Femoral neck fractures are fractures that are classically described in older adults with osteoporosis. Thus, these fractures are particularly common in postmenopausal women, while they are relatively rare in children and younger people, and are usually the result of major trauma. In elderly patients, even minor trauma can cause fractures due to bone fragility, such as femoral neck fractures classified as fragility fractures.
Anatomy
The femur is the largest and hardest bone in the body. The proximal end forms the hip joint with the acetabulum of the pelvis, while the distal end forms the knee joint with the tibia, fibula and patella. The proximal 1/3 of the femur is divided into three specific areas. The key to the treatment of femoral neck fractures is to understand the specific anatomy of these special sites. The femoral neck extends upward and inward to form the femoral head, a hemispherical structure with a smooth surface that covers the articular cartilage and forms the joint with the cup-shaped acetabulum. However, the neck of the femur forms a flat cone connecting the femoral head to the body of the femur, with the base being the widest. At an angle of approximately 125° from the femoral stem to the femoral head, the joint capsule attaches to the base of the femoral neck and has two bony elevations, the greater and lesser trochlea, which are the attachment points for the hip muscles. The intertrochanteric ridge is called the intertrochanteric ridge.
The femoral stem is a cylindrical bone that is curved, mildly convex anteriorly and slightly concave and flattened posteriorly. The blood supply to the femoral head is derived from the profunda femoris artery (a branch of the femoral artery), which supplies the femoral head through three pathways: the first is the most important vessel that enters the base of the femoral neck through the distributive joint capsule support band. It is important to know where the vessel penetrates the femur, as a fracture of the femoral neck above this site can result in inadequate blood supply to the proximal femoral head. The second is the intra-femoral l vasculature that enters through the bone distribution. Finally, the femoral round ligament artery, a very small nutrient artery that connects the femoral head to the acetabulum, provides only a smaller blood supply in the elderly and may actually be deficient.
Types of fractures
There are two main mechanisms of injury that lead to fractures in these areas, namely, rotational injuries to the hip that often result in fractures within the joint capsule or direct impact injuries to the outside of the hip that result in fractures outside the capsule.
Intracapsular fractures can result in interruption of the blood supply from the joint capsule and femoral l, leaving only a smaller blood supply from the round ligament artery. Another confusing aspect of intracapsular fractures is the nature of the bone within the capsule: there is only a thin periosteum with no soft tissue connections thus preventing the formation of a bone scab. In addition, bleeding at the intracapsular fracture site leads to a hematoma and an increase in intracapsular pressure, which in turn hinders the blood supply and affects healing. These factors can lead to ischemic necrosis of the femoral head.
Intracapsular fractures of the joint can be further divided into: subcapsular (femoral head at the level of the junction with the femoral neck) transcervical (fracture line through the femoral neck) cervical base (femoral neck at the level of the junction with the body)
Base of the neck fractures are usually extracapsular, yet the fracture line often extends through the femoral neck and is accompanied by soft tissue damage involving tearing of the joint capsule. This means that they should often be treated as intracapsular fractures. Intracapsular fractures are classified into 4 types according to Garden’s staging.
In practice, the question that really affects the patient’s treatment, whether the fracture is displaced or not. It is accepted that Garden’s types I and II are nondisplaced fractures, while types III and IV are displaced fractures.
For extracapsular fractures, the fracture does not disrupt the articular capsule vessels because the fracture does not disrupt the articular capsule vessels. This allows for a more reliable blood supply to the femoral head, promoting fracture healing and avoiding the various complications associated with intracapsular fractures.
Surgical treatment
Once a thorough evaluation of the patient and the fracture staging has been determined, a surgical treatment plan can be initiated. There are five general (though obvious but not singular) treatment options for intracapsular fractures: 1. non-surgical treatment 2. hemiarthroplasty 3. power compression hip screw 4. hollow hip screw 5. l-internal hip screw.
Cases of initial total hip arthroplasty have also been reported in older patients who are fit and active and who enjoy a reasonable quality of life. Even if the femoral neck fracture severely damages the blood supply to the femoral head, there is a potential for blood flow restoration after fracture reduction. This is generally recommended for early fracture reduction and fixation.
Undisplaced intracapsular fractures
Undisplaced intracapsular fractures generally require hollow hip screws or 2-hole power hip screws for fixation. However, there is also a close to 20% chance of ischemic necrosis of the femoral head and these patients may require further intervention in the future. In those patients who are uncooperative with internal fixation therapy or have serious other health problems, further management may not be safe. Artificial femoral head replacement may certainly be prudent as the treatment of choice over hollow screws or power-compression hip screw systems.
When hollow hip screws are applied, several screws (usually 3) are used to achieve fixation through the fracture end and to create compression of the femoral head toward the neck. This technique can be performed through a percutaneous or small incision and requires an anatomical repositioning prior to fixation, which is performed on a fluoroscopically accessible fracture reduction table under the guidance of electrical fluoroscopy.
