Poly(D,L-lactide) coating is capable of enhancing osseous integration of Schanz screws in the absence of infection

Pin loosening is a major complication in external fixation. Biological and mechanical conditions play an important role in the maintenance and enhancement of the implant-bone interface in fracture fixation. It is thought that biodegradable coatings may be capable of preventing pin track infection and pin loosening. The goal of this study was therefore to analyze the influence of a biodegradeable coating on the osseous integration of Schanz' screws during fracture treatment. Standardized osteotomies (3-mm fracture gap) of the right tibiae were performed on 16 sheep and stabilized by an AO mono-lateral external fixator. Additional, mechanically less loaded Schanz' screws were also mounted. All screws were randomly coated with biodegradable poly(D,L-lactide). The sheep were sacrificed after 9 weeks. All screws were removed and rolled on blood agar plates for microbiological analysis. Histological sections of the pin tracks were histochemically and morphometrically analyzed. Clinically, no signs of severe infection were visible. Microbiological analysis revealed 14.8% colonization by Staphylococcus aureus in the coated and 29% in the uncoated screws. Histomorphometry of the bone surrounding the Schanz' screws revealed that significantly more osseous integration had occurred on poly(D,L-lactide)-coated screws in the absence of bacterial colonization. Significantly more bone remodeling and a higher osteoclastic activity was seen near the screw-bone interface in the uncoated screw group. Up to a threefold increase in new bone formation and more severe remodeling was observed around the screw entry compared to the pin exit in all groups. Loaded screws showed significantly more callus formation around the exit sites than their less loaded counterparts. In the present study, poly(D,L-lactide) coating of Schanz' screws was found to enhance osseous integration in the absence of bacterial colonization in sheep by causing less cortical remodeling and less osteoclastic activity in the cortices compared to uncoated screws. Additionally, the coating appeared to reduce the instances of pin track infections. Mechanical loading showed an adverse effect on bone formation and remodeling. It has been shown that both biological and mechanical factors play an important role in the maintenance of osseous integrity of the pin-bone interface. Poly(D,L-lactide) coating of Schanz' screws does not prevent osseous destruction and severe bacterial colonization along the pin tracts, but can improve osseous integration of Schanz' screws in the absence of infection.     

Hydroxyapatite-coated orthopaedic screws as infection resistant materials: in vitro study

The authors evaluated in vitro the adherence of a Staphylococcus epidermidis strain to hydroxyapatite-coated stainless-steel screws-used in orthopaedic surgery for external fracture fixation-in comparison with the adherence to uncoated screws. Evaluations were also performed on analogous groups of screws immersed for 72 and 168 h in a solution at 37 degrees C, in order to simulate the interstitial fluid in a simplified way. Adherence values on coated prostheses resulted significantly lower compared with those observed on metal prostheses, both in basal conditions and after immersion in saline solution. Moreover, both on coated and on uncoated screws a significant reduction in bacterial adherence was noted related to the duration of the prosthesis permanence in saline solution.     

Biomechanical and histomorphometric study on the bone-screw interface of bioactive ceramic-coated titanium screws

The purpose of this study was to compare the osseointegration of 4 different kinds of bioactive ceramic-coated screws with uncoated screws by biomechanical and histomorphometric analysis. Calcium pyrophosphate (CPP), apatite-wollastonite 1:3 glass ceramic (W3G), apatite-wollastonite 1:1 glass ceramic (WAG) and bioactive CaO-SiO2-B2O3 glass ceramic (CSG) coatings were prepared and coated by the dipping method. Coated and uncoated titanium screws were inserted into the tibia of 18 adult mongrel male dogs for 2, 4, and 8 weeks. The insertion torques, radiographs, undecalcified histology, histomorphometric analysis, and extraction torques were evaluated. No difference of insertion torque was found among the five screw types. At 2 and 4 weeks after implantation, the extraction torque of ceramic-coated screws was significantly higher than that of uncoated screws (p < or = 0.0001). At 8 weeks, the extraction torques of CPP-, W3G-, and WAG-coated screws were significantly higher than those of CSG-coated and uncoated screws (p<0.0001). At 2, 4, and 8 weeks, the extraction torques of 4 different ceramic-coated screws were significantly higher than the corresponding insertion torque. Strong fixation was observed even at 2 weeks in the CPP-, W3G- and WAG-coated screws. The bone-screw contacts of the 4 different coated screws at 2 and 4 weeks were statistically higher than that of the uncoated screws, and the bone-screw contacts of the CPP-, W3G- and WAG-coated screws at 8 weeks were also statistically higher than that of the uncoated screws. The fixation strength was increased by the presence of osteoconductive coating materials, such as CPP, W3G, and WAG, which enabled to achieve higher fixation strength even as early as 2-8 weeks after the insertion.     

