BACKGROUND:Studies demonstrated that,the probability of middle and distal end of femur bone fatigue or fracture reaches maximum when the moving loads increase or under an impact load.OBJECTIVE:To analyze the stress-strain distribution,principle stress vectors and displacements of femur during gait.METHODS:The contour curves of femur and muscles attached to femur were extracted slice by slice based on the serial CT data from a healthy male volunteer,which were used to build musculoskeletal system models.And the straight-line muscle models of the lower extremities were constructed to evaluate muscles forces and joints forces by using a multi-objective optimization method based on gait analysis.The finite element models of femur during gait were built by taking muscle forces and joint forces as boundary conditions in ANSYS 10.0 to obtain the stress-strain distribution and displacements.RESULTS AND CONCLUSION:The maximal displacement occurred on the femur head,and the maximal stress occurred in the middle and distal end of femur during the whole gait.There exists bigger tensile stress in the location of the femur neck and middle and distal end of corpus ossis femoris.The result validates the fact that femur fracture often happens at the middle and below of femur stem from the viewpoint of biomechanics.

Objective To analyze the practical experiences of design and its clinical application of custom-made tumor prostheses of knee. Methods A retrospective study of 41 cases of distal femur or proximal tibia tumors treated surgically from June 1999 to October 2002, was carried out. In the study, there were 29 males and 12 females aging from 11 to 69 years with an average of 35.0 years. The location of tumors were at distal femur in 23 cases and 9 cases at proximal tibia, of which 15 were osteosarcoma, 13 giant cell tumor, 3 chondrosarcoma, 5 solitary metastatic bone tumor, and 1 each of fibrosarcoma, malignant fibrohistocytoma, Ewings sarcoma, small round cell sarcoma and syndesmofibroma. The custom-made semi-constrained knee prosthesis with femoral or tibial component was implanted after extra-capsular resection of the tumor bone segment. A special femoral component with elongated construction was used in an 11-year old case for further femur lengthening. Resection of femoral artery involved by tumor and reparation by great saphenous vein was performed in one case. Results The operations of the 41 cases were all smoothly performed. 33 cases were followed up from 8 to 37 months with an average of 20.2 months. The daily life ability was recovered in 3 months after the operation. Among them, no loosening or failure of the prostheses was found, and local recurrence was found in 2 cases and distant metastasis in 3 cases. The design of knee prosthesis could provide some proper internal/external rotation and adduction/abduction movements accompanying with the flexion and extension of the knee joint without affecting the stability of the joint. For the case of proximal tibia tumor, a special design and surgical technique was developed to provide the reconstruction of patellar ligament insertion with rather good results; and the recovery of knee extension and stability were satisfied. Conclusion The custom-made semi-constrained tumor prosthesis of knee could be used as an effective method for the limb-savage management either the distal femur or proximal tibia tumor cases.

BACKGROUND:Prosthesis selection for total hip replacement is determined by geometrical matching with femoral medullary cavity of patients and the optimal biodynamics.It is of great significance for elevating outcomes of total hip replacement.OBJECTIVE:To evaluate the biomechanics of four groups of femoral stem prostheses matched with a femar and to get a stem whose mechanics distribution is similar to the normal femur.DESIGN:Controlled observation.SETTING:Department of Orthopaedics of Oriental Hospital Affiliated to Tongji University,Department of Orthopaedics of Changhai Hospital of Second Military Medical University of Chinese PLA,and Department of Mechanical and Power Engineering of Shanghai Jiao Tong University.MATERIALS:Experiments were performed at the Laboratory of Life Quality and Machinery Engineering of Department of Mechanical and Power Engineering of Shanghai Jiao Tong University from December 2004 to October 2005.A male volunteer aged 40 years with the normal proximal ferout(175 cm height and 78 kg weight),free from hip disease,were selected.X-ray image of the eutopic femar was shot and wrote into memory in the format of DICOM.The volunteer signed an infonned consent.The experiment was approved by Hospital Ethical Committee.No.Ⅰ prosthesis,Zimmer versys Fiber Metal Taperl 1#,No.Ⅱ prosthesis,Plus APL 2#,No.Ⅲ prosthesis,Welink Ribbed system cementless01#,and No.Ⅳprosthesis,Lima F2L 1# were used in this study.METHODS:The ezDICOM software was used to read files with DICOM format of femoral X-ray image,which was converted into files with bmp format.The image files with bmp format of the proximal femar X ray were introduced with Matlab software after regulation,and the two-dimensional contour data of femar were extracted.Prosthesis matched with the template was set in PhotoShop 7.0 software.The two-dimensional contour data of prosthetic femar were extracted in MATLAB software.The ANSYS software was used to establish the model of geometrical and two-dimensional nonlinearity finite element ncluding femur and femur-femoral stem.Stress distribution in the proximal femur was analyzed and compared by loading.MAIN OUTCOME MEASURES:Stress istribution of the proximal femur.RESULTS:Stress value and distribution of No.Ⅰ prosthesis and No.Ⅳ prosthesis in proximal femur were similar to the normal femar.Moreover,No.Ⅰ prosthesis was better than No.Ⅳ prosthesis.CONCLUSION:The biomechanics of femoral stem prostheses has been evaluated by analyzing and comparing the two-dimensional biomechanics of the femoral stem prostheses based on X-ray and template,which can offer support in optimal rosthesis selection.

