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Internal fixator is usually adopted in the treatment of bone fractures. In order to achieve anatomical reduction and effective fixation of fractures, the placement of internal fixators should comply with the biology force line of the bone and adapt to the specific anatomical morphological characteristics of the cortical bone. In order to investigate the distribution characteristics and formation regularity of biology force line and cortical thickness of human bone, three-dimensional model of proximal femur is established by using three-dimensional reconstruction technique in this paper. The normal physiological stress distribution of proximal femur is obtained by finite element analysis under three kinds of behavior conditions: one-legged stance, abduction and adduction. The structural topology optimization method is applied to simulate the cortex of the proximal femur under the combined action of three kinds of behavior conditions, and the anatomic morphological characteristics of the proximal femur are compared. The distribution trend of biology force line of proximal femur and the characteristics of cortex are analyzed. The results show that the biology force lines of bone structure and the morphological characteristics of cortex depend on the load of human activities. The distribution trend of biology force line is related to the direction of trabecular bone and the ridge trend and firmness of cortex when bone is loaded physiologically. The proposed analytical method provides a solution to determine the biology force line of bone and the distribution characteristics of cortex. The conclusions obtained may guide the reasonable placement of internal fixator components of fracture.
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Objective To study the efficacy and complications of total hip arthroplasty (THA) with rivet system for reconstruction of joint capsule and external rotator muscles.Methods Data of 170 patients managed with THA of femoral neck fracture between January 2009 and January 2012 were reviewed retrospectively.Hip fracture was the result of a fall and all were subcapital fractures.The fracture patterns were classified as Garden Ⅳ in 139 patients and Garden Ⅱ in 31 patients according to the degree of displacement.In all,85 patients (37 males and 48 females;age between 61 and 84 years,mean 73 years) underwent joint capsule as well as external rotator muscle reconstruction by rivet system (study group).The remaining 85 patients (36 males and 49 females;age between 64-87 years,mean 74 years) were served as control group.The MOS 36-item short form health survey (SF-36),dislocation rate and complications were evaluated at postoperative follow-up.Results Duration of follow-up was 36 to 60 months (mean,46 months).SF-36 questionnaire scale was (45.95 ±4.27)points in study group and (45.38 ± 4.67) points in control group before operation (P ＞ 0.05),while (83.67 ± 3.93) points in study group and (82.16 ± 3.21) points in control group at postoperative follow-up (P ＜ 0.05).Six patients in control group suffered from early prosthetic dislocation,but none in study control.Perioperative incidence of complications was comparable between the two groups (P ＞0.05).Conclusions Application of rivet system for reconstruction of joint capsule and external rotator muscles in THA of patients with femoral neck fracture can reduce incidence of prosthetic dislocation after operation.The operation is simple and will not increase the rate of perioperative complications.
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10.3969/j.issn.2095-4344.2013.26.001
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Objective To explore the effect of persistent stress on the ultrastructure of cancellous bone in the process of fracture healing.Method A transverse osteotomy on both sides of the femoral tuberositas was performed in 20 adult dogs. One side was fixed with a self-designed tuberositas memofy-pressure connector (TMC) which was made of NiTi shape memory alloy, and the other with compressive steel-wire (SW) cerclage.Five animals in each group were sacrificed at 2, 4, 8, 12 weeks after operation and observed under transmission electron microscope.Results The fracture healing was accelerated in the TMC group.The osteoblasts, chondroblasts and collagen fibers at the fracture sites showed significantly different morphology between the 2 groups at every observation time.Most cells and collagen fibers in the TMC group grew along the same direction as the stress, but those in the SW group grew in disorder.Both the number and functional activity of the osteoblasts and chondroblasts were higher in the TMC group than in the SW group.Conclusion Persistent stress can enhance healing and bone reconstruction following a cancellous bone fracture.
