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Biomedical subjects

D M Spengler

Publications and source records attributed to D M Spengler.

At least 73 records · Page 4Linked to original sources
PubMed1986

The reliability of measurements of the lumbar spine using ultrasound B-scan.

Diagnostic ultrasound is used in research and clinical settings to determine the size of the lumbar spinal canal. When the technique was first introduced, measurements were obtained directly from an A-scan while concurrently viewing a B-scan. However, measurements obtained directly from a B-scan are now commonly used despite the undetermined reliability of the technique. To determine the reliability, 50 randomly selected ultrasound B-scan examinations were read on two separate occasions by three investigators. For each spinal level, the mean intraobserver error (same investigator), from the first to the second reading was determined, as was the interobserver error (between investigators) and the error due to variability in obtaining the ultrasound images. The resultant errors were approximately double those reported previously for the technique using A-scan. Interobserver variations were the major source of measurement error.

Adult↗
PubMed1986

Back injuries in industry: a retrospective study. I. Overview and cost analysis.

To evaluate the impact off back injury on industry, the authors conducted a retrospective analysis of injuries among hourly employees of a large industrial manufacturer in western Washington. The Boeing Company provided injury information on 31,200 employees for a 15-month period from July 1, 1979 to September 30, 1980. Of the 4,645 injuries reported, 900 were back injuries. Claims related to back injuries constituted 19% of all workers' compensation claims but were responsible for 41% of the total injury costs, or approximately $1,800,000. The 90 most expensive back injury claims (10% of all back injury claims) were responsible for 79% of the total back injury costs. The percentage of back injury claimants with claims having a total incurred cost exceeding $10,000 (6.5%) was significantly higher than the corresponding percentage of claimants (1.5%) with claims for other than back injuries (P = 0.000). A similar significant difference was found concerning the tendency of back injury claimants to have multiple claims compared with the non-back injury claimants. This retrospective study reaffirms the significant economic impact of back injuries on industry, and specifically high-cost back injuries. In addition, it provides insight into factors associated with back injury and points to positive measures that may be taken to reduce back pain and economic loss. Characteristics of the back injury and employee-related factors associated with back injury are presented in two subsequent articles.

Back Injuries↗
PubMed1986

Back injuries in industry: a retrospective study. II. Injury factors.

To evaluate the impact of back injury on industry, the authors conducted an extensive retrospective analysis of injuries among hourly employees of The Boeing Company, the largest industrial manufacturer in western Washington. The Boeing Company provided injury information on 31,200 employees for a 15-month period from July 1, 1979 to September 30, 1980. From this information, we analyzed 4,645 injury claims filed as of February 28, 1981 by 3,958 different employees. There were 900 back injuries in this group. Claims were categorized according to total incurred cost (TIC), made up of the medical costs and indemnity costs. High-cost claims were defined as those with a TIC greater than $10,000, and low-cost claims were those with a TIC less than $10,000. Among 857 claimants with 900 back injuries, lifting or material handling was much more commonly considered the cause of injury than accidents such as slips or falls. Accidents, however, had a much greater tendency to result in an expensive claim. The authors could not make reliable conclusions regarding injuries and 32 job skill classifications. The rate of injury did not vary according to day of the week or month, but a significantly higher rate of high-cost back injuries was noted on the day shift than on the evening or night shifts.

Absenteeism↗
PubMed1986

Back injuries in industry: a retrospective study. III. Employee-related factors.

To evaluate the impact of back injuries on industry, the authors conducted a retrospective analysis of injuries occurring among a group of 31,200 employees of The Boeing Company, a large industrial manufacturer in Western Washington. They analyzed 4,645 injury claims (including 900 back injuries) made by 3,958 different employees. Two previous articles give an overview of the study, provide a detailed analysis of the costs associated with these back injuries, and analyze the characteristics of the injury. This article focuses on employee-related factors associated with back injuries. Claims were categorized according to severity, as indicated by total incurred cost (TIC), the sum of the medical costs, and indemnity costs. High-cost claims were defined as those with a TIC greater than $10,000 and low-cost claims as those with a TIC less than $10,000. Employees younger than 25 years of age had a statistically significant increased risk of back injury, although their claims tended to be low-cost ones. This finding tends to discredit the premise that back problems are related to aging of the lumbar spine. While older employees had a lower injury rate, they did have a significantly increased risk of incurring high-cost back injury claims. The 31-40-year age group was the most susceptible to high-cost back injuries. Newer employees tended to have a significantly increased risk of back injury. The data show that women had fewer injuries than men but a statistically significant increased risk of becoming a high-cost injury claim.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Fatigue of immature baboon cortical bone.

Strain-controlled uniaxial fatigue and monotonic tensile tests were conducted on turned femoral cortical bone specimens obtained from baboons at various ages of maturity. Fatigue loading produced a progressive loss in stiffness and an increase in hysteresis prior to failure, indicating that immature primate cortical bone responds to repeated loading in a fashion similar to that previously observed for adult human cortical bone. Bone fatigue resistance under this strain controlled testing decreased during maturation. Maturation was also associated with an increase in bone dry density, ash fraction and elastic modulus. The higher elastic modulus of more mature bone meant that these specimens were subjected to higher stress levels during testing than more immature bone specimens. Anatomical regions along the femoral shaft exhibited differences in strength and fatigue resistance.

Animals↗
PubMed1985

The pathomorphology of spinal stenosis as seen on CT scans of the lumbar spine.

This study examines different morphologic measurements in the evaluation of patients with lumbar spinal stenosis. Preoperative CT scans from 24 patients who underwent surgery for central lumbar stenosis were analyzed. No correlation was observed between the size of the bony spinal canal and the size of the dural sac. A new measurement, the transverse area of the dural sac, is introduced. Normal values are provided. Correlation between the cross-sectional area of the dural sac and the anteroposterior diameter of the dural sac was excellent.

