Axis odontoid fracture

Introduction to the odontoid fracture Axonal fractures are not uncommon, accounting for 10% to 15% of adult cervical fractures and dislocations. Unfortunately, there are still reports of odontoid fractures being missed at the first visit, and there is persistent pain in the neck after any trauma. Patients with stiff, with or without neurological symptoms should be given repeated X-rays, including CT, to avoid possible odontoid fractures. basic knowledge Sickness ratio: 0.01%-0.02% Susceptible people: no specific population Mode of infection: non-infectious Complications:

Causes of odontoid fractures

Motorcycle accidents are a common cause of odontoid fractures in young people, and the most common cause of these injuries in the elderly is a simple fall.

Pathogenesis

There are several different systems for classification of odontoid fractures. Schatzker et al. are classified into high and low according to the fracture line located above or below the collateral ligament. Althoff divides the odontoid fracture into A, B, C, D. The fracture line of the type IV, type A fracture passes through the isthmus of the odontoid process, and the fracture line of the other three types of fracture is located at a lower anatomical location.

The most popular classification in the clinic is the Anderson and DAlonzo classification: the odontoid fractures are divided into three types: I, II, III:

Type I fracture, also known as cusp fracture, is an oblique fracture of the odontoid ligament and one of the flank ligament attachments, accounting for about 4%;

Type II fracture, also known as basal fracture, is the most common fracture of the odontoid junction with the vertebral body, accounting for about 65%;

Type III fracture is a central body fracture with a large cancellous bone base below the fracture end. The fracture line often involves one or both sides of the superior articular surface, accounting for about 31%.

Most authors believe that this classification method is clinically instructive, based on it, combined with the degree and direction of the fracture, and the age of the patient, can choose an effective treatment plan and judge the prognosis of the fracture, but Among the type II odontoid fractures, some subtypes have been proposed by the author: Hadly et al proposed a type IIA odontoid fracture, defined as: odontoid basal fracture, with a large free bone below the fracture end, inherent Unstable fractures, Pederson and Kostuil propose type IIB and IIC fractures, type IIB fractures are anderson and DAlonzo classification and type II fractures and type B fractures of type Althoff; type IIC fractures are defined as at least one or both sides of the fracture line Located above the collateral ligament, it is equivalent to a type A fracture classified by Althoff.

In addition, there is a special type of odontoid fracture: osteophyte separation, a secondary ossification center at the top of the odontoid at about 2 years old, and fused with the main part of the odontoid process after 12 years old. The odontoid itself begins to fuse with the vertebral body at the age of 4, and most of the fusion can be completed at the age of 7 years. Therefore, before the age of 7 years, the odontoid fracture is characterized by osteophyte separation.

There are also rare cases of vertical odontoid fractures. So far, only 2 cases have been reported in the English literature: 1 case was reported by Johuson in 1986, and 1 case was reported by Bergenheim in 1991 and cannot be classified as above. Classification.

The odontoid fractures are obviously involved in a variety of different injury mechanisms. Althoff performed a biomechanical study on the cervical spine specimens, and applied the dorsiflexion, overextension and horizontal shear to the atlantoaxial joints without causing odontoid fractures. Therefore, he believes that the external forces in the horizontal direction mainly cause the destruction of the ligament structure without causing the odontoid fracture; in further experimental research, the different types of loads causing the odontoid fracture are: horizontal shear Cut + axial compression, 45 degrees of anterior or posterior lateral impact with the sagittal plane, side impact, so the proposed horizontal shear + axial compression is the main mechanism of the odontoid fracture, and the side The square blow is the necessary external force to cause the odontoid type A (IIC type) fracture. Mouradian et al also found that the lateral load can cause the odontoid fracture in the experiment. Doherty et al. considered the lateral or oblique lateral load through biomechanical experiments. Leading to type II odontoid fractures, and over-extension violence leads to type III odontoid fractures, but clinically, the injury mechanisms described in some patients are not the same, Pederson reports 1 case 77 In the male patient, the frontal sac was subjected to a front-to-back violence, resulting in a type IIc odontoid fracture with a 20 mm posterior displacement of the fracture. The injury mechanism of this patient can be assumed to be a hyperextension through the anterior arch of the atlas. Transmission to the odontoid, causing fractures, displacement, and a direct violent vector is a vector from the front to the back, transmitted to the anterior arch of the atlas by the skull, and then transmitted to the odontoid, forming a level of shear violence.

