Paediatric Pelvis and Hip Trauma

Paediatric pelvis and hip trauma ranges from the common sports-related apophyseal avulsion to rare, high-risk injuries: traumatic hip dislocation, acetabular fracture and paediatric femoral neck fracture. Each injury family has different priorities.

Why the child is different. The child's pelvis has open physes, apophyses, thick periosteum, relatively elastic bone and important growth centres. These features change both the fracture patterns and the complications.

The mechanism points to the family. A low-energy sprinting or kicking injury in an adolescent suggests an apophyseal avulsion. A fall from height, road trauma or crush injury should raise concern for pelvic ring injury, acetabular injury, hip dislocation, femoral neck fracture and associated injuries.

The low-energy femoral neck fracture. A normal child should not fracture the femoral neck with trivial force. A low-energy femoral neck fracture, especially without a clear major trauma mechanism, should prompt assessment for a tumour-like lesion, metabolic bone disease, endocrine disease, infection or non-accidental injury in the right clinical setting.

The paediatric pelvis and hip contain multiple growth-related weak points, and each one changes management.

The triradiate cartilage. It contributes to acetabular growth, so a displaced acetabular injury can cause growth disturbance as well as incongruity. Its injuries are classified by Bucholz (see Classification).

The proximal femur. The proximal femoral physis, femoral neck and greater trochanteric apophysis influence proximal femoral growth and alignment, and the physis matters for the head-neck relationship. A transphyseal injury raises high concern for both AVN and growth arrest.

The femoral head blood supply. It is vulnerable after both femoral neck fracture and traumatic hip dislocation. Displacement, fracture location, intracapsular pressure and reduction quality all contribute to AVN risk, which is why reduction timing, reduction quality and long follow-up matter. It is also why a child who otherwise heals fractures well can have devastating sequelae after proximal femoral trauma.

The apophyses. Pelvic apophyses are traction sites for powerful muscles, so an adolescent athlete can avulse a fragment through the physis or apophysis before the tendon fails. The ASIS, AIIS, ischial tuberosity, iliac crest and lesser trochanter can all avulse.

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The elastic ring. A child can have major internal injury with only subtle bony injury. Do not rely on fracture displacement alone to judge the severity of the trauma.

Pelvic ring. Injury occurs when force overcomes the elasticity of the ring and its ligamentous restraint. Stable injuries may involve isolated pubic rami or iliac wing fractures. Unstable patterns can involve anterior and posterior ring disruption, vertical displacement, bleeding and major associated injury.

Where the bleeding comes from. In children, haemodynamic instability is often from associated injury rather than pelvic bleeding alone, but severe pelvic haemorrhage still occurs. The source may be pelvic, abdominal or both.

Hip dislocation. Force drives the femoral head out of the acetabulum. Posterior dislocation is classically associated with dashboard-type mechanisms, but children can dislocate with lower energy because their soft tissues are more elastic, and the low-energy dislocation of the younger child differs from high-energy adolescent trauma. The longer the hip remains dislocated, the greater the concern for femoral-head perfusion and chondral injury.

Femoral neck fracture. Uncommon but dangerous. The fracture line, the displacement and the treatment itself can compromise femoral-head perfusion, and poor reduction or inadequate fixation can produce nonunion or coxa vara.

Apophyseal avulsion. A traction injury: the muscle-tendon unit pulls off an apophyseal fragment during sprinting, kicking or sudden eccentric contraction.

Classify first by injury family, because the family decides which feature drives treatment.

Pelvic ring: Torode and Zieg. The adult terms (APC, LC, vertical shear) are borrowed for the pelvic ring, but the paediatric scheme is the Torode and Zieg classification, which stratifies by stability and by the risk of associated injury and bleeding:

• Type I, avulsion fracture: apophyseal avulsion of the bony pelvis (e.g. ASIS, AIIS, ischium); benign, the sports injury family.
• Type II, iliac wing fracture: from a direct lateral force (including iliac apophyseal avulsion/"bucket-handle"-type); generally stable.
• Type III, simple ring fracture: a stable ring injury (e.g. pubic rami, or a ring fracture without an unstable segment).
• Type IV, ring disruption (unstable): bilateral pubic (straddle) fractures, anterior and posterior ring disruption, or a fracture involving the acetabulum. This is the resuscitation-and-associated-injury group, carrying the highest energy, transfusion, associated-injury and mortality risk.

