The speedboat vertebral fracture: a hazard of holiday watersports

Abstract

Purpose

The purpose of this study was to describe and characterise spinal fractures sustained by watercraft occupants due to splashdown of light watercraft when riding over uneven water surfaces.

Methods

A retrospective review of all patients presenting with these injuries to St Luke’s and Mater Dei state hospitals in Malta over a 10-year period was undertaken to determine patient demographics, the nature of spinal injuries sustained and the incidence of any associated extra-spinal injuries.

Results

Twenty-one patients (mean age 41.2 years) suffered 25 fractures. Injuries were seasonal, occurring exclusively between the months of May and October. One patient was local whilst 20 were from other countries. All fractures were Magerl type A fractures and occurred around the thoracolumbar junction. The L1 vertebra was most commonly affected (12 patients). Four patients sustained two vertebral fractures. There were no extra-spinal injuries.

Conclusions

Watercraft splashdown can transmit significant forces to occupants, resulting in Magerl type A vertebral fractures around the thoracolumbar junction. These injuries occur under compression. They are highly consistent in their morphology and localisation and should be excluded in individuals complaining of back pain after watercraft use. Almost all patients were from outside Malta and injuries were seasonal, providing opportunities for targeted injury prevention campaigns.

Keywords

Vertebra fracture watercraft jet-bike speedboat sea spine bow slamming waves

Introduction

The recreational use of light watercraft is a common feature of island states and seaside resorts. Multiple studies have reported increasing use of light watercraft for leisure purposes over the last 20 years, accompanied by increasing numbers of injuries attributable to them.^1–6 Various forms of light watercraft exist, including high-speed, lightweight speedboats, jet-pump propelled personal watercraft (jet-bikes), rigid inflatable boats and inflatable structures that can be towed at high speed behind powered watercraft. Injuries occurring as a result of collisions between watercraft,^2,3,7 falls off watercraft,³ propeller^8–11 and jet stream injuries³ and injuries to bathers struck by these watercraft⁷ have been widely described in the literature. In various places, guidelines^12,13 and legislation restricting their use to certain zones or requiring driver licensing and passenger personal flotation devices have been enacted to improve safety to both users of light watercraft and bathers.^1,3,7

The senior author encountered a number of patients with acute vertebral fractures after riding on light watercraft, but occurring in the absence of any collision, fall, ejection or specific accident. Review of the medical literature revealed three case reports describing acute vertebral fracture due to watercraft splashdown in the non-orthopaedic literature,^14–16 and one report of five patients in the orthopaedic literature, who each sustained their injuries after a hard landing on jet-bikes.¹⁷ Only two technical maritime reports on such injuries could be identified.^18,19 In summary, very little is known about this type of injury, with no sizable series showing characterisation of consistent features. Consequently, awareness of these injuries is not widespread.

The aim of this study was to describe and characterise spinal injuries sustained by individuals as a result of riding light watercraft over uneven water surfaces and to describe the demographics of those injured in this way.

Materials and methods

A retrospective review of all patients presenting to emergency departments in Malta with acute spinal injury over a 10-year period was undertaken. All those who sustained their injury whilst riding in motorised watercraft were identified. Patients with injuries sustained as a result of collisions, or a fall in or off the watercraft, were excluded. Written medical records, X-ray and CT studies were reviewed for all patients to determine patient demographics, seasonality, the nature and level of the spinal injury and the presence of any associated injuries. Spinal fractures were classified according to the Magerl/AO classification.²⁰ No patients were recalled specifically for this study. Approval for this study was obtained from the institutional ethics committee and data protection officer.

Results

Patient demographics

Twenty-one patients suffered 25 vertebral fractures whilst riding on motorised watercraft in the period under review, in the absence of any fall, collision or ejection from the watercraft (Table 1). All patients reported sudden onset of acute back pain whilst riding, in a sitting position, on a watercraft over waves, purely as a result of the impact of the craft with water. Nineteen patients were on a speedboat (high-powered, light, open topped watercraft), one was riding a jet-bike and one was being towed behind a speedboat on an inflatable ‘sausage’ ride.

Table 1.

Patient characteristics.

