摘要:

Many studies have examined the mechanics of the lumbar spine in various planes, but only a limited number of three-dimensional investigations have been reported. Analysis of the low back during complex, dynamic postures demands rigorous representation of the trunk musculature. The data of this study demonstrated the force and torque contributions of approximately 50 laminas of various trunk muscles to flexion-extension, lateral bending, and axial twisting torque at the L4-L5 joint. This analysis was conducted with the spine in an upright standing posture and when fully flexed (60°), laterally bent (25°), and axially twisted (10°) together with two examples of combined postures. Maximum moment potential, muscle length excursions, and the resultant compressive, anteroposterior shear, and lateral shear forces on the joint were also computed. The results indicate that the position of the vertebrae and their orthopaedic axes, which are a function of spinal posture, are an important factor in the reasonable determination of joint compressive, lateral shear, and anteroposterior shear loads. Muscle length changes that exceeded 20% of their respective length during upright standing were not observed during a full axial twist, but were observed in portions of the abdominal obliques during lateral bending, and in some extensors during full flexion. Extreme postures tended to change the torque potential of some muscles and influence joint load. Various portions of erector spinae were observed to have appreciable potential to generate torque about all three orthopaedic axes. This observation supports the notion held by some therapists that conditioning of the erector spinae is of utmost importance.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Twelve dogs were divided into two equal groups and given lumbar intradiscal injections of 10, 50, or 100 U/ml of chondroitinase ABC reconstituted in sodium acetate buffer. Radiographs of the lumbar spine were made before and after surgery in both groups. Additional films were made at 5 days after surgery in Group I and at 7, 14, and 21 days after surgery in Group II. All spaces injected with 50 or 100 U/ml chondroitinase ABC demonstrated significant radiographic narrowing in both groups compared with uninjected control and buffer injected discs (P < 0.001). Discs injected with 10 U/ml of chondroitinase ABC showed increased narrowing over time from 7 to 21 days (P < 0.05). A zone of safranin O depletion was present in the ventral anulus fibrosus adjacent to the nucleus pulposus in all treated discs, indicating proteoglycan loss. All histologic effects of chondroitinase ABC were confined to intervertebral disc tissues. Chondroitinase ABC appears to be effective for chemonucleolysis in dogs.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Six chemical agents were evaluated for their efficacy in preventing epidural scar formation following laminectomy in rabbits. One agent was carboxymethylcellulose and the other five agents represented various compositions of modified carboxymethylcellulose. Four weeks after laminectomy, spines were harvested and decalcified, and transverse sections were prepared for histologic analysis. Subjective evaluation suggested that two agents appeared to inhibit epidural scar formation compared with the untreated controls. Objective evaluation was performed by quantitating scar tissue area at the laminectomy site with a digitizing tablet. In agreement with the subjective evaluation, two agents were found to have significantly reduced epidural scar tissue area compared with the control (control = 0.418 ± 0.16 SE mm2vs. Agent 2 = 0.067 ± 0.02 [P < 0.05] and Agent 5 = 0.089 ± 0.02 [P < 0.05]). Of the remaining four agents, one of which was the unmodified carboxymethylcellulose, none showed significant reduction in scar tissue formation. These findings indicate that viscous preparations of modified carboxymethylcellulose can act as a barrier against epidural scar formation following laminectomy.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The costs and circumstances of low-back impact injuries, and non-low-back injuries among field employees of an offshore petroleum drilling company, 1979-1985, were compared. The objectives were to identify worker and workplace factors associated with low-back injuries, to identify factors differentially associated with lost-time injuries, and to formulate recommendations for the control of low-back injuries. Low-backimpact injuries resulted largely from falls. Efforts to prevent falls would have a potential to reduce other serious consequences as well as back injuries. Workers performing the heaviest physical labor were at highest risk of low-back strains. Based on activities precipitating the injury, modifications of work site, equipment, and procedures to help reduce low-back strains are recommended. Only job was a predictor of whether a low-back strain was likely to be associated with lost time. Even this association was lacking for low-back impact injuries. Cost control by preventing the small proportion of high cost injuries may not be feasible. Rather, subsets of low-back injuries defined, for example, by work site or activity can suggest options for intervention.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Trends in rates of low-back strains, low-back impact injuries, and non-low-back injuries among field employees of a petroleum drilling company, 1979–1985, were examined to investigate the relationship between economic factors and the incidence of low-back and other injuries. Economic indicators included the rate of resignations, a surrogate for turnover, and the rate of layoffs. Only lost-time low-back strain rates increased during times of worker layoffs. Non-low-back injury rates were highest during periods of high turnover and no layoffs. Although the increasing age of the work force and the anxiety generated by an industry-wide depression may have played a role, it is likely that the increase in lost-time low-back strain injuries was a worker response to possible layoff.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Four practical questionnaires used for assessing disability associated with chronic low-back pain were investigated. Comparison of findings among 93 patients disclosed a moderate level of agreement (r = 0.44-0.63) between the scales, providing limited evidence that a single construct is being measured by each. The questionnaires were more strongly related to each other than to psychosocial scales, which suggests that findings are distinguishable from distress. However, higher distress was significantly associated with greater reports of disability. This was most discernible in the form of more enduring characteristics that may reflect neuroticism. These findings allow modest support for the construct validity of the four questionnaires and suggest a need for caution with their use because persistently negative affect may be a biasing factor.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The problems presented by unsuccessful posterior lumbar interbody fusion (PLIF) have not been addressed. The cases of 12 patients who presented with failed PLIF were reviewed. Five patients were male and seven female (age range, 24-50 years; mean age, 40 years). All patients underwent at least one PLIF; many had undergone other procedures. A total of 37 procedures had been performed on the 12 patients. Chronic radiculopathy was present in all patients, as detected with electromyographic or nerve conduction velocity examination. At the time of reconstructive surgery, in the 11 patients in whom the canal was explored, all had extensive epidural fibrosis. Nine of the 12 patients had pseudarthrosis of the previous PLIF. Four patients had evidence of motion segment dysfunction at nearby levels: two had positive discograms adjacent to the PLIFs; one developed a facet syndrome at L5-S1, caudal to an L4-5 PLIF; and one demonstrated frank segmental instability at L2-3, cranial to a previous PLIF at L3-4. Twelve patients underwent a total of 22 procedures after referral. Eleven patients initially underwent decompression and fusion, and one patient underwent a sympathectomy. Seven patients underwent an additional 10 procedures, including repeat decompression, repair of pseudarthrosis, and implantation of an epidural analgesic pump system. After all surgical treatment, five patients rated their pain as improved. Seven patients were thought to have a solid fusion. The presence of a solid fusion did not correlate with satisfactory relief of pain (chi-square). Continued extremity pain was the predominant complaint of all the patients. Two shortcomings of the PLIF were evident. The first was biomechanical: Adjacent unfused segments became symptomatic in four patients. The second problem was one of chronic radiculopathy, on the basis of extensive epineural and endoneural fibrosis provoked by the more extensive epidural manipulation required by the PLIF. The first problem, mechanical dysfunction, can be addressed by stabilization with rigid internal fixation. However, the clinical utility of this is thus far unclear. For the second and major symptomatic problem, chronic radiculopathy, there is currently no good solution.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID