The rising number of underfoot accidents after the menopause causes both fractures and non-fracture injuries.

To test our hypothesis that the onset of the menopause would be associated with an increased number of underfoot accidents in the female population for both fracture and non-fracture injuries, we analysed 90061 accidents recorded by the Home Accident Surveillance System and classified them as to (a) whether a fracture resulted, and (b) whether they were 'underfoot'. We defined 'underfoot' accidents to have an event such as a trip, slip, missed footing, twisted or turned ankle, on the level or on stairs. All other accidents, including falls from or off structures, or falls caused by medical conditions were classified as 'not underfoot'. Overall, 51.3% of women and 32% of men were injured in underfoot accidents. There was an increase with age in the percentage of fractures in both men and women, mainly due to an increased risk of fracture in underfoot accidents: underfoot accidents caused 75.9% of all fractures in women and 55.4% in men. The number of women who had fractures following underfoot accidents increased sharply after the age of 50 years, and the number continued to rise up to 80 years. The number of non-fracture injuries in elderly women from underfoot accidents also increased with age. Osteoporosis on its own does not explain our result, and changes in muscle strength and reaction time, with age in both men and women, and at a greater rate in postmenopausal women, may be an important factor in underfoot accidents.

An investigation of underfoot accidents in a MAIM (Merseyside Accident Information Model) database.

Underfoot accidents taken from a study of patient interviews have been analysed to investigate factors that may be implicated in the causes of the accidents. Within the sample of patients in this study women holding items are more at risk than men from underfoot accidents. Carrying items such as shopping and handbags may obstruct the line of sight to underfoot hazards, affect balance and adversely affect reflex corporal movements that may help prevent injury.

The effect of roughness, floor polish, water, oil and ice on underfoot friction: current safety footwear solings are less slip resistant than microcellular polyurethane.

Research over a period of about 18 years has shown that a microcellular polyurethane known as AP66033 is the most slip-resistant safety footwear soling material on oily and wet surfaces. In recent years it has been replaced in commercially available footwear by a dual density polyurethane (DDP) which has a dense outer layer and a soft microcellular backing. This research programme has compared the slip resistance of AP66033 with DDP and some rubber solings. In addition, data were obtained on the effects of soling and floor roughness, and floor polish on slip resistance. Some data were also obtained for walking on ice. The coefficient of friction (CoF) of the solings was measured on 19 water wet surfaces in three conditions: (I) when the solings were new, (II) following abrasion to create maximum roughness and (III) after polishing. The CoF was measured on four oily surfaces after each of 11 abrasion or polishing treatments. The profound effects of the roughening of all soles and of floor roughness on the CoF were demonstrated for both wet and oily surfaces. The superior slip resistance of AP66033 was confirmed for oily and wet conditions; however, some rubbers not suitable for safety footwear achieved higher CoF values on wet floors. All of the floor polishes reduced the CoF of all floors when contaminated with water. The mean CoF of DDP solings was lower than the mean for AP66033 on wet and oily surfaces. No safety footwear soling provided adequate grip on dry ice and the CoF was reduced by water on the ice. A rubber used for rock climbing footwear was one of the most slip-resistant solings on wet surfaces in the laboratory but recorded the lowest CoF on ice. It is concluded that the incidence of occupational injuries caused by slipping could be reduced by the following: (A) returning to safety footwear soled with the microcellular polyurethane AP66033; (B) abrading all new and smooth footwear solings with a belt sanding machine coated with P100 grit; (C) avoiding the use of floor polish; (D) informing the general public about the poor slip resistance of ordinary footwear on ice and the lowering of slip resistance in cold weather.

Occupational slip, trip, and fall-related injuries--can the contribution of slipperiness be isolated?

