摘要:

Study Design.This study determined whether entrapment of a rabbit intervertebral disc in alginate gel helped to promote the retention of normal metabolic activities by the nucleus pulposus and anulus fibrosus in tissue culture.Objectives.To establish anin vitroculture system to study the metabolism of the intervertebral disc as a whole integral organ.Summary of Background Data.In vitrostudies of the metabolism of intervertebral discs have been scarce because of the difficulties involved in maintaining the integrity of the tissues, especially that of the nucleus pulposus, in culture medium.Methods.Rabbit intervertebral discs were embedded in alginate gel and maintained in culture for as long as 1 month. At weekly intervals, experiments were performed to measure the rate of proteoglycan synthesis and to characterize proteoglycans newly synthesized by cells in the anulus fibrosus and nucleus pulposus. In addition, at these same time intervals, the contents of sulfated proteoglycans, antigenic keratan sulfate, hyaluronan, and collagen in these two intervertebral disc tissues were measured to evaluate tissue integrity. Intervertebral discs cultured in medium alone were used as controls and analyzed in parallel.Results.The anulus fibrosus and nucleus pulposus of intervertebral discs cultured in alginate gel sustained a higher rate of proteoglycan synthesis and maintained a higher content of extracellular matrix components than the respective controls at all times.Conclusions.This new alginate tissue culture system should prove useful for studying the metabolism of whole intervertebral discs.

ISSN:0362-2436    

出版商:OVID    

年代:1998

数据来源: OVID

ISSN:0362-2436    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Study Design.The pullout strength of unicortical and bicortical screws in thoracic and lumbar vertebral bodies was measured as a function of bone mineral density.Objectives.To determine the influence of bone mineral density and screw insertion technique on the stability of anterior thoracolumbar spine screw fixation.Summary of Background Data.No previous study has addressed the specific technique of screw insertion or stability of screw fixation in the anterior spine.Methods.Fifty-one human thoracic vertebral bodies were tested in pullout with 6.55-mm cancellous screws inserted using unicortical and bicortical techniques.Results.Pullout force increased exponentially with increasing bone mineral density for unicortical and bicortical screws. Bicortical screws were significantly stronger in resisting pullout than unicortical screws.Conclusion.Advancing an anterior vertebral body screw to engage the second cortex increases resistance to pullout by 25-44%, depending on vertebral bone mineral density. The difference in resistance between unicortical and bicortical techniques was smaller in specimens with low mineral densities.

ISSN:0362-2436    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Study Design.Fifteen specimens of the first cervical vertebra were tested by the application of pure tensile forces to failure. Seven specimens had intact transverse ligaments, and eight had transection of the transverse ligament before testing. Specimens were tested to failure by the rapid application of laterally directed tensile force to the ring; this force then was exerted through the lateral masses to simulate the mechanism of injury for this fracture as proposed by Jefferson.Objectives.To measure the biomechanical characteristics of the C1 ring, including the fracture patterns created with tensile loading, and to describe the influence of the transverse ligament on the behavior of the ring as it failed under tension.Summary of Background Data.Jefferson fractures have been reproduced in the laboratory by subjecting head and neck preparations to axial load. However, no previous detailed biomechanical studies of the fracture characteristics of the isolated C1 vertebra have been reported.Methods.Specimens were tested to failure by rapid application of laterally directed tensile forces to the ring.Results.Eleven two-part and three three-part fractures occurred. The mean tensile strength of the atlas was found to be 2,280 N. The average deformation required to fracture the C1 ring was 1.57 mm. The total energy absorbed by the ring averaged 1.99 N-m. There was no statistically difference between those specimens with the transverse ligament intact and those without a transverse ligament.Conclusions.The results of this study show that fractures of the C1 ring of greater than two parts can occur with pure tensile loading. The ring will fracture with as little as 1 mm of deformation.

