In order to analyse the effects of flexion-extension motion of lumbar spine on the position and shape of lumbosacral dural sac, measurements were performed on 10 flexion/extension lateral myelograms of cadaver specimens of normal lumbar spine.It could be seen that from flexion to extension both sagittal diameter and length of the dural sac increased significantly, the dural sac moved caudally, and the sagittal diameter of the anterior epidural space decreased in the mid-vertebral level but increased in the inter vertebral level.The dynamic changes of the dural sac, the influence factors and the clinical relevances were discussed.

A mechanical model was constructed with three-dimensional finite element method to analyse the statusof stress distribution in the isthmus of the neural arch. It was found that the stress concentrate significantlyin the isthmus with spine upright. flexed and extended, and most obviously in extension position. The auth-ors conclude that spondylolysis is mainly the fatigue fracture due to locally increased stress and is contribut-ing most by backward extension of lumbar spine.

In the field of biomechanics, there have been many discoveries concerning the cervical spine injuries in recent years. With the help of biomechanical knowledge, we can not only judge the stability of the cervical spine and have a clear idea of the factors that may affect the stability but also conduct an appropriate classification of the injuries. In this article, we summarize the effects of the stiffness and preinjury biomechanical characteristics of the cervical spine (such as alignment, mass, inertial properties) on the injury, changes of the spinal canal during injury, and the rapidly developing research on finite element models of cervical spine injuries in the past few years.

Objective. To delineate the clinical spectrum and treatment choice of sacral fractures.Methods. In this series, 39 sacral fractures were retrospectively reviewed and classified utilizing Denis′ classification. There were 21 Zone Ⅰ fractures, 6 Zone Ⅱ fractures and 12 Zone Ⅲ fractures. Neurological deficits were present in seven patients. Thirty seven patients were treated conservatively and two underwent surgical management.Results.Thirty eight patients were followed up for three months to 19 years. Thirty three have recovered, four improved, and one remained disabled.Conclusion.The treatment of sacral fractures requires assessment of pelvic stability and existing nerve injury. The patients with pelvic ring instability and neurological deficits should be treated with fracture reduction and stability reconstruction. When the patients with pelvic fracture are complicated with neurological deficits, sacral fracture should be first suspected. Once the diagnosis of sacral fracture is made, fracture reduction should be indicated. Conservative treatment usually permits satisfactory results.

In this paper the latest studies on the role of estrogen for the development of osteoarthritis and osteoporosis in postmenopausal women are reviewed.Estrogen can influence the pathophysiology of osteoarthritis through its interactions with the estrogen receptors,type Ⅱ collagen,cytokines and reactive oxygen species.While in the process of osteoporosis,estrogen can not only influence the estrogen receptors,cytokmes,reactive oxygen species,but also affect the sex hormone binding globulin and estrogen receptor-related receptor.

Objective To investigate the diagnosis measures and treatment methods of white line hernia. Methods Analyze the clinical data of 12 cases of white line hernia who were treated by surgery. We performed peritoneal adipose tissue before resection on hernia without hernial sac type. And for those with hernial sac type, apothesis of material in hernia were firstly made, then ligated the hernia sac neck and resection were made. Then according to the white line defect size, we used pure involution suture and Onlay without tension patch repair to repair defect in the white line. Results Surgery of all the 12 cases were successful. 2 cases of them merged postoperative renal dysfunction and infection, and after hemodialysis and anti-infection treatment, they both recoverd well without recurrence. Conclusion There is no spe-cific symptoms and signs in white line hernia, but incarceration and strangulation may cause life threaten, so we should pay more attention to it. For symptomatic, large, difficult, incarcerated or strangulated white line hernia,we should take timely surgical treatment.

The lumber ligaments play an important role in spinal bsomechanics. The results of three-dimensional finite element analysis showed that one of functions of lumbar ligaments is transmission of the tensile load between the lumbar vertebrae. The anterior longitudinal ligament is loaded in extension of lumbar spine and the resistance to the tensile load in flexion is provided by other ligaments. These ligaments are subject to much more tension with degsneration of the intervertebral disc so that a series of pathological changes occur. Relevant significance in clinical aspect is also discussed.

Objective. To report the magnetic resonance imaging (MRI) findings of acute cervical central cord syndrome and to determine their correlation with the prognosis. Methods. MRI findings of 35 patients with acute central cord syndrome were studied and compared with the recovery rate of ASIA score at presentation and in follow-up. Results. MRI data demonstrated spinal cord compression for 32 patients, spinal cord swelling for 16 patients, and abnormal signal intensity within the spinal cord for 19 patients, including 14 with edema and 3 with hematoma. No significant difference of the recovery rate was noted between the patients treated nonoperatively and operatively (P >0.05). There was a significant inverse correlation between the recovery rate and the degree of spinal cord compression as shown in MRI scans (P<0.01). The presence of hematoma in MRI scans was associated with poor prognosis, as demonstrated by a significant difference of the recovery rate (P< 0.01) among the patients with normal intensity, edema and hematoma within the spinal cord. Conclusions. MRI scans provide an efficient assistance for decision-making and accurate prognostic information regarding neurological function, and therefore should routinely be performed within the early phase of acute central cord syndrome.

Objective: To provide the experience in imaging diagnosis of cervical spine and spinal cord injuries in children.Methods: Imaging data of cervical spine and spinal cord injuries in 62 children were retrospectively reviewed.The routine radiography including the lateral,anteroposterior and open-mouth odontoid views were performed in all the patients. Tomography was available for 25 patients, and flexion-extension lateral views for 28patients, CT scanning for 21 patients, MRI for 26 patients.Results: Of these patients, 46 patients were identified with injuries of upper cervical spine (9 with atlantal arch fracture, seven with axial fracture, 21 with odontoid fracture, 1 with atlantal arch fracture combining with odontoid fracture, and 1 with atlantal transverse ligament disruption); 7 patients sustained injuries of lower cervical spine (3 fractures of vertebral body, 2 dislocations and 6fracture-dislocations ); 2 patients had multiple noncontiguous cervical injuries; and 3 had cervical spinal cord injury without radiographic abnormalities (SCIWORA).Conclusions: Imaging assessment is of great importance in the diagnosis of cervical spine and spinal cord injuries in children. Whenever cervical spine and spinal cord injuries are suspected for children patients, and the three-views should be routinely indicated. MRI should be routinely performed in all children with cervical SCIWORA.

Objective. To investigate the role of amputation in management of severely injured extremities and factors that may influence decision making.Methods. Thirty six patients with amputations following severe injuries of the lower extremities were retrospectively reviewed.Results. There was one death from multiple organ failure. Among the remaining 35 cases, primary and delayed wound healing was achieved in 22 and 13 patients, respectively.Conclusion. Amputation is an important means for management of severely injured lower extremities. When salvage is unlikely to lead to the functional reconstruction of the limb, amputation should be indicated.