Objective To compare the difference of static balance ability in different aged people, with the maximum angle of center of mass (COM) and center of pressure (COP). Methods 37 healthy people without cardiovascular and cerebrovascular diseases including 15 young people (18~40 years old), 10 middle age people (41~65 years old) and 12 old people (>65 years old) participated in this study. The maximum angle of COM-COP and the corresponding envelope areas were recorded in 4 standing posture: natural standing, close eyes standing, single leg standing and single leg standing with eyes closed. Results There was no significant difference in the maximum angle of COM-COP among 3 groups in 3 states (nature standing, close eyes standing, single leg standing with eyes closed) (P>0.05), but there was significant difference in the state of single leg standing (P<0.05) between the young and the old, and the middle-aged and the old. Conclusion The maximum angle of COM-COP in the state of single leg standing can sensitively detect the deterioration of stability of older people. It may be a new index of static balance in clinic.

BACKGROUND:Hip segmentation based on CT image has been widely used in computer-assisted surgery planning, prosthesis design and finite element analysis. OBJECTIVE:To explore application effects of automatic segmentation method for hip joint based on Bayesian Decision Theory in computer-assisted hip surgery. METHODS:An accurate outer surface segmentation and extraction remain chal enging due to deformed shapes and extremely narrow inter-bone regions. In this paper, we present an automatic, fast and accurate approach for segmentation of femoral head and proximal acetabulum. The outline of the femur was segmented and extracted by contrast enhancement, thresholding algorithm and region growth algorithm. The boundaries of the bone regions are further refined based on Bayes decision rule. RESULTS AND CONCLUSION:Automatic segmentation method for hip joint based on Bayesian Decision Theory is an accurate segmentation technique for femoral head and proximal acetabulum and it can be applied in computer-assisted hip surgery and prosthesis design.

When a traditional method is used to repair residual dental root with horn-shaped orifice, this kind of dental root often has to be extracted since the success rate in clinic is very low. The main reason is that the stress often concentrates on the neck and root apex, therefore the wall at the orifice is too thin to bear this kind of pressure. A new repairing method is proposed trying to preserve the residual dental root with horn-shaped orifice. Then compare the anti-fracture ability of this kind of tooth with that of no repairing. The results show that it is very effective to prevent the fracture of residual dental root repaired by chemical hard synthetic resin followed by making the post and core. However, there is no obvious difference between non-repaired and residual dental root groups repaired by traditional glass ionic adhesives. The results also provide the great possibility to preserve the residual dental root with horn-shaped orifice in clinic.
Dental Restoration, Temporary ; Glass Ionomer Cements ; therapeutic use ; Humans ; In Vitro Techniques ; Post and Core Technique ; Resins, Synthetic ; therapeutic use ; Tooth Injuries ; surgery ; Tooth Root ; injuries

Trabecular microstructure is an important factor that influences the bone biomechanical properties. In this paper, studies on digital image analysis of trabecular microstructure are reviewed with special emphases on the serials parameters as well as on the measurement methods of trabecular microstructure characteristic. The future researches and advances are also prospected.
Algorithms ; Bone and Bones ; anatomy & histology ; ultrastructure ; Computer Simulation ; Finite Element Analysis ; Humans ; Image Enhancement ; methods ; Image Interpretation, Computer-Assisted ; methods ; Imaging, Three-Dimensional ; Magnetic Resonance Imaging ; Tomography, X-Ray Computed

The main reason of invalidation of prosthetic hip joint is the prostheses flexibility and shift, dislocation and disjunction. Promoting the long time stability of the prostheses is the key of improving the long term hip joint replacement effect. Former research work was focused on the upper segment of femur, and assumed the acetabulum cup to be a spheric concave, and the external form of acetabulum prostheses was basically semi spheric. This paper presents a method of acquiring the point data on the surface of the hip bone using the reverse engineering technology. By analyzing the acetabulum surface fitting error we use rotating elliptical surface to fit the acetabulum surface, together with the optimal technique to build up the CAD model of acetabulum surface. We compare the fitting error between the sphere fitting and rotating elliptical surface fitting and get the result that the rotating elliptical surface fitting error is smaller than the sphere fitting error, and the rotating elliptical surface can describe the shape of the acetabulum better.
Acetabulum ; anatomy & histology ; Anthropometry ; Arthroplasty, Replacement, Hip ; Computer Simulation ; Computer-Aided Design ; Hip Joint ; anatomy & histology ; Hip Prosthesis ; Humans ; Models, Anatomic ; Prosthesis Design