The revised Torode-Zieg splits Type III into IIIa (stable, isolated anterior ring) and IIIb (anterior ring fracture with a non-displaced posterior ring injury). IIIb behaves with more morbidity than a truly isolated anterior fracture, because the occult posterior injury raises the risk.

Femoral neck: Delbet. Delbet classifies the paediatric femoral neck fracture by location.

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Triradiate cartilage: Bucholz. Acetabular growth-plate trauma is classified by Bucholz on Salter-Harris lines:

• Type I (Salter-Harris I/II pattern): the fracture runs through the hypertrophic zone, sparing the germinal layer. Growth potential is preserved, so the prognosis for continued acetabular growth is good.
• Type II (Salter-Harris IV pattern): the fracture crosses the germinal/metaphyseal portion, with a higher risk of bony bridge and growth arrest.
• Type V (Salter-Harris V, crush): a compression/crush injury of the triradiate cartilage, with the worst prognosis.

Apophyseal avulsion sites. The site points to the muscle that pulled the fragment off and the typical mechanism.

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The child first. Start with the primary survey, analgesia and immobilisation. Stabilise the child and define associated injuries before focusing on definitive orthopaedic reconstruction.

History in high-energy trauma. Ask about:

• Mechanism, speed, height, crush, seatbelt and pedestrian impact
• Loss of consciousness
• Abdominal pain, urinary symptoms and perineal pain
• Neurological symptoms and pain in other limbs

What to document. Record:

• Haemodynamic status and abdominal findings
• Perineal bruising and blood at the urethral meatus
• Rectal tone when indicated
• Lower-limb neurological function and distal perfusion

Pelvic ring injury. Look for pelvic pain, instability, abdominal tenderness and perineal bruising. Document haemodynamics, associated injuries, urogenital signs and neurology.

Hip dislocation. The hip sits in a fixed posture with severe pain and shortening; held flexed, adducted and internally rotated, it is a posterior dislocation. Record limb position and sciatic and femoral nerve function before reduction, provided this does not delay urgent care, and record them again after reduction.

Femoral neck fracture. Groin pain, inability to weight bear and a painful log roll. Avoid repeated painful or forceful movement, and document distal neurovascular status.

Apophyseal avulsion. The history is usually a sudden sport-related pop or sharp pain at a specific apophyseal site, followed by difficulty running or kicking. Look for local tenderness at the ASIS, AIIS, ischium or iliac crest, and record the sport mechanism, symptoms suggesting displacement, and any hamstring or hip flexor weakness.

Sorting the presentation. Once the child is safe, the presentation usually points to one family and its first question:

Radiographs first. Initial imaging usually includes an AP pelvis in trauma, plus targeted hip and femur views if pain localises to the hip or proximal femur. They give a fast initial classification and fracture screen.

CT with reconstructions defines what radiographs cannot. Use it for:

• Pelvic ring displacement and the posterior ring
• Acetabular fracture, joint congruity and posterior wall injury
• Intra-articular fragments
• Post-reduction assessment of a hip dislocation
• Complex trauma planning

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MRI is useful for:

• Occult injury, including occult femoral neck fracture
• Chondral injury, labrum and soft tissue
• Femoral-head perfusion concern
• Marrow oedema

After a hip reduction. A reduced-looking radiograph can hide fragments. Post-reduction radiographs, plus CT or MRI when indicated, look for loose bodies, the femoral head, the posterior wall and concentricity.

The suspicious femoral neck. When a femoral neck fracture may be occult or pathological, MRI and targeted laboratory or tumour workup where indicated avoid missing a stress, pathological or infection-related fracture.

Apophyseal avulsion. Plain radiographs often diagnose displaced fragments. MRI is useful when radiographs are negative but symptoms strongly localise to an apophysis, or when differentiating avulsion from infection or tumour-like conditions; it shows oedema, avulsion and soft-tissue injury.

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Pelvic ring

Stable injuries. Stable rami or iliac wing fractures are usually treated with analgesia and mobilisation as tolerated or protected weight-bearing. Associated injury still needs screening.

Unstable injuries and haemodynamic instability. These need trauma-team resuscitation: the primary survey, a transfusion strategy, haemorrhage control with a pelvic binder or external stabilisation when indicated, and operative or interventional control of bleeding.

The unstable posterior ring goes to specialist pelvic fixation planning, with CT-based classification and growth-aware implants.

Open pelvic injury. Antibiotics, debridement, contamination control and multidisciplinary care, with a deliberate search for perineal, rectal and urogenital injury.