Adherence of staphylococci to intravascular catheters

Adherence of seven strains of Staphylococcus epidermidis and three strains of S. aureus to three types of intravascular catheters was assessed by ATP bioluminescence, by culture after ultrasonication and by scanning electronmicroscopy. The catheter materials studied were silicone elastomer, thermoplastic polyurethane and polyurethane coated with Hydromer, a coating which absorbs water and provides a hydrophilic sheath around the catheter. The adherence assays were performed in phosphate-buffered saline on a rotary shaker at 37 degrees C, with the catheters precoated with serum and uncoated, and the results were correlated with bacterial hydrophobicity. There was wide strain-to-strain variation in bacterial adherence; S. aureus and slime-producing S. epidermidis strains adhered better than did non-slime-producing strains. Overall, there was less bacterial adherence to Hydromer-coated catheters than to polyurethane and silicone catheters but it was unrelated to bacterial hydrophobicity. Serum coating of catheters resulted in marked reduction of bacterial adherence.     

Silver coated materials for external fixation devices: in vitro biocompatibility and genotoxicity.

The most significant complication in external fixation is pin tract infection causally related to the highly adaptive ability of bacteria to colonise the surfaces of "inert" biomaterials or of adjacent damaged tissue cells. The hypothesis that coating a pin with a silver-containing compound will decrease bacterial colonisation and/or pin tract infection has been confirmed in other studies in vitro and in vivo experiments. In this work, biocompatibility of silver-coated orthopaedic external fixation pins was compared with stainless steel controls in an in vitro study. Human peripheral blood lymphocytes were used to assess the possible genotoxic effect of silver, studying the frequency of sister-chromatid exchanges and micronuclei while fibroblasts (NIH 3T3) and osteoblast-like cells were used for cytotoxicity and cytocompatibility studies. These studies have shown that silver is neither genotoxic nor cytotoxic as compared to stainless steel, a material in wide use as a metal implant. At 4 days cells cultured on the silver-coated material evidenced good cell spreading and a higher cell count with respect to the uncoated material. It appears that the addition of silver onto implantable medical devices could be beneficial when specific biological properties, such as antibacterial behaviour, are required. Based on these and the previous bacterial studies it seems like the toxicity towards bacteria was quite a bit greater than that towards the human cells.     

An investigation of the effects of hydroxyapatite coatings on the fixation strength of cortical screws

Hydroxyapatite (HA) are commonly applied to orthopaedic implants for acceleration of osteointegration and so overcoming the loosening problems such as in cortical screws. Electrophoretic deposition (EPD) of hydroxyapatite was applied for coating of cortical screws in this work. The effects of hydroxyapatite-coated and uncoated cortical screws on insertion and extraction torque were investigated through in vivo experiments. Three groups of screws were undertaken: first group with no coating, second group coated with HA and the third group coated with HA+interlayer, a synthetic calcium silicate compound. Five sheep were operated, and 60 cortical (20 x 3) screws from those of groups were implanted in cortical femurs to observe the effect of HA and interlayer on screws. Results show that as an alternative to plasma spray coating method, the EPD process enables to produce a quick, easy, cheap and uniform adjustable coating layer. Also from biomechanical and SEM examinations, HA coating by EPD method of cortical screws resulted in extremely improved fixation with reduced risk of loosening problem.     

Measurement of insertion torque of tapered external fixation pins: A comparison between two experimental models.

The aim of this study was to compare an in vitro versus an ex vivo experimental model to test the insertion torque of two different types of external fixation pins. A torque measuring machine was developed in order to perform accurate measurements. Forty tapered pins made of stainless steel were utilized. Half of the pins were plasma-spray coated with hydroxyapatite (HA) and the other half remained uncoated. For the in vitro model 20 cylinders were used that were made of synthetic polymer according to ASTM standards. For the ex vivo model 10 fresh femora harvested from adult sheep were used. All the pins were implanted after predrilling, and insertion torque was measured. Statistical analysis of the in vitro versus the ex vivo model showed significant differences in both coated (p < 0. 0005) and uncoated (p = 0.002) external fixation pins. These results may be due to the surface roughness that caused significant friction between the HA coating and the polyvinylchloride in the in vitro model. The significant difference between the in vitro and ex vivo results lead us to state that the in vitro model does not realistically simulate the behavior of external fixation pins implanted in bone.     