Patient number	Residential status	Age	Sex	Date of injury	Cause	Fractured vertebrae	Fracture classification	Other injuries	Neurological deficit	Alcohol intoxication
1	Tourist	50	M	July 2001	Jolt whilst on a speedboat	L1	A 3.1.1	None	None	No
2	Tourist	20	F	May 2002	Jolt whilst on a speedboat	L2	A 1.1	None	None	No
3	Tourist	53	M	August 2002	Jolt whilst on a speedboat	L1	A 3.1.1	None	None	No
4	Tourist	37	M	August 2002	Jolt whilst on a speedboat	T12	A 1.2.1	None	None	No
5	Tourist	42	F	October 2002	Jolt whilst on a speedboat	L1	A 1.2.1	None	None	No
6	Tourist	70	M	June 2005	Jolt whilst on a speedboat	L1	A 1.2.1	None	None	No
7	Tourist	47	M	July 2006	Jolt whilst on a speedboat	L1	A 1.2.1	None	None	No
8	Local	23	M	September 2006	Jolt whilst on a speedboat	L1	A 1.2.1	None	None	Yes
9	Tourist	47	M	May 2007	Jolt whilst on a speedboat	L2	A 1.2.1	None	None	No
10	Tourist	33	M	July 2007	Jolt whilst on a speedboat	T11, T12	A 1.2.1 (T11) A 1.1 (T12)	None	None	No
11	Tourist	27	F	August 2007	Riding a jet-bike	L1,L3	A 3.1.1 (L1) A 1.2.1 (L3)	None	None	No
12	Tourist	63	F	September 2007	Jolt whilst on a speedboat	L2	A 1.2.1	None	None	No
13	Foreign resident	49	M	August 2008	Jolt whilst on a speedboat	T11, T12	A 1.2.1 (T11) A 1.2.1 (T12)	None	None	No
14	Tourist	26	F	September 2008	Jolt whilst on a speedboat	L1	A 2.3	None	None	No
15	Foreign resident	24	F	October 2008	Jolt whilst on a speedboat	L1	A 3.1.1	None	None	No
16	Tourist	54	M	May 2009	Jolt whilst on a speedboat	T12	A 1.2.1	None	None	No
17	Tourist	53	F	May 2009	Jolt whilst on a speedboat	L1	A 3.2	None	None	No
18	Tourist	48	F	May 2009	Jolt whilst on a speedboat	T11, T12	A 3.1.1	None	None	No
19	Tourist	22	F	August 2009	Riding on inflatable ‘sausage’, towed behind a speedboat	T12, L1	A 1.2.1 (T12) A 3.1.1 (L1)	None	None	No
20	Tourist	27	F	May 2010	Jolt whilst on a speedboat	L2	A 1.2.1	None	None	No
21	Tourist	51	F	August 2010	Jolt whilst on a speedboat	L1	A 1.2.1	None	None	No

There were 10 males (mean age 46.3 ± 12.9 years) and 11 females (mean age 36.6 ± 15.1 years). The difference in age between genders was not statistically significant (p = 0.13, two-tailed Student’s t-test). One patient was a local whilst 21 were tourists (19) or temporary residents (2) of the Maltese Islands.

Seasonal variation

All injuries were sustained between May and October, during the local bathing season (Figure 1).

Figure 1.

Number of patients admitted with spine fracture due to watercraft splashdown by month of injury. The graph illustrates the seasonal nature of these injuries.

Fracture level and configuration

All patients sustained a vertebral fracture around the thoracolumbar junction (T11–L2). L1 was the most commonly affected vertebra (12 patients). Four patients sustained fractures at two vertebral levels and one of these suffered non-contiguous fractures (at L1 and L3 level). There were no injuries proximal to T11 or distal to L3 (Figure 2).

Figure 2.

Number of observed vertebral fractures sustained whilst riding motorised light watercraft at each vertebral level.

Fractures were classified according to the Magerl/AO classification²⁰ (Table 2). There were 17 type A1 fractures (impaction type), seven type A3 (burst) fractures and one A2 (pincer) fracture (Figure 3). Two patients underwent surgical management with posterior instrumentation locally in Malta and one was offered surgery but declined this. The remainder were managed non-operatively whilst in Malta.

