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.

What is at stake. 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.

Mechanism. 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 clinical sequence. In practice the steps run:

• 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.

The femoral head and its vessels. The head is an articular segment at risk of avascular necrosis and collapse. Displacement can directly injure its blood supply through the retinacular vessels, which is why anatomical reduction and the avoidance of repeated forceful manipulation matter.

Capsular pressure. In Delbet I and II injuries the intracapsular haematoma may raise pressure within the capsule. That is the reason capsular decompression enters senior planning for displaced intracapsular fractures.

The physis. The proximal femoral physis is threatened in transphyseal injuries and by fixation choices. Protecting it has to be balanced against the need for stable fixation.

Neck mechanics. Vertical or varus fracture lines create shear and instability, so varus malreduction and inadequate fixation are not accepted. Progressive varus later on reflects collapse, malunion, non-union or growth disturbance, which is why the neck-shaft angle is measured during follow-up rather than only checking union.

The Delbet classification describes fracture location. Location correlates with femoral-head perfusion risk and fixation strategy: the more proximal the fracture, the greater the threat to the femoral-head blood supply, and the pooled avascular-necrosis risk falls stepwise from roughly 38% in type I to 28%, 18% and about 5% in type IV. Name the type, then always pair it with displacement, reduction quality, child age and associated injuries.

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• Type I, transphyseal. Through the proximal femoral physis at the head-neck junction, with or without hip dislocation. It carries the greatest avascular necrosis and growth-plate concern because the injury is closest to the femoral head and physis, and reduction and stabilisation are time-sensitive.
• Type II, transcervical. Through the femoral neck. The classic high-risk paediatric femoral neck fracture, with high AVN, non-union and displacement risk, and usually treated operatively when displaced.
• Type III, basicervical or cervicotrochanteric. At the base of the neck. AVN risk is lower than in types I and II, but coxa vara, varus collapse and fixation failure remain major concerns, so stability and the neck-shaft angle are monitored.
• Type IV, intertrochanteric. Between the greater and lesser trochanters, and extracapsular. AVN risk is lower than in the intracapsular patterns and mechanical stability matters more than femoral-head perfusion, but displacement, comminution and child size still matter and AVN vigilance is still required.

Displacement. Displaced fractures need urgent reduction and stable fixation. Varus displacement is especially important because it increases shear, non-union risk and coxa vara, and rotational malalignment is easy to underestimate on a single AP image.

What else changes the plan. The same Delbet type may need different treatment depending on:

• Age and skeletal maturity
• Fracture level, verticality, Pauwels angle and comminution
• Polytrauma and an associated ipsilateral femoral shaft fracture
• A low-energy mechanism or underlying bone lesion
• Whether an anatomical closed reduction can be obtained
• Whether fixation must cross the physis to achieve stability

History

Typical presentation. The child presents after high-energy trauma with severe hip or groin pain and inability to bear weight. Ask exactly where it hurts: the groin, lateral hip, thigh or knee.

Mechanism and function. Ask about road trauma, fall height, sports collision, crush injury or a direct lateral blow to the hip, and whether the child could stand, transfer or bear weight. Most true paediatric femoral neck fractures are high-energy, and a low-energy injury needs a pathology workup. Inability to weight bear supports urgent hip imaging and protected handling.

Preceding symptoms. A previous limp, night pain, fever, weight loss or a known bone lesion suggests pathological fracture, tumour, infection or metabolic bone disease.

Associated trauma. Ask about head, chest, abdominal, pelvic, femoral shaft, knee and neurological symptoms. High-energy trauma can produce competing injuries and a missed ipsilateral femoral shaft fracture.

Timing. Record the time of injury, the transfer and any delay in presentation. It frames urgency, counselling and the discussion of complication risk.

Examination

Examine the child using trauma principles before focusing on the hip. A displaced femoral neck fracture is painful, and repeated log rolling or forced positioning is unnecessary.

Radiographs first. Obtain an AP pelvis and a safe lateral view of the injured hip, which together confirm the Delbet level and displacement. Do not force frog-lateral positioning in a painful fracture: 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.

The whole femur. Image it when the mechanism is high energy, when thigh pain is present or when an ipsilateral shaft fracture is possible. A femoral shaft fracture can distract attention from a proximal femoral injury, and the reverse is also true. Pelvic and wider trauma imaging as indicated prevents a missed shaft, pelvic, abdominal or head injury.

