BACKGROUND: In spite of some good successes of nickel-titanium alloy have been achieved in orthopaedic surgery, there are still serious limitations in clinical application, such as potential leakage of elements and ions, which could be toxic to cells, tissues and organs. OBJECTIVE: To review the research progress and the exiting problems of nickel-titanium shape memory alloy in orthopaedics and to provide theoretical supports for safe use of the alloy in clinical practice.METHODS: A computer-based online search of Springerlink and CNKI was performed for articles published between 2003 and 2010 both in Chinese and English. The search was conducted respectively with the key words of "nickel-titanium shape memory alloy (NiTi-SMA), biocompatibility, modifications, orthopaedics". Researches regarding nickel-titanium shape memory alloy and its properties, clinical applications, corrosion performance, biocompatibility, corrosion resistance by surface/structure modifications and the long-term challenges were included. Irrelevant or repetitive articles were excluded. RESULTS AND CONCLUSION: Nickel-titanium shape memory alloy has special value in medical field due to favorable shape-memory and superelasticity. However, due to the nickel toxicity, it is of great importance to elevate corrosion resistance of nickel-titanium alloy. The modifications of the alloy are the main focus and direction for further research.

BACKGROUND:There are less studies on static magnetic field, and its biological effects are stil unclear. OBJECTIVE:To investigate the static magnetic field effect on the secretion of nerve growth factor from Schwann cel s. METHODS:Schwann cel s were randomly assigned into three groups:0.05 mT sciatic magnetic field group, 0.1 mT sciatic magnetic field group and control group. At 2 days of inoculation, the cel s were exposed to the sciatic magnetic field, 12 hours per day. Cel s in the control group were not exposed to the sciatic magnetic field. After 6 days of exposure, RT-PCR method was used to detect nerve growth factor mRNA expression in Schwann cel s, and ELISA was adopted to detect the level of nerve growth factor secreted from Schwann cel s. RESULTS AND CONCLUSION:The mRNA expression and secreted level of nerve growth factors in the culture supernatant were significantly higher in the two sciatic magnetic field groups than the control group (P<0.05), especial y in the 0.1 mT group. However, there was no difference between the 0.05 mT and 0.1 mT groups (P>0.05). These findings indicate that the static magnetic field with certain intensity can promote the secretion of nerve growth factors from Schwann cel s.

Objective To investigate the cytotoxic activities of γδT cells against methotrexate (MTX)-resistant osteosarcoma (OS) cells.Methods The MTX-resistant U2OS cell line (U2OS/MTX) was established by in vitro exposing the parental cells to MTX at stepwise-increasing concentrations.Periph-eral blood mononuclear cells ( PBMCs) were isolated from healthy subjects and stimulated with zoledronate ( ZOL) in combination with IL-2 to induce the proliferation ofγδT cells.The cytotoxicity ofγδT cells against U2OS/MTX cells was analyzed by using a standard lactate dehydrogenase release assay (LDH).Flow cy-tometry analysis and ELISA were performed to detect the expression of CD69 and IFN-γby γδT cells, re-spectively.Results The γδT cells derived from healthy subjects showed cytotoxicity against the U2OS/MTX cells.Moreover, stronger cytotoxic activities of γδT cells were detected after pretreatment of U2OS/MTX cells with ZOL (1 μmol/L) for 24 hours (P<0.01).Stimulation with U2OS or U2OS/MTX cells in-creased the expression of CD69 onγδT cells and enhanced the secretion of IFN-γbyγδT cells (P<0.05). Increased expression of CD69 and enhanced secretion of IFN-γwere induced in γδT cells in response to stimulation with ZOL-pretreated U2OS/MTX cells (P<0.01).Conclusion TheγδT cells showed cytotox-icity against U2OS/MTX cells.Pretreatment of U2OS/MTX cells with ZOL could enhance the cytotoxic ac-tivity of γδT cells.

Objective To discuss parallel fibular osteoseptocutaneous flap apply in heel defect reconstruction Methods From February,2006 to December,2011,parallel fibular osteoseptocutaneous flap were used to repair calcaneus and skin defects in 4 cases.The causes included road accident in 2 cases and strangulation in 2 cases.The defect locations were at the back of the calcaneus (1/2 of calcaneus in 2 cases and 2/3 in 2 cases,respectively).Results Followed up 24-72 months,all cases achieved bone union in allograft and had no complications of absorption,infection and repulsion.The flaps survived completely in 4 cases ; the distal flaps necrosed partly in 1 case and healed by dressing.According to USA foot-malleolus scores of AOFAS,1 case was excellent,2 good,and 1 fair.Conclusion Parallel fibular osteoseptocutaneous flap reconstruction heel defect can recover patients visage and heel function,improve their life quality.

