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Acta Neurochirurgica

, Volume 161, Issue 1, pp 139–145 | Cite as

A summer wave of vertebral fractures: the “deck-slap” injury

  • Aurore SellierEmail author
  • Mohammed Al Falasi
  • Christophe Joubert
  • Nicolas Desse
  • Nathan Beucler
  • Aurélien Renard
  • Cédric Bernard
  • Laurent Allanic
  • Arnaud Dagain
Original Article - Spine trauma
  • 96 Downloads
Part of the following topical collections:
  1. Spine trauma

Abstract

Background

Every summer, several patients who suffer from vertebral fractures are hospitalized at the Sainte-Anne Military Hospital after going on a boat trip around the French Riviera. The uniqueness of these fractures lies in their mechanism of injury, called the “deck-slap” injury. The aim of this study is to describe the characteristics of the “deck-slap” injury.

Methods

The data of 26 vertebral fractures that occurred during boat trips between January 2010 and September 2017 were collected and analyzed.

Results

The mechanism of injury observed was similar for every patient. Patients sitting on the front of the boat, or bow, (77% of cases, n = 20); patients being on a rigid-inflatable boat (65% of cases, n = 17); and when the sea state was calm (62% of cases, n = 16). The patients were bounced up in the air because of a strong wave and landed in a sitting position. The affected population was young (mean age of 42.5 years) and women were the main victims (sex ratio of 0.3). The lesion topography was found near the thoracolumbar junction in each case. It was always a vertebral body compression. Twenty-three percent of them (n = 6) suffered from neurologic complications.

Conclusion

This type of fractures, frequently encountered during the summer, has not previously been described in the literature, yet is a relevant cause of hospital admissions to the emergency departments of the south of France. A better knowledge of this mechanism would provide a more efficient approach to prevention measures that should be imposed to potential boat passengers.

Keywords

Vertebral fracture Boat Deck-slap Spinal injury Thoracolumbar junction 

Introduction

The Var is a department in southern France that overlooks the Mediterranean Sea. During the summer, the towns situated in this area of the French Riviera (Toulon, Hyères, Saint-Tropez...) are the most popular destinations for French tourism. Many tourists practice water sports or leisure activities. Therefore, the frequency and incidence of trauma at sea increases during this period.

The uniqueness of the studied spinal fractures resulting from boat trips lies in their mechanism of injury. The victims consistently described a vertical projection while crossing a wave, before falling heavily back down on the boat seat. This corresponds to a mechanism known by spine specialists as the “deck-slap” injury. The term originates from World War II. It referred to correspond to the injuries of seafarer victims of naval mines. Although this specific fracture process is in fact very frequent and can be potentially serious, it is very little described in the literature. There is no actual recommendation for the prevention of these accidents in sports medicine.

The purpose of this study is to describe the features of this particular mechanism as well as the resulting vertebral lesions.

Materials and methods

This retrospective monocentric study includes patients who suffered from a vertebral fracture caused by an indirect “deck-slap” trauma that was admitted to the emergency department of the Sainte-Anne Military Hospital between January 2010 and September 2017. The “deck-slap” is defined by the vertical projection of a patient sitting on a boat during an impact with a strong wave, followed by a sudden fall in a sitting position. Patients whose trauma was due to a direct impact on the back during the fall were excluded, as well as Jet Ski and tubing, even though the mechanism could be considered similar.

We noted for each patient:
  • Epidemiological data:

Age, sex, and month of the year during which the trauma occurred.
  • The characteristics of the boat and excursion:

The state of the sea (calm, slightly agitated, or agitated), the speed of the boat (fast, moderate, slow, or stationary), the reason for the sea excursions (cruise, transit, fishing, or as a hobby), the type of wave leading to the accident (ships’ wake waves, rogue wave, waves during rough seas, or groundswells), and the number of waves leading to the accident (1st wave, 2nd wave, or more than two waves). The type of boat was also described (rigid or “rigid-inflatable boat” (RIB)). A RIB is a lightweight but high-performance boat constructed with a solid hull and inflatable tubes at the gunwale, unlike conventional rigid hull boats.
  • The characteristics of the patients on board:

Sitting or standing, with a vertical straight bust or leaning forward, at the front or at the back of the boat, and passenger or pilot. We also noted the patient’s experience on a boat (good, moderate, poor, or none). Their experience at sea was good if they were regularly sailing throughout the year, moderate if it was at least once a year or several times during the summer, poor if they had sailed only a few times, and null if it was their first time on a boat.
  • The characteristics of the vertebral fracture:

Their type was evaluated according to the AOSpine thoracolumbar spine injury classification system [11].