Bisphosphonate coating on titanium screws increases mechanical fixation in rat tibia after two weeks

Recently published data indicate that immobilized N-bisphosphonate enhances the pullout force and energy uptake of implanted stainless steel screws at 2 weeks in rat tibia. This study compares titanium screws with and without a bisphosphonate coating in the same animal model. The screws were first coated with an approximately 100-nm thick crosslinked fibrinogen film. Pamidronate was subsequently immobilized into this film via EDC/NHS-activated carboxyl groups within the fibrinogen matrix, and finally another N-bisphosphonate, ibandronate, was physically adsorbed. The release kinetics of immobilized (14)C-alendronate was measured in buffer up to 724 h and showed a 60% release within 8 h. Mechanical tests demonstrated a 32% (p = 0.04) and 48% (p = 0.02) larger pullout force and energy until failure after 2 weeks of implantation, compared to uncoated titanium screws. A control study with physically adsorbed pamidronate showed no effect on mechanical fixation, probably due to a too small adsorbed amount. We conclude that the fixation of titanium implants in bone can be improved by fibrinogen matrix-bound bisphosphonates.     

Simple coating with fibronectin fragment enhances stainless steel screw osseointegration in healthy and osteoporotic rats

Metal implants are widely used to provide structural support and stability in current surgical treatments for bone fractures, spinal fusions, and joint arthroplasties as well as craniofacial and dental applications. Early implant-bone mechanical fixation is an important requirement for the successful performance of such implants. However, adequate osseointegration has been difficult to achieve especially in challenging disease states like osteoporosis due to reduced bone mass and strength. Here, we present a simple coating strategy based on passive adsorption of FN7-10, a recombinant fragment of human fibronectin encompassing the major cell adhesive, integrin-binding site, onto 316-grade stainless steel (SS). FN7-10 coating on SS surfaces promoted α5β1 integrin-dependent adhesion and osteogenic differentiation of human mesenchymal stem cells. FN7-10-coated SS screws increased bone-implant mechanical fixation compared to uncoated screws by 30% and 45% at 1 and 3 months, respectively, in healthy rats. Importantly, FN7-10 coating significantly enhanced bone-screw fixation by 57% and 32% at 1 and 3 months, respectively, and bone-implant ingrowth by 30% at 3 months compared to uncoated screws in osteoporotic rats. These coatings are easy to apply intra-operatively, even to implants with complex geometries and structures, facilitating the potential for rapid translation to clinical settings.     

Modification of central venous catheter polymers to prevent in vitro microbial colonisation

The efficacy of an antimicrobial catheter for the prevention of bacterial colonisation was investigated. The catheter was hydrophilic coated (Hydrocath) and impregnated with the quaternary ammonium antimicrobial agent, benzalkonium chloride (BZC). Microbial colonisation of this central venous catheter was compared to that of polyurethane catheters with or without a hydrophilic coating. Adherence of five strains ofStaphylococcus epidermidis to the three catheter types was determined with a microbial colonisation model. Adherence of three strains ofStaphylococcus epidermidis to Hydrocath catheters was significantly reduced in comparison to polyurethane catheters (p<0.01). BZC-impregnated Hydrocath catheters prevented bacterial colonisation of both the internal and external catheter surfaces (p<0.01). These results were confirmed by scanning electron microscopy. The findings demonstrate that hydrophilic-coated Hydrocath catheters can inhibit bacterial adherence in vitro. Bacterial colonisation was further restricted by the addition of BZC to these coated catheters.     

