Ultrasonic measurement of lumbar canal diameter: a screening tool for low back disorders?

Preventive screening measures for low back pain are limited. Despite considerable evidence that anatomic narrowing of the lumbar spinal canal is a risk factor for specific back problems, difficulty in measuring the canal without unacceptable radiation exposure, cost, or discomfort has limited the assessment of its clinical significance. Using ultrasound to measure the lumbar canal is relatively easy to do, and provides accurate values. In this paper we review the reports on this use of ultrasound, including our own experience in a case control study, and discuss the potential use of ultrasonic measurement as a screening tool to identify narrow lumbar canals.

Ultrasound lumbar canal measurement in hospital employees with back pain.

The oblique parasagittal diameter of the lumbar spinal canal at the L5-S1 level was measured in 49 employees of the Wm Jennings Bryan Dorn Veterans' Hospital using real time ultrasound in a case-control study. Individuals with a canal diameter of less than 14 mm represented the lowest 10th percentile in this population and being in the narrowest 10th percentile constituted a risk factor for time missed from work because of low back pain (odds ratio 10.7). Whereas numbers in this pilot study are small, results are consistent with earlier ultrasound studies done in the United Kingdom and with other research showing increased morbidity from low back pain in individuals with small lumbar canals. Ultrasound has advantages over other modalities for measuring the size of the lumbar canal and may be useful as a preplacement screening examination in industry.

Calculating expected deaths: a comparison of two methods.

A comparison is presented between the traditional "person-years" and more recently described "prospective model" methods for calculating mortality expectations. Problems arising from the fact that expectations under the person-years method are calculated on the basis that a null hypothesis is true, which results in artificial figures that, at least theoretically, are meaningless if the hypothesis is rejected, are discussed. Data are presented from two studies in which expectations have been calculated both ways, showing important differences between the two methods with an exaggeration of the expectation when the study group has an above normal mortality experience. It is suggested that the person-years methodology should be replaced by that of the prospective model.

Use of industrial hygiene and safety professionals: a survey of South Carolina manufacturing plants.

There has been considerable debate about manpower adequacy in industrial hygiene and safety, but little indication as to which industries make use of these professionals and to what extent. This paper presents the results of a survey of manufacturing industry in South Carolina, which suggest that plants not only make less use of the services of industrial hygiene and safety engineers than might seem desirable, but have only a limited perception of the need.

Occupational health services in South Carolina manufacturing plants: results of a survey.

A mailed survey of occupational health and safety practices in industrial manufacturing plants with more than 50 employees was carried out in South Carolina, with a response rate of 60 percent. The responding plants represented 73 percent of the total workforce in the industries. Data were analyzed in relation to the types of industry as delineated by the Standard Industrial Code. Eighty-three percent of the responding plants (a percentage that represented more than 92 percent of the total workforce in the industries) had some arrangements for the medical or nursing care of employees. For the study, occupational health services were defined at three levels: basic (mandatory), secondary (beneficial to management), and tertiary (health promotion-preventive medicine). The basic services provided by most of the industries surveyed appeared to be adequate. Secondary services were well developed except in the apparel and lumber industries. Tertiary services, in terms of five selected preventive programs, were moderately developed only in the paper, petroleum, and chemical industries. Only alcohol abuse control programs were commonly offered in the other types of industry. The size of the workforce in a plant partly dictated the level of occupational health services it offered but did not always account for all inter-industry variation.

Economic evaluation of corporate medical programs.

The cost of corporate medical programs is receiving increasing attention in times of financial austerity. This article reviews the published data on economic evaluations of such programs. It develops a framework within which profitability and cost-effectiveness can be assessed. Critical evaluation of the available data confirms the probable cost benefit of preemployment examinations, and absenteeism and alcohol abuse control programs. It is noted that the data are limited to a small and unrepresentative sample of industry.

Identifying the cause of ischemic heart disease/myocardial infarction syndrome: a new approach.

