Paediatric Femoral Neck Fractures

Paediatric femoral neck fractures are rare compared with adult hip fractures, but they are treated with a different level of urgency because the biology is different. The child has an open physis, a cartilage-rich proximal femur, a vulnerable femoral-head blood supply and many years of growth remaining. A well-aligned fracture can heal quickly; a poorly reduced or vascularly compromised fracture can leave the child with avascular necrosis, coxa vara, non-union, limb-length difference and early hip degeneration.

Most injuries follow high-energy trauma: road trauma, fall from height, sports collision or crush injury. A low-energy femoral neck fracture is not routine trauma until proven otherwise. It should trigger consideration of bone cyst, tumour-like lesion, metabolic bone disease, endocrine disease, infection, non-accidental injury in the right age group, or medication-related bone fragility.

The practical clinical sequence is:

• Identify the fracture and associated injuries.
• Classify with Delbet type and displacement.
• Decide whether the fracture is intracapsular and whether decompression is relevant.
• Restore an anatomical reduction.
• Stabilise the fracture without violating the joint.
• Protect weight bearing.
• Follow for union, femoral-head shape, neck-shaft angle and growth.

The proximal femur in a child is not a smaller adult hip. The proximal femoral physis contributes to growth, the greater trochanter has its own apophysis, and the femoral head relies heavily on vessels that run near the femoral neck. A displaced intracapsular fracture can injure the retinacular vessels directly. Intracapsular haemarthrosis can also raise pressure around the femoral head. Both mechanisms explain why a child with a displaced femoral neck fracture may later develop avascular necrosis even if union appears satisfactory.

Key structures to understand:

• Femoral head: the articular segment at risk of avascular necrosis and collapse.
• Proximal femoral physis: threatened in transphyseal injuries and by some fixation strategies.
• Femoral neck: short bridge between head and trochanteric region; shear across this segment promotes instability.
• Retinacular vessel contribution: clinically important for femoral-head perfusion.
• Hip capsule: contains intracapsular haematoma in Delbet I and II patterns.
• Neck-shaft angle: progressive varus reflects collapse, malunion, non-union or growth disturbance.

The Delbet classification describes fracture location. It is useful because location correlates with femoral-head perfusion risk and fixation strategy. It should always be paired with displacement, reduction quality, child age and associated injuries.

History

A typical child presents after high-energy trauma with severe hip or groin pain and inability to bear weight. Some children describe thigh or knee pain, so a hip injury can be missed if the assessment stops at the knee. The history should establish mechanism, timing, ability to stand after injury, pain location, associated trauma symptoms and whether there was preceding hip pain.

Ask specifically about:

• Road trauma, fall height, sports collision, crush injury or direct lateral hip blow.
• Inability to weight bear or severe pain with transfer.
• Groin, lateral hip, thigh or knee pain.
• Previous limp, night pain, fever, weight loss or known bone lesion.
• Neurological symptoms, distal limb symptoms and other injuries.
• Timing of injury and any delay in presentation.

Examination

Examine the child using trauma principles before focusing on the hip. A displaced femoral neck fracture is painful; repeated log rolling or forced positioning is unnecessary. Document baseline neurovascular findings and examine the pelvis, femoral shaft, knee and spine because high-energy trauma often produces more than one injury.

Look for:

• Shortened or externally rotated limb posture, although this may be subtle.
• Guarding and severe pain with any hip movement.
• Pain with gentle log roll.
• Groin tenderness or proximal femur tenderness.
• Associated femoral shaft swelling, knee injury, pelvic pain or abdominal injury.
• Skin compromise in open or severe crush trauma.
• Distal perfusion, motor function and sensation.

Initial imaging

Obtain an AP pelvis and a safe lateral view of the injured hip. In a painful fracture, do not force frog lateral positioning. A cross-table lateral or other safe lateral projection is preferable. The AP pelvis gives the contralateral hip for comparison and helps identify associated pelvic injury.

