Femoral neck fractures and the Garden classification
The radiological evaluation of femoral neck fractures is based on the Garden classification (Garden classification). It takes into account the radiographic presentation and the degree of bone fragment displacement.
- Type I: Incomplete fracture, no displacement. Includes impacted fractures with valgus deformity. On the radiograph, it may appear as a subtle interruption of trabecular lines or indistinct transverse sclerosis of the femoral neck.
- Type II: Complete fracture, but without fragment displacement.
- Type III: Complete fracture with partial displacement and varus deformity.
- Type IV: Complete fracture with absolute fragment displacement.
Injuries of types III and IV carry the highest risk of developing avascular necrosis (avascular necrosis) of the femoral head. Severe comminuted intertrochanteric fractures are easier to identify on radiographs; their treatment typically involves plate and dynamic screw fixation or intramedullary nailing.
Diagnostic challenges and occult fractures
About 1% of proximal femur fractures are initially not visible on standard radiographs. If a patient is still unable to fully bear weight on the injured limb 24 hours after trauma, an occult fracture (occult fracture) must be ruled out. Early weight-bearing on such a leg leads to secondary displacement of bone fragments.
- MRI is the most highly specific and sensitive method of choice in such controversial situations. Tomography (e.g., in the coronal projection, STIR sequence) clearly visualizes bone marrow edema as high signal zones and a low signal fracture line.
- If MRI is unavailable or contraindicated, CT is prescribed as an alternative.
- Fractures of the pubic rami or the greater trochanter can completely mimic the clinical presentation of a femoral neck fracture. Furthermore, a significant number of isolated trochanteric fractures turn out to be intertrochanteric on MRI due to occult propagation.
When analyzing images, it is important to remember artifacts. Air trapped in the groin skin crease produces a linear radiolucency (skin crease artifact) that is easily mistaken for a fracture line or, conversely, may obscure a genuine injury. To differentiate, this line must be traced—the artifact is visually separated from the bone and continues into the soft tissues.
Atypical injuries and oncological alertness
Fractures occurring with minimal physical impact or without any trauma require special attention from the radiologist.
- Atypical femoral fractures: There is a causal relationship between long-term use of bisphosphonates (used to treat osteoporosis) and the development of such injuries. They are localized in the subtrochanteric zone and are often bilateral. Pathogenetically, the process begins in the lateral cortical layer, which appears thickened on radiographs (beaking deformity). A complete transverse fracture produces a characteristic medial unicortical bone spur.
- Lesser trochanter fracture: Isolated injuries of this zone are rare. In adolescent athletes, this is usually an avulsion injury due to a sharp and powerful contraction of the iliopsoas muscle. However, in adult patients with no history of significant trauma, this is an extremely ominous sign that raises suspicion of metastatic tumor infiltration into the bone tissue.
Additionally, it is advisable to screen all patients under 75 years of age with hip fractures for osteoporosis (densitometry — DEXA) and adjust treatment accordingly.
Knee joint injuries and lipohaemarthrosis
When evaluating the knee joint on an anteroposterior radiograph, the fibula always serves as a reliable lateral landmark. Normally, joint spaces should be equal in width, and the cortical layers of the tibial plateau should be sclerotic and have clear contours. An important rule: a line dropped perpendicularly from the lateral femoral condyle should meet the edge of the adjacent plateau (protruding laterally by a maximum of 5 mm is permissible). Exceeding this distance indicates a depressed fracture, which typically occurs with a forced valgus impact. Fractures of the medial plateau are significantly less common—in only 10% of cases.
Following any knee trauma, a lateral radiograph must be performed with a horizontal beam (patient supine). This allows for the detection of lipohaemarthrosis (lipohaemarthrosis), a sign of a fluid level in the suprapatellar pouch. Since the only source of fat at body temperature is bone marrow, dark fat floating on top of blood serves as a 100% marker of an intra-articular cortical bone tear.
Briefly: answers to topical questions
Which blood vessels are damaged in femoral neck fractures, leading to the development of avascular necrosis?
Sources indicate that in adults, the primary blood supply to the femoral head is provided by the circumflex femoral arteries (circumflex femoral arteries), while the artery of the ligament of the head (foveal artery) passes through the ligament of the head. However, the sources do not specify which exact vessels are damaged during a femoral neck fracture and lead to avascular necrosis.
What diagnostic imaging methods are used to search for occult hip fractures, and what is their diagnostic accuracy?
To detect occult proximal femur fractures not visible on standard radiographs, the following methods are used:
- MRI (MRI) is the method of choice; it is a highly specific and sensitive method.
- CT (CT) is used if MRI is unavailable or contraindicated.
- Radiography is the standard primary method, although approximately 1% of fractures are initially occult and not detected on standard radiographs.
Sources do not provide specific numerical values for sensitivity and specificity.
What surgical treatment methods are used for femoral neck fractures depending on the Garden type?
Surgical tactics for femoral neck fractures vary depending on the degree of displacement and the Garden classification type:
- Garden types I–II (stable fractures without displacement): Osteosynthesis using preferred fixation devices is applied. The use of tri-fin nails or blade plates is not recommended.
- Garden types III–IV (incomplete varus and/or complete displaced fracture): In patients under 60 years of age, emergency osteosynthesis may be performed using three cancellous cannulated screws, a dynamic hip screw, or three dynamic bone screws fixed in a plate. In patients over 60 years of age with osteoporosis, hip arthroplasty (total or hemiarthroplasty) is indicated.
Class and exam questions
What is the primary danger of an occult femoral neck fracture?
If an occult fracture is missed on a radiograph and the patient is allowed to bear weight on the leg, secondary displacement of fragments will occur. This critically increases the risk of developing severe avascular necrosis of the femoral head.
How to differentiate a skin fold artifact from a true fracture on a radiograph?
Air accumulation in the groin crease creates a linear radiolucency projecting over the bone. Detailed study of the image shows that this line is visually separated from the bone tissue and continues into the soft tissues.
Why is a horizontal-beam lateral view mandatory in knee trauma?
A specific patient positioning on the back with a horizontal beam direction allows visualization of fluid layering (fat floating above blood)—lipohaemarthrosis. This condition reliably confirms the presence of an intra-articular bone fracture.
What else to study on this topic
- Radiographic diagnosis of comminuted intertrochanteric fractures and selection of the osteosynthesis method.
- Simulation of femoral neck fracture symptoms in injuries of the pubic rami.
- MRI presentation of bone marrow edema (STIR sequence) in occult bone injuries.
- Radiographic anatomy of the tibial plateau and the 5 mm rule.
- Densitometry (DEXA) technique in patients with pathologic fractures.
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