Patient handling with and without slings: an analysis of the risk of injury to the lumbar spine

Abstract

Health professionals handling patients are known to be at risk of sustaining work related low back injuries. It is not known whether the use of lifting slings reduces the risk of injury to the lumbar spine for patient handlers. This study used kinematic variables and subjective ratings of body part stress and lifter preference as measures of relative risk for three two-person techniques for carrying a patient from one chair to another chair. The techniques used no slings, one and two slings respectively. Twenty-two nurses performed five trials each of the three techniques. Kinematic measures of angular displacement, velocity and acceleration were obtained using the lumbar motion monitor and visual analogue scales were used to obtain measures of body part stress for seven body parts. Angular displacement, velocity and acceleration were significantly greater (p<0.05) in the frontal, sagittal and transverse planes for the no sling technique compared to techniques using slings. Comparatively small yet significant differences between techniques using slings were recorded for sagittal flexion and rotation. There was no significant difference between one and two sling techniques for other dependent variables. Mean total body stress rating was higher for the no sling technique and all subjects indicated that their first preference was for slings. Although all three measures of risk rated the no sling technique as carrying a higher level of risk than the techniques using slings. No single measure adequately captured all aspects of relative risk. The elimination of manual patient handling is thought to be the best option for the reduction of work related back injuries in patient handlers. Where resources or technology are not yet adequate to provide practical alternatives and where the use of manual technique for a seat to seat task is unavoidable, the use of patient handling slings will reduce the risk.

Introduction

Musculoskeletal injuries, particularly those involving the lumbar spine are thought to be common among health professionals involved in patient handling (PH). The high incidence and prevalence of work related back injuries (WRBI) in professions involved in patient handling has been frequently reported (Buckle, 1987; Drury, 1991; Harber et al., 1985; Hignett and Richardson, 1995; Manassah, 1984; Pheasant and Stubbs, 1992; Scholey and Hair, 1989; Stubbs et al., 1983a). For example, the annual prevalence of WRBI in nurses has been found to be as high as 431 per 1000 at risk (Stubbs et al., 1983a) with patient handling associated with WRBI in 36% of nurses’ cases (Pheasant and Stubbs, 1992) and 50% of physiotherapists’ cases (Drury, 1991).

Although the cost of WRBI in health professionals is generally acknowledged to be high (National Back Pain Association and Royal College of Nursing, 1998; Karas and Conrad, 1996; Straker, 1991), quantifying these costs is difficult due to the number and nature of the costs and also due to limitations in information systems (Straker, 1991). Direct costs for the employer may include treatment and compensation for injured workers. Indirect costs such as the expenses associated with the recruitment and training of new staff, decreased productivity and reduced staff morale may be more difficult to evaluate. There are also costs for injured employees who suffer not only physically, but also financially and emotionally.

As WRBI is clearly a common and costly problem to the health industry, the effective minimisation of risk is important. One commonly advocated strategy to minimise risk is to identify high risk tasks, determine which risk factors are important for those tasks, then modify these risk factors.

Whilst some attempts have been made to identify risk factors for patient handling, the literature appears to be lacking a common language for describing patient handling techniques and tasks. Research papers often provide insufficient detail on tasks and techniques which results in difficulties making comparisons between different studies. There is, however, sufficient evidence to suggest that the category of seat to seat tasks (bed to wheelchair, wheelchair to toilet, etc,) is an important category of tasks on the basis of the frequency with which these are performed (Bell et al., 1979; Pietrocola, 1995) and the physical stress reported by patient handlers (Bell et al., 1979; Garg et al., 1992; Pietrocola, 1995).

The nature of the load is thought to be an important risk factor for manual handling. Detailed patient assessments such as those outlined in National Back Pain Association and Royal College of Nursing (1998) and Tuohy-Main (1994) can assist the patient handler in identifying possible risk factors associated with moving a human load. A patient is capable of assistance or resistance (Hignett, 1994; Tuohy-Main, 1994), resulting in a patient load which may not be constant or predictable from one patient handling task to another. The human body is also comparatively fragile, particularly if the patient is ill or elderly. Nurses have indicated that professional responsibility and a duty of care may cause them to place the physical safety of the patient above their own (Hignett and Richardson, 1995). The human body is also an awkward and changeable shape. Anthropometric data demonstrate the variety in human girth, width and length (Pheasant, 1986), while age and disease may alter the relative proportions and orientation of limbs and the trunk and therefore change a patient's centre of gravity. Furthermore, the human body is not a compact mass and is comparatively difficult to grip in the absence of convenient handles (Harber et al., 1985).

Characteristics of the load and other task and environmental variables such as the height of furniture (Pheasant, 1987) and cramped workspaces may affect the posture of patient handlers. Non-neutral spinal postures, that is postures where there is angular displacement of the spine from a neutral position, have been shown to be commonly adopted by nurses performing patient handling and non-patient handling tasks (Engels et al., 1994a, Engels et al., 1994b; Harber et al., 1985; Hignett, 1996; Takala and Kukkonen, 1987; Videman et al, 1989). This suggests that angular displacement is a significant risk factor for WRBI in patient handlers. Non-neutral postures of the spine, are associated with increased moments and forces on the lumbar spine (Chaffin and Anderson, 1984) and increased intradiscal pressures, particularly for lateral flexion and flexion with rotation (Andersson et al., 1973). Extreme angular displacement may result in injuries to the intervertebral discs (Adams and Hutton, 1982; Hickey and Hukins, 1980).