This paper presents a unit free-form deformation (FFD) method applied to rapid three-dimensioanl (3D) bone reconstruction, which was based on traditional FFD. With the femur as an example, we reconstructed a 3D model of femur from two X-ray images and a standardized model by taking advantage of unit FFD algorithm. The X-ray images and its parameters were taken by C-arm device. Those parameters and X-ray contour are contributed to 3D reconstruction. The out contours of X-ray image and standard model were connected by point matching algorithm. The unit-FFD lattice was built to reconstruct standard model and finally made the contour of X-ray image and standard model exactly the same. Experiments on shape accuracy, robustness and time consuming, carried out by 35 specimen from cadaver, showed that mean error of shape (0. 52 mm) and mean construction time (112 s) were lower than those using traditional method (0.7-2.6 mm, 8-20 min). The method proposed in this paper shows a good prospect in clinical application and related research.
Algorithms ; Femur ; anatomy & histology ; diagnostic imaging ; Humans ; Imaging, Three-Dimensional ; Models, Anatomic ; Radiography

Objective To evaluate the feasibility of the porous titanium/chitosan/hydroxyapatite (Ti/Ch/HA) composite scaffold as a bone repair substitute.Methods Additive manufacturing (3D printing) technology was used to fabricate porous Ti scaffolds as supporting structures.Chitosan/hydroxyapatite (Ch/HA) sponge was prepared within the macro-pores of Ti scaffolds using freeze drying technology.Thus,a kind of composite porous Ti/Ch/HA scaffold with good cell affinity was obtained.Osteoblastic cells were seeded and cultured in pure porous Ti scaffolds and composite Ti/Ch/HA scaffolds for 7 days.The cellular morphology,seeding efficiency and proliferation were examined and compared between the 2 kinds of scaffolds using scanning electron microscopy (SEM) and MTT assay.Results The SEM examination showed that the macro-pores of Ti/Ch/HA scaffolds were full of the composite sponge structure of Ch/HA,with a micropore size of 50 to 200 μm.Like the pure porous Ti scaffolds,composite Ti/Ch/HA ones have a compressive strength of 168.2 to 192.6 MPa,a yielding strength of 137.1 to 154.1 MPa,and a Young's modulus of 3.21 to 4.51 GPa.After culture for 7 days,a large number of flat cells adhered onto the surface of Ti scaffolds while the cells adhering onto the Ti/Ch/HA composite scaffolds were fusiform.The seeding efficiency of osteoblastic cells in the composite Ti/Ch/HA scaffolds (73.218％ ± 3.748％) was significantly higher than that in the pure porous Ti scaffolds (21.352％ ±4.365％) (P ＜0.05);the OD value of the composite Ti/Ch/HA scaffolds (0.783 ±0.043) was significantly higher than that of the pure porous Ti scaffolds (0.382 ± 0.036) (P ＜ 0.05).Conclusions Ti/Ch/HA composite scaffolds can match human bone in mechanical properties.Compared with pure porous Ti scaffolds,the Ti/Ch/HA composite ones are more suitable for adhesion and proliferation of osteoblasts,making them an ideal kind of bone repair substitute.

