To our knowledge, this study is the first in the Netherlands and the most recent worldwide to analyze technical incident databases in combination with data from medical information systems. The last study dates from 2007 [11]. More recent publications have only analyzed skydiving-related incidents using a technical database [1, 3, 7]. The main findings of this study are that since 2016 the incidence of skydiving accidents has been increasing, whereas the trend was decreasing up to 2016. The data indicates that most injuries occur during the landing phase not only with the inexperienced jumpers, but more importantly with the more experienced skydivers, often resulting in major injuries. Therefore, prevention and protective measures in skydiving should be made mandatory.

Rise in incidence

Several potential reasons could explain the increase in skydiving injuries documented between 2016 and 2020. For example, the KNVvL stated that the higher number of reports, seems to be influenced by both a higher willingness to report incidents by skydivers, and the better functioning of a safety manager, introduced at dropzones in 2011 [14]. Furthermore, the start of the COVID pandemic in late 2019 contributed to fewer jumps [15]. In several incidents, a link exists to the low number of jumps made in the last 12 months (currency). Currency is determined by the number of jumps made in the past 12 months. In general, the more aggressive the parachute characteristics the more jumps must be made to remain current. If a jumper (regardless the license) has not jumped for six months or more, he is not longer considered current [13].

Other studies have suggested that the increased popularity of high-performance canopies and aggressive flying techniques is a more significant contributing factor [1, 3, 14, 16]. Their findings agree with the finding in this study that 31% of the 234 injuries that occurred during landing were caused by an incorrect flare (parachute decelerations). This is a phase of the jump that is pushed to the limit in skydivers flying with high performance canopies and with aggressive flying techniques.

Combining these arguments (lack of currency and the increased popularity of high-performance canopies) leads us to an alternative explanation for the increased incidence as of 2016: the increasing popularity of wind-tunnel flying. In a wind-tunnel, freefall skills can be accelerated rapidly: 1 h of tunnel flying, which can be done in a day, compares to 60 jumps from a plane. Therefore, for people with relatively few skydives, the rapidly increased frefall skills could lead to an overestimation of canopy flying skills and consequently an increased risk of accidents [17]. Jumpers and their peers can overestimate their skills.

Injury rate

The injury rate in this study is lower than the incidence of injury reported by previous (older) studies [3, 4, 18,19,20]. This difference could be explained by improvements in equipment (e.g., the change from round to square parachutes, and the implementation of automatic opening devices), better training (e.g., the implementation of accelerated freefall instructors), and a better understanding of contributing factors [7]. Furthermore, in 2011 the KNVvL decided to increase safety within the organization by introducing a safety management system [21].

Comparison with other (extreme) sports

In skydiving, BASE jumping and paragliding, the incidence of injuries is expressed per jump. In other (extreme) sports, the incidence of injuries is expressed per 1,000 h of sports practice. To compare skydiving with other sports, we calculated the number of injuries per 1,000 h of sport practice, assuming that one jump is equivalent to 1 h of sport practice. This assessment was based on the following numbers; a preparation and parachute packing time of 15 min, a flight time of up to 20–30 min and a free fall or parachute flight time of 5–10 min. In this study, the incidence of injuries per 1,000 h of skydiving is 0.72. Skydiving compares favorably with other extreme sports, such as kitesurfing, mountain biking, and rock climbing, with 10.1, 16.8 and 9.8 injuries per 1000 h of practicing the sport, respectively [22, 23]. Regarding similar sports (e.g., BASE jumping and paragliding, with 393 and 1,080 injuries per 100,000 jumps, respectively), skydiving also compares favourably with 72 injuries per 100,000 jumps [24, 25].

Skydiving injuries

From 1995 to 2020, the most common locations for an injury were the ankles/feet, lower legs and spine. The most common types of injury where fractures, contusions, and strains. This finding agrees with other studies that have also indicated a predominance of these types and locations of injury [1, 3, 10, 11, 26]. Most injuries occur during the landing phase in either the inexperienced and perhaps surprisingly, in the moderately to highly experienced jumpers.