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OBJECTIVE: To compare the clinical effect between Gamma nail and proximal femoral nail (PFN) on the treatment for femoral intertrochanteric fractures in the elderly.METHODS: A total of 131 cases (39 males and 92 females; aged 70?81 years, mean age of 76 years) with femoral intertrochanteric fractures were collected from the Department of Orthopaedics, the Affiliated Changhai Hospital of the Second Military Medical University of Chinese PLA from January 2005 to January 2008. Femoral intertrochanteric fractures were classified based on AO system, including type A1 (n=56) and type A2 (n=75). All cases were randomly divided into Gamma nail group (n=65) and PFN group (n=66). Pre- and post-operative blood loss, blood transfusion volume, operating time, and length of stay were recorded, while the complications were detected following nail implantation. Functional changes of injured limbs were detected after 9 months.RESULTS: At 9 months after following up, there was no significant difference in blood loss, blood transfusion volume, operating time, and length of stay between the two groups before and after implantation (P> 0.05). Furthermore, complications did not occur during or after implantation. Six cases in the PFN group had infection in which of them had diabetes mellitus. There were no complications such as cutting out of femoral head, femoral shaft fractures, breakage of internal device or pushing out phenomenon. All cases got bone union at the final follow-up of nine months and did not get nonunion, delayed union of fractures or shortening of injured extremity.CONCLUSION: Gamma nail and PFN have equal effect on the treatment of femoral intertrochanteric fractures in the elderly.
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Objective To design a new method of posterior wall reconstruction for severely corn-minuted and obsolete fracture of the posterior wall of the aeetabulum. Methods (1) Biomechanical study (from two perspectives: the stability and the stress distribution on the femoral head and the acetabu-lure) : six fresh adult' s pelvis and femur specimens were collected and divided into experimental group ( consisted of the left sides) and control group ( consisted of the right sides). After the defects of the pos-terior wall were made, the defects were anatomically reconstructed with the harvested ilium by acetabular tridimentional memory fixation system (ATMFS) in the experimental group, whereas the acetabular frag-ments were repositioned to the defect sites and fixated by the plates and screws in the control group. Lon-gitudinal and latitudinal displacement, stability of the anatomically reconstructed posterior wall of the ace-tabulum, the fitness of femoral head to the acetabulum after anatomical reconstruction and mean and maxi-mum pressure of anterior wall, posterior and cupuh of the acetabuhm were analysed and compared. (2) Cinical study: The posterior wall defect on the harvested ilium piece was repaired with 3-directional loc-king of ATMFS in 10 male patients (at age of 16-50 years, mean 36.4 years) from January 2000 to June 2002. There were seven patients with flesh acetabular fractures and three with old acetabular fractures.The period from fracture to reconstruction for the patients with old fractures was 58-251 days ( 137.7 days an average). The patients were foUowed up for 5.8 years (average 5.2-7.1 years). Results (1) Biomechanical study showed no statistical difference upon stability and fitness of femoral head to acetabu-lum after reconstruction in experimental and control groups. (2) Clinical study: postoperative X-ray film showed no repeated displacement of the fracture and the patients began out-of-bed movement with weight bearing after 1.6 months (1.2-2.1 months). Heterotopic ossification was found in two patients, with no influence on the joint function. According to the elinieal ranking standard of Modified d' Aubigne and Postal, the excellence rate was 93%. Conclusions Anatomical reconstruction of posterior wall of the acetabulum by using serf ilium with ATMS has good stability and stress distribution of the femoral head and the reconstructed acetabulum in clinical application and offers a new method for treatment of severely comminuted and obsolete fracture of posterior wall of acetabulum.
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BACKGROUND:Swan-like memory connector (SMC) can form a three-dimensional fixation on long bone shaft,ensure the stability of fracture ends,and produce a continuous dynamic compressive stress on the fracture ends.Insulin-like growth factorⅠ (IGF-Ⅰ) regulates bone development and metabolism,cell differentiation,as well as mitosis.During the union process of fracture,IGF-I is effective to promote cellular proliferation,stimulate bone formation and result in chondrogenesis.OBJECTIVE:To quantitatively determine the effect of SMC and conventional dynamic compression plate (DCP) on the concentration of local IGF-Ⅰ in the union duration of rabbit humerus fracture.DESIGN,TIME AND SETTING:A controlled observational animal study was performed in the laboratory,Department of Orthopaedics,Changhai Hospital,the Second Military Medical University of Chinese PLA from January to May in 2007.MATERIALS:SMC was Ni-Ti alloy panel,comprising 50%-53% Ni,was customized by Lanzhou Seemine Shape Memory Alloy Co.,Ltd.The temperature of shape recovery was (33±2) ℃.METHODS:Thirty adult New Zealand rabbits were used in this study and were processed into osteotomy.The experiment sides of rabbit humerus were cut and fixed with SMC at random,serving as SMC group,and the other sides were cut at the same position and fixed with DCP,serving as DCP group.Each five animals were put to death at the time points of 2,3,4,6,8,and 12 weeks after internal fixation.Specimens were obtained from the areas that were 0.5 cm besides the fracture line.MAIN OUTCOME MEASURES:Following internal fixation,the contents of local IGF-Ⅰ in the specimens of different time points (2,3,4,6,8,and 12 weeks) were determined in both SMC group and DCP group.RESULTS:In the SMC-treated group,the contents of IGF-I increased 2 weeks after internal fixation,reached the maximum at 6 weeks,and then decreased at 8-12 weeks.In the DCP-treated group,the contents of IGF-Ⅰincreased 2 weeks after internal fixation,reached the maximum at 8 weeks,and then decreased at 12 weeks.No significant differences were found between the SMC group and the DCP group at 2,8,12 weeks after internal fixation (P ＞ 0.05).Compared with the DCP group,the SMC group had a remarkably higher content of IGF-Ⅰ at the time points of 3,4 and 6 weeks (P ＜ 0.05).The difference was the most statistically significant at 4 weeks.CONCLUSION:Compared with conventional DCP,the SMC could better promote the secretion of IGF-Ⅰin fracture and facilitate the fracture union due to the continuous dynamic compressive stress and three-dimensional fixation.