By using the reverse engineering (RE) technology, the mesh surface model of acetabulum was reconstructed by triangulation. Based on this kind of model, the local morphological analysis (LMA) and global morphological analysis (GMA) could be processed. The fitting minimal quadric surface method was applied to calculate the curvature of any point on the acetabulum bony surface, the local morphological character of its surface could be acquired, and its global surface character could be determined by GMA. The results showed that the acetabulum bony surface is elliptical surface, and its three eigenvalues (lambda1, lambda2, lambda3) relations on the three axes (x, y, z) are as follows: lambda1 is short than lambda2 and lambda3, lambda2 is close to lambda3.
Acetabulum ; anatomy & histology ; Humans ; Models, Anatomic

The research on the morphology features of the acetabulum bone joint surface area would be helpful to establishing the acetabulum 3D model for the purpose of the biomechanical analysis of hip joint, and therefore might have its important clinical significance. However, in former studies, the acetabulum was simply considered as a semi sphere. In this study, based on the acetabulum 3D-point data acquired by the 3D laser surface scanner and the reverse engineering technology together with the optimal fit algorithm, two kinds of best-fit model were achieved by a sphere surface and a rotating elliptical surface respectively approaching to the acetabulum bone joint surface. Both fitting errors were then compared and analyzed. The results showed that the fitting error of the rotating elliptical surface was significantly less than that of the sphere surface (P < 0.001). The average radius of fitting sphere was 24.37 +/- 2.22 mm and the average long axis of fitting rotating elliptical surface was 26.02 +/- 2.76 mm while its short axis was 24.17 +/- 2.16 mm. These findings would be helpful to our new recognition of the acetabulum since they were results of the first quantitative analyses for the acetabulum bone surface and also might serve as an important reference base in its further studies and application.
Acetabulum ; anatomy & histology ; Adult ; Algorithms ; Humans ; Imaging, Three-Dimensional ; Models, Anatomic

Objective To compare the three-dimensional （3D） gait characteristics of patients with medial meniscus injury of the knee before and after arthroscopic surgery. Methods Fifteen patients with medial meniscus injury and fifteen healthy subjects were included in the study. The 3D gait parameters were collected, including spatiotemporal parameters, kinematic parameters and kinetic parameters. Results (1) The preoperative walking speed and step length of the injury group were significantly lower than those of the control group. There was no significant difference in walking speed and step length after surgery between the injury group and the control group. (2) In the sagittal plane, the preoperative knee flexion-extension range of motion (ROM), the maximum flexion angle in load-bearing phase and swinging phase were significantly lower than those in the control group (P＜0.001). The maximum knee flexion in load-bearing response phase was significantly increased after surgery (P＜0.05), but the maximum flexion angle in swing phase and the knee flexion-extension ROM after surgery were still significantly lower than those of the control group (P＜0.05). In the coronal plane, the preoperative knee adduction-abduction ROM and the maximum adduction angle in gait cycle were significantly lower than those of the control group (P＜0.001). The postoperative parameters significantly increased compared with the preoperative ones (P＜0.05), but they were still significantly lower than those of the control group (P＜0.001). (3) In the sagittal plane, the postoperative first and second peaks of knee flexion moment in stance phase of the injury group increased, compared with the preoperative ones (P＞0.05), but they were still significantly lower than those of the control group (P＜0.05). In the coronal plane, the postoperative first and second peaks of knee adduction moment in stance phase of the injury group increased, compared with preoperative ones, but they were also significantly lower than those of the control group (P＜0.05). Conclusions Patients with medial meniscus injury have their own unique gait patterns, usually with stiffening gait to reduce the knee load. Arthroscopic meniscusplasty can significantly improve knee gait characteristics, but patients still cannot return to normal gait in a short period of time.

Objective To analyze human gait stability by acceleration signal at the head and lumbar under different walking conditions, and make comparison with parameters by the traditional COM (center of mass)-COP(center of pressure) method, so as to discuss the reliability of applying wearable sensors to analyze human gait stability. Methods The harmonic ratio (HR) parameter at the head and lumbar based on acceleration signal was applied to analyze gait stability of 18 healthy young adults under 3 walking conditions (footwear normal walking, barefoot normal walking and barefoot walking at different velocities), and the results were compared with the assessment results from the COM-COP method. Results Walking at normal velocity was most stable, with the maximum HR parameter. Compared with footwear walking, HR parameters were significantly decreased (P＜0.05) during barefoot walking, indicating that gait stability was reduced. The results were consistent with the assessment results from the COM-COP method. Considering the factors of walking velocity and footwear, the gait stability parameters obtained by the two methods showed a significant negative linear correlation (R2＞0.50). Lumbar HR parameter and COM-COP parameters showed a stronger linear correlation (R2＞0.65). Conclusions The application of acceleration signal-based analysis algorithm could effectively and reliably evaluate the stability of human gait, and acceleration at the lumbar was more sensitive than the head signal for analyzing gait stability.