Surface immobilized bisphosphonate improves stainless-steel screw fixation in rats

An increase in the mechanical fixation in bone of metallic biomaterials is considered advantageous in joint replacement and fracture surgery. Different approaches to improve fixation may be e.g. surface roughening, Ca-mineral coating or surface immobilization of growth factors or drugs. In the present work, bisphosphonate, a class of drugs that inhibit bone resorption, was immobilized onto stainless-steel screws.The screws were first roughened and coated with immobilized and cross-linked fibrinogen. Subsequently, an N-bisphosphonate, pamidronate, was immobilized onto fibrinogen, and another N-bisphosphonate, ibandronate, adsorbed on top of this. The so coated screws were inserted into the tibiae of eight male Sprague-Dawley rats. Another eight rats received screws prepared in the same way, but without the bisphosphonate coating. Pullout strength tests were performed after 2 weeks of implantation.The results showed a 28% (p=0.0009) higher pullout force and 90% increased pullout energy for the bisphosphonate coated screws, and support the idea that surface immobilized bisphosphonates can be used to improve biomaterials fixation in bone.     

A randomised RSA study of Peri-Apatite HA coating of a total knee prosthesis

BACKGROUND: In total knee replacement, sound early fixation of the prosthesis is crucial for achieving a good long-term result and for minimising the risk of loosening. Various types of prosthetic material, different surface textures and shapes and the incorporation of screws or pegs have been used to achieve good fixation, particularly in the uncemented knee. Hydroxyapatite (HA) coating of prosthetic joint components is another technique used to enhance early stability and so to improve the longevity of the prosthesis-bone fixation. HA ceramic coatings are mostly plasma sprayed onto the fixation surface of the implant. Plasma spraying is largely a 'line of sight' technique and as such there are difficulties involved when covering three-dimensional planes, such as porous beaded fixation surfaces typically found on several knee prostheses. The objective of this study was to assess the clinical performance of the solution-deposited HA coating, Peri-Apatite , with regard to its ability to stimulate an endurable and stable implant fixation. PATIENTS AND METHODS: We randomised 60 patients into two groups; one group received the porous coated prosthesis with solution-deposited HA, and the other group received a prosthesis without HA. Radiostereometric examination was used as the primary tool for measuring migration in the prosthetic components. RESULTS: There was a lower incidence of early subsidence in the Peri-Apatite group. At 24 months there were no differences in clinical scorings or maximal total point motion. CONCLUSION: Addition of solution-deposited HA coating appears to provide better early stable fixation in a porous coated knee prosthesis.     

In Vitro Evaluation of the Antibacterial Activity of Three Different Central Venous Catheters Against Gram-Positive Bacteria

The aim of this study was to evaluate the activity of three different catheters against Staphylococcus aureus ATCC 29213 and the slime-producing Staphylococcus epidermidis ATCC 35984 (RP62A). Three central venous catheters were evaluated: one impregnated with silver sulfadiazine–chlorhexidine, one to which minocycline/rifampin is bonded and a novel one into which silver, platinum and carbon are incorporated. A nonantiseptic catheter was used as the control catheter. One-centimeter trisected pieces of catheter were immersed in phosphate-buffered saline (0.01 mol/l) with 0.25% dextrose and incubated. On days 1, 3, 7, 14 and 21, a 1 ml standardized inoculum was added for 30 min and then replaced with phosphate-buffered saline with 0.25% dextrose. One-third of the samples were immediately sonicated and plated to determine bacterial adherence. The remaining segments were incubated for 4 and 24 h to determine the persistence of bacterial adherence. Bacterial adherence to the catheters impregnated with silver sulfadiazine-chlorhexidine was reduced 91–98% for the first 7 days. Adherence of Staphylococcus aureus to catheters into which silver, platinum and carbon are incorporated was reduced 70% on day 1 and 35% on day 3. Adherence to minocycline/rifampin-bonded catheters was quite variable. There was an 85.6–99.8% reduction in the persistence of bacterial adherence to the three catheters compared to controls. Bacteriostatic and bactericidal studies indicated that the effluents from the catheters impregnated with silver sulfadiazine-chlorhexidine were bactericidal, while effluents from the minocycline/rifampin-bonded catheters were bacteriostatic. The antibacterial activity of the effluents from catheters impregnated with silver sulfadiazine-chlorhexidine dissipated by day 7, while the activity of effluents from the minocycline/rifampin-bonded catheters continued to show activity at day 21. No measurable antibacterial activity was detected in the effluents of the catheters into which silver, platinum and carbon are incorporated. These data suggest that catheters coated with antibiotic/antibacterial agents and the novel catheters that incorporate antiseptic agents have different activities against initial bacterial adherence. All of them, however, effectively prevent bacterial colonization by gram-positive bacteria. Electronic Publication     

Tibial implants: biomechanical and histomorphometric studies of hydroxyapatite-coated and uncoated stainless steel and titanium screws in long-term ovariectomized sheep.