A odontoid fracture can also occur in a flexion-type injury, resulting in a forward displacement. In this sickle-like mechanism, a complete transverse ligament is sufficient to deliver enough energy to cause a odontoid fracture and forward displacement. In the combined effect of multiple kinds of violence, reversing the existence of violence will make the odontoids prone to fracture. The mechanism has the following three points: (1) the flank ligament has been stretched to the maximum when rotating; (2) when rotating The ligaments and muscles are in tension, the small facet joints are tightly engaged, and the damage of other planes is minimized; (3) the atlantoaxial joints account for 50% of the neck's rotational activity, and the parts are subjected to rotational violence. The load is also the largest. In short, the mechanism of odontoid fracture is complicated. Flexion, extension, lateral flexion and rotational violence are all involved. In a patient, the relationship between fracture type, fracture displacement and head and face attachment injury is often analyzed. The mechanism of damage can be inferred.

Prevention of odontoid fracture

The disease is mainly caused by traumatic factors, especially violent factors, so prevention of daily life damage is the key to prevent this disease.

Complications of odontoid fractures Complications

Among the complications caused by this disease, mild paraplegia and neuralgia are the most common. There have been reports of odontoid fractures with the tenth and twelfth pairs of cranial nerve spasms. The severity of the symptoms is the degree of fracture displacement and compression of the spinal cord. Depending on the location, severe respiratory arrest can occur, more common in the elderly, often on the spot.

The rate of non-union of odontoid fractures caused by untreated or improper treatment is 41.7%72%, and there is potential atlantoaxial instability. Once displaced, it may lead to acute brain stem, spinal cord or nerve root. Chronic injury, causing severe quadriplegia, respiratory dysfunction and even death.

Symptoms of odontoid fractures common symptoms occipital and posterior neck pain, paraplegia, neck stiffness, neuralgia

The occipital and posterior neck pain is the most common clinical symptom, and there is often radiation pain in the area of the occipital nerve. The neck stiffness is forced position. The typical sign is that the patient supports the head by hand to relieve pain. Clinically uncommon, 15% to 33% of patients have neurological symptoms and body parts, of which mild paraplegia and neuralgia are most common, there have been odontoid fractures with tenth and twelfth pairs of cranial nerve spasms According to reports, the severity of symptoms depends on the degree and location of the fracture displacement oppression of the spinal cord, severe respiratory arrest can occur, more common in the elderly, often died on the spot.

The clinical manifestations of odontoid old fractures are relatively hidden, because the history of trauma is sometimes not obvious. Crockard et al reported a group of 16 patients with old odontoid fractures, and 3 patients had forgotten the history of neck trauma. The other patients were diagnosed with a new diagnosis. The physician's estimate of the importance of his trauma is too low to miss the diagnosis. Symptoms include C2 nerve root pain, weak hands and difficulty walking.

Examination of the odontoid fracture

The examination of this disease is mainly imaging examination:

(1) X-ray examination

For patients with suspected diagnosis, ordinary X-ray examination is the first choice, including cervical vertebrae, open position and lateral extension, flexion, but because of the patient's neck often stiff or even forced position, standard, clear X-ray films are sometimes difficult to obtain at one time. There is no clear anatomical relationship or clear fracture signs in the initial X-ray examination. When there are still clinical doubts, the two open tablets and the two occipital neck lateral slices should be regarded as routine. Check to confirm the diagnosis.

