In traffic accidents involving motorcycles, injuries can occur in various regions of the body through different mechanisms. Given their severity, these injuries can lead to the victim’s fatality or, if not fatal, can offer valuable insights into the dynamics of the accident. The first five paragraphs discuss the characteristics of the injuries, based on a literature review, categorised by the body regions affected (head, neck, thorax-abdomen, pelvis and limbs). The sixth paragraph discusses the evaluation of injury prevention tests and technologies. Given the broad timespan of the literature review (1970–2023), each paragraph shows the chronological arrangement of cited sources corresponding to the respective topics under discussion. The final section examines elements critical to forensic assessment, including the role of injuries in causing fatalities and their importance in reconstructing accident dynamics.

Head and facial injuries are the most frequent injuries observed in motorcycle accidents, with brain damage being the leading cause of death among motorcyclists [5, 34, 71, 131]. These injuries can result from various mechanisms. One major cause is the impact of victims’ head with other vehicles, fixed obstacles, or the ground when they are forcefully thrown after a collision due to the high inertia involved [71]. Additionally, brain injuries are often caused by deceleration forces, as the brain is not fixed, allowing it to relative movement within the skull. This can lead to various deceleration effects, such as multifocal vascular ruptures, cerebral concussion, or diffuse axonal damage [146]. Furthermore, injuries to the brainstem and pontomedullary region can result from significant movements like hyperextension, antero-flexion, and torsion of the head, caused by either direct contact trauma or acceleration-deceleration forces [147,148,149].

The most common head traumas observed in motorcycle accidents are concussions, followed by brain contusions or haemorrhages, facial and skull fractures [40, 143]. Wearing helmets prevents them: full-face helmets specifically reduce the incidence of brain contusions more effectively than the open-face type. However, the prevalence of skull fracture, subdural hematoma, and subarachnoid haemorrhage does not differ significantly between the two kinds of helmets [42]. Nonetheless, full-face integral crash helmets can also cause skull base fractures, as a portion of the impacting force is transmitted to the skull base through the chinstrap, involving the mandibular rami and condyles [15]. Moreover, heavier helmets are more likely to result in partial or complete ring fractures of the base of the skull when subjected to axial loading [25].

Brain injuries can also be linked to facial bone fractures. Studies have shown that fractures of the upper part of the face, such as the zygomatic and orbital bones, are more commonly associated with brain injuries than fractures of the lower part of the face, such as the mandibular bone [98, 150, 151].

Papers addressing skull fractures caused by direct impact have been distributed over the past 20 years [5, 34, 40, 42, 71, 98, 131]. Papers discussing severe ring fractures at the base of the skull associated with the use of full-face helmets originate from the 1990s [15, 25].

The most prevalent neck injuries due to motorcycle accidents include hemorrhage in the carotid sheath, subluxation in the occipital-atlanto-axial complex, hemorrhage in the muscles and triangles of the anterior neck, and damages along the vertebral artery [39].

The cervical spine region is the most affected part in case of fatal crashes [34]. Specifically, when the head undergoes hyperextension during a crash, the forces are transmitted through the cervical spine, leading to tissue damage [98]. The effectiveness of helmets in preventing cervical spine injuries remains a topic of debate. Some studies suggest their usefulness [116, 127], but Hitosugi et al. reported that the prevalence of cervical fractures was slightly higher in individuals wearing full-face helmets compared to those wearing the open-face type [42].

Regarding other helmet-related injuries, the helmet buckle can also cause fractures in the neck cartilage, primarily affecting the thyroid cartilage. The energy from the trauma results in the displacement of the helmet, and its buckle subsequently exerts pressure on the surrounding tissues. If the helmet buckle is positioned over the larynx at the moment of impact, it can exert enough force to potentially fracture the laryngeal cartilages [117].

Concerning neck vascular injuries, internal carotid artery dissection, though rare, has a high mortality rate after motorcycle accidents [124]. This type of injury may occur due to hyperextension and rotation of the neck, reflecting traction on the internal carotid artery as it crosses the transverse processes of the second and third cervical vertebrae. Another possible mechanism is abrupt full flexion of the neck, which can directly compress the internal carotid artery between the angle of the mandible and the upper cervical vertebrae [152]. Additionally, the pressure applied by the helmet strap on the soft tissues of the neck could also contribute to vascular damage [120]. A traumatic injury to the vertebral artery may determine death, especially in low-speed accidents, where the person may not immediately complain of specific symptoms after the accident. Instead, they may start feeling unwell hours or even days later, typically experiencing neurological symptoms like nausea, vomiting, and eventually leading to coma and death. The traumatic dissection of the vertebral artery causes cerebral infarction, followed by edema and compression of the brainstem. The vertebral artery is particularly susceptible to longitudinal stretch, and it can be hurt during sudden neck movements involving hyperextension and/or rotation. Therefore, in cases of delayed symptom presentation, forensic examination should take into account the possibility of vertebral artery dissection as a potential cause of death [61, 153].

Although rare, severe high-energy trauma can lead to the complete separation of neck tissues, even resulting in decapitation. The latter may be caused by different mechanisms, but it is often due to an impact against an immovable object [114]. Decapitation can also be attributed to the action of the lower edge of a full-face helmet during an incident. When a full-face helmet is worn during a traumatic event, the lower edge of the helmet can exert a significantly powerful force on the surrounding tissues, potentially leading to a complete cervical spine amputation [67, 88]. Additionally, instances of decapitation have been reported in the literature due to the interaction with motorcycle components. Ihama et al. reported a case in which a motorcyclist’s neck became entangled in a rotating motorcycle chain, resulting in complete decapitation [10].