To determine if the contribution of slipperiness to occupational slip, trip and fall (STF)-related injuries could be isolated from injury surveillance systems in the USA, the UK and Sweden, six governmental systems and one industrial system were consulted. The systems varied in their capture approaches and the degree of documentation of exposure to slipping. The burden of STF-related occupational injury ranged from 20 to 40% of disabling occupational injuries in the developed countries studied. The annual direct cost of fall-related occupational injuries in the USA alone was estimated to be approximately US$6 billion. Slipperiness or slipping were found to contribute to between 40 and 50% of fall-related injuries. Slipperiness was more often a factor in same level falls than in falls to lower levels. The evaluation of the burden of slipperiness was hampered by design limitations in many of the data systems utilized. The resolution of large-scale injury registries should be improved by collecting more detailed incident sequence information to better define the full scope and contribution of slipperiness to occupational STF-related injuries. Such improvements would facilitate the allocation of prevention resources towards reduction of first-event risk factors such as slipping.

The role of surface roughness in the measurement of slipperiness.

Surface roughness has been shown to have substantial effects on the slip resistance between shoe heels and floor surfaces under various types of walking environments. This paper summarizes comprehensive views of the current understanding on the roles of surface roughness on the shoe and floor surfaces in the measurement of slipperiness and discusses promising directions for future research. Various techniques and instruments for surface roughness measurements and related roughness parameters are reviewed in depth. It is suggested that a stylus-type profilometer and a laser scanning confocal microscope are the preferred instruments for surface roughness measurements in the field and laboratory, respectively. The need for developing enhanced methods for reliably characterizing the slip resistance properties is highlighted. This could be based on the principal understanding of the nature of shoe and floor interface and surface analysis techniques for characterizing both surfaces of shoe and floor. Therefore, surface roughness on both shoe and floor surfaces should be measured and combined to arrive at the final assessment of slipperiness. While controversies around the friction measurement for slipperiness assessment still remain, surface roughness measurement may provide an objective alternative to overcoming the limitations of friction measurements.

Detecting and eliminating slippery footwear.

A recently developed walking traction test has proved to be a reliable and rapid method of measuring coefficient of friction (c.o.f.) of floor surfaces and footwear, and is a suitable method for ranking the grip of footwear solings on slippery floors. This paper describes four new experiments in which footwear samples were ranked. The first experiment compared mean rank orders on water wet (wet) and oily surfaces of seven flat solings. Spearman's rank correlation coefficient rs was 0·893, P < 0·005. In the second experiment, five pairs of women's shoes were ranked on wet and oily surfaces. On the wet surfaces, three samples recorded maximum attainable c.o.f. but rank orders on two oily surfaces were identical, rs = 1·0, P < 0·01. In the third experiment, thirteen pairs of discarded footwear were ranked using three different test methods. The test surfaces were oily stainless steel plates cut from the same sheet. Rank orders of the three test methods were significantly similar. Kendall's coefficient of concordance w = 8·68, P < 0·001. In another experiment samples of commercially available footwear were issued to factory workers and recalled for c.o.f. measurements at intervals. Their rank orders on wet and oily surfaces were not statistically similar but when wet surface results obtained at 4 months, were compared with those at 10 months, rank orders were significant; rs = 0·994, P < 0·01. Also on oily surfaces, rank orders of two measurements were significant, rs = 0·982, P <0·01. Although most experiments have revealed significant correlations between footwear samples on wet and oily surfaces there are examples where a soling performs well on wet surfaces but is at the lower end of rank order on oily surfaces. It is concluded that rank orders on wet, oily and icy surfaces should be calculated but also it is necessary to examine rank orders on each surface-lubricant combination, by comparing results obtained at intervals during the useful lives of the solings. In future, samples at the lower end of the rank orders of c.o.f. will be eliminated from the varieties available to workers.

Analysis of 100 upper limb injuries using the Merseyside Accident Information Model.

More than 2 million upper limb injuries occur each year in Britain. Information about the precise sequence of events leading up to an accident may help prevention of similar injuries by alteration of the work environment or through safety education. The first impression of the cause of an accident may not identify the key event triggering it. The Merseyside Accident Information Model (MAIM; Manning, 1987) provides a structured questionnaire, based on a menu-led computer programme. This not only allows the first unforeseen event to be identified from the history, but is also the basis of a database. Pooled data can then be analyzed. We present an analysis of 100 consecutive cases presenting to one Plastic Surgery Unit.