The stability of the fracture, the level of the fracture, the displacement of the posterior wall, and the extent of the stenosis of the spinal canal (> 50% or < 50%) were analyzed.
  • Clinical data:

The type of pain (immediate or delayed; mild, moderate, or severe), the presence of an existing neurological deficit (none, medullary syndrome, radicular syndrome, sphincter disorders only).
  • The treatment received:

Thoracolumbar brace, vertebroplasty, surgery by posterior osteosynthesis, or posterior and anterior osteosynthesis.
  • Present sequelae:

Sequential neurological deficits were assessed, and the residual spinal pain was evaluated according to the Low Back Outcome Scale (LBOS), which has been used since 1993 to evaluate chronic low back pain [7]. It ranked patients’ status in four items (excellent, good, acceptable, and weak), using criteria of chronic pain, employment, sports skills, and elements of daily life.

The data came from the neurosurgery service database, and we recalled each patient to obtain the missing information.

Continuous variables are presented in the form of the median with a range (minimum–maximum). Quantitative variables are presented in the form of the number of patients and percentage. Missing data were listed for each category and excluded from the results.

Results

From January 2010 to December 2017, 26 patients were admitted to the Sainte-Anne Military Hospital for a vertebral fracture following a “deck-slap” trauma. The median age was 45.5 years (min 22 years old, max 67 years old). The female population was predominantly affected (sex ratio of 0.3).

Injuries occurred mainly during school holidays: 23.1% in July (n = 6) and 34.6% in August (n = 9) (Fig. 1).
Fig. 1

Frequency of “deck-slap” injuries depending on the month of the year. (Number of patients on the ordinate, month on the abscissa)

Boat and sea conditions

The details of the boat and the sea conditions can be found in Table 1 and Table 2.
Table 1

Characteristics of the sea/boat

Characteristics

Patients

Percentage

Type of boat

 Rigid

n = 7

26.9%

 RIB

n = 17

65.4%

 NK

n = 2

7.7%

State of the sea

 Calm

n = 16

61.5%

 Slightly agitated

n = 2

7.7%

 Agitated

n = 6

23%

 NK

n = 2

7.7%

Speed of the boat

 Fast

n = 12

46.2%

 Moderate

n = 5

19.2%

 Slow or stationary

n = 6

23.1%

 NK

n = 3

11.5%

Reason of the sea trip

 Cruise

n = 18

69.2%

 Transit

n = 4

15.4%

 Hobby

n = 2

7.7%

 NK

n = 2

7.7%

NK, not known

Table 2

Characteristics of the waves

Characteristics

Patients

Percentage

Type of wave

 Ships’ wake waves

n = 15

57.4%

 Wave during rough sea

n = 6

23.1%

 Groundswells

n = 1

3.8%

 Rogue wave

n = 2

7.7%

 NK

n = 2

7.7%

Number of the wave

 1

n = 13

50%

 2

n = 7

26.9%

 > 2

n = 2

7.7%

 NK

n = 4

15.4%

Patient on board ship

The characteristics of the patients and what they were doing on board are summarized in Table 3. They were all passengers on the boat, seated (88.5%, n = 23), usually on the bow of the boat (76.9%, n = 20).
Table 3

Position in the boat and the patient’s sea experience

Characteristics

Patients

Percentage

Location in the boat

 At the front

n = 20

76.9%

 At the back

n = 4

15.4%

 NK

n = 2

7.7%

Position

 Sitting

n = 23

88.5%

 Standing

n = 1

3.8%

 NK

n = 2

7.7%

Bust position

 Straight

n = 16

61.5%

 Leaning forward

n = 7

26.9%

 Leaning back

n = 1

3.8%

 NK

n = 2

7.7%

Boat Experience

 Good

n = 9

34.6%

 Moderate

n = 6

23.1%

 Poor

n = 5

19.2%%

 None

n = 4

15.4%

 NK

n = 2

7.7%

NK, not known

Initial clinical data

The patients systematically complained of back pain after the accident, which they characterized as immediate and severe. Twenty-three percent (n = 6) had an immediate post-traumatic neurological deficit: three radicular injuries (11.5%), two spinal cord compressions (7.7%), and one sphincter disorder (3.8%).

Vertebral fractures

The fractured vertebra was most often located at the thoracolumbar junction (Fig. 2). The vertebrae T12 (19.2%, n = 5), L1 (46.1%, n = 12), and L2 (23.1%, n = 6) were the most frequently affected. In two cases, there were multiple vertebral involvements (T11 and T12 for one, and T10, T12, and L3 for the other). All were compression fractures, type A of the of the AOSpine Thoracolumbar Classification System [11]: wedge-compression (42%, n = 11), split fractures (3.8%, n = 1), incomplete burst fractures (34.6%, n = 9), or complete burst fracture (19.2%, n = 5). There was a posterior wall displacement in 65.4% of the cases (n = 17), with stenosis of more than 50% of the width of the spinal canal for 64.7% (n = 11/17) of them.
Fig. 2

Topography of the fractured vertebra. (Patients on y-axis, topography on the x-axis)

Treatment received

The treatment proposed was the usual treatment of compression fractures: surgery (65.4%, n = 17), vertebroplasty (19.2%, n = 5), or thoracolumbar brace (15.4%, n = 4). Among the 17 patients treated surgically, there were eight (30.8%) percutaneous osteosynthesis (53.8%), six (23%) had an open posterior surgery with laminectomy, and three (11.5%) were treated with combined posteroanterior surgery.