This study was designed to evaluate osteointegration of HA-coated and uncoated titanium and stainless steel screws in the cortical bone of long-term (24 months) ovariectomized sheep (OVX group), in comparison with Sham-aged sheep (control group). The screws were tested biomechanically (extraction torque) and histomorphometrically (affinity index: Al) 12 weeks after their implantation in tibial diaphyses. Tibial cortical bone parameters showed significant differences between the groups, showing a reduction of the selected parameters in the OVX group. ANOVA showed significant effects for both material and ovariectomy factors on obtained extraction torque (material: F=159.26, p < 0.0005; ovariectomy: F=20.04, p < 0.0005) and Al data (material: F=8.04, p < 0.001; ovariectomy: F=7, 17, p < 0.05). In both groups the extraction torque for coated screws of both materials was significantly higher than for uncoated screws, and uncoated titanium had a better extraction torque than uncoated stainless steel. In the OVX group, the HA-coated stainless steel and titanium Al data were significantly higher than uncoated Al data. In conclusion, the biomechanical and histomorphological results obtained suggest employing HA-coated screws in the presence of osteopenic cortical bone.     

Long-term active antimicrobial coatings for surgical sutures based on silver nanoparticles and hyperbranched polylysine

The goal of this study was to develop a long-term active antimicrobial coating for surgical sutures. To this end, two water-insoluble polymeric nanocontainers based on hyperbranched polylysine (HPL), hydrophobically modified by either using glycidyl hexadecyl ether, or a mixture of stearoyl/palmitoyl chloride, were synthesized. Highly stabilized silver nanoparticles (AgNPs, 2–5?nm in size) were generated by dissolving silver nitrate in the modified HPL solutions in toluene followed by reduction with L-ascorbic acid. Poly(glycolic acid)-based surgical sutures were dip-coated with the two different polymeric silver nanocomposites. The coated sutures showed high efficacies of more than 99.5% reduction of adhesion of living Staphylococcus aureus cells onto the surface compared to the uncoated specimen. Silver release experiments were performed on the HPL-AgNP modified sutures by washing them in phosphate buffered saline for a period of 30?days. These coatings showed a constant release of silver ions over more than 30?days. After this period of washing, the sutures retained their high efficacies against bacterial adhesion. Cytotoxicity tests using L929 mouse fibroblast cells showed that the materials are basically non-cytotoxic.     

Improved neo-endothelialization of small diameter ePTFE grafts with titanium coating

BACKGROUND: Patency of small synthetic bypass grafts is inferior compared to autologous grafts for revascularization procedures. Titanium coating of foreign surfaces has shown to decrease thrombogenicity, enhance biocompatibility and promote adhesion of endothelial cells. The aim of this study was to test the effect of titanium coating of small diameter ePTFE grafts on short term patency, neo-endothelialization and neointimal proliferation. METHODS: Bilateral carotid graft interposition was performed in 5 pigs with uncoated (n=5) and titanium-coated (n=5) ePTFE grafts (internal diameter=4 mm, length=5 cm), thus each pig served as its own control. At the end of the study (30 +/- 3 days), patency and stenosis severity was assessed by carotid angiography. Animals were sacrificed and grafts were excised for histology and scanning electron microscopy. Morphometry of histologic sections was carried out to determine neointimal proliferation and percentage of neo-endothelial coverage. RESULTS: Patency rate was 80% for uncoated and titanium-coated grafts. Quantitative angiography did not show any significant difference in lumen size between two groups. Morphometry revealed a significantly higher cellular coverage with CD31 positive endothelial cells for titanium-coated (84 +/- 19%) than uncoated grafts (48 +/- 26%, p<0.001). There was a non significant trend (p=0.112) towards increased neointimal proliferation in titanium-coated (94 +/- 61 micron2/micron) compared to uncoated grafts (60 +/- 57 micron2/micron). CONCLUSIONS: Patency rate in uncoated and titanium-coated ePTFE grafts is similar at one month. However, titanium coated grafts show a significant improvement in neo-endothelialization compared to uncoated grafts.     