Slip-shod or safely shod: the bighorn sheep as a natural model for research.

Over a million injuries caused by slipping of footwear are believed to require treatment by doctors every year in the United Kingdom and many domestic animals are injured by slipping. Recent research has revealed that surface roughness of solings and floors is an important determinant of grip on lubricated surfaces and it is also known that soling friction is affected by hardness. The bighorn sheep (Ovis canadensis) an animal species which has adapted to a slippery environment, was studied to elucidate optimum roughness and hardness and other features which influence grip. Four adult ewes were examined in the London Zoo. The cloven hooves of this species are very mobile and the cranial tips of the hooves are the first parts to make contact with the ground. A very small contact area ensures penetration of a film of water. Mean roughness of the contact area was found to be 53 microns Rtm and the mean hardness 63 Shore A. These characteristics appear to facilitate an excellent grip on wet slippery rock but not on smooth ice. Further studies of the feet of wild species could contribute to an understanding of the factors which determine the safety of solings and floors.

Studies on the footpads of the polar bear (Ursus maritimus) and their possible relevance to accident prevention.

The incidence of slipping accidents is unknown, but accident and emergency departments in the United Kingdom probably treat over one million injuries per annum caused by slipping of the feet. Many injuries to farm livestock are caused by slipping. Previous research led to speculation that some animal species may have developed slip-resistant feet and the polar bear was chosen for a study of adaption to a slippery environment. Feet were photographed and a footpad was sectioned and examined by light and electron microscopy. Hardness of the footpads of two tranquillized bears was measured. The footpads were found to have a rough papillary surface overlying a soft dermis containing a dense network of collagen and elastic fibres. These findings support a hypothesis that shoe solings for use on an icy substrate should be soft with a hardness value in the region of 24 on the Shore A scale. The surface should be covered in conical projections having a mean diameter of 1 mm. Further work on the feet of animal species could lead to a better understanding of slip-resistance and reduce injuries to humans and livestock.

Body movements and events contributing to accidental and nonaccidental back injuries.

During 1980, 1153 employees attended the Occupational Health Department with back pain out of a working population of 13,958 in a car factory. Four hundred one were absent from work and a further 64 patients were restricted by back pain and unable to perform their normal work. One hundred forty-seven cases of back pain arose at work, and 71 in and around the home. All those who were absent or restricted were questioned about the onset of back pain in order to distinguish between accidental and nonaccidental injuries (NAI), and an accident model was used to structure the information. There were 122 accidents, 114 NAI, and 165 patients who could not attribute a cause to their back pain. A significantly higher proportion of the NAI arose at home and, conversely, a higher proportion of accidents occurred at work. Eighty (66%) of the accidents were underfoot accidents, including 57 slips. There were highly significant differences between the body movements contributing to accidents and NAI. Significantly more of the NAI than the accidents involved load handling, but 52% of the patients able to attribute a cause to their back pain were not moving loads. While handling of loads is important, attention should be directed to other contributory factors such as unsafe floor surfaces and bending and twisting movements--not only at work but also in and around the home.

Slipping accidents causing low-back pain in a gearbox factory.

An accident model was used to analyze data in terms of the first event in all reported accidents occurring in a gearbox factory during 1974. The data were used to study the causes of lumbosacral injuries. A labor force of 2000 men sustained 99 lumbosacral injuries, 54 of which led to absence of one or more days. Twenty of the 54 were initiated by slipping, and 17 presented as a sudden onset of low-back pain without any preceding accidental event. A review of all patients who were absent following a slipping accident disclosed that the lumbosacral region was by far the commonest part of the body injured. Tripping was an infrequent cause of these injuries. Slipping rarely features in the literature as a cause of low-back pain. It is suggested that this is due to confusion between various contributory factors and events forming an accident.