Sequelae

Among the six patients who were affected by a post-traumatic neurological deficit, only one suffered from residual neurological sequela (3.8%). The patient still presents radicular pain and loss of sphincter control. The rest of the patients are no longer neurologically symptomatic.

On the other hand, 61.5% of the patients (n = 16) had a persistent low back pain several months or even years after their trauma.

The residual spinal syndrome is described in Fig. 3 according to the LBOS scale. Only 19.2% (n = 5) of patients do not suffer from any lingering pain anymore.
Fig. 3

Residual spinal syndrome according to the LBOS Score: classification in four groups (excellent, good, acceptable, and weak status). Status on the y-axis, Patients on x-axis; NK, not known; LBOS, Low Back Outcome Scale

Discussion

Origin

The term “deck-slap” is an expression that spine specialists borrowed from war medicine. Historically, the term “deck-slap” was first used during World War II to described seafarer’s casualties from sea-mine attacks, with skeletal injuries. In 1946, Barr et al. [3] reported 50 casualties from mine attacks. Most of them presented symptoms of a fractured calcaneus, however, spinal injuries were also very common (18%, n = 9), with all fractures found between T9 and L4. Afterwards, the term was used in Iraq and Afghanistan to describe calcaneal injuries caused by vertical deflection of a vehicle floor after an explosion. When an IED (improvised explosive device) explodes under a vehicle, a high-pressure wave transfers large amounts of energy to the skeleton, with the lower limbs being especially affected. The blast energy travels vertically, and the thoracolumbar spine absorbs nearly pure vertical load [9]. During these attacks, spinal injuries were the second most frequent injury after calcaneum fractures, and the vertebral casualties were mainly compression fractures located at the thoracolumbar junction due to a vertical acceleration in sitting position. The similarity of the fracture mechanism explains why the term “deck-slap” is used to describe the fractures of the spine while on a boat, caused by a vertical projection of the patient in a sitting position during an impact with a wave.

Wave formation, “second wave” effect

The waves are mostly generated by the wind. By blowing on a large surface of the water, it generates energy transfer which, in its turn, creates a wave. This wave is called a swell, and will then spread to the coast. There is, however, no movement of the matter: the water particles of the surface follow the vertical movement of the wave, creating circular oscillations, without lateral displacement. Thus, when a wave passes under a boat, the boat is lifted in a vertical axis, before returning to its original position, without being projected forward. The wave is periodic: the swell is characterized by a wavelength, a period, and a height [8]. Each wave can hide subsequent waves, which can potentially be dangerous as they are not necessarily expected by the boat passengers. The latter will protect themselves during the crossing of the first wave, only to relax and be caught by surprise by the following waves. This “second wave” effect is not negligible as it is responsible for 34.6% of the vertebral fractures described in our study. That effect is common during a ship’s wake waves, forming a “V” in the track of boats in movement [4]. It consists of two wave crests that diverge, and are the cause of fractures due to the aforementioned effect of surprise created by the crossing of the second wave.

Epidemiology

Traumatic vertebral fractures are often the result of falls from a height or motor vehicle accidents and usually concern the younger age group. Fractures following minor trauma, such as the case here, are rare or occur in patients with osteoporosis or inflammatory conditions. However, the average age of our analyzed population is young, half of them were at least 40 years old, and had no particular past medical history. The referenced young age corresponds to the one currently described in the literature. Six “deck-slap” injuries were mentioned, two of which were described by Chukwunyerenwa et al. and were 46 and 56 years old [6], and the four others were listed by Allami et al. and their age varied between 26 and 39 years old [1].

Characteristics of the sea, the waves, and the boat

The few existing clinical cases of “deck-slap” [1, 6] injuries do not offer a description of the boat, the position of passengers, or the sea state.

In our study, we note that accidents are more likely to occur in a calm sea (61.5% of cases). These traumas happen when patients expect it the least, as demonstrated by the 57.4% of fractures that take place during the passage of a ship’s wake wave, which is sudden. The agitation of the sea is not primarily involved in the occurrence of these injuries, and it was connected to only 23% of the accidents. This is probably due to the increased caution shown by the boat passengers when faced with difficult maritime conditions, contrarily to the low alertness observed in calm conditions that lead to fractures by surprise effect.