Objective:To investigate the effect of typeⅠIFN on the cytotoxic activity ofγδT cells from peripheral blood mono-nuclear cells ( PBMCs) of healthy donors and osteosarcoma patients stimulated by zoledronate ( Zol) and IL-2 against OS.Methods:PBMCs from healthy donors and osteosarcoma patients were stimulated with Zol+IL-2 or Zol+IL-2+typeⅠIFN,respectively.After 14 days of culture,ex vivo expandedγδT cells were assessed by flow cytometry.γδT cell cytotoxicity against target cells was analyzed using a standard lactate dehydrogenase release assay.IFN-γsecreted fromγδT cells was determined by ELISA kits.Results:γδT cells from PBMCs of healthy donors and patients with OS were selectively expanded by Zol+IL-2 or Zol+IL-2+typeⅠIFN in vitro,respectively, and showed cytotoxicity against OS.In addition,γδT cells pre-treated by TypeⅠIFN showed significantly higher cytotoxicity against OS cells.Conclusion:Type I IFN can enhance humanγδT cells’ cytotoxic activity against OS.

BACKGROUND: Up to now, no universally successful therapy to treat substantial articular cartilage defects has been available. Numerous therapeutic approaches can only improve clinical symptoms of joint lesions, but not stimulate the regenerative and reactive capacity of the biological tissue in the defect, and not restore an articular surface capable of functional load bearing.OBJECTIVE: To investigate the curative effects of homograft of mesenchymal stem cells (MSCs) seeded onto cancellous demineralized bone matrix (DBM) on articular cartilage defects.DESIGN, TIME AND SETTING: A randomized controlled study which conducted in Orthopaedics Institute, the Second Hospital of Lanzhou University from January to March 2005 and Central Laboratory of Guilin Medical Collage from May to August 2008.MATERIALS: Bone metaphysis and vertebral cancellous bone were derived from rabbits to prepare DBM materials. MSCs were seed on DBM stent and cultured in vitro. All 36 rabbits were randomly divided into combination group (DBM/MSCs), DBM alone group, and blank control group, with 12 rabbits per group.METHODS: Full-thickness cartilage defect model of knee joint was frilled using a cylinder of 4 mm diameter and 3 mm thickness on intercondylar fossa. The cartilage defects in the intercondylar fossa were filled with MSCs/DBM in combination group A, with only DBM in the DBM group, and nothing was treated in the blank control group.MAIN OUTCOME MEASURES: Four rabbits were killed at three time points, which were 4, 8 and 12 weeks after the operation in each group, and the reparative tissue samples were evaluated grossly, histologically, immunohistochemically and graded according to gross and histological scale.RESULTS: Tirty-six rabbits were included in the final analysis. The defects of MSCs/DBM transplantation were repaired by byline-like tissue, and the other defects were repaired by fibrous tissue. Gross and histological grading scale was made on 12 weeks postoperatively. Gross and histological scores in the MSCs/DBM group were significantly lower than DBM group and control group (P<0.05); while, the scores in the DBM group was significantly lower than control group (P<0.05).CONCLUSION: The full-thickness cartilage defects of rabbits were repaired with homograft of mesenchymal stem cells seeded onto cancellous demineralized bone matrix, which is a promising way for the treatment of cartilage defects.

Objective:To investigate whether celastrol can increase the cytotoxic activity of γδ T cells against osteosarcoma (OS) cells line HOS through TRAIL way. Methods:The death receptors 4/5 (DR4/5) protein levels in the OS cell lines HOS was in-vestigated by Western blot analysis. Zoledronate ( ZOL) was used to induceγδT cells from PBMCs of healthy volunteers.γδT cell cy-totoxicity against HOS cells was investigated by a standard lactate dehydrogenase release assay ( LDH ) . Results:Celastrol increased DR4/5 protein expression in HOS ( P<0. 05 ) .γδ T cells from PBMCs of healthy volunteers showed cytotoxicity against HOS ( P<0. 05). Following co-culture with HOS pre-treated with celastrol (1 μmol/L) for 24 h,γδ T cells showed significantly higher cytotoxicity against HOS (P<0. 05). The induction of DR4/5 molecules increased lysis of HOS by γδ T cells which was abolished by addition of a blocking TRAIL antibody. Conclusion:Celastrol can enhance γδ T cells'cytotoxic activity against OS cells line HOS through TRAIL way.