Adult↗
PubMed1985

Role of computed tomography and myelography in the diagnosis of central spinal stenosis.

In order to evaluate radiographic methods for diagnosing central lumbar stenosis, we reviewed the computed tomography scans and myelograms of twenty-four patients who underwent surgical decompression for central lumbar stenosis. In the diagnosis of central lumbar stenosis, the measurement of the anterior-posterior diameter of the osseous canal by computed tomography was less reliable than the measurement of the dural sac by myelography. The dimensions of the canal derived from computed tomography provided a correct diagnosis in 20 per cent of the patients, while myelography was accurate 83 per cent of the time. The effectiveness of computed tomography was improved when the cross-sectional area of the dural sac was measured. We suggest that a narrow dural sac, demonstrated by myelography or by computed tomography, reliably indicates central spinal stenosis.

Adult↗
PubMed1984

Pressure changes within the cauda equina following constriction of the dural sac. An in vitro experimental study.

In order to register pressure changes within the cauda equina, a highly sensitive pressure measuring catheter was inserted through a hole in the dural sac. Its tip was placed among the nerve roots of the cauda equina at levels L2, L3, and L4 in seven freshly removed human specimens. The cross-sectional area of the dural sac then was decreased gradually by constriction of a circular clamp. The inside diameter of the clamp and the corresponding area was determined when further reduction of the circumference of the clamp caused the first signs of a pressure increase, the critical size, among the nerve roots. The average critical size was 76.9 mm2 at the L2 level, corresponding to a diameter of 11.4 mm At the L3 level, the corresponding figures were 71.5 mm2 and 11.1 mm, and at the L4 level 64.8 mm2 and 10.6 mm, respectively. It seemed reasonable to assume that the critical sizes determined in this way could be threshold values below which a further constriction of the size of the dural sac would cause an impairment of the circulatory and/or the nerve function of the cauda equina.

Aged↗
PubMed1984

The load on the lumbar spine during isometric strength testing.

Reports of back discomfort and even back injuries during isometric strength testing in specific lifting positions indicated an analysis of the loads on the lumbar spine during this type of testing. A biomechanical analysis, which has been validated against EMG and intravital disc pressure measurements, was used for the calculations of the loads in four test persons. The calculations indicated compressive loads on L3 ranging from 5000-11,000 N during squat and torso lifting. Such loads in vitro have been found to cause structural failures of the vertebral endplates. Similar loads also may result in damage to the spine in vivo.

Adult↗
PubMed1984

Measuring functional impairment associated with pain: psychometric analysis of an exploratory scoring protocol for activity pattern indicators.

Behavioral science theorists who study pain have advocated the development of measures designed to assess aspects of behavior. Recently, Diller , Fordyce , Jacobs, and Brown developed a 64-item self-report activity measure. Assessment of functional impairment associated with pain is a potentially appropriate application for the Activity Pattern Indicators (API). The API provides a description of actual functioning; frequency of behavior is the unit of measurement. Currently, no agreed upon scoring protocol is available for this measure. We propose to design, in accordance with measurement theory, a psychometrically sound yet practical scoring protocol. The API data presented allow an acceptable degree of reliability and sensitivity to group differences. Results of the present study support continued psychometric exploration of: the current scoring protocol, alternative scoring protocols, and the Activity Pattern Indicators.

Activities of Daily Living↗
PubMed1983

Effects of spaceflight on structural and material strength of growing bone.

Rats in space for 18.5 days did not exhibit the normal gain in femoral bone strength of terrestrial controls. The strength deficit may have been caused by multiple factors including a diminished bone formation and an inhibition of the gain in tissue material strength. Centrifugation at 1g in space substantially enhanced bone strength, possibly by promoting more normal tissue maturation. Full recovery of bone strength was achieved 25 days after reentry.

Animals↗
PubMed1982

In vivo strain gage implantation in rats.

A technique for the fabrication of encapsulated micro-miniature rosette strain gages for in vivo implantation is described. The gage units have an overall area of ten square millimeters (2.5 mm X 4.0 mm), and hence can be installed in very small experimental animals, particularly rodents. Using a rat model, strain data for up to 12 days have been obtained and in vitro studies have validified the in vivo strain recordings.

Animals↗
PubMed1981

Fixation of porous titanium implants in cortical bone enhanced by electrical stimulation.

The effect of in vivo electrical stimulation on the interfacial strength between porous titanium implants and cortical bone was studied in mongrel dogs. The interfacial shear strength of the stimulated implants was consistently greater than that of controls. No difference could be observed in the quality of bone ingrowth. The data suggest that the rate and quantity of bone ingrowth were enhanced by electrical stimulation.

Animals↗
PubMed1981

Fatigue behavior of adult cortical bone: the influence of mean strain and strain range.

Uniaxial fatigue tests were conducted of devitalized cortical bone specimens machined from human femora. Specimens were tested at strain ranges from 0.005 to 0.010 under physiologic loading rates. The influence of compressive, zero, and tensile mean strains on fatigue life and on the stress/strain histories during fatigue were examined. Results showed that bone fatigue is a gradual damage process accompanied by a progressive increase in hysteresis and a loss of bone stiffness. The total number of cycles to fatigue failure was influenced only by the total strain range and was not affected by mean strain. Bone was shown to have extremely poor fatigue resistance. Fully reversed cyclic loading to one half of the yield strain caused fatigue fracture in 1000 cycles. Biological implications. The bone regions which experience the highest strain ranges in vivo generally have a compressive mean strain. The results of this study indicate that mechanical fatigue damage accumulates more rapidly in these "compressive" areas than in "tensile" areas of bone.

Aged↗