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Objective To discuss biomechanical mechanism of reconstructed joint capsule ligament stabilizing hip joint by means of three-dimensional finite element analysis.Methods A finite element model of total hip arthroplasty(THA)including ischiofemoral ligament reconstruction was construtted by using finite element analysis software Unigraphics NX 2.0 and SolidWorks 2006 to simulate seated leg crossing and obtain peak resisting moment and range of motion prior to impingement.Results The current form of finite element model was characterized by large deformation multi-body contact,large interfacial sliding and high elasticity and could clearly reflect real anatomy and biomechanical behavior of ischiofemoral ligaments.Compared with model with only metal,model of ischiofemoral ligament reconstruction could reduce the peak polyethylene stress at the impingement site and at the head egress site by typically 17%and 31%respectively,increase peak resisting moment by nearly 57%and provide 2.29-fold stability.Conclusions As a discrete structure within the posterior capsule of the hip joint,the ischiofemoral ligament may be the most important contributor to the mechanical integrity of the posterior stability structure.The joint capsule ligament must be reconstructed in hip arthroplasty.
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0.05).CONCLUSION:Application of DHS,GN and PFN in treatment of intertrochanteric fractures in elderly exhibits no significant difference in efficacy.Gamma nail and PFN can shorten the operation time to reduce the amount of blood loss and postoperative complications.For the stable fracture,all three fixtures can be used,and the DHS is the cheaper;for instable fracture,PFN and GN due to the biomechanical advantages are good choices.
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[Objective]To evaluate the effect of continuous dynamic pressure stress on experimental humeral fracture healing and to explore the role of COX-2 /PGE2 /cAMP signaling pathway in healing promotion induced by the special biomechanical condition.[Method]A total of 120 New Zealand rabbits were divided randomly into three groups: Group A,unilateral humeral fracture was fixed with shape memory connector(SMC),producing axial continuous dynamic pressure stress on fracture gap.Group B,fixed with 4-hole DCP,and Group C,fixed with SMC and gavaged with aqueous suspensions of celecoxib(3 mg/kg/day) after fracture.COX-1 and COX-2 mRNA expressions in fracture gap were determined by real-time RT-PCR at 0,3,7,14,21,28 and 56 days after operation,as well as the contents of PGE2 and cAMP were measured by radioimmunoassay(RIA).Bone-specific alkaline phosphatase(B-ALP) activity was determined by measuring p-nitrophenol and osteocalcin concentrations were measured using enzyme-linked immunosorbent assay(ELISA) for serial collected blood samples.Callus specimens fixed by formalin were used for histopathological examination.[Result]The COX-2 mRNA levels normalized with GAPDH mRNA as well as the contents of PGE2 and cAMP showed significant difference along with the 56-day period and also between the two internal fixations.Histopathological observation and determination of serum biochemical markers of bone formation revealed that the endochondral bone formation and the callus remodelling took place earlier in Group A than in Group B.The accelerated healing process and increased serum values of the bone formation markers induced by continuous dynamic pressure stress of SMC were inhibited by celecoxib,a specific COX-2 inhibitor.[Conclusion]The persistent dynamic longitudinal pressure stress produced by SMC contributed to endochondral bone formation and callus remodelling,resulting in an acceleration of fracture healing,which was considered to be closely correlated with the COX-2/PGE2/cAMP signal transduction pathway.