The subanalysis combining technical and medical data for all skydiving incidents with an injury from 2015 to 2020 at Teuge indicated that most of the skydivers with minor injuries were inexperienced. Fractures of the lower legs and ankles are the most common injuries in that category, with a corresponding ISS of 4. The observation that inexperienced jumpers are more prone to accidents seems intuitive, as they are not yet fully skilled. Most likely due to the more docile canopies, their injuries are relatively minor. Within the group of skydivers with major injuries, about half were experienced to highly experienced (licence C/D), and the most common injuries were neurological damage to the head and spinal fractures. The increased and more major injuries of experienced jumpers may be explained by their use of aggressive and high-speed landing techniques, which became popular in the early 2000s. An increase in incidents for this reason has been observed previously [27, 28]. As discussed previously in the rise in incidences section, we believe lack of currency is an important contributor to errors of judgment during high speed landings.

Prehospital and hospital care of the injured

In this study, outpatient treatment was insufficient for all of the included patients. All patients went to a Level 1 or 2 trauma center, and of those, 30% required an ambulance and 13.3% a trauma helicopter to reach the hospital. Ambulance and HEMS crews arriving at the scene of a skydiving accident should always assume that the person has fallen from a height (unless otherwise stated by the staff) and stabilize the patient according to the Advanced Trauma Life Support (ATLS) principles.

Experienced jumpers presenting to the emergency room after an accident should always be considered to have “high-energy trauma,” as depicted in serious injuries found in skydiving injuries. Treatment should follow the standard trauma guidelines according to the ATLS. Clinicians must be aware of spinal fractures and traumatic brain injuries and adequately assess the extremities to optimize the care and outcome of injured skydivers.

Clinicians should also be alert for a relatively rare injury in skydiving. The speed at which the parachute deploys and jumpers hit the ground can lead to friction between the skin and other materials (e.g., clothing, harnesses, lines and the parachute), which can lead to friction burns, a phenomenon already known to occur in road traffic accidents [29]. Previously, Ellitsgaard et al. also described these “friction burns” of injured skydivers [4].

Protective measures

Most injuries occur during the landing phase. The vast majority injured skydivers were wearing low sport shoes without any rigidity at the ankle. Twelve skydivers dit not even wear a helmet. In the basic safety regulations for sports parachuting, the KNVvL stated that solid footwear is compulsory only for skydivers without a C license. A hard helmet is compulsory when a skydiver does not possess an A license, and head protection is compulsory when skydivers do not possess a C license [13].

As suggested by Ellitsgaard et al. in 1987, solid boots can protect the ankles during landing [4]. More recent studies have also demonstrated the effectiveness of ankle braces in preventing injuries [30, 31]. Westman et al. described the relatively low number of head injuries as an encouraging outcome of helmet requirements [11]. Therefore, the mandate of wearing solid shoes/braces and helmets for all skydivers could help to prevent injuries.

Meteorological-related factors in skydiving

Previous studies have mentioned that knowledge gaps exist in the field of meteorological factors contributing to injuries in skydiving [1]. Weather-related factors, such as ground windspeed (at landing), wind speed at the opening height (is the intended landing area reachable?), and visibility or cloud cover are significant in skydiving. Rules are defined in the basic safety regulations for sports parachuting promulgated by the KNVvL [13].

In this study, most injuries occurred during conditions of good visibility and cloudy conditions with a ground wind speed of less than 5 m/s. In low visibility conditions or with high cloud coverage, skydiving is not permitted. Typically, the parachutist slows when landing against the wind. In low wind speed conditions, the parachutist can reach a higher speed at landing relative to the ground, which can be a critical contributing factor. This finding indicates that excessive speed at landing is a contributing factor to injury; however, it has not been previously reported in the literature [7]. Moreover, a comparatively higher percentage of severe injuries occur in skydivers landing with a higher ground wind speed.

Strengths and limitations

This retrospective study is based on three databases covering a period of 25 years; with missing data and an unequal sample size, making statistics difficult. Therefore the relationships may only be suggested, except for the jump type variable. The database was completed by comparing skydiving injuries with hospital data (only for the 2015 to 2020 data). Furthermore, insufficient medical knowledge among skydivers can lead to misclassification bias in the database.

A further limitation is the relatively few cases included from the medical databases. Still, we believe this crucial data contributed to a better understanding of the injury patterns compared to what the technical database alone could provide. We believe the sample is representative of the whole group of injuries that occurred at the dropzone at Teuge. Because 39% of all the jumps were performed at Teuge, it is representative of all skydives performed in the Netherlands.