The rate at which loading of the lumbar spine occurs is also thought to be a risk factor for WRBI (Marras et al., 1995). Increasing velocity has been found to increase extensor moments for both stoop lifting and squat lifting tasks (Dolan et al., 1994) and also rotation, flexion/extension and lateral flexion moments at the lumbrosacral junction for an asymmetric lifting and lowering task (Gagnon and Gagnon, 1992). Rotational moments were also significantly increased for the lowering task at the fast velocity compared to the slower velocity in Gagnon and Gagnon's study (1992). In an extensive investigation of lumbar spine injury in 403 jobs involving manual handling in an industrial setting, Marras et al. (1995) demonstrated that velocity of movement in the transverse and frontal planes is a significant risk factor for WRBI.

Estimates of rotation, flexion/extension and lateral flexion moments have also been found to increase with the application of a strong initial acceleration to the load during lifting (Gagnon and Gagnon, 1992). By comparing their results with the average maximal muscular moments for male subjects obtained from two other studies, Gagnon and Gagnon (1992) found that the accelerated lifting condition required 30% of the subjects’ capacity in the transverse plane and 83% of the subjects’ capacity in the sagittal plane. They concluded that the rate of lifting was important in evaluating the risks associated with manual handling tasks.

There is now increasing interest in the kinematics of the lumbar spine in manual handling (Ferguson and Marras, 1992; Ferguson et al., 1992; Kumar, 1995; Kumar and Garand, 1992; Li, 1993; Marras et al., 1995; Marras et al., 1990; Marras and Mirka, 1989; Parnianpour et al., 1991; Vink et al., 1992). The detailed consideration of risk factors such as the characteristics of the load and the kinematics of specific patient handling tasks and techniques should indicate measures for the reduction of the risk of lumbar spine injury for patient handlers.

Risk reduction for patient handling has traditionally emphasised training with equivocal impact on the prevention of WRBI (Stubbs et al., 1983b; Venning, 1988; Videman et al., 1989). Consequently, job redesign has been proposed as a more promising measure for reducing risk for manual handling in general (Snook, 1978; Health and Safety Executive, 1992) and specifically for patient handling (Venning, 1988; National Back Pain Association and Royal College of Nursing, 1998).

Health care policies have recently advised the elimination of manual lifting of patients. Mechanical aids such as hoists have been used to lift patients (Garg and Owen, 1992; Le Bon and Forrester, 1997). Other aids have been used to facilitate transfer at patients (where less than the full weight of the patients is taken). For example, Gagnon et al. (1988) used a waterproof padded sheet to roll patients and Zelenka et al. (1996) used a series of rollers and a semi-rigid board to shift patients in a bed.

Many patient handling advisors now believe that the manual lifting of patients can be avoided in most situations in a well resourced institution and recent guides such as that produced by National Back Pain Association and Royal College of Nursing (1998) provide mechanical alternatives for many patient handling situations. However many health care systems in the world cannot afford expensive mechanical hoists. Further, where patient handling is conducted in uncontrolled environments, for example by ambulance and reserve personnel, manual lifting may be unavoidable with current mechanical aid technology.

Whilst there is consensus that elimination of manual lifting is the preferable approach to reducing the risk in patient handling, where this is not feasible, other measures should be taken to reduce the risk.

Another approach to job design is to improve the features of the patient as a load. The type of coupling between the patient handler and patient may affect the patient handler's ability to control the patient load. The nature of coupling is partly determined by the choice of either an aided or unaided manual technique. Coupling in a manual unaided patient handling technique is achieved by various handholds (Hollis, 1991), but these may place unacceptable stress on the patient's skin (Mattner, 1984) or be uncomfortable for the handler's hand or wrist. The use of aids, for example the provision of `handles’ by using slings, has been recommended to improve the quality of coupling during manual handling.

Increasingly, literature on patient handling techniques has included information on manual aids for patient handling (Farmer, 1987; Hayne and McDermott, 1982; Seymour, 1995; Treveylan, 1996; Le Bon and Forrester, 1997) in addition to mechanical aids, such as the hoist. The use of patient handling slings has been recommended in manuals on patient handling (Hollis, 1991). Several types of patient handling slings or belts incorporating handles are available. These include slings such as the blue polymer patient handling straps produced by MEDesign^TM (Southport, UK) and slings made of fabric (Pelican Manufacturing, Perth, WA, Australia). Patient handling belts which encircle the patient's hips or trunk such as the Jonybelt^TM (Kinkumber, NSW, Australia) may also be used.

Patient handling slings have been used with some success in ergonomic programmes designed to reduce WRBI in patient handlers in the health industry (Garg and Owen, 1992; Head and Levick, 1996). Other studies have demonstrated that patient handling aids can reduce stooping and twisting of the trunk (Takala and Kukkonen, 1987). Estimations of compression and shearing forces at L5/S1, trunk moments in lateral flexion and flexion, and erector spinae forces have also been lower when slings and similar patient handling aids were used compared to manual unaided techniques for wheelchair to bed and bed to wheelchair tasks (Garg et al., 1991). Subjective ratings of perceived stress were also lower in this study.

The limited literature available for review on patient handling slings is not entirely supportive of the use of slings and similar aids. Tuohy-Main (1994) suggests that using slings can increase the length of the moment arm or force the patient handler to rotate and side flex the spine under load in a trade-off to reduce flexion of the spine. A study by Gagnon et al. (1986) compared the use of a patient handling belt with a manual unaided technique for a sitting to standing task. Despite acknowledging some limitations in their use of a mannequin as a patient in this study, they found that the technique with the patient handling belt resulted in higher estimates of maximum compression forces at the level of L5/S1 than the manual unaided technique.

As yet, there does not appear to be any published research using kinematics for the investigation of patient handling tasks, and specifically the use of patient handling slings. It is still not known whether the use of slings reduces the relative risk of lumbar spine injury in patient handlers.

This study therefore aimed to investigate whether the use of patient handling slings for lifting a patient from one seat to another reduces the risk of injury to the lumbar spine compared to a similar technique without using slings.