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[Objective]To explore the cause and treatment of refractory nonunion of patella combined with handicapped joint function.[Method]Retrospective analysis was given to twenty-four patients diagnosed as patellar nonunion that had been admitted to our hospital from Jan 1992 to Jan 2006.The series included fifteen males and nine females with an average age of 36(range 12-71) years.Initial treatment of the original fractures was nonoperative in 3,cerclage with wiring or suture silk in 11,tension band wiring in 6 and modified tension band wiring in 4.All fractures progressed to symptomatic nonunion at an average of 18 months from original injury(range 5-32).All patients were given open reduction and internal fixation,which consisted of Nickel-Titanium patella concentrator(NT-PC) in 9,NT-PC combined with cannulated compression screws in 6,combined with Kirschner wire in 5 and tension band wiring in 4.[Result]Twenty-four patients were followed up with an average of 35(range 6-168) months.The time of bone union averaged 4.2(range 3-6) months.No bone block displacement,loosening or breakage of internal fixation happened.According to Xu Shaoting' s knee function scores,the results were excellent in 14 cases,good in 6 cases,fair in 3 cases and poor in 1 cases.The excellent and good rate was 83.3%.[Conclusion]Operative reconstruction of smooth joint surface,rigid internal fixation and early functional exercise are effective remedies to refractory nonunion of patella combined with handicapped joint function.
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[Objective]To explore the effect of continuous physiological osteogenic stress on the bone healing of canine iliopectineal crest.[Method]Ten adult mixed breed dogs without significant individual difference were made transverse fracture at bilateral iliopectineal crest 1.5 cm above the dome of acetabulum,which were fixed with ATMFS or steel plate respectively. The animals were sacrificed and specimens were procured at 2,4,6,8 and 12 weeks after operation.Samples from the fracture gaps were investigated by histology of HE and Masson staining,image pattern analysis of new bone formation.[Result]The formation of cartilaginous tissue and the maturity of cortical and trabecular bone and collagen fibers of ATMFS sides were earlier than that of steel sides obviously.There was significant difference of the integrated optical density (IOD) of new bone formation between two groups (P
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BACKGROUND: The biomechanical features of Swan-like memory compression connector designed for fractures in hemerus or the parts adjacent to joints are analyzed through biomechanical calculation and experimental measurements.OBJECTIVE: To analyze the relative memory biomechanieal significance through biomechanical measurement of Swan-like memory compression connectorDESIGN: Both biomechanieal calculation and the experimental measurement were conducted for mutual supplementation and confirmation SETTING: The Orthopaedic Department of Changhai Hospital Affiliated to Second Military Medical University of Chinese PLA and the Life Science and Tissue Engineering Institute of Tongji University MATERIALS: This experiment was conducted at the laboratory of Orthopaedic Department of Changhai Hospital Affiliated to Second Military Medical University of Chinese PLA and the Life Science and Tissue Engineering Institute of Tongji University between January 2001 and May 2003.Totally 20 hemerus from adult males who died of craniocerebral injury were chosen.METHODS: Humid hemerus from the adult corpse was chosen to prepare fracture. Encircling the prescale followed by fixation of Swan-like memory compression connector, then we measured the stress produced by compression part and encircle part at fixing the fracture.MAIN OUTCOME MEASURES: ①The stress of holding part; ② the stress of the compression part RESULTS: The stress range of holding part contacting with humerus was 2.42-22.68 N, and the stress in the fracture face, which was produced by compression part, was about 13.6 Mpa.CONCLUSION: The stress of holding part of Swan-like memory compression connector is useful in fixing the fracture parts of humerus, and the stress of compression part is suitable for the healing of fracture.
