfactant as co-templates. The microstructure of the scaffold was characterized using scanning electron microscopy (SEM) and synchrotron radiation microcomputer tomography (SRμCT). Fourier transform infrared spectroscopy (FTIR), SEM, X-ray diffraction (XRD), and mechanical experiments were used to analyze the products composition, inner microstructure, morphology, and mechanical strength before and after its surface modification. These methods were also used to assess the degree to which minerals became deposited on the scaffold after soaking in simulated body fluid (SBF). Confocal laser scanning microscopy (CLSM) was used to evaluate the antibacterial properties and biocompatibility of the scaffolds at various time intervals. Finally, biocompatibility was demonstrated by studying the in vitro proliferation and viability of human mesenchymal stem cells (hMSCs). The results showed that the fabricated scaffolds possessed well-ordered, three-dimensional structures and the NMA-HACC–silk modification rendered the pore network more uniform and continuous, leading to the significant improvement in bioactivity and in hMSC attachment, cell spreading and cell proliferation. Furthermore, the NMA-HACC–silk modification significantly prolonged the antibacterial activity of the MBG scaffold.

Application of a Shape-Memory Alloy Concentrator in Displaced Patella Fractures: Technique and Long-Term Results

&NA; Operative treatment is usually recommended in displaced patella fractures. Several techniques have been advocated for internal fixation of patella fractures. Despite the relatively good clinical outcomes that have been demonstrated in many studies, postoperative morbidities such as fixation failure, nonunion, infection, and knee stiffness are not uncommon. We present a new alternative treatment technique for displaced patellar fractures. Between April 1995 and May 2005, we used the Nitinol Patella Concentrator (NTPC) to treat 156 consecutive patients with displaced patellar fractures. Injuries arose from vehicular accidents in 56 (35.9%) cases, direct falls onto the knee in 85 (54.5%) cases, and sports injuries in 15 (9.6%) cases. The mean patient age was 46.3 years (range, 25‐77 years). Clinical assessments were made using the Böstman knee score and the MOS SF‐36 questionnaire (Medical Outcomes Study 36‐item short‐form health survey), which were both recorded at the final follow‐up visit. The mean follow‐up was 7.3 years (range, 6‐17 years). At the final follow‐up, the Böstman knee scores were excellent in 88 cases (28‐30), good in 55 (20‐27), and unsatisfactory in 13 (<20). According to the MOS SF‐36 evaluation, the average score was 84.5 (range, 62‐91). Treatment of patellar fracture with the NTPC not only may serve as an effective and rigid fixation method in multifragmented displaced and inferior pole fractures, but also may provide continuous concentrative compression during the osseous healing process. Thus, use of the NTPC may help restore the functional integrity of the extensor mechanism and permit early rehabilitation with a lower incidence of postoperative complications.