All reported articles on neck injuries have been published within the last 20 years. Notably, certain articles focusing on helmet-related injuries [116, 127] and vertebral artery dissections [120, 124] encompass publications from the last 5 years.

Injuries to the thorax and abdominal regions pose a significant risk of death due to severe blood loss, asphyxiation caused by thorax compression, and vertebral spine fractures [5, 33, 63, 121]. Common lesions in these areas include lung contusion and liver laceration, often occurring simultaneously with rib fractures [34, 81]. Impact during falls, especially between the left side of the abdomen and the end of the motorcycle handlebars, can cause splenic and pancreatic damages [44].

In high-velocity trauma, injury to the aorta is a typical and highly fatal occurrence. The ascending aorta is the most common affected segment, followed by the arch, thoracic, and abdominal sections [140]. Traumatic events in the ascending aorta or arch should be considered in cases of cardiac tamponade, aortic valve regurgitation, and myocardial contusion [84]. According to Richens et al., the aorta is subjected to various mechanical forces in anatomically vulnerable sites. Sudden deceleration can cause a stretching effect, leading to laceration of the isthmus as the ascending aorta and aortic arch are more mobile than the fixed distal descending part. Additionally, the aorta may rupture due to a sudden increase in blood pressure and entrapment between the anterior chest wall and the vertebral column [154]. The primary physiopathological mechanism of aortic laceration can be difficult to ascertain because of the diversity and complexity of crash scenarios, particularly when victims have been exposed to multiple external forces [112].

In major traumas, the thoracic spinal column may fracture. These injuries exhibit an “all or nothing” phenomenon, irrespective of the cause of the trauma, and tend to be more severe compared to similar lesions in the cervical region [127]. The thoracic spinal column may extensively suffer the trauma, or it remains intact with no damage. This effect is caused by the restraining effect of the ribs and sternum on the thoracic spine, making it less mobile. Consequently, if a force is powerful enough to break through a segment, the adjacent mobile segments are unable to absorb the remaining force, leading to displacement and significant injury to the spinal cord. Moreover, the thoracic canal provides slightly less space per segment compared to the cervical spine, favouring even slight displacement more dangerous [155].

Complete trunk severance cases are rare and typically associated with accidents involving high impact speeds. Muggenthaler et al. [76] documented a case of complete trunk severance resulting from a collision with a road signpost.

The articles mentioned in this paragraph have all been published in the last 20 years. Specifically, the articles addressing injuries to the aorta [112, 140] and spine [127] are from the last 5 years.

These are often attributed to contact with the motorcycle fuel tank during the collision [101]. These injuries can include fractures of the pelvic ring bones, damage to internal organs within the pelvic cavity, associated with pelvic haemorrhages of varying degrees, as well as lesions to the soft tissues of the lower abdomen, perineum, groin, or testicular area [9, 52].

Fuel tank injuries are typically experienced by the motorcycle driver, particularly in frontal collisions, when after impact, a sudden deceleration can propel the driver forward, colliding with the tank [71, 101, 156]. Interestingly, drivers who attempt to avoid a collision and topple over immediately before the impact are less likely to experience fuel tank injuries [52].

Even passengers can suffer groin injuries in accidents involving two riders on a motorcycle. In fact, passengers who are seated behind the driver often slide on the saddle, sometimes even onto the fuel tank, and then may hit the driver’s buttocks and back. However, the protection of the driver’s buttocks and back, can reduce the passengers’ risk of underbelly injuries [104].

The articles mentioned in this paragraph have all been published in the last 20 years. Specifically, some articles addressing fuel tank injuries [52, 101, 104] are from the last 5 years.

Motorcycle riders are particularly susceptible to limb injuries due to their heightened exposure to direct impacts [5]. Non-fatal limb injuries are the most frequent, encompassing ligamentous lesions, fractures, and dislocations [34, 38, 93]. These lesions occur when limbs become entrapped between the motorcycle and the ground or impact with fixed road signs or poles [48, 59, 97].

Regarding the upper limbs, the most common limb injuries are fractures of the shoulder, forearm, and hand [59, 97], reflecting the motorcyclist’s position, with flexed elbows being farthest from the impact point [132].

Forearm and hand injuries have been associated with lower mortality rates, because upper extremities act like a “crumple zone” when crash at highway speeds, protecting the head and neck region from direct impact in head-first hit damages in frontal crashes [95]. The distal portion of the upper extremity absorbs the energy of the collision, potentially reducing severe proximal trauma to the head and neck [12].

Hand lesions are more common in motorcycle drivers than in passengers, because during a collision, the driver instinctively locks their elbows and firmly holds onto the handlebars, redistributing the resulting force into the palm and metacarpal base. Thumb carpometacarpal joint injuries are particularly common due to the thumb’s position onto the handlebar grip making it more vulnerable to trauma [5, 103].

Concerning the lower limbs, the tibia is the most common site, followed by the proximal femur, particularly in lateral impact, patella and foot [20, 34, 125]. The heel is particularly susceptible with calcaneus fractures, Achilles tendon ruptures, and defects. The motorcycle’s lack of spoke guards or poorly designed guards favours the entrapment of the pillion passenger’s heel between the spokes and the frames, resulting in crushing and grinding injuries from the continuously rotating wheels [30, 74].

The articles cited in this paragraph cover a wide range of time periods, from the 1970s to the 1990s [12,