BACKGROUND:Cervical kyphosis post laminectomy is a common iatrogenic,and progressive abnormality of the curvature of cervical spine,and can influence the function of cervical spine of children and adults.OBJECTIVE:To explore the effect of multiple levels of laminectomies on the curvature of cervical spine,and analyze the role of the elastic modulus of cervical intervertebral disc and ligaments on maintaining curvature of postlaminectomy cervical spine.DESIGN,TIME AND SETTING:Three-dimensional finite element analysis was performed in Changzheng Hospital,Second Military Medical University of Chinese PLA between January 2003 and January 2004.MATERIALS:The highly resolution pictures of the cross-section of cervical spine(interval distance of layer 1 mm) were came from male cross-section of cervical spinal of American visible human project,which was freely downloaded from The Visible Human Project.METHODS:The highly resolution pictures of cervical spinal cross-section were used as data to reconstruct the three-dimensional multiple levels postlaminectomy cervical spine models including all structure of spine from cranial base to the first thoracic vertebrae except the vertebral lamina,spinous process,ligamentum flavum,interspinous and supraspinous ligament from the second to the seventh cervical spine.The finite element and elastic modulus of the structures of cervical spine were defined according to previous reports.With this model and Ansys6.1 finite element analysis software,the effect of laminectomy on the curvature of cervical spine and impact of the elastic modulus of intervertebral disc and ligament to the curvature of postlaminectoy cervical spine were analyzed.MAIN OUTCOME MEASURES:The influence of the elastic modulus of cervical intervertebral disc and ligament(anterior and posterior longitudinal ligaments) on the curvature of the postlaminectomy cervical spine.RESULTS:The physical lordosis of multiple levels postlaminectomy cervical spine was reduced after multi-level loading,and the physical lordosis of the superior cervical spine disappeared with only slightly kyphosis.The kyphosis was aggravated after reducing the elastic modulus of intervertebral disc and ligament(anterior and posterior longitudinal ligaments).Following increased elastic modulus of intervertebral disc and ligament,the kyphosis of cervical spine was reduced even disappeared,and gradually regained the normal lordosis of cervical spine.CONCLUSION:Multiple levels cervical laminectomy can significant reduce the physical lordosis of cervical spine,and convert the physical cervical lordosis to cervical kyphosis.The elastic modulus increase of cervical intervertebral disc and ligament can inhibit kyphosis formation post laminectomy.

The scale of local structure is a key parameter in medical image registration. Unfortunately, no much attention has been paid to the scale selection for the local structures in the images. This paper proposes a data-driven scale selection method for local structures in the image. By using minimal description length criterion to maximize the posterior probability of local structure region with coherence constraint based on the Markov random field model, an optimal scale for each local structure, which is segmented with super-pixel representation, is assigned in terms of variance in a discrete anisotropic scale space. Therefore, the local structure's scale can be selected for further non-rigid medical image registration.
Algorithms ; Image Enhancement ; methods ; Image Processing, Computer-Assisted ; methods

Objective To investigate the prevalence and pattern of androgenetic alopecia (AGA) in Shanghai through a community-based survey. Methods A cluster sampling survey was done among the residents in Beixinjing Community, Changning District, Shanghai. All the subjects were asked to fill a questionnaire to provide their general information, including sex, age, native place, physical status, life habit, family history, etc. The diagnosis of AGA was made by dermatologists. To determine the pattern of hair loss,Norwood-Hamilton classification system and Ludwig classification system were used for male AGA and female AGA, respectively. All the data were statistically analyzed by EpiData and SPSS11.5 software. Results Totally, 7056 subjects completed the questionnaire, including 3519 males and 3537 females, and the response rate was 72.5%. AGA was diagnosed in 809 patients, consisting of 701 males aging from 19 to 91 years (mean 64.16±11.9 years) and 108 females aging from 35 to 91 years (mean 70.46±18.89 years). The standardized prevalence (SP) was 9.47% in total, 15.73% in males and 2.73% in females; the difference was significant between males and females (χ2=356.00, P<0.001). A family history of AGA was observed in 52.7% of all subjects including 391 (55.78%) males and 35 (32.41%) females. Type Ⅲ vertex involvement was the most common type in men aging from 20 to 70 years old, and type Ⅵ in those over 70 years old. Grade Ⅰ and Ⅱ predominated in female AGA. Conclusions The results of this survey indicate that the prevalence of AGA is remarkably higher in men than that in women. Furthermore, the prevalence is steadily increased with advancing age in Shanghai.