Figure 3.

(a) Lateral X-ray (left) and (b) sagittal CT scan image (right) of T12 type A1 ‘compression’ fracture (light grey arrow) and L1 vertebra type A3 ‘burst’ fracture with retropulsion of posterior vertebral body fragment into the vertebral canal (dark grey arrow).

Table 2.

Fracture types according to the AO/Magerl classification.

Fracture type	Number of fractures observed
A 1.1	2
A 1.2.1	15
A 2.3	1
A 3.1.1	6
A 3.2	1

Associated injuries and alcohol use

No patients had associated head, bony or visceral injuries. No patients sustained a neurological deficit as a result of their spinal injury. One patient was intoxicated at the time of injury. Interestingly, this was the only local patient.

Discussion

We report a series of vertebral injuries sustained by occupants whilst riding light watercraft over waves. These fractures exhibited a consistent morphological pattern (Magerl type A), were localised to the thoracolumbar junction and occurred almost exclusively in foreign nationals.

We feel it is important that the existence of such injuries is brought to the attention of the wider medical community. Practitioners in both primary and secondary care may encounter these injuries in coastal areas. However, they may also encounter these patients in their countries of origin, where they may present on return from holiday with ongoing back pain. This may be mistaken for mechanical back pain if a detailed history is not sought. Increased recognition of these injuries as a specific entity and awareness on the part of regulatory and public health authorities may also facilitate injury prevention.

Patient demographics

It is striking that all but one injury occurred in foreign nationals. The local population in Malta has been estimated at 429,344 with 1,203,000 yearly tourist arrivals between May and October.²¹ No data are available for the number of locals or tourists who use light watercraft, so absolute exposure for each group could not be calculated, but it is common knowledge that both groups use light watercraft in large numbers during the bathing season.

Malta welcomed a mere 1.97 million (0.16%) of the world’s 1.235 billion tourists in 2016,²² whilst in England alone, 144 million domestic seaside day visits occur annually.²³ It is therefore possible that these injuries are occurring in large numbers worldwide.

Visitors to coastal areas have been implicated in these injuries in one medical report of two cases¹⁴ and in two separate technical incident reports^18,19 but the size of the current series enables this recurring theme to be identified and highlighted for the first time. Our findings imply some degree of protection for locals. Identifying the reasons for this was beyond the scope of the current study, but may relate to experience and an ability to ‘ride the waves’ with pre-emptive body tone and movements, to avoid unexpected impacts and mitigate the effects of compressive and flexion forces. Inexperience has been implicated as a risk factor for injury in watercraft collisions,^5,7,24 but not specifically in the incidence of these relatively ‘passive’ spinal injuries.

Seasonal variation

There was an obvious seasonal nature to these injuries, all of which occurred during the bathing season (May–October). Light watercraft are used most frequently during this period and this also coincides with the months when most tourists visit Malta.²² This finding is therefore not surprising, but does highlight an opportunity to target preventive campaigns.

Fracture level, configuration and mechanism of injury

All described injuries were Magerl type A fractures (Figure 3). These fractures have been reported to occur with flexion and axial compression forces,²⁰ mechanisms consistent with the experience of occupants as a watercraft slams down on the water surface, when forces are transmitted from the hull, up the spine of seated occupants. Type A fractures are reported to occur predominantly around the thoracolumbar junction²⁵ which was the case in the current series. Magerl type A1 fractures (Figure 3) are impaction fractures. They are stable wedge compression injuries and are the least severe vertebral body fractures. These accounted for approximately two-thirds of observed fractures (17 of 25). The remainder were A2 (pincer type fracture, one of 25) and A3 fractures (burst fractures, seven of 25), indicating progressively increasing severity. Neurological deficits were not encountered in the current series; however, there is potential for such injury, particularly with type A3 fractures, which were encountered in one-third of patients. In these injuries, retropulsion of bony fragments into the spinal canal can occur (Figure 3). Fracture patterns associated with distraction (Magerl Type B) and rotational (Magerl Type C) forces were not encountered.