However, due to the excessive overlap of the neck and occipital bones, occasionally the normal X-ray examination will have a negative result when the odontoid fracture is not accompanied by displacement. Therefore, it is necessary to take a sagittal and coronal tomographic slice in the following cases. :

(1) Clinically suspected odontoid fracture but normal X-ray film showed negative;

(2) Ordinary X-ray examination suggests suspicious fracture signs, which is the most common indication;

(3) Definite odontoid fractures, but suspected adjacent concomitant fractures.

X-ray films show odontoid fractures mainly due to bone disruption, displacement and angulation. The most reliable indication is displacement. Sometimes the lateral flank of the ostium is the only sign, a high quality Lateral radiographs are necessary for the diagnosis of odontoid fractures, as odontoid fractures are often accompanied by anterior and posterior displacement and angulation, and information on the direction of displacement is instructive for treatment, but occasionally odontoid anatomical abnormalities In the case of backward tilting, misdiagnosis as a fracture should be avoided. The value of indirect signs such as pre-vertebral soft tissue shadows may be limited to the location of the injury, and sometimes the soft tissue of the anterior vertebra is normal, especially when examined immediately after injury. Sometimes, the fracture of the head and face can also cause swelling of the soft tissue of the vertebral body.

(2) CT examination

CT examination can clearly show the fracture and displacement, especially when the patient's forced position causes the anatomical structure of the ordinary X-ray film to be unclear.

(3) MRI examination

MRI can clearly show the compression of the spinal cord caused by fracture displacement and the extent of spinal cord injury, as well as the adjacent soft tissue injury.

Diagnosis and diagnosis of odontoid fracture

diagnosis

Detailed and accurate injury history and physical examination often enable physicians to consider the possibility of such injuries. Motorcycle accidents are a common cause of odontoid fractures in young people. The most common cause of these injuries in the elderly is simple. The fall, the odontoid fracture with posterior dislocation is more serious than the anterior dislocation, and the probability of neurological symptoms is greater, more common in the elderly.

X-ray examination is the main basis and means for diagnosing odontoid fracture. When the diagnosis is suspected, it should be repeated, and a tomographic slice or CT examination should be performed. MRI examination can provide spinal cord injury on the transverse section and dentate. The protrusion and the spinal cord each account for 1/3 of the sagittal diameter of the spinal canal, and the remaining 1/3 is the buffer gap (Fig. 1). The distance between the posterior margin of the anterior arch of the atlas and the odontoid (AO spacing) is 2 mm to 3 mm. Children are slightly larger, ranging from 3mm to 4mm. Exceeding this range, odontoid fractures and/or ligament structures should be considered. The dentate processes on the open piece are asymmetrical on both sides. The damage should be suspected in this area. Clear opening The radiograph can show odontoid fractures and fracture types. The lateral radiographs can show the type of fracture and the displacement of the anterior or posterior and the atlantoaxial dislocation. Also, attention should be paid to the presence or absence of deformities and fractures in other parts of the neck occipital region.

The diagnosis of a odontoid fracture should include the following five points:

(1) the type of odontoid fracture;

(2) Whether there is displacement and direction;

(3) Whether there is nerve damage;

(4) Whether there is adjacent bone and soft tissue damage with the marrow;

(5) Whether there is damage to other parts of the body.

Differential diagnosis

The diagnosis of this disease needs to be distinguished from the transverse ligament rupture of the atlas, the transverse ligament avulsion and the atlantoaxial posterior dislocation.

When the transverse ligament is broken, the AO spacing is more than 5mm, the odontoid process is complete, and the transverse ligament can be seen when the transverse ligament is ablated, and the irregular bone is seen between the lateral vertebral vertebral blocks. The CT scan can confirm the diagnosis and show the small defect of the atlanto-lateral block surface. And free bone mass, posterior atlantoaxial dislocation on the lateral radiograph shows that the anterior arch and odontoid position are reversed, sometimes there are small fracture fragments in front of the odontoid or at the apex, in addition to the presence or absence of occipital neck Abnormalities, such as the atlanto-occipital pillow, flat skull base.

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