Handlebar Grip Related Injury Prevention (GRIP) Study: Are Exposed Metal Handlebar Ends a Risk Factor for Injury?

Injuries are the most common cause of death of children aged 1-14 years in the European Union[11]. In the United States cyclist injuries are the 3rd most common mechanism of injury in 7-13 year olds, after motor vehicle collisions (MVC) and falls[1]. Bicycle injuries have remained one of the most common causes of paediatric abdominal trauma for over 60 years[2,3]. The vast majority (95-98%) of child cyclists admitted due to abdominal trauma are over 5 years old[2,3]. As with most mechanisms of injury, boys are injured more frequently than girls. Around three quarters of injured child cyclists are boys[12].

In a recent UK study, handlebar end impact was the mechanism that most frequently resulted in major intra-abdominal trauma in children. Impact with a handlebar end was implicated in 29% of cases. This was ahead of falls (20%), pedestrians (8%) and MVC occupants (8%)[3]. A study conducted in Australia found 15% of child cyclist injuries involved impact with a handlebar, and 10% of all child cyclist injuries were abdominal handlebar injuries[4]. A study in Philadelphia found that 8% of all paediatric bicycle-related trauma admissions involved handlebars impacting the abdomen resulting in an injury with an Abbreviated Injury Scale (AIS) score of 2 or greater[13].

The majority of handlebar injury case series reported in the literature relate to children's abdominal injuries. The peak incidence occurs between 6 and 14 years of age[4]. However, adults can also sustain serious handlebar related injuries[14-16] and 36% of all handlebar injured patients sustain only extra-abdominal injuries[4]. It is not just pedal cyclists who are at risk of these injuries. Incidents also involve non-motorized kick scooters, moto-cross bikes, motorbikes and quad bikes[3,4].

Crash investigations have found that serious handlebar injuries often occur after apparently minor incidents; they are not unique to riders performing stunts or those riding BMX bikes[5,6]. There is a typical sequence of events common to many of these handlebar injuries[5]. The child loses control of the bike and begins to fall. The front wheel rotates through 90 degrees so that it is perpendicular to the child's body. The child continues to fall forwards, landing on the upturned handlebar end.

Children's bikes and scooters often have damaged rubber grips with exposed metal handlebar ends. This occurs through day-to-day use. Each time the child drops their bike or scooter on its side, the handlebar end contacts the ground. When it does so, the metal tube inside the rubber grip cuts into that rubber. With time, a circle is cut from the rubber end, exposing the metal pipe within.

Handlebar end injuries can occur both when the handlebar ends are exposed and when they are intact. Two studies from the 1990s have looked at the condition of the handlebar end implicated in such injuries[5,6].

Acton et al published a series of 21 patients who reported handlebar impact as the cause of their injuries. Re-interview found that metal handlebar ends were exposed on bikes of all 10 children who sustained a major abdominal injury, whilst exposed handlebar ends were present on only one bike of 8 respondents with minor abdominal injuries[6].

Winston et al included detailed analysis on 4 riders who sustained serious abdominal injuries due to landing on a handlebar end. They found that these serious injuries occurred in 3 riders despite the presence of protective rubber covering on the handlebar ends. The rider who impacted an exposed metal handlebar end, however, had a particularly serious injury. He was a 6-year-old boy who sustained a life threatening liver laceration[5].

Identifying if there is an association between the condition of handlebar grips and the likelihood of sustaining an injury is the ultimate aim of the main GRIP study. This feasibility study aims to test the intended methodology prior to rolling out a nationwide multicentre study. The feasibility study will allow power calculations to be performed for the nationwide study. The primary outcome of the nationwide study will address whether children falling onto exposed metal handlebar ends are at a greater risk of sustaining an injury than those who fall onto handlebars with intact rubber grips. A sub-study will explore whether there is any relationship between injury severity and grip condition.

Our clinical experience tells us that serious handlebar injuries do occur even when handlebar grips are intact. The investigators also know through anecdotes that some riders fall onto their handlebar ends and never attend hospital because no injury or only a minor injury is sustained. The cases presenting to tertiary paediatric units represent the 'tip of the iceberg'. A study to accurately identify the number of children who fall onto a handlebar but do not present to hospital is unlikely to be feasible. This is why the investigators have designed a case-controlled study.

If the nationwide multicentre GRIP study rejects the null hypothesis, then the investigators can focus on passive injury prevention strategies relating to handlebar ends. There are two aspects that could easily be addressed by safety standards. Grip durability and grip end minimum diameter. Improved durability should reduce the number of bikes or scooters in circulation with exposed metal handlebar ends. Larger diameter ends distribute any end-on impact over a larger surface area and hence reduce the pressure exerted on the point of contact.

Currently only one of the many applicable European safety standards includes a drop test of handlebar grip durability[9]. This standard for BMX bikes was introduced in 2012. However, the drop test has not been included in the more recently published standard for Bicycles for Young Children[10].

A minimum grip diameter requirement has been included in the standard for Bicycles for Young Children. It specifies that handlebars shall be fitted with handlebar grips, and that such grips shall be of resilient material and shall have an enlarged and covered end not less than 40mm in diameter[10]. That standard applies only to bikes suitable for children up to around 5 years of age. There is no such minimum handlebar end diameter requirement applied to bicycles ridden by children over 5 years of age, or to kick scooters. These standards simply require the handlebar to be fitted with handgrips or end plugs[7-9].

If, however, the nationwide multicentre GRIP study accepts the null hypothesis, the investigators can focus handlebar-related injury prevention on more complex mechanical solutions such as steering limiters or compressible handlebar ends, and on design of effective protective clothing. Some of the secondary outcomes the investigators propose addressing will be useful if it is found that exposed handlebar ends are not a risk factor for this injury mechanism.