Putting the muscle into X-rays

March 1, 1999
Occupational injuries in the radiology department can be prevented by implementing the principles of ergonomics.

Occupational injuries in the radiology department can be prevented by implementing the principles of ergonomics.

Janet L. Rogers, PhD, and

Dan Jefferies, MS

In the past few years, a tremendous amount of attention has been devoted to ergonomics in the workplace. This is due in part to the United States Bureau of Labor Statistics reporting that the most prevalent and fastest growing occupational injuries are repetitive stress injuries (RSIs), which occur when stress and fatigue overpower the body`s natural ability to heal itself. This has been especially true for the dental hygiene profession. Much has been written about repetitive stress injuries, such as carpel tunnel. experienced by dental hygienists. The discussion surrounding prevention of RSIs among dental hygienists has focused primarily on chairside posture and the proper way to handle instruments. This article will focus on radiological tasks that are performed by the dental hygienist.

The most effective way to prevent RSIs is by implementing the principles of ergonomics. The major idea behind ergonomics is to fit the job to the employee, which results in a reduction in injuries and absenteeism, greater productivity, and improved employee satisfaction.

Ergonomics addresses human performance and well-being in relation to the job, equipment, tools, and the environment. This science works to improve the health and efficiency of the individual and to make the workplace more conductive to productivity and well-being. Ergonomics integrates engineering, anatomy, physiology, kinesiology, biomechanics, and the behavioral sciences.

When principles of ergonomics are applied, it is assumed that the workplace can be designed to suit human characteristics, capabilities, and limitations. A major principle of ergonomics is that all work activities cause some level of physical and mental stress. The intensity of this stress can produce musculoskeletal symptoms, which generally are caused by incompatibility between the worker`s capabilities and the demands of the job. Work areas should be designed to minimize excessive force, stress, and effort by and on the worker. The design must consider anthropometric factors, biomechanical efficiency of the body in different working postures, and principles of prevention.

Primary prevention, which reduces the occurrence of injury, goes hand-in-hand with ergonomics. Examples of ergonomics as primary prevention include:

* Evaluating tasks and work areas to determine biomechanical stresses

* Changing work-area layouts to reduce postural stresses

* Assessing postural requirements to eliminate fatigue and cumulative trauma

* Educating workers to increase their awareness of ergonomic prevention

Job analysis

The first step in planning for ergonomic prevention is to perform a job analysis that addresses the most commonly performed work-related activities of dental hygienists when performing the radiological requirements of their job. Traditionally, job analyses have been used as a means of designing jobs for maximum production. The results of job analyses also can be used to evaluate and reduce the load on the worker`s musculoskeletal system and reduce the risk of injury or illness.

A job analysis was performed to identify the specific tasks required to perform the work of radiography in a dental hygiene clinic. Specifically, we wanted to identify which required job tasks may cause worker injury or when done repetitively may cause injury. The radiology professor in the dental hygiene clinic at Southern Illinois University did a step-by-step analysis of the physical requirements to perform the work required to perform dental radiography. These tasks then were reviewed in terms of demands placed upon the musculoskeletal system.

The most frequently identified job tasks that may lead to worker injury include:

> Raising and lowering the intraoral tube head and panoramic overhead

> Placing on and removing the lead apron which weighs approximately 7-14 pounds

> Positioning of X-ray film packets which requires bending and rotating of the back and neck

> Reaching for the X-ray exposure switch while watching the patient

> Rotating the patient`s chair from side-to-side to position the patient and tube head

> Lifting to access process machine for film development

> Removing and reinstalling automatic processor racks and/or manual tanks in order to perform periodic maintenance procedures

> Lifting chemical jugs in order to replenish developer/fixer fluids

> Bending to clean automatic processing racks and/or manual tanks


Recommendations for improved ergonomic changes and general considerations for physical work demands will be addressed as they pertain to the most frequently required demanding job tasks. The recommendations will use applied ergonomics that address using the body in the manner in which it is intended. Applied ergonomics does not entail working harder, but working smarter with a more biomechanically correct position.

The problems caused by poor posture are commonly overlooked. Poor posture may result in cumulative trauma disorders such as low back pain, upper back pain, and carpal tunnel. In all work activities, try to change posture position frequently. When standing, try not to stand in a bent-over position for extended periods of time. Concrete floors offer no shock absorption to the spinal column of standing workers, which creates cumulative stress and static loading on back and leg muscles. Fatigue is a common problem for workers who stand for extended periods of time. Most individuals compensate for this by developing poor postural habits. Standing postures can be assisted by using footrests to shift body weight and intermittently working from a seated position such as from a high stool. The effects of continuous standing on the back and legs can be lessened by resilient floor matting (antifatigue mats) and wearing good supportive shoes.

Proper lifting techniques go hand in hand with preventive back management. Since dental hygienists performing radiologic job requirements do heavy lifting frequently, it is important to develop safe lifting habits. Proper lifting should involve performing the task without signs of fatigue, abnormal muscle recruitment, or change in technique with repetition. It generally is accepted by most back specialists that all lifting techniques should include: having the lifters maintain their backs in a lumbar lordotic position (maintain a curve in the low back area), keeping the weight to be lifted as close to their body as possible, and performing the lift as quickly as possible. The three lifting techniques recommended here all have the common key element of maintaining the lumbar spine in the position of slight lordosis. The lifter will have to determine which of the following techniques to use depending upon the size and position of the object to be lifted.