Objective To investigate the effects of metal particles produced by metal prosthesis on oxidative stress levels in human mononuclear cells . Methods Mononuclear cells obtained from peripheral blood of 15 healthy volunteers .Coculture mononu-clear cells with iron particles , cobalt particles , chromium particles , titanium particles and physiological saline , respectively .Levels of reactive oxygen species ( ROS) , malondialdehyde ( MDA) , superoxide dismutase ( SOD) and glutathione peroxidase ( GSH) were as-sessed in mononuclear cells at 6 h, 12 h, 24 h, 36 h, 48 h, respectively . Results Levels of ROS and MDA were higher in the parti-cle groups than that in the control group at 6 h, 12 h, 24 h, 36 h, 48 h, respectively (P<0.05).Levels of ROS and MDA were higher in cobalt particle, chromium particle and iron particle groups than that in the titanium particle group (P<0.05).Levels of SOD and GSH were lower in particle groups than that in the control group (P<0.05).Levels of SOD and GSH were lower in cobalt particle , chromium particle and iron particle groups than that in the titanium particle group (P<0.05). Conclusion Oxidative stress levels increased and anti-oxidant levels decreased in mononuclear cells when cocultured with metal debris .Cobalt particles , chromium parti-cles and iron particles induced higher changes than that in titanium particles .Oxidative stress may play an important role in metal deb-ris-mediated osteolysis .

BACKGROUND: Total hip replacement in middle-aged patients is challenging regarding restoration and survival,because these patients are more active than old patients.OBJECTIVE: To retrospectively investigate whether a cementless prosthesis could restore hip function,decrease osteolysis,wear,and enhance prosthesis survival in middle-aged patients.METHODS: Clinical and radiological evaluations of patients undergoing single-side total hip replacement with cement and cementless prosthesis were analyzed preoperatively as well as at 6 months,1,4 and 7 years postoperatively.The outcomes of total hip replacement were assessed using Harris hip scores and survival rate.End point was loosening or revision of the femoral component for any reason.RESULTS AND CONCLUSION: Cementless prosthesis had gained better Harris hip scores than that of cement prosthesis group at 6 months,1,4 and 7 years postoperatively(P < 0.05).The survival rate was greater in cementless prosthesis compared with cement prosthesis during 7-year follow-up(P < 0.05).Results have suggested that cementless prosthesis achieves high rate of functional restoration and a low rate of complications in middle-aged patients following total hip replacement.

BACKGROUND:Several researches have highlighted the selective dissolution of Ni ion from the nickel-titanium (NiTi) alloy during the corrosion process,which can lead to potential damage to human body.Different surface treatments will improve the corrosion resistance of NiTi implants.In modern medicines,it is necessary to analyze the characteristics of surface modified NiTi implants.OBJECTIVE:To study the effects of coated and uncoated materials made by elastic nickel-titanium alloy internal fixator on fracture healing and to compare the effects of continuous compressive stress after internal fixator of different types on fracture healing by setting up control group of bone nail internal fixation.DESIGN,TIME AND SETTING:A randomized,controlled,animal experiment was performed at the Laboratory of Tissue Engineering,Institute of Orthopedics,Second Hospital Affiliated to Lanzhou University between September 2004 and March 2005.MATERIALS:Diamond-like carbon coated and nickel-titanium alloy and uncoated nickel-titanium alloy embracing fixator (type 4H8-40) were provided by Lanzhou Ximai Memory Co.,Ltd.,China.Intramedullary nails (type ZQY-01) were purchased from Tianjin Jinxingda Industries Co.,Ltd.,China.METHODS:Thirty Chinchilla rabbits of 4-6 months old were randomly divided into 3 groups (n = 10):diamond-like carbon coated nickel-titanium alloy embracing fixator (group A),uncoated nickel-titanium alloy embracing fixator (group B),and intramedullary fixator (group C).Following anesthesia by injection of 1% sodium pentobarbital (25 mg/kg),transverse fracture models in middle part of the femur were made through a lateral femoral incision and fixed with diamond-like carbon coated nickel-titanium alloy embracing fixator,uncoated nickel-titanium alloy embracing fixator,and intramedullary fixator respectively.MAIN OUTCOME MEASURES:The inorganic substance level,osteocalcin,alkaline phosphatase (ALP) and tumor necrosis factor (TNF) expression in callus surrounding fracture site were detected 4 weeks postoperatively.Ni ion level in muscles surrounding fracture site,live tissue,and brain tissue were also detected.RESULTS:Inorganic substance level and ALP,osteocalcin,and TNF expression were significantly higher in the groups A and B than in group C (P＜0.05).Ni ion level in the liver tissue,brain tissue,and muscles surrounding the fracture were significantly lower in the groups A and C than in group B (P＜0.05).CONCLUSION:Elastic fixation promotes fracture healing.Diamond-like carbon coated nickel-titanium alloy embracing fixator has a better histocompatibility than uncoated group.