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BACKGROUND: The most frequently encountered problem that an orthopedic doctor encounters in treating humerus fracture is how to choose the exact direction and amount of load applied on humerus.OBJECTIVE: To explore the clinical significance of establishing a three-dimensional model and finite element analysis in treating humerus fracture and to provide theoretical basis for applying appropriate axial stress.DESIGN: The three dimensional model of humerus was reconstructed, on which compression from different directions was applied.SETTING: Orthopedic department of an affiliated hospital and life science laboratory of a university.MATERIALS: A humerus specimen received CT scanning and the trial was conducted in Shanghai Changhai Hospital and Life Science Laboratory of Tongji University from April 2002 to April 2004.METHODS: The three dimensional model of humerus was established and relevant calculation was completed with ANSYS 5.6 software. The humerus model was divided into 2 729 nodes and 49 041 units based on a three-dimensional ten-node tetrahedron as one unit. The distribution and intensity of axial compression on the fracture gap section were calculated and analyzed in the following conditions, i. e. when the humerus was fixed in X, Y and Z directions and the fracture gap section was 30°, 45°, 90° to Z axis.MAIN OUTCOME MEASURES: The axial pressure on the fracture gap section in different conditions to provide evidence for clinical treatment.RESULTS: The stress applied on the fracture gap was relatively concentrated and was 2 -3 times stronger than that in other areas, and it was generally symmetrically distributed within 10 mm around the fracture gap.CONCLUSION: The required load on humerus fracture should be calculated before a suitable implant is applied to accommodate the movement of humerus without compromising healing of the fracture.
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BACKGROUND: Various therapies can be used to treat humeral fracture,but serious complications like bone disunion, etc. Are often left over. New biomechanical analytical methods are tried to be applied to provide new approaches for the functional prognosis in humeral fracture and bone disunion.OBJECTIVE: To construct humeral three-dimension model to explore its correlated biomechanical significance.DESIGN: To construct humeral three-dimension finite element model. SETTING: Department of orthopedics of a military medical university-affiliated hospital and institute for biological science and bioengineering of a university.PARTICIPANTS: The study was conducted in Shanghai Changhai Hospital and the Laboratory of Biological Science of Shanghai Tongji University. One piece of typical adult wet humerus sample was selected.INTERVENTIONS: Cross section image of each humeral layer was obtained from the selected wet humerus sample by CT scanning, and humeral three-dimensional model was constructed by large finite element analytic software ANSYS5.6.MAIN OUTCOME MEASURES: ① Biomechanical features of the constructed humeral three-dimension mode; ② Differences from clinical reality and key similarities.RESULTS: The constructed humeral three-dimensional model vividly reflected the true humeral anatomic morphology and biomechanical behavior. Its precision was judged by the comparison with CT image.CONCLUSION: The construction of humeral three-dimension finite element model provides a precise model for the researches of normal humeral mechanical behavior and the basic mechanics of internal fixation after fracture.
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BACKGROUND: The biomechanical features of arch-dental shape memory connector designed for fractures in pelvis or the parts adjacent to joints are analyzed through biomechanical calculation and experimental measurements.OBJECTIVE: To explore the relationship between the changes in shape of arch-dental shape memory connector and the load on it.DESIGN: Both biomechanical calculation and the experimental measurement were conducted for mutual supplementation and confirmation.SETTING: The Orthopedic Department of Changhai Hospital Affiliated to the Second Military Medical University of Chinese PLA and the Life Science and Bioengineering College of Tongji University.MATERIALS:The trial was conducted from at Shanghai Changhai Hospital and Life Science Laboratory of Tongji University from April 2002 to April 2004. The subjects were arch-dental shape memory connectors.METHODS: We calculated the stress in and around the fracture face produced by arch-dental shape memory connector according to Moire principle and we also measured the changes in the shape of arch-dental shape memory connector. The relationship between load and the changes in the shape of arch-dental shape memory connector was explored.MAIN OUTCOME MEASURES: To explore whether the results of biomechanical calculation and those of the experimental measurement are consistent.RESULTS: Biomechanical calculation found that the relationship between the load (P) and the displacement(δ) in arch-dental shape memory connector was P = 13.69δ. The experimental measurement found that the load on the connector and the displacement were in a linear relationship.CONCLUSION: The relationship between the load and the displacement in arch-dental shape memory connector was linear within its elastic range and the biomechanical calculation results were consistent with the results of the experimental measurement.