(1) The deep squat is correctly performed with the level of the hips below the level of the knees. The lifter`s feet straddle the object and arms are positioned parallel to each other. The lifter grasps the object on each side or under the bottom. The trunk is maintained in a vertical position, and the lumbar spine remains in lordosis.

(2) Using the power lift, a half squat is performed so that the hips remain above the level of the knees. The lifter`s feet stay behind the object and parallel to each other. The lifter grasps the sides or under the bottom of the object. The trunk leans slightly forward keeping the lumbar spine in lordosis.

(3) The straight leg lift is performed with the lifter`s knees only slightly flexed and with the legs either parallel to each other or straddled over the object. The object is grasped on each side and lifted with the lumbar spine being maintained in a lordotic position.

Maintaining the low back in a lumbar position is important due to anatomic and mechanical relationship. Maintaining a lumbar lordosis when lifting reduces the intervertebral pressure, which may protect the posterior area of the disk and reduce the tendency toward disc herniation or bulging. This position also increases the stability of the lumbar spine. Lifters unaccustomed to using these lifting techniques may feel awkward or uncomfortable at first. With practice these techniques can become habitual and may be performed with comfort and ease.

Many of the principles applied to lifting also are applied to pushing and pulling objects, such as when raising and lowering the intraoral tube head. Whenever possible, push instead of pull and keep knees in slightly flexed position. This position brings the object`s center of gravity closer to yours, which increases stability, reduces energy expenditure, and improves control of the object. The force of the pull or push should be applied parallel to the surface and in line with the direction of movement. More force is required to initiate the movement of a stationary object than to continue its movement. Therefore, preparation needs to be made to exert greater effort when beginning the push or pull. Redirect an object by pushing harder with one upper extremity than with the other, by pulling with one upper extremity and pushing with the other, or by positioning your body at one corner of the object and pushing or pulling at an angle to the line of forward motion.

Reaching for the X-ray exposure switch while watching the patient could be improved by providing a window or moving the switch. If remodeling is possible, the chair setup could be considered in the design. Ergonomic specialists suggest that work areas requiring occasional reaching tasks be within a 20-inch distance.

Vertical-reach distances should minimize forward elevation of the shoulder to less than 90 degrees and sideward reaches to less than 60 degrees. This reduces muscle fatigue that may result from increase in arm elevation. Reaches behind or to the sides that require twisting should be avoided at all times. When positioning X-ray packets in the patient`s mouth, stand as close to the patient as possible to reduce the distance of the reach. The hygienist`s knees should be bent when leaning over to check the positioning of the packet. This would help to avoid repeated bending at the waist and upper back, which causes repetitive trauma on the spine.

Making use of the swivel feature on a swivel-based chair can eliminate torquing on the spine. When using the swivel feature on the chair, it is important for dental hygienists to keep their backs in straight alignment to avoid loading the spine on one side more than the other.

Carrying objects correctly is as important as proper lifting techniques. When carrying the lead apron, chemical jugs, tanks, or racks, hold the object as close to your body as possible and use both arms to evenly distribute the weight. While carrying the apron, use arms as short levers and keep the apron close to your center of gravity, which is generally near the pelvis.

Cleaning tanks require both lifting and standing in a flexed trunk position. When cleaning tanks, apply safe lifting procedures and avoid staying in a continually bent over position for extended periods of time.


Ergonomics assumes that the work environment can be designed and employees taught techniques that make the work environment safer from physical stresses that can produce musculoskeletal symptoms. Implementing a few, simple ergonomic safety measures will provide savings to the employer in the form of reduced worker`s compensation claims, reduced absenteeism due to painful musculoskeletal conditions, and an increase in worker productivity. For employees, ergonomics provides the environment and information necessary to perform their job safely. Using ergonomic recommendations will improve the health and efficiently of both the individual and the employer.

Janet L. Rogers is an assistant professor in the physical therapist assistant program, Department of Health Care Professions, College of Applied Sciences and Arts at Southern Illinois University, Carbondale. Dan Jefferies is an assistant professor in the dental hygiene program, Department of Health Care Professions, College of Applied Sciences and Arts at Southern Illinois University.


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The Principles of Ergonomics

* Avoid any excessive or sustained bending or unnatural postures whenever possible. For example, alternate between maxillary and mandibular films when performing a full mouth x-ray series to avoid bending for long periods.

* Avoid lifts directly from the floor level possibly through the use of wall-mounted hangers for lead aprons.

* Position yourself as close as possible to the object to be lifted.

* Avoid twisting while lifting; turn with your whole body rather than turning with the torso alone.

* Use pushing rather than pulling actions whenever possible such as when positioning the tubehead.

* Minimize forward and sideward reaches to below shoulder-level height.

* Arrange the work area so that you can work with your elbows at an angle of about 90 degrees.

* Limit the areas of frequent work to a semicircle within 10 inches of your body.

* Keep the wrists as straight as possible while working.

* Use tools that are task specific and that distribute forces throughout the hand.

* Avoid unnecessary repeated and rapid arm or hand movements.

* Pad counter edges or use forearm supports to lessen the weight on the hand while performing hand-intensive work.

* Arrange work areas to be within a direct field of vision.

* Perform work sitting down if you can. Alternate standing tasks with sitting ones whenever possible.

* Use chairs with adjustable features and good back support.

* Avoid heavy lifting whenever possible by purchasing supplies in smaller sizes.

Modified from Work in Progress: Occupational Therapy in Work Programs, 1989, page 146.