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. It should answer a management question and should not delay urgent treatment of an obvious displaced fracture.

MRI and laboratory work are considered when the mechanism is low energy, when there was preceding pain, when the radiograph shows a lesion, or when infection or tumour is possible. The answer changes biopsy caution and definitive management.

Watching for AVN. Developing avascular necrosis is looked for on serial radiographs, with MRI if concern persists. MRI can help if AVN is suspected before radiographic collapse is obvious.

A child with a painful, non-weight-bearing hip after trauma does not always have a femoral neck fracture, and each alternative has a different urgency, imaging pathway and pitfall. The dangerous traps are a slipped capital femoral epiphysis (SCFE) mislabelled as a transphyseal fracture, and a low-energy "fracture" that is really a pathological lesion.

The first hours. Start with analgesia, trauma assessment and immobilisation, and keep the child non-weight bearing in a safe position. Avoid repeated painful examination and forced frog-lateral positioning. Involve senior paediatric orthopaedics early, especially if the fracture is displaced, intracapsular, transphyseal, pathological or part of polytrauma.

How urgent. Displaced or unstable fractures need urgent anatomical reduction and stable fixation. Delbet type, displacement and reduction quality influence the urgency of fixation and the intensity of follow-up, and in practice urgency is judged on displacement, pain, transfer time and theatre access. Pooled data have not shown that operating within 24 hours lowers AVN; Controversies below explains why expedient treatment is still the practice.

Reduction. The goal is an anatomical reduction, checked on AP and lateral imaging, because poor reduction increases AVN, non-union and coxa vara risk. Closed reduction is reasonable if it produces a truly anatomical result without forceful repeated attempts. If it leaves varus, translation, rotation or a blocked reduction, open reduction is appropriate: a small incision is not a virtue if the price is malreduction.

Fixation. The implant is chosen by child size, fracture level, stability and physeal status. Options include cannulated screws, pins, paediatric hip screw constructs, plates or other proximal femoral fixation, depending on age and pattern, and the construct must hold the reduction during healing. The rules that apply to all of them:

• Stability usually matters more than avoiding the physis at all costs in a dangerous unstable fracture
• Screw threads should not distract the fracture
• Implants must not enter the joint
• Multiple views are needed to confirm implant position
• Cast or spica support may be used in younger children, depending on fixation and compliance

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Capsular decompression. Many surgeons consider aspiration, capsulotomy or open decompression for displaced intracapsular fractures, because capsular haemarthrosis may increase pressure around the femoral head. The evidence is not uniform (see Controversies), but in a high-risk displaced Delbet I or II fracture decompression should be part of senior planning rather than an afterthought.

Aftercare. The child usually needs protected or non-weight bearing, serial radiographs, wound review, implant checks and progressive rehabilitation once healing allows. Protect the fixation until union, then restore motion and gait: fixation failure, coxa vara and stiffness are preventable follow-up targets. Tell the family early that the fracture may unite before the femoral-head risk is fully known.

Undisplaced fracture. It is not automatically harmless. Confirm it on high-quality AP and lateral imaging, treat it as high risk even when displacement is absent, and review it serially. Many paediatric femoral neck fractures still undergo fixation because secondary displacement is dangerous. Non-operative care is rare, reserved for a very selected stable pattern under specialist oversight with protected weight bearing and close monitoring, and only where follow-up will be reliable. Counsel about AVN and late deformity.

Displaced intracapsular fracture. The classic urgent case. Classify it as Delbet I or II where appropriate, reduce it anatomically, fix it stably, consider capsular decompression, and watch carefully for AVN, non-union and coxa vara.

Pathological fracture. A low-energy mechanism, preceding pain or a visible lesion changes the problem. Stabilise the fracture while investigating the underlying diagnosis, and do not rush into biopsy through an inappropriate approach if malignancy is possible. The radiographic pattern directs the search among cyst, non-ossifying fibroma, fibrous dysplasia, infection, metabolic bone disease and malignancy.

Polytrauma. Follow trauma priorities first and coordinate timing with head, chest, abdominal and vascular injuries. Competing injuries should not create unnecessary delay in a displaced intracapsular fracture once the child is safe for surgery.

What follow-up tracks. Weight bearing progresses only as fixation and healing allow. Alongside the radiographs, follow pain, range, gait and abductor strength.