ISSN:0362-2436    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Study Design.Fifty-seven patients with dens fractures were identified from 1986 to 1996 at the authors' institution. Forty-six were available for reevaluation by two independent observers with a mean follow-up period of 26 months.Objective.To determine by age and fracture type which treatment regimen provided the best functional outcome in patients with dens fractures.Summary of Background Data.There were no Type I fractures, but there were 37 Type II and 20 Type III fractures. Twenty-nine patients were under 60 years of age, and 28 were 60 years and older. Six patients had been treated by immediate C1-C2 posterior fusion, and five received treatment with a Philadelphia collar only. Forty-six patients were placed in a halo thoracic immobilizer with a symptomatic nonunion rate of 19.5%. These patients ultimately required posterior cervical fusion.Methods.Final functional outcome, level of pain, and cervical range of motion were all statistically evaluated using multivariate analysis (Wilcoxon's two-sample test). The influence of age, fracture type, and treatment method were determined.Results.There were no cases of short- or long-term neurologic deterioration in any of the patients in the study group. There was a significantly higher rate of complications associated with halo use in the older population. Pain scores were higher in Type II fractures and in patients treated conservatively with halo immobilization, especially those patients over 60 years of age. No statistically significant difference in these paramefers were found. Older patients treated surgically did not have a better functional outcome score than those treated nonoperatively (P< 0.8). Persons over 60 years of age treated in a halo had a significantly (P< 0.05) decreased range of motion when compared with younger patients treated similarly.Conclusion.Patients over 60 years of age with a dens fracture had a higher complication rate and lower cervical range of motion when treated conservatively with a halo. Final functional outcome and overall pain levels, however, did not differ significantly by age group or treatment modality.

ISSN:0362-2436    

出版商:OVID    

年代:1998

数据来源: OVID

ISSN:0362-2436    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Study Design.Randomized, controlled, single-blinded study.Objectives.To determine the physiologic effectiveness of lumbar medial branch blocks.Summary of Background Data.Zygapophysial joint pain can be diagnosed by anesthetization of the joint or its nerve supply (the medial branch divisions of the dorsal rami). The physiologic effectiveness of lumbar medial branch blocks has been assumed but not proven.Methods.Eighteen asymptomatic individuals were randomly assigned to either L4-L5 or L5-S1 zygapophysial joint injections with contrast medium until capsular distention elicited pain without extracapsular contrast spread. One week later, 15 blinded individuals underwent two randomized saline or 2% lidocaine medial branch injections that correlated to the innervation of the previously injected joint. Medial branch injections were performed such that inadvertent venous uptake was avoided in 14 individuals. Thirty minutes after medial branch injections, these 14 individuals underwent repeat capsular distention of the same zygapophysial joint provoked the prior week in an attempt to elicit another painful response.Results.All five control individuals who received saline medial branch i njections felt pain on repeat capsular distention. Nine individuals received 2% lidocaine medial branch blocks; eight felt no pain, and one felt pain on repeat capsular distention.Conclusions.There was a significant effect of 2% lidocaine (versus saline) medial branch injections on anesthetization of the zygapophysial joint when venous uptake was avoided during these injections. When properly performed, lumbar medial branch blocks successfully inhibit pain associated with capsular distention of the lumbar zygapophysial joints at a rate of 89%.

ISSN:0362-2436    

出版商:OVID    

年代:1998

数据来源: OVID

ISSN:0362-2436    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Study Design.Lumbar peripheral nerves were examined to determine whether they were responsive to electrical stimulation of the ventral portion of the lumbar disc in anesthetized rats.Objectives.To confirm by electrophysiologic means the neural correspondence between the ventral portion of the lumbar disc and the groin.Summary of Background Data.Patients with a degenerated lumbar disc occasionally report groin pain. However, its pathogenesis has not been investigated. The authors of the current study found that chemical stimulation of the ventral portion of rat lumbar disc caused cutaneous plasma extravasation in the groin, and thereby hypothesize the neural relation between the lumbar disc and the groin.Methods.The ventral portion of rat L5-L6 disc was electrically stimulated, and the elicited action potentials were recorded from the iliohypogastric, genitofemoral, lateral femoral cutaneous, sural, and sciatic nerves. The roles of the lumbar sympathetic trunks and spinal cord in the generation of the action potentials were examined.Results.Action potentials were elicited principally in the genitofemoral nerve; the action potentials of the genitofemoral nerve were not influenced by transection of the cervical spinal cord, whereas they disappeared immediately after death, which indicates that they are induced by a spinal reflex. The action potentials were reduced considerably after destruction of the lumbar sympathetic trunks, suggesting that they comprise an afferent path of the reflex.Conclusions.The ventral portion of the lumbar disc had spatial relation to the groin area via a spinal reflex. Such a relation suggests that a disorder in the ventral portion of the lumbar disc may be a possible source of groin referred pain.

ISSN:0362-2436    

出版商:OVID    

年代:1998

数据来源: OVID

ISSN:0362-2436    

出版商:OVID    

年代:1998

数据来源: OVID