Displaced intracapsular fractures
Displaced intracapsular fractures always require artificial femoral head replacement because of the high rate of ischemic necrosis of the femoral head. Artificial femoral head replacement is the replacement of the femoral head with an artificial prosthesis. To protect the normal hip joint, hollow screw fixation is more appropriate in younger patients and artificial femoral head replacement is not usually used. In this type of fracture, due to the high rate of ischemic necrosis of the femoral head (up to 40%), it is necessary to reset the head as soon as possible in order to reduce the ischemic time of the femoral head. Although, the failure rate is high in young patients, this rate is often acceptable if their young normal hip is removed by other means and replaced with a prosthesis that itself has many problems. There are two types of artificial femoral head replacement operations: cemented and uncemented. The uncemented design uses a compression fit between the implant and the femoral medullary cavity to achieve stability, which can encourage bone to grow on the surface of the prosthesis or grow into the prosthesis, such as the Austin-Moore prosthesis.
Cemented prostheses such as the Thompson’s prosthesis present good advantages in the treatment of hip fractures. Cemented prostheses provide immediate stability between the bone and the endophyte. It can be less painful than non-cemented prostheses while allowing for early postoperative weight-bearing activities and rehabilitation. In elderly patients with osteoporosis, the bone density is reduced and the medullary cavity is enlarged, thus lacking the environmental mechanisms for bone ingrowth and pressure-matching stabilization.
Non-cemented prostheses are also commonly used in relatively frail patients with poor mobility (that is, bed to wheelchair users). With uncemented prosthesis replacement, the surgical procedure is quicker, reduces the risk of anesthesia and the risk of damage to the cardiovascular system from the cement, and reduces the impact of rehabilitation weight bearing on the prosthesis in patients who are already less mobile.
Other characteristics that need to be understood when using artificial femoral head replacement are the differences between unipolar and bipolar femoral head replacements. Most artificial femoral head replacements are unipolar head replacements, that is, the head and stem of the prosthesis are one piece. However, it has been reported to have acetabular wear, especially in younger patients who have a long life expectancy and high activity level, and less frequently in older patients with osteoporotic femoral neck fractures. bipolar femoral heads were first reported in 1974. The artificial bipolar femoral head prosthesis has a head separated from the stem, which consists of a larger metal acetabular cup and a polyethylene liner with an articular recess that snaps inside the metal acetabular cup. Having two movable joints improves greater range of motion and reduces wear on the acetabulum. Another advantage of the design is that for patients who require total hip replacement in the future, the artificial bipolar head can be removed and the stem, which is still stably fixed in the femoral medullary cavity, can be retained and reused to simplify revision surgery.
The surgical approaches for artificial femoral head replacement are usually anterolateral and posterior approaches. The patient is placed on the operating table on his or her side with the affected side facing upward. Each of these approaches has its own advocates and advantages and disadvantages and is chosen according to the operator’s preference and proficiency.
Extracapsular fractures can also be intertrochanteric and subtrochanteric fractures. While intertrochanteric fractures are usually treated with DHS, subtrochanteric fractures can be considered fractures of the femoral stem rather than true femoral neck fractures, which are classified as transverse or spiral/oblique. Spiral fractures are usually fixed with longer DHS plates and transverse fractures are fixed with intramedullary nails.
Intertrochanteric fractures
Power hip screws are commonly used to fix intertrochanteric fractures. They are also used for base of femoral neck fractures and occasionally for Garden’s type I and type II femoral neck fractures. Occasionally, an anti-rotation pin or screw is added. The thicker hollow tension screw slides freely in a metal slide that is attached to the plate and fixed to the lateral aspect of the femoral stem by the screw. Weight-bearing causes tight dynamic compression of the femoral head through the screw and femoral neck against the broken end. When pressurized, the tension screw slides along the metal slide to maintain the fracture in place.
Dynamic compression of the fracture end promotes fracture healing, compression produces stable fixation, and allows early weight bearing and simplifies the rehabilitation process. Tension screws are less resistant to rotation and may rotate the femoral head when screwed in with force, causing vascular injury. In these cases with a higher risk of possible rotation, the application of an anti-rotation pin or screw is recommended. In these intertrochanteric fractures, where the fracture line extends below the trochanter, or in spiral row subtrochanteric fractures, an elongated DHS plate may be applied. To improve reliable fixation, the lengthened plate needs to pass through the fracture line for a sufficient length. Before applying DHS fixation, anatomic repositioning is required, preferably on a fluoroscopically guided fracture repositioning bed, and correct repositioning is achieved by means of fluoroscopic guidance.
Subtrochanteric fractures
Any fracture in which the fracture line extends below the trochanter or in which the medial cortical bone of the femur is severely comminuted requires a longer intramedullary nailing system such as the Gamma nail. The patient is placed supine on the operating table and the intramedullary nail is inserted in an advancing fashion into the femoral stem through the greater trochanter or ramus dorsi fossa. The intramedullary nail is passed down through the femoral stem and the tension screw passes through the main nail into the femoral head along the femoral neck. The proximal and distal locking nails are inserted percutaneously under x-ray guidance. In unstable fractures (loss of medial support), where fixation is difficult to obtain, the proximal and distal grips of the intramedullary nail are used to provide reliable fixation of the fracture end. The integrity of the femoral intertrochanteric space is important in the application of this technique, since there is a risk of proximal fracture fragmentation during insertion of the intramedullary nail. The application of an extended DHS plate is often appropriate in such cases.
Conclusion
Numerous textbooks have a long and many articles talking about this topic, but a clear surgical approach to guide femoral neck fractures has not been developed. The purpose of this review is to quickly review and summarize some of the current concepts for the treatment of femoral neck fractures, as common as they may be. Of course, each fracture is different and the patient should be evaluated as a whole to select the best treatment based on individual differences.