Objective To research a fast method on establishment of simplified model of the spine.Methods The 3D geometry of the spine is reconstructed using a multiview radiography reconstruction technique through the two plane X-rays by extracting the spinal anatomy information combined with the statistical geometrical information.Results The entire spine finite element modeling including the thoracic spine(T1-T12),lumbar spine(L1-L5) and the sacrum was reconstructed,and the analysis proved that lateral corrective force can correct scoliosis to a certain extent.Conclusion Because the method needs less time,and causes less radiation to patients,it can be brought much convenience and support to the clinical application.

Objective To apply the three-dimensional pre-operative simulation and intra-operative real-time navigation in the reconstruction of old maxillofacial fractures so as to increase the surgical precision. Methods Six patients with old maxillofacial fractures were enrolled, and the diagnosis of unilateral old maxillofacial fractures was confirmed by clinical and imaging examinations. Virtual three-dimensional skull models were reconstructed from pre-operative CT images. The fractured bone was moved or rotated, and was reposed in a desired site according to the mirrored part from the healthy side. After patient-to-image registration, the surgical instruments and patients were tracked in real-time by optical tracking system during operation, and in this way the maxillofacial fractures were reposed satisfactorily guided by the virtual image. Results Three-dimensional simulation before operation and real-time navigation of patients and instruments during operation were realized. The error of registration was less than 1 mm. The post-operative CT examinations of these six patients revealed that the fracture reposition was same to the pre-operative planning, and the difference between them was less than 1.5 mm. The operations were minimally-invasive, with no complications. Conclusion Computer-aided surgical simulation and navigation system can effectively increase the surgical precision of reconstruction of old maxillofacial fractures.

Species identification of biological samples is widely used in such fields as forensic science and food industry. A variety of accurate and reliable methods have been developed in recent years. The cur-rent reviewshows common target genes and screening criteria suitable for species identification, and de-scribed various DNA-based molecular biology methods about species identification. Additionally, it dis-cusses the future development of species identification combined with real-time PCR and sequencing technologies.

Objective In order to avoid potential injuries imposed to human body,it could be feasible to use the musculoskeletal models which can be reconstructed from the cadaver color cryosection(CCC)images,computerized tomography(CT)images,magnetic resonance(MR)images or other images to analyze the dynamic properties of muscles in vivo during human movement.Mothod We reconstruct the lower limb musculoskeletal model and define the uniform ioint coordinate system(JCS)on the model and the subject.The coordinate transformation of the muscle attachment points both on the model and the subject is described in detail.Results The length and the moment arm of the biceps femoris(short head)during knee flexion are calculated and analyzed.Conclusion This method plays an important role in improving the kinematics and dynamic simulation and the muscle force estimation.

ObjectiveTo investigate the effect of artificial femoral head replacement surgery in the treatment of elderly patients with intertrochanteric fracture.MethodsThere were 120 cases with intertrochanteric fracture according to the different surgical procedures,they were divided into the observation group with 60 cases and the control group of 60 cases.The observation group were taken hemiarthroplasty.The control group were taken dynamic hip fixation.The situations for the two groups of patients after surgery were compared.ResultsThe observation group:the blood loss was (413.6 ± 125.2) ml,operative time was (65.2 ± 9.8 ) min,ambulation time was (5.9 ± 2.3 ) d,length of stay was ( 15.6 ± 2.6 ) d,complication rate was 11.7 ％.The control group:blood loss was (440.5 ± 126.3 ) ml,operative time was (81.2 ± 12.1 ) min,ambulation time was ( 16.4 ± 4.2) d,length of stay was (25.7 ± 3.1 ) d,complication rate was 33.3％.The blood loss,operative time was not different between two groups.The ambulation time,hospital stay,complication rate were significantly different.There were statistical significance ( P ＜ 0.05 ).ConclusionThe hemiarthroplasty was safe,patients with weight-bearing take exercise early,and bed time was short,had less complications,and could achieve satisfied clinical results,it should be widely applied.