Fraktur Femur

01Pathophysiology

The femoral neck is the segment of bone connecting the femoral head to the intertrochanteric region. It is intracapsular, meaning it lies within the hip joint capsule. This anatomic detail is the single most important concept for understanding why these fractures behave differently from intertrochanteric or subtrochanteric fractures. The blood supply to the femoral head arrives primarily through the medial femoral circumflex artery, which gives rise to the lateral epiphyseal arteries (also called the retinacular vessels). These vessels travel along the femoral neck under the joint capsule. When a fracture displaces the femoral neck, these retinacular vessels are stretched, kinked, or torn, which interrupts perfusion to the femoral head.

This vascular anatomy directly explains the two feared complications of femoral neck fractures: avascular necrosis (AVN) and nonunion. The more displaced the fracture, the greater the vascular disruption. A Garden I fracture (valgus-impacted, incomplete) has minimal vascular compromise, while a Garden IV fracture (complete displacement with loss of contact between fragments) has near-total disruption. This is why displaced fractures in young patients are treated as orthopedic emergencies requiring reduction within hours, and why elderly patients with displaced fractures are offered arthroplasty rather than fixation, since the risk of fixation failure, AVN, and reoperation is unacceptably high.

The ligamentum teres artery (from the obturator artery) provides a small contribution to the femoral head, but in adults this vessel is often insufficient to maintain viability of the femoral head on its own. This explains why even with urgent fixation, AVN rates in displaced femoral neck fractures remain significant (15 to 30 percent or higher for Garden III and IV injuries).

In elderly patients with osteoporotic bone, the femoral neck is a zone of structural weakness. The cortical bone in this region thins with age, and cancellous bone density decreases, particularly along the tensile (superior) trabeculae. A simple ground-level fall generates enough force to fracture through this weakened segment. In young adults, the same fracture requires a much larger force, and the treating physician should consider underlying pathology (stress fracture, metabolic bone disease, malignancy) if the mechanism seems disproportionately low.

02Classification and Clinical Manifestation

The Garden classification divides femoral neck fractures into four types based on the degree of displacement seen on the AP radiograph of the hip. It is the most commonly tested classification system for this injury.

For exam purposes, the classification is often simplified into two functional groups:

The classic "stargazer" or "Garden alignment" trap occurs in Garden IV fractures: because the femoral head floats freely and re-aligns itself within the acetabulum under the weight of the limb, the trabecular lines of the head may appear to align with the acetabular trabeculae on the AP film. An inexperienced reader may mistake this for a Garden II (non-displaced) fracture. The key discriminator is the lack of cortical continuity along the femoral neck and the disrupted trabecular pattern of the femoral shaft relative to the head.

03Diagnostic Workup

The workup begins with standard AP pelvis and cross-table lateral hip radiographs. In a patient presenting with hip or groin pain after a fall who cannot bear weight, these films will identify the fracture in the majority of cases. The AP view is used to classify the fracture using the Garden system by examining the alignment of the medial compressive trabeculae of the femoral head relative to those of the acetabulum and femoral shaft.

When the clinical presentation is convincing (groin pain, painful log-roll, inability to bear weight) but the initial radiographs appear normal, the diagnosis is occult femoral neck fracture until proven otherwise. The next step is MRI, not repeat X-rays in a few days. MRI has near-perfect sensitivity for detecting trabecular fractures, bone marrow edema, and non-displaced fracture lines that are invisible on plain films. This is a high-yield testing point: the exam may present an elderly patient who falls, has groin pain and a negative X-ray, and then ask for the next best diagnostic step. The answer is MRI, not CT, not bone scan, and not "reassurance and follow-up films."

CT can be used when MRI is contraindicated (pacemaker, severe claustrophobia) or unavailable, but it is less sensitive than MRI for non-displaced injuries without cortical breach. Bone scintigraphy is outdated for this indication and carries the added disadvantage of delayed sensitivity (false negatives in the acute period).

Preoperative laboratory evaluation should be obtained promptly but should not delay surgical intervention beyond what is medically necessary for stabilization. Current guidelines favor surgery within 24 to 36 hours of admission for hip fractures, as delays beyond this window are associated with increased mortality, pneumonia, pressure ulcers, and thromboembolic events.

04Management and Treatment

Acute stabilization begins in the emergency department with pain control (regional anesthesia via a fascia iliaca block is preferred over systemic opioids when available), intravenous fluids, and medical optimization. A Foley catheter and DVT prophylaxis (low-molecular-weight heparin such as enoxaparin 40 mg subcutaneously daily, or mechanical compression devices) should be initiated early.