Risk factor identification in the coronary heart disease/ myocardial infarction syndrome has failed to account for the epidemic pattern of increase in this century with recent decline. It is hypothesized that the true cause remains unidentified and that innovative application of traditional epidemiologic techniques, to correlate the identifiable peaks in different regions with possible agents, may prove successful.

Occupational cancer: experience in Ontario.

This paper reviews the experience of the Workmen's Compensation Board of Ontario in identifying cases of cancer that could be attributed to occupational hazards. Worker's claims for compensation are allowed if there is reasonable medical evidence that their cancer was caused by exposure to risk factors associated with their occupation. Details of the types of cancer associated with specific carcinogens or fields of employment are discussed. About 50% of the cases were related to exposure in particular industrial operations that functioned for relatively brief periods. The number of deaths from cancer identified as being caused by occupational factors is compared with the total for cancer from all causes in Ontario during the period 1971 through 1975. Although all workers eligible for compensation may not have been identified, the data suggest that less than 1% of cancer is presently caused by occupational factors.

Respiratory cancer in a cohort of nickel sinter plant workers.

A study was undertaken of a cohort of nickel refinery workers from a sinter plant that operated from 1948 to 1962. A complete follow-up of the 495 workers has been carried out by searching death records and other measures. Incidence cases known to the Workmen's Compensation Board of Ontario have been included. Fifty-four cases of lung cancer and eight of sinus cancer (including two in men who subsequently developed primary lung cancer) were located. The risk of lung and sinus cancer was much higher in the earlier days of operation of the plant, with an increase rate of over 40% for those employed in the first year of operation. The dose-response relationship has been examined by regressions of standardised morality ratios (SMR) and standardised incidence ratios (SIR). The SIR suggests that the risk doubled at levels of exposure of 12 months (six months in the earlier years).

Laryngeal cancer: an explanation for the apparent occupational association.

The apparent association of laryngeal cancer with asbestos and possibly other occupational exposures can be accounted for by the hypothesis that chronic vocal abuse peculiar to certain working conditions will act as a promoting factor for active carcinogens found mainly in tobacco smoke.

The epidemiology of primary lung cancer in uranium miners in Ontario.

This paper reviews the epidemiology of lung cancer in uranium miners in northern Ontario whose cumulative exposure was relatively low and who were exposed only for a short period of time. The development of the "epidemic" is demonstrated chronologically and in terms of latency. An apparent difference between the effects of short-term and of more prolonged radiation is shown. A dose-response effect is demonstrated at all levels. Analysis of tumor type suggests that there may be a difference in dose-response between the two principal types encountered. The relationship of the geographic location of exposure to the final residence at death is reviewed.

Occupational lung cancer and smoking: a review in the light of current theories of carcinogenesis.

This paper considers modern theories of carcinogenesis as they apply to the induction of lung cancer by tobacco smoking and occupational exposure to carcinogens. Some of the known and postulated factors affecting carcinogenesis are discussed, with particular reference to syncarcinogenesis and thresholds. Factors affecting the intensity of smoking exposure are reviewed, and the generally accepted occupational lung carcinogens are listed. Relative risks for the various carcinogens according to smoking status (where known) are presented. The carcinogens are considered individually, and known or postulated interactions with smoking are discussed. It is concluded that the effects of lung carcinogens can be explained on the basis of current theories that support a rational definition of priorities for the prevention of occupational lung cancer.

Permanent disability evaluation in terms of dynamic function.

This article reviews the concepts of impairment and disability. It is argued that traditional methods of disability assessment based on passive function do not adequately reflect actual loss of function and that it is possible to arrive at a much fairer assessment of residual abilities. The techniques suggested are derived from those already established in the rehabilitation field by the proponents of the GULHEMP System. It is suggested that raditional methods are falling into disrepute because of thier inadequacy and that this reflects on the profession as a whole.

Permanent disability evaluation.

This paper is a review of the theory and practice of disability evaluation with emphasis on the distinction between medical impairment and disability. The requirements for making an accurate assessment of medical impairments are discussed. The author suggests three basic standards which can be used for establishing a simplified method of assessing physical impairment.