Biological assessment of the bone-screw interface after insertion of uncoated and hydroxyapatite-coated pedicular screws in the osteopenic sheep

The sheep seems to be a promising model of osteoporosis and biomaterial osteointegration in osteopenic bone. The long-term ovariectomized sheep model was used for the biological investigation of bone healing around uncoated and hydroxyapatite (HA)-coated pedicle screws in osteopenic bone. Four sheep were ovariectomized and four sheep were sham-operated. Twenty-four months after surgery, the animals were implanted with uncoated and HA-coated stainless steel screws in the lumbar vertebral pedicles. Four months later, bone-to-implant contact, bone ingrowth, and bone hardness were measured around screws. Uncoated stainless steel presented significantly (p < 0.0005) lower bone-to-implant contact in healthy and osteopenic bone compared with HA-coated stainless steel. HA significantly improved bone ingrowth in healthy bone (p < 0.05) compared with uncoated stainless steel. Osteopenia significantly (p < 0.05) reduced the area of bone ingrowth around the screw threads for both types of implants. In the inner thread area, bone microhardness significantly increased (p < 0.05) in HA-coated surface versus uncoated for healthy and osteopenic bone. HA coating significantly enhances bone-to-implant contact also in osteopenic bone in comparison with uncoated stainless steel surfaces. Bone ingrowth and mineralization are ameliorated by the osteoconductive HA coating. However, osteopenia seems to greatly influence bone ingrowth processes around the implanted screws regardless of the characteristics of the material surface.     

Biological efficacy of electroless-deposited silver on plasma activated polyurethane

Silver coating of catheters has been shown to have inhibitory effects on bacterial growth and adhesion to catheter surfaces. In this study, plasma-modification was used to enhance the adhesion of an electroless silver coating on polyurethane. Both the antibacterial and antiadhesive properties of these coatings were investigated. Bacterial growth was inhibited in cultures exposed to silver-treated polyurethane compared to unmodified polyurethane. Higher growth inhibition was observed for polyurethane surfaces with lower silver coverage. Bacterial adhesion was completely inhibited on all silver-coated surfaces.     

Investigation of recombinant human elastin polypeptides as non-thrombogenic coatings

We investigated the use of a recombinant human elastin polypeptide as a coating on synthetic materials with a view to determining if these polypeptides could improve the blood compatibility of cardiovascular devices such as vascular conduits and arterial/venous catheters. Platelet adhesion and activation were studied in vitro using three commercially available synthetic materials: polyethylene terephthalate (Mylar), a poly(tetrafluoroethylene/ethylene) copolymer (Tefzel) and a polycarbonate polyurethane (Corethane). Coated with adsorbed polypeptide, all three synthetic materials demonstrated reduced platelet activation and adhesion in platelet rich plasma in vitro. Compared to non-coated controls, there was a significant decrease (p=0.05) in both platelet microparticle release and P-selectin expression for the polypeptide-coated surfaces. Scanning electron microscopy indicated fewer adhering platelets on coated surfaces compared to non-coated controls. In vivo, in a rabbit model, evaluations of polyurethane catheters coated with the polypeptide showed a marked increase in catheter patency and a significant decrease in fibrin accretion and embolism when compared to uncoated controls. This polypeptide shows a strong potential for use as a non-thrombogenic coating for small diameter vascular grafts. In addition, the results of this study indicate that the elastin polypeptide would be a valuable component of a tissue engineered vascular conduit.     

不同内固定方法对胫腓连结固定效果的实验研究

目的　探讨胫腓连结的活动度及不同内固定方法对胫腓连结效果的影响。 方法　新鲜冷藏的成人小腿标本8侧,常温下解冻,自踝关节离断,剔除皮肤、肌肉等软组织,保留胫腓关节、胫腓连结和骨间膜的完整,置于SWD10万能材料实验机上,测量胫腓连结的正常活动度,完全切断胫腓连结,分别用普通螺丝钉、拉力螺丝钉和“U”形钉固定,测量固定后的活动度。 结果　胫腓连结正常的生理活动度为前→后(1.83±0.38) mm、后→前(1.89±0.38) mm、外→内 (1.42±0.34) mm、内→外(1.36±0.65) mm。胫腓连结用普通螺丝钉和拉力螺钉固定后,外踝的活动明显受限,虽然拉力螺钉固定更牢,但二者相差不显著,与正常比较相差非常显著;用“U”形钉固定后,活动度与正常比较相差不显著。 结论　胫腓连结是一个具有一定活动度的弹性结构,用螺丝钉固定后活动度明显变小,使用胫腓连结钩或“U”形钉进行弹性固定可保留胫腓连结的生理活动。