Four of 22 patients (18%) suffered injury to two vertebrae and in one case these were non-contiguous. The phenomenon of multilevel spinal injuries is well described, with reported incidence ranging from 10 to 29%.^25–28 These findings highlight the need for vigilance after diagnosis of a single vertebral fracture, to exclude other spinal injuries.

We suggest that spinal fractures sustained due to the impact of powered watercraft with an uneven water surface are of predictable nature in both their level and their configuration, and should be specifically excluded in patients presenting with back pain after riding in light watercraft, in a similar way to that in which patients falling from a height have calcaneal, hip and thoracolumbar junction injuries excluded as a matter of routine.

Associated injuries

Unlike spinal injuries due to other mechanisms (e.g. fall from height and road traffic accidents),^25,26,28,29 this type of injury was not associated with a high incidence of non-spinal injuries.

Study implications and injury prevention

The concept of transient hydrodynamic forces acting on the hull of a vessel impacting with almost incompressible seawater at relatively high velocity is well described in the maritime literature.^30,31 Studies have shown that even in light to moderate sea conditions, when travelling at high speeds, passengers in light watercraft can expect frequent shocks in the region of 2 g (twice the acceleration due to gravity), regular shocks of 6–10 g and occasional shocks of up to 20 g.³¹ The larger shocks are associated with the vessel dropping off the peak of a wave. Simultaneous pitching and rolling motions of the watercraft further contribute to ‘destabilisation’ of the passengers, which could make maintaining protective posture more challenging, particularly for the inexperienced.³¹

Various measures and watercraft adaptations have been proposed to reduce the risk of injury. These include the use of handrails,^18,32 specialised suspension seats, foot straps and passenger restraints, which have been advocated in certain high performance watercraft.^12,18,31,32 It was beyond the scope of this study to determine whether these measures are effective.

Passenger posture is important: leaning to one side significantly reduces the spine’s ability to withstand compressive forces.^31,32 It is also known that positions closer to the bow are exposed to higher shock forces.^18,19,31 Therefore, simple measures such as seating passengers towards the stern can reduce exposure to shock forces.^31,32

Competent ‘skippering’ is also important and may be one reason why inexperienced foreign visitors appear to be at higher risk of these injuries. Approaching a wave at the correct angle and easing off the throttle at the top of a wave can significantly reduce the force of impact with the water.^31,32 Furthermore, a knowledge of the local waterscape and prevailing wave patterns may reduce the risk of injury,¹⁸ whilst careful assessment of weather conditions prior to embarking on any journey is imperative. Thus, experience (or at least being instructed) may allow both passengers and crew to take a number of measures to avoid bow slamming and its potential effects. Current legislation restricting use of light watercraft in bathing areas and mandating the use of personal flotation devices is important in reducing injuries and deaths at sea, but would have little impact on the type of injury described in this study.

The particular at-risk population (tourists and temporary residents) identified in this study is, by their nature, easily identifiable, thus offering an excellent opportunity for targeted intervention and injury prevention campaigns. They can be targeted at the point of sale of boat services or at major points of tourist entry or congregation, particularly when bearing in mind the seasonal nature of these injuries, which has clearly been demonstrated. Preventive strategies may therefore include targeted education of individuals at risk, watercraft skippers and tour operators, as well as technical watercraft modification.

We acknowledge that this study has limitations. It is retrospective and therefore dependent on the quality of recorded data. However, records for all patients presenting with spinal fractures were reviewed to identify those whose injuries were sustained through the described mechanism and full records for all patients presenting with these injuries during the period under review were available for analysis, including CT imaging of all injuries.

Now that these injuries have been identified as a discrete entity, further studies should seek to more accurately define the mechanical nature of the forces involved and the efficacy of various preventive measures.

Conclusion

Use of high-speed, light watercraft over uneven water surfaces can cause Magerl type A vertebral fractures around the thoracolumbar junction. Tourists and temporary residents of seaside resorts are prone to these seasonal injuries. They are highly consistent in their morphology and localisation and should be excluded in individuals complaining of back pain after watercraft use. Identification of a specific population at risk may provide opportunities for targeted preventive measures.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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