Femoral neck fractures have various staging methods, and each staging method is closely related to the selection of its treatment and prognostic assessment, depending on the perspective and focus of the study.
I. Fracture typing according to the anatomical site of the fracture
According to the anatomical site of the fracture, there are four types.
1. subhead type: the fracture line is completely under the femoral head, the entire femoral neck is distal to the fracture, and the femoral head can rotate freely in the acetabulum and joint capsule. This type of fracture is most common in elderly patients. The blood supply to the femoral head is severely damaged, and even if the round ligament artery exists, it can only supply blood to a small area of bone near the round ligament recess; and the round ligament artery gradually degenerates or even occludes with age. Therefore, this type of fracture is difficult to heal, and the incidence of ischemic necrosis of the femoral head is high, and the prognosis is poor.
2. Head and neck type: i.e. oblique fracture of the femoral neck. Since most of the femoral neck fractures are caused by torsional violence, true subtrochanteric and cervical fractures are rare, while most subtrochanteric fractures are associated with a femoral neck fracture block of varying size, making the fracture line oblique. This type of fracture is difficult to reset and has poor stability after reset, and the damage to the blood supply of the femoral head is second only to the subtrochanteric type.
The transcervical fracture is often an artifact, and is often confirmed to be a cephalocervical fracture when repeatedly photographed.
4. Basal type: The fracture line is located at the base of the femoral neck. The fracture end has good blood flow, is easy to maintain stability after repositioning, the fracture is easy to heal, and the prognosis is good, so some scholars include it in the rotor fracture.
The fracture line of the first three types of fractures is located in the hip capsule, which is called intracapsular fracture; the fracture line of the basal type is located outside the capsule, which is called extracapsular fracture.
Second, according to the degree of fracture displacement typing
Type I: Incomplete fracture of the femoral neck, that is, “abductor” or “insertion” fracture, the distal fracture end is slightly abducted and externally rotated, and the X-ray shows that the upper edge of the femoral neck resembles the illusion of insertion, while the bone trabeculae at the medial craniocervical junction are bent in a green branch shape, and the femoral head is inward and posteriorly The head of the femur is tilted inward and backward.
This type of fracture has no displacement, good proximal blood flow, easy fracture healing and good prognosis, but will become a complete fracture if not carefully protected. The most characteristic of this type of fracture is that the symptoms are atypical at the first visit and the X-ray film is insidious, so it is easy to misdiagnose.
2. Type II: Complete fracture without displacement or mild displacement. If the fracture is subcranial, healing is still possible, but head necrosis and deformation often occur. If it is trans-neck and basal type, the fracture heals easily and the head necrosis rate is lower.
3.Type III: The femoral neck is completely fractured and partially displaced, mostly the distal end is displaced upward or the distal inferior angle is embedded in the proximal section, forming an abduction and internal rotation of the femoral head, and the neck stem angle becomes smaller.
Type IV: The fracture end is completely displaced, the distal fracture end is fully externally rotated and upwardly displaced, the two fracture ends are completely separated, and the femoral head can be in normal position, the joint capsule and synovium are severely damaged in this type, and the blood vessels are also easily damaged, causing ischemic necrosis of the femur.
The fracture end is completely dislocated and the distal fracture end is externally rotated and upwardly displaced, which is a serious injury to the blood vessels and has a high possibility of osteonecrosis of the femur.
The posterior edge of the femoral neck can be fragmented if the violence is large, and it can also be continuously externally rotated, and the bone on the posterior side of the femoral neck can be defective due to compression.
According to the fracture line
According to the size of the angle between the fracture line and the vertical axis of the femoral stem (Linton angle), there are three types.
1. the angle <30° is type I, the most stable.
2. type II with an angle between 30° and 50°, which is the second most stable.
3. those with an angle >50° are type III and are the least stable.
This typing method uses the inclination of the fracture line to reflect the amount of shear stress suffered.
Linton I fractures of the femoral neck are more stable than Linton III fractures, which are extremely unstable and easily displaced by external rotation and shortening.
Due to the displacement and rotation of the femoral head and neck, it is often difficult to determine the alignment of the fracture line. For the measurement of the inclination of the fracture line, the affected limb must be placed in the internal rotation position to eliminate the anterior femoral neck inclination before the measurement can be taken. The fracture can be measured at the time of postoperative radiographs in order to understand the stability of the fracture and to estimate the prognosis in order to take appropriate preventive measures.
The fracture is classified according to the direction of displacement between the fracture segments
1. Abduction type: The two fracture segments are in an abduction relationship, the femoral head is in a relatively inward position, the distal upper part of the fracture is inserted into the femoral head, there is no misalignment or rotation of the medial cortex, and the neck stem angle is increased. It is also called the insertion type fracture, with stable position, less destruction of joint capsule blood flow, better prognosis and highest healing rate.
2. Intermediate type: X-ray orthopantomogram shows an abducted insertion relationship, but the lateral X-ray shows the femoral head is flexed anteriorly, forming a posterior angle with the femoral neck, and the two fracture segments appear separated in the anterior square. The fracture position is not completely stable and is actually an intermediate stage of transition to the inversion type.
3. Inclusion type: The two fracture segments are completely dislocated, the femoral head is in the external booth, the femoral neck is displaced upward due to muscle pulling and externally rotated due to the weight of the lower limb, and the relationship is inward. This type of fracture has very little insertion of the fracture end, which is subjected to high shearing force and instability, so it is mostly displaced and has a large destruction of blood flow in the joint capsule and the lowest healing rate.
V. Other classification methods
1, according to the cause of fracture can be divided into traumatic and pathological femoral neck fracture (such as primary or metastatic bone tumor of the femoral neck, osteomyelitis, bone tuberculosis, osteofibrodysplasia and hyperthyroidism, etc.), medical fracture of the femoral neck (such as congenital hip dislocation reset improper force, chronic osteomyelitis improper removal of large pieces of dead bone can cause fracture).
2, according to the time of fracture occurrence fresh and old femoral neck fracture. The latter includes those who have been injured for more than 3 weeks or treated but not healed.