How long. Surveillance has to run past union. In a level I paediatric trauma cohort of 70 patients followed to union, osteonecrosis occurred in 20 (29%) and was diagnosed at a median of 7.8 months, long after most of these fractures have united and long after a routine fracture clinic would have signed the child off. A normal early radiograph does not exclude AVN. Warn the family at the outset that a good six-week film does not settle the question; otherwise the first sign of collapse is a limping child returning months later.

What predicted it. In the same cohort, displacement and fracture location were the independent predictors on multivariable analysis, while age, fixation type, mechanism, postoperative alignment and capsular decompression were not, a reminder that much of what gets argued about in theatre is less predictive than the injury the child arrived with.

Relative trochanteric overgrowth. A specific growth sequela the examiner expects. If the proximal femoral capital physis arrests (from the injury, from fixation crossing it, or after AVN) while the greater trochanteric apophysis keeps growing, the trochanter ends up relatively high. That shortens the abductor lever arm and the femoral neck (coxa breva) and produces abductor weakness and a Trendelenburg gait, even when the neck-shaft angle is acceptable. It is distinct from coxa vara, a true reduction in the neck-shaft angle, though the two often coexist.

Treating it. Recognition matters because management differs. A young child with remaining growth can be treated with greater trochanteric epiphysiodesis to let the head and neck "catch up", whereas an established deformity in the older child needs trochanteric transfer (distal-lateral advancement) to restore the abductor moment arm. In follow-up, measure the articulotrochanteric distance, not just the neck-shaft angle.

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.

There is no single randomised trial or dedicated international guideline for this rare injury; practice is built from cohort series, two meta-analyses and society fracture-management principles. The picture below is a global synthesis rather than any one country's protocol.

Global epidemiology

• Paediatric femoral neck fractures represent less than 1 percent of all paediatric fractures and roughly 1 percent of hip fractures across age groups.
• Bimodal mechanism: high-energy trauma (road traffic, falls from height) in most series, with a smaller pathological-fracture group.
• Delbet type II (transcervical) is the most common pattern; type I (transphyseal) is the rarest but carries the highest osteonecrosis risk.
• Pooled osteonecrosis rates by Delbet class are approximately 38, 28, 18 and 5 percent for types I to IV respectively (Moon and Mehlman), with contemporary cohorts reporting overall AVN around 23 to 29 percent.

Registry and high- versus limited-resource practice

• Unlike adult hip fractures, this injury is too rare for dedicated arthroplasty-style registries; evidence comes from single-centre cohorts and the pooled meta-analyses above. National paediatric trauma networks (rather than implant registries) are the practical data source.
• High-resource settings: rapid imaging, sub-specialist paediatric orthopaedic cover, image-intensifier-guided reduction and fixation, and structured multi-year AVN surveillance.
• Limited-resource settings: delayed presentation is common and a recognised cause of established non-union and coxa vara in toddlers; valgus osteotomy with minimal fixation is a described salvage where early anatomical fixation was not feasible.
• Regardless of setting, the modifiable lever is the same — achieve and hold an anatomical reduction and follow the head for years.

Paediatric femoral neck fracture is often taught as if it were settled, and it is not. A consultant-level answer names where the evidence genuinely conflicts and then states a defensible position.

The effect sizes. Across 34 studies and 1332 children, the largest pooled paediatric dataset, the significant predictors of osteonecrosis were initial displacement (RR 2.98), poor reduction quality (RR 2.43), Delbet type I or II (RR 1.96) and age 12 or older (RR 1.40). The timing question looks different: pooling six comparative studies and 231 fractures, surgery under versus over 24 hours gave OR 1.19 (95% CI 0.56 to 2.51). That is no significant effect, and the confidence interval is wide enough that a real effect cannot be excluded either. In the same analysis, displacement carried OR 3.81 and Delbet I or II OR 2.43.

Reading them together. The fracture's biology outweighs the clock by a wide margin, and the one large lever the surgeon actually holds is reduction quality. In the long-term (5-year-plus) subgroups, delayed reduction did increase AVN (RR 2.63) and closed reduction outperformed open (RR 0.40). Expedient treatment therefore remains the right practice, because an unhurried anatomical reduction by an experienced surgeon beats a fast imperfect one. Before quoting the reduction-route finding, note its caveat: the apparent advantage of closed reduction may partly reflect that more severe fractures get selected for open surgery.

Against the single-centre cohort. The 70-patient cohort under Complications found postoperative alignment was not predictive, whereas the 1332-child pooled analysis found poor reduction quality was. Quote both, and say which dataset each comes from.