摘要:

Study DesignThis study examined the torsional and shear stiffness of Type II odontoid fractures that were stabilized with two 3.5-mm cannulated AO screws or a single 4.5-mm cannulated Herbert screw.ObjectiveTo determine the stability of a commonly used two-screw method versus a single-screw fixation method, Insertion of a single screw could make the procedure technically easier.Summary of Background DataBiomechanical studies have shown the 4.5-mm Herbert screw to generate greater compressive forces than 3.5-mm cannulated screws, which are commonly used to anteriorly stabilize Type II odontoid fractures. No previous biomechanical studies have compared the shear or torsional stiffness of Type II odontoid fractures stabilized with these screws.MethodsTwelve cadaver C2 vertebrae were harvested and an osteotomy was performed to simulate a Type II fracture pattern. Six were stabilized with two 3.5-mm cannulated screws, and the remaining were stabilized with a single 4.5-mm cannulated Herbert screw. Each specimen then was tested in torsion through ±0.75°, ±1.25°, and ±1.75° for 10 cycles each. Shear forces then were applied from an anterior to posterior direction to a maximum load of 44.48 N.ResultsThe mean torsional stiffness for the Herbert screw was 1196 N-m/deg, which was significantly greater than the mean stiffness of the 3.5-mm screw fixation, which measured 434 N-m/deg. The mean shear stiffness for the Herbert screw fixation was 105.9 kN/m, compared to 86.1 kN/m for the 3.5-mm cannulated screw. This was not statistically significant.ConclusionsThe biomechanical properties of the 4.5-mm cannulated Herbert screw suggest it may lend itself for use in fixation of Type II odontoid fractures. With only a single screw to insert, this technically demanding procedure may be less daunting.

ISSN:0362-2436    

出版商:OVID    

年代:1995

数据来源: OVID

ISSN:0362-2436    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Study DesignThe stabilizing potential of the Caspar Trapezial Osteosynthetic Plate was studied using unicortical and bicortical screw placement in cadaveric cervical spines.ObjectiveTo determine if Caspar plates secured with unicortical screws provide the same degree of stability as those anchored with unlocked bicortical screws.Summary of Background DataPrevious work has demonstrated that bicortical cervical vertebral screws are superior to unicortical screws in terms of pull out strength and decreased wobble. However, these two methods of plate fixation have not been directly compared in a clinically relevant cadaveric model.MethodsThe immediate and post-fatigue stabilizing potential of Caspar plates secured with unlcortical or bicortical screws was assessed using a model of complete segmental instability.ResultsUnicortical screw placement resulted in inadequate stabilization in half of the cervical specimens.ConclusionsOur results suggest that, for the Caspar screw, bicortical fixation provides greater flexion-extension stability.

ISSN:0362-2436    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Study DesignThis study analyzed the accuracy of Risser signs staging on posteroanterior radiographs.ObjectiveTo correlate the Risser sign on a posteroanterior radiograph with that on an anteroposterior radiograph.Summary of Background DataOn the posteroanterior view of the spine, the full length of iliac apophysis is difficult to interpret. No report has assessed the relation of these findings.MethodsThe staging of the Risser sign was examined in 89 girls. In 52 subjects, the stage of the Risser sign was identical on both views, whereas in 37 (42%) the interpretations were different.ResultsOn evaluation of the iliac apophysis using a skeletal specimen, the posteroanterior views produced a distorted image of the iliac apophysis, and the medial and lateral aspects of the apophysis were superimposed over the ilium.ConclusionsAs a result of these findings and the fact that the Risser staging was developed for the anteroposterior radiograph, the appearance of the iliac apophysis on the posteroanterior radiograph cannot be used as a reliable indicator of skeletal maturity.

ISSN:0362-2436    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Study DesignLower extremity polysyraptic reflexes and descending neuroganic motor and ascending somatosensory activity were recorded.ObjectiveTwo cases are presented to illustrate the intraoporative use of lower extremity reflex recordings for detecting compromise of spinal cord function.Summary of Background DataLower extremity reflex processing can be used to measure integrated spinal cord activity, whereas descending neurogenic and ascending somatosensory potentials measure only long tract function.MethodsEight channels of lower extremity polysynaptic reflex activity were recorded simultaneously after unilateral lower extremity mixed nerve stimulation. Sequential descending neurogenic and ascending somatosensory activity was recorded simultaneously with reflex recordings.ResultsIn these two patients with idiopathic scoliosis, intraoperative reflexes changed before descending neurogenic and before ascending somatosensory activity changed. High-amplitude synchronous persistent reflex activity correlated with a postoperative neurologic deficit. Low-amplitude asynchronous transient reflex activity was not associated with a postoperative neurologic deficit.ConclusionIntraoperative lower extremity reflex changes are more sensitive to spinal cord compromise than are changes in long tract function. Lower extremity polysyneptic reflexes monitor the integrated activity of the spinal cord that is responsible for the control of complex motor behavior.