One of the parameters that can be modified in order to reduce the number of accidents is the speed of the boat. The majority of the studied accidents occurred at a fast or moderate speed. The type of boat also plays a considerable role in the occurrence of these fractures. In fact, the majority of the reported “deck-slap” injuries happened on the RIB.

The position of the patients during the impact was taken into consideration in order to determine if it could be corrected. All the patients were seated except one. Specifically, a vertical bust position was documented in 61.5% of the cases. Undoubtedly, when the patient is bounced up in the air in a straight position, he will land on his buttocks creating an axial compression of the spine, leading to a vertebral fracture. If the patient is tilted forward during the impact, he risks being propelled then fall forward.

An evident risk factor found in our study is the location of the patients when sitting on the front of the boat (77% of cases). The bow is the part of the boat that is the most elevated by the wave.

Characteristics of the fracture

All of the fractures mentioned involve the thoracolumbar junction. In general, about 90% of fractures occur at this level, between the vertebrae T11 and L4 [1]. This is explained by the specific anatomy of this area, a transition zone between the relatively stiff and kyphotic thoracic spine, which is stabilized by the costovertebral articulations, and the lordotic and more mobile lumbar spine [6]. The cervical spine was never affected in the cases described in this study.

Every fracture in our study was caused by a type A compression mechanism of the AOSpine Thoracolumbar Classification system [11]. Compression injuries are the most common for the thoracolumbar spine (48% of all thoracolumbar fractures) and represent 58% of all major spinal injuries [1].

The mechanism of the injury implicated in these compression fractures consists of two phases: first the boat’s elevation due to the wave and the flexing of the patient’s spine, then followed by the descent of the boat that generates an impact of the patient’s buttocks on the seat, causing a sudden flexion and compression on the thoracolumbar junction.

The six “deck-slap” injuries found in the literature describe the same compression fracture located in the thoracolumbar junction. Even if very few case studies exist on the topic, the deck-slap fracture can still be compared to other similar vertebral fractures found in the literature, that present similar mechanism of injury; such as in patients sitting on a bus traveling at a high speed and hitting a speed bump [2], patients on a watercraft [5], or a horseback rider on a jumping horse [10].

Treatment

The high number of surgical treatments (n = 17) corresponds to the high rate of burst fractures. Most A1 and A2 fractures were stable and conservatively managed. But if the kyphosis was most important, we chose a posterior stabilization with percutaneous screws, as we did for burst fractures. For the six patients with a neurological deficit, they were operated on by open posterior surgery with stabilization and laminectomy. Finally, if there was a post-traumatic deformity, it was restored with an anterior procedure.

Vertebroplasty is an effective minimally invasive procedure for the treatment of painful vertebral body compression fractures. We chose this treatment for some selected patients, among the oldest one or those who refused conservative treatment.

Prevention

In summary, simple methods of prevention could reduce the risk of potentially serious vertebral fractures. Sitting in the back of a RIB or simply slowing down could prevent spinal trauma. In addition, the boat passengers’ caution is especially crucial, even under good weather conditions, particularly in relation to other boats and the wake waves they produce.

Limitations

Our study was retrospective and based on a collection of data from a single institution, which explains the small number of patients. Furthermore, there may be some degree of recall bias, as patients have been questioned several months after their trauma. However, most of them had very good memories of the circumstances of their accident which allowed us to collect a lot of data.

Nevertheless, the results are quite obvious, with marked trends. This is why we believe that the external validation of this work is preserved. Moreover, no study presenting a higher number of cases has been displayed at this time.

Conclusion

Boat rides have become a frequent leisure activity for people on holiday in the south of France. The fracture risk on RIB remains little known. The mechanism injury and the type of vertebral fractures are strikingly similar in all patients with “deck-slap” injuries. This reinforces the idea that a prevention policy is needed and could have a great impact on the incidence of vertebral fractures during boat rides.

Notes

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee (ethics committee of Sainte-Anne military Hospital, number 2018/003) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

For this type of study formal consent is not required.

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Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2018

Authors and Affiliations

  • Aurore Sellier
    • 1
    Email author return OK on get
  • Mohammed Al Falasi
    • 2
  • Christophe Joubert
    • 1
  • Nicolas Desse
    • 1
  • Nathan Beucler
    • 1
  • Aurélien Renard
    • 3
  • Cédric Bernard
    • 1
  • Laurent Allanic
    • 4
  • Arnaud Dagain
    • 1
    • 5
  1. 1.Department of NeurosurgerySainte-Anne Military HospitalToulon Cedex 09France
  2. 2.Department of NeurosurgeryRashid HospitalDubaiUnited Arab Emirates
  3. 3.Emergency DepartmentSainte-Anne Military HospitalToulonFrance
  4. 4.Departement of AnesthesiaSainte-Anne Military HospitalToulonFrance
  5. 5.French Military Health Service Academy—Ecole du Val-de-GrâceParisFrance

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