Image the whole femur when the mechanism is high energy, when thigh pain is present or when ipsilateral shaft fracture is possible. A femoral shaft fracture can distract attention from a proximal femoral injury, and the reverse is also true.

When CT helps

CT is useful when fracture anatomy is unclear, when reduction planning is difficult, when displacement is subtle, or when an associated pelvic or acetabular injury is suspected. CT should answer a management question; it should not delay urgent treatment of an obvious displaced fracture.

When MRI or laboratory work helps

MRI, blood tests and broader workup are considered when the mechanism is low energy, when there was preceding pain, when X-ray shows a lesion, or when infection or tumour is possible. MRI can also help later if avascular necrosis is suspected before radiographic collapse is obvious.

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Avascular necrosis

AVN is the feared complication. It may present as pain, stiffness, radiographic sclerosis, fragmentation, collapse or loss of femoral-head sphericity. The risk is greatest in transphyseal and transcervical injuries, with displacement, delayed treatment and vascular disruption increasing concern. Early X-rays can be falsely reassuring.

Coxa vara

Coxa vara can result from varus malreduction, fixation failure, non-union, physeal injury or collapse. It matters because it shortens the limb, weakens the abductors, alters gait and may require corrective osteotomy if progressive or symptomatic.

Non-union and malunion

Non-union is promoted by vertical shear, inadequate reduction, unstable fixation and biological compromise. Malunion, especially varus or rotation, can produce limp, pain and abductor dysfunction.

Physeal arrest and limb-length difference

Transphyseal injury, AVN and fixation across the physis can all affect growth. The practical question is not just whether the fracture healed; it is whether the proximal femur continues to grow and maintain shape as the child matures.

Joint degeneration

Femoral-head collapse, incongruity, deformity and altered mechanics can lead to early degenerative change. This is why follow-up often extends beyond the period of fracture union.

Paediatric femoral neck fracture is an emergency because the femoral head blood supply is vulnerable and complications are common. The treatment plan should be built around timing, displacement, Delbet type, reduction quality, fixation stability, capsular pressure and long-term surveillance for avascular necrosis.

Non-operative care is rare and reserved for selected nondisplaced stable injuries with specialist oversight. Most displaced injuries need urgent reduction and internal fixation. The debate around capsulotomy or decompression should be addressed explicitly: if there is a tense intracapsular fracture haematoma, many surgeons decompress to reduce tamponade concern, but the evidence is not perfectly uniform.

Postoperative care should protect fixation until union, then restore motion and gait. The family must be warned that avascular necrosis may declare late, and a normal early radiograph does not end follow-up.

Structured clinical approach

Start with the injury pattern:

• "This is a paediatric femoral neck fracture."
• "I would classify it by Delbet type and displacement."
• "I would treat displaced intracapsular patterns as urgent because of femoral-head perfusion risk."
• "My goals are anatomical reduction, stable fixation, capsule pressure management where indicated and long-term surveillance."

Then add the modifiers:

• Age and skeletal maturity.
• Whether the fracture is transphyseal, transcervical, basicervical or intertrochanteric.
• Whether the child has polytrauma.
• Whether the mechanism is too low energy for a normal fracture.
• Whether there is an associated shaft fracture or pelvic injury.
• Whether closed reduction is anatomical.

Common pitfalls

• Treating the injury like an adult neck-of-femur fracture.
• Saying "hip fracture" without naming Delbet type.
• Forgetting to ask why a low-energy fracture happened.
• Accepting varus reduction.
• Avoiding open reduction when closed reduction is poor.
• Focusing on implant type but not reduction quality.
• Missing joint penetration on postoperative imaging.
• Stopping follow-up once the fracture unites.

Counselling points

Families need a clear explanation that this is rare and serious. The fracture can heal but still develop late femoral-head or growth problems. They should understand the need for repeat imaging, protected weight bearing, monitoring for pain or stiffness, and longer follow-up than many other childhood fractures.