An odontoid process fracture is a serious injury involving the stability of the atlantoaxial region and occurs in approximately 10% of cervical spine injuries. Because of its unique anatomy, it also has a high incidence of nonunion and the presence of instability factors that can lead to acute delayed cervical spinal cord compression and life-threatening injuries.
Pontine odontoid fracture – etiology
Often caused by external forces to the head and neck in different directions.
Pathogenesis.
A fracture of the dentition is caused by external forces to the head and neck in different directions. A fracture of the dentition of the cardinal spine caused by violent head and neck flexion (common), supination and extension and rotation is usually accompanied by atlantoaxial dislocation, while a simple fracture of the dentition caused by the sudden suspension of violence during this process is relatively rare and accounts for about 8% of all cervical fractures. Therefore, clinical attention should be paid to prevent missed diagnoses.
Pontine odontoid fracture – Symptoms
Clinical presentation.
The clinical symptoms and signs are basically similar to those of mild to moderate cases of atlantoaxial dislocation, and are dominated by neck pain, localized pressure, restricted movement (especially rotational neck movement), and forced head position with both hands. Attention should be paid to the presence of concomitant concussion and other injuries. In cases without atlantoaxial dislocation, there is usually no cervical medullary compression; however, improper manipulation may also cause adverse consequences during lifting and treatment, which should be noted.
Simple odontoid fractures can generally be divided into three types as follows.
1, Type I: Type I odontoid apical fracture is uncommon, and its may be the result of pterygoid ligament avulsion. Because the apical ligament of the odontoid is attached to the apical part of the odontoid with two oblique pterygoid ligaments, most of the fractures in this part are stable with oblique tearing of the fracture line, the incidence of which is about 5%, and its stability can be confirmed by extension and flexion power lateral radiographs. Since this type is mostly nondisplaced, there are few complications and the prognosis is better.
2. Type II: The lumbar fracture of the odontoid process is common and accounts for about 70% of simple odontoid fractures, mostly due to lateral head flexion violence. This type of fracture can also be caused by posterior extension force, but rarely by supination violence. Because of the poor blood supply, the healing rate is about 1/4 of this type, so a higher percentage of fractures require surgery.
3. Type III: Type III fractures with the fracture line located at the base of the odontoid process have an incidence of about 25%; they are mainly caused by flexion violence to the head and neck; the fracture line often extends to the upper part of the cardinal vertebrae and the atlantoaxial joint. However, the fracture is more stable here, and the prognosis is generally good if there is no poor healing.
Recently, some scholars have proposed type IV, which is based on type III, when a comminuted fracture occurs at the fracture line; it is more difficult to treat and the prognosis is less favorable.
Complications.
Dentition discontinuity is not uncommon in clinical practice and is the most common complication of dentition fractures. Dentition discontinuity is particularly common in type II fractures where the fracture line passes through the dentition lumbar region mainly because this type of fracture is prone to dislocation, as the fracture can be separated by the pulling of the dentition apical ligament and the pterygoid ligament, and can be displaced by the pushing of the posterior transverse ligament. In addition, the tissues attached to the lumbar part of the odontoid process include two collateral ligaments from the anterior side, the other end of which is attached to the lateral block of cervical 1. When a fracture of the odontoid process occurs at the base of the odontoid process, these ligaments can cause a separation between the head end of the fracture and the vertebral body end of cervical 2. In addition, the extension and rotation activity of the cervical 1 to cervical 2 joints transmitted to the fracture site is also a factor in the discontinuity.
Diagnosis.
The main bases for the diagnosis of a pivotal odontoid fracture are.
1. A detailed history of trauma should be asked.
2, Clinical manifestations are mainly cervical symptoms and attention to the forced position of the head and neck.
3.Imaging examination has an important role in confirming the diagnosis and typing. Conventional X-ray plain film and tomography can obtain clear images (open position is especially important); CT and MRI examination not only help to show the fracture line, but also facilitate the observation of the state of the transverse atlantoaxial ligament. The degree of fracture displacement should be noted when reading the films, and healing is more delayed in those with a displacement of more than 5 mm.
In addition, it can be judged based on the widening of the cervicopharyngeal space (i.e., the distance between the posterior pharyngeal wall and the body of the 3rd cervical vertebra, which is normally within 4 mm). There is no difficulty in diagnosis based on imaging examinations such as X-ray plain film, CT scan and MRI.
Differential diagnosis.
In addition to the need to distinguish it from other injuries of the upper cervical segment, it is mainly distinguished from congenital dentition dysplasia.
Pontine odontoid fracture – examination
Imaging is important in confirming the diagnosis and staging. Conventional radiographs and tomography provide clear images (open position is particularly important); CT and MRI not only help to show the fracture line, but also facilitate observation of the state of the transverse atlantoaxial ligament.
In addition, it can be judged based on the widening of the cervicopharyngeal space (i.e., the distance between the posterior pharyngeal wall and the body of the 3rd cervical vertebra is normally within 4 mm). There is no difficulty in diagnosis based on imaging such as X-ray, CT scan and MRI.
Fracture of the pontine process – Treatment
1.Non-surgical treatment
(1) Indications: For type I, type II and type III without displacement, non-surgical treatment is generally safe, stable and easy to use.
(2) Specific operation: Glisson band or cranial traction with a weight of 1.5~2kg is appropriate after admission, do not overload to prevent delayed healing. After traction for 1 to 2 weeks, bedside radiographs were taken to observe the alignment of the fracture line. After 3-6 weeks of continuous traction, the head-neck-thorax cast or Halo device can be replaced (the latter is more used abroad, but the Chinese are not used to it and it is difficult to promote it), and then gradually get up and move around.
2.Surgical treatment: About 1/3 of the cases need surgical treatment.
(1) Indications: mainly used for type II fractures with displacement or pseudo-articular formation and type III fractures with delayed healing, the former accounts for the majority of cases.
(2) Specific operation: an anterior approach via the oral cavity or via the neck can be used. For fresh fractures, internal fixation with slender screws (1 or 2 screws) is mostly chosen. For old fractures that do not heal, atlantoaxial fusion is feasible and can be performed either anteriorly or posteriorly or through a lateral anterior approach.