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BACKGROUND: During the therapy of the fracture of humerus, the main problem is the loading direction and power of the stress.OBJECTIVE: To analyze the choice of the different loading manners using Swain Memory Compression Bone Reduction Apparatus so as to provide the clinical evidence for the set position of the internal fixation apparatus, the loading direction and power during the therapy of the fracture of humerus.DESIGN: To construct the three-dimensional finite element model of the fracture of humerus with different loading manners.SETTING: Department of Orthopaedics of Changhai Hospital of Second Military Medical University of Chinese PLA; College of Life Sciences and Bioengineering of Tongji University,MATERIALS: The study was conducted during the period from January 2001 to May 2003 in the Orthopedic Laboratory of Changhai Hospital of Second Military Medical University of Chinese PLA and the laboratory of Life Science and Bioengineering Academy of Tongji University. The samples of the humerus taken from the wet adult cadavers, and the Swain Memory Compression Bone Reduction Apparatuses of the corresponding size were prepared.METHODS: The CT scanning was done on the samples of the wet humerus to obtain the cross section image of each layer of the humerus.The images were analyzed by a large-scale finite element analysis software ANSYSS.6 to construct the three-dimensional model of the humerus, Swain Memory Bone Reduction Apparatus and the fixed humerus using Swain Memory Bone Reduction Apparatus.MAIN OUTCOME MEASURES: To get the reference values for the clinical therapy through the comparison of the power endurance with different loading manners.RESULTS: The three-dimensional model of the fixed humerus using Swain Memory Bone Reduction Apparatus reflects the real anatomical configuration and the biomechanics behavior; meanwhile the status of the power endurance of humerus with different loading manners is also obtained.CONCLUSION: The three-dimensional model of the fixed humerus using Swain Memory Bone Reduction Apparatus may provide an accurate model for the basic study of the biomechanics behavior of the normal and fixed humerus after the fracture.
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Objective To discuss the therapy for acetabular comminuted fractur e combined with compressive defects. Methods From July 1997 to February 2005, 43 cases of comminuted acetabular fracture combined with compressive defect were t reated. 25 cases were obsolete, 16 fresh, and 2 malformed (90 days after injury) . 34 cases were complicated fractures with defects, and 9 simple fractures with defects. The defect volumes ranged from 3 to 9 cm3, averaging 4.5 cm3. They were treated with ATMFS (acetabular tridimensional memory fixation system) to fixate the comminuted bone fragments tridimensionally. The modified acetabular approac h, reduction of acetabular comminuted articular face, anatomical reconstruction of posterior wall of acetabulum with autogenous ilium, autogenous and artificial bone implantation and bone wax isolation were used. The follow-ups lasted from 5 to 86 months, averaging 15.7 months. Results 31 cases achieved anatomical red uction by filling up the compressive defects. 12 cases were treated by anatomica l reconstruction of posterior wall. On average, 5.3 months after operation, the injured hip joint was as good as the healthy one in 40 cases. Ischemia necrosis of femoral head occurred in 1 case, and 2 cases experienced heterotopic ossifica tion with ischemia necrosis of femoral head which led to osseous fusion of hip j oint. Conclusion The new methods for treatment of acetabular fractures with comp ressive defects elevate the reduction rate of acetabulum and femoral head, and a re effective for the functional recovery of hip joint.
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Objective To investigate the effects of swan shaped memory connector(SMC) on the bone mineral density and mechanical properties of humeral fracture in rabbits in order to disclose the mechanism of SMC stimulating fracture healing. Methods Shafts of both humeri of 40 rabbits were osteotomized. One side was selected to fix with SMC, but the contralateral side was fixed with the 4 hole dynamic compression plate (DCP). Eight rabbits were sacrificed and the humeri were harvested respectively at 2, 4, 8, 12 and 16 weeks after operation. The bone mineral density(BMD) was examined by dual energy radiographic absorptiometry(DRA). The mechanical properties were assessed by mechanical traction test. Results From 4 to 16 weeks after operation, the BMD in SMC group was significantly higher than that in DCP group ( P
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Objective:To analyze the causes of early dislocation after total hip replacement and explore its preventions and treatments. Methods:From July 1997 to October 2002, there were 12 cases of dislocation after total hip replacement. The strength of their hip abductor was tested and the X-ray films were measured. If closed reduction failed, capsular repairing was used. Results:There were 3 cases of malposition, 5 cases of abnormal soft-tissue tension, 3 cases of malposition and abnormal soft-tissue tension and 1 case of over motion. Close reduction was succeeded in 5 cases, 7 cases failed to close reduction, and were treated successfully by repairing the hip capsule and readjusted the prostheses when necessary. Conclusion:Abnormal soft-tissue tension has become the main causes of dislocation after total hip replacement. Those cases in which closed reduction has failed can be treated by repairing the hip capsule.