For non-displaced fractures (Garden I and II), the standard of care across all age groups is internal fixation to prevent secondary displacement. Three cannulated screws placed percutaneously in an inverted triangle pattern provide compression across the fracture site and rotational stability. Weight bearing as tolerated is typically allowed postoperatively, and the patient is monitored with serial radiographs for signs of AVN (which can develop months to years after injury).

For displaced fractures (Garden III and IV) in young patients, the priority is emergent anatomic reduction and fixation. The goal is to restore alignment and re-establish blood flow through the retinacular vessels before irreversible ischemia develops in the femoral head. The widely cited time window is within 6 to 12 hours of injury, though some evidence suggests benefit up to 24 hours. Closed reduction is attempted first under fluoroscopic guidance; if inadequate, open reduction through an anterior (Smith-Petersen) or anterolateral approach is performed. Fixation is achieved with cannulated screws or a sliding hip screw.

For displaced fractures in elderly patients, arthroplasty is the treatment of choice. The decision between hemiarthroplasty and total hip arthroplasty depends on several factors:

Hemiarthroplasty (replacing only the femoral head and neck with a prosthetic stem and head) is appropriate for patients who are less active, have cognitive impairment, or have limited life expectancy. It is a shorter operation with lower dislocation risk. An anterolateral or posterior approach may be used.

Total hip arthroplasty (replacing both the femoral head and the acetabular surface) provides better long-term functional outcomes and lower rates of reoperation in patients who are cognitively intact, independently mobile, and have a reasonable life expectancy (generally more than 5 years). It is associated with a higher dislocation rate, particularly through the posterior approach, and a longer operative time.

Long-term management includes DVT prophylaxis for 28 to 35 days postoperatively (enoxaparin 40 mg subcutaneously once daily or rivaroxaban 10 mg orally once daily), physical therapy beginning on postoperative day one with early mobilization, osteoporosis evaluation and treatment (DEXA scan, calcium 1200 mg daily, vitamin D 800 to 1000 IU daily, and bisphosphonate therapy if indicated), and fall prevention counseling.

Contraindications to note: Bisphosphonates should not be started in the acute postoperative period; they are generally initiated after fracture healing is established (typically 2 to 3 months), as there is theoretical concern about impaired callus formation. In patients with renal insufficiency (creatinine clearance below 30 to 35 mL/min), bisphosphonates are contraindicated, and referral to endocrinology for alternative agents (denosumab) is appropriate.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students lose points on femoral neck fracture questions is by failing to recognize the occult fracture scenario. The vignette presents an elderly patient who falls, has groin pain and difficulty bearing weight, but has "normal" hip radiographs. The student either selects "reassurance" or "repeat X-ray in 2 weeks" instead of the correct answer: MRI. This tests the competency of recognizing that a negative X-ray does not rule out a femoral neck fracture, and that delayed diagnosis leads to displacement, AVN, and poor outcomes.

The second major trap involves management selection based on displacement and age. The exam will present a displaced fracture (Garden III or IV) in an active 70-year-old and offer both "open reduction and internal fixation" and "hemiarthroplasty" as answer choices. Students who reflexively choose fixation (because "save the joint" sounds right) will miss that arthroplasty is the standard of care for displaced femoral neck fractures in the elderly due to unacceptable failure rates with fixation. Conversely, a displaced fracture in a 30-year-old demands urgent fixation, not arthroplasty, because preserving the native femoral head is paramount in a young patient.

A third tested concept is the urgency of reduction in young patients with displaced fractures. The vignette may describe a young adult with a displaced femoral neck fracture and ask for the next step. The answer is not "schedule for surgery tomorrow morning" but rather emergent reduction and fixation within 6 to 12 hours to minimize AVN risk. The exam is testing whether you understand the vascular anatomy and the time-dependent nature of femoral head ischemia.

Finally, watch for the Garden IV "false non-displaced" trap: a fully displaced fracture where the femoral head re-aligns in the acetabulum and the trabecular pattern of the head appears to match the acetabulum on the AP film. This can mimic a Garden II fracture on superficial reading. The clue is the disrupted trabecular continuity along the femoral neck shaft and the clinical picture of a markedly shortened, externally rotated limb that does not match a "non-displaced" classification. Always correlate imaging findings with the clinical examination.