ISSN:0362-2436    

出版商:OVID    

年代:1995

数据来源: OVID

ISSN:0362-2436    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Study DesignThis was a cross-sectional analytic study of patients with chronic low back pain.ObjectiveTo investigate whether the criteria for internal disc disruption, as adopted by the International Association for the Study of Pain, could be satisfied in patients with chronic low back pain and to test whether there were any conventional clinical features that could identify this condition.Summary of Background DataInternal disc disruption has been postulated as an important cause of low back pain. To diagnose this condition, the International Association for the Study of Pain taxonomy requires that pain be reproduced on provocation discography and that computed tomography discography reveal internal disc disruption, provided that as a control, stimulation of at least one other disc fails to reproduce pain.MethodsNinety-two consecutive patients with chronic low back pain and no history of previous lumbar surgery were studied. Each patient underwent a standard physical examination. Computed tomography discography was performed at a minimum of two levels.ResultsThe diagnostic criteria for internal disc disruption were fully satisfied in 39% of patients, most commonly at L5-S1 and L4-L5. None of the clinical tests used could differentiate between those patients with internal disc disruption and other patients.ConclusionsA diagnosis of internal disc disruption can be made in a significant proportion of patients with chronic low back pain, but no conventional clinical test can discriminate patients with internal disc disruption from patients with other conditions.

ISSN:0362-2436    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Study DesignFrom a random population sample, those experiencing frequent headaches were identified. They were examined to determine how many fulfilled the 1990 international Headache Society classification criteria for cervicogenic headache.ObjectiveTo estimate the prevalence of cervicogenic headache in the general population and in the group experiencing frequent headaches.Summary of Background DataOnly with the publication of the 1990 headache classification criteria did a generally accepted clinical definition of cervicogenic headache emerge. The prevaience of this form of headache has been estimated only in two highly selected in-clinic patient populations. No data exist regading the prevalence in representative unselected populations.Methods. Ashort questionnaire on headaches was mailed to 826 randomly selected residents of a midsized Danish town. A group of 57 individuale in the age range 20–59 years who reported having headache episodes on 5 or more days in the previous month were identified. Forty-five of the 57 were eventually interviewed and examined with respect to the IHS criteria for cervicogenic headache (the radiological criteria were omitted on ethical grounds).ResultsOf the 45 persons examined, eight fulfilled the diagnostic criteria for cervicogenic headache, equivalent to a prevalence in the headache group of 17.8% (95% confidence interval = 8%-32%).ConclusionsCervicogenic headache appears to be a relatively common form of headache, similar to migraine in prevaience.

ISSN:0362-2436    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Study DesignThis report gives the results of a population-based cross-sectional mailed questionnaire, with prospective follow-up of survey responders and nonresponders.ObjectiveTo determine the 1-month period prevalence of low back pain in an adult population in the United Kingdom and to estimate the effect of nonresponse bias.Summary of Background DataPrevious United Kingdom population studies have reported a 1-year period prevalence of low back pain of 37%. However, the definitions of low back pain have varied, and the influence of nonresponse rarely has been reported.MethodsThe study population was made up of all 7669 adults (18 to 75 years old) registered with two family practices in a sociodemographically mixed suburban area. The questionnaire, including a pain drawing to identify the site of any pain, was mailed to the entire study population. Two repeat mailings were sent to nonresponders. Family practice consultations about low back pain by individuals from the study population were monitored over the following 12 months using computerized records of all surgery contacts.ResultsOf the study population, 4501 (59%) responded. The 1-month period prevalence of low back pain was 39% (35% in males, 42% in females). The age distribution was unimodal, with peak prevalence in those aged 45 to 59 years old. Responders to the first mailing had a small but nonsignificant increase in prevalence compared with those who responded to the second or third mailing. Nonresponders had a subsequent consultation rate for low back pain that was 22% lower than that for the survey responders.ConclusionsAfter considering potential differences in nonresponders, the estimated 1-month prevalence of low back pain was between 35% and 37%. Prevalence figures in survey responders may overestimate the true population prevalence by a modest amount.

ISSN:0362-2436    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Study DesignThis was a biomechanical study of the effect of the initial horizontal distance between a person lifting and the load. Experimental data were analyzed using a dynamic rigid link model.ObjectiveTo determine the effect of the initial horizontal load placement on the moments acting on the lumbar spine and the lower extremity joints during lifting, and to determine the role of the lower extremities during lifting from the floor.Summary of Background DataEpidemiologic studies have implicated lifting as a cause of back pain, and over 80% of all worker's compensation back injuries are considered to be caused by manual material handling. Guidelines have been proposed to increase the safety of lifting, but they are primarily based on static biomechanical analyses, psychophysical data, and physiologic limitations.MethodsEach of 12 male subjects lifted a weight box containing 0 to 300 N, in 100-N increments. Each subject performed 20 lifts—four weights at five horizontal distances (20, 30, 40, 50 and 60 cm). Motion was measured with an optoelectronic system, ground reaction forces were measured with a force plate, and moments were calculated using a rigid link model.ResultsThe peak predicted L5-S1 moment increased as the weight and horizontal distance increased. The influence of horizontal distance on moment magnitude was nonlinear. As the distance changed from 20 to 40 cm, the distance-related rate of increase was approximately one-half of that occurring with a distance change from 40 to 60 cm. This can be explained by the need to reach out further, beyond 40 cm, which is accomplished by a deeper flexion of the knees and ankles and an anterior translation of the upper body and arms.ConclusionAs the horizontal distance at the start of a lift increased, the peak moment acting on the lumbar spine also increased, but the increase was nonlinear. This is explained by a change in the technique of lifting when the distance is 40 cm or greater.

ISSN:0362-2436    

出版商:OVID    

年代:1995

数据来源: OVID