Hip dislocation

Reduce promptly. Reduce with adequate analgesia, sedation or anaesthesia. Obtain pre-reduction radiographs if they do not delay reduction and are needed to exclude fracture. Urgent reduction relieves pressure on the femoral head and shortens the time of chondral injury.

Do not force it. Repeated forceful attempts can create an iatrogenic fracture; an irreducible hip goes to open reduction (see Surgical Technique).

After reduction. Document neurovascular status again and assess concentricity with the imaging described under Investigations. Protect weight-bearing until pain, imaging and associated injuries allow progression. Protected rehabilitation lets pain and soft tissues settle, but too much immobilisation causes stiffness.

Where the 6-hour target comes from. The 6 hours in the summary is a convention anchored to the classic observation (Mehlman et al., paediatric traumatic hip dislocation series) that AVN was many-fold more frequent when reduction was delayed beyond about 6 hours. It is a small-numbers retrospective association, not a validated threshold. It points the right way, the cost of speed is trivial, and no one has proposed a reason to wait: treat it as "reduce this hip in this admission, now", not as permission to use the full six hours.

Femoral neck

Urgent, senior, anatomical. Displaced paediatric femoral neck fractures require urgent senior planning. Displaced Delbet I and II fractures carry the highest AVN and nonunion concern and need urgent reduction and stable fixation. The aim is anatomical reduction, with stable fixation to avoid nonunion and coxa vara.

Closed or open. Open reduction is preferable to accepting an imperfect closed reduction, because reduction quality affects union and coxa vara. A high-quality closed reduction is accepted, and some series favour closed reduction for lower AVN (see Controversies).

Capsular decompression. Consider it in high-risk intracapsular fractures.

Apophyseal avulsion

Most heal without surgery. Most adolescent pelvic apophyseal avulsions are treated non-operatively with rest, analgesia, protected weight-bearing, progressive physiotherapy and staged return to sport. For the minimally displaced acute avulsion, most return to sport with staged rehabilitation.

Surgery is selective. It is considered, after careful discussion, for large displacement, persistent symptoms, painful nonunion, neurological irritation or elite/high-demand requirements. Fixation is decided case by case, balancing faster restoration against surgical risk, and "large" has no validated number (see Controversies).

The ischial tuberosity with sciatic symptoms needs early specialist review, because sciatic irritation and nonunion can be disabling.

Chronic pain or nonunion. Review with MRI or CT and consider delayed surgery. Persistent symptoms may prevent sport despite healed-looking radiographs.

Technique depends on the injury family. The common principle is that paediatric fixation should restore alignment and stability while respecting growth plates, cartilage, the soft-tissue envelope and future growth.

Femoral neck fixation. Position on a radiolucent table and obtain AP and lateral imaging. Reduce anatomically and fix with screws or a plate construct depending on age and pattern. Avoid joint penetration, avoid physeal damage when possible, compress the fracture and protect the blood supply.

Open reduction of the femoral neck. Use an approach that allows direct reduction, clear interposed tissue, reduce under vision and confirm fluoroscopically. Do not accept varus or rotational malreduction.

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Open reduction of a hip dislocation. Indicated for an irreducible dislocation, an incarcerated fragment or a nonconcentric reduction. Avoid repeated closed-force attempts; inspect and remove the obstacles.

Acetabular fixation. A specialist approach chosen by the fracture and the triradiate involvement. Aim for a congruent joint while minimising growth-plate injury.

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Apophyseal avulsion fixation. Approach the fragment directly, protect nearby nerves, then reduce and fix it with a screw or suture construct. Do not overtreat small avulsions; the ischial tuberosity requires sciatic nerve awareness.

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AVN is the feared complication after paediatric femoral neck fracture and traumatic hip dislocation. It can present late, as can growth problems, and early normal imaging does not exclude it.

Growth disturbance. Triradiate cartilage injury, proximal femoral physeal injury and pelvic growth asymmetry can produce deformity or early arthritis.

Functional failure. Persistent pain, coxa vara, nonunion, stiffness, chondrolysis, nerve injury and failure to return to sport can matter more to the child than radiographic union alone.

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Postoperative care must match stability and biology. After a pelvic ring injury the child needs pain control, a mobilisation plan, skin care and care of associated injuries, and adolescents need a venous thromboembolism risk assessment. After femoral neck fixation weight-bearing is protected, and serial radiographs watch for joint penetration or loss of fixation. After a hip dislocation, follow range, pain and weight-bearing progression.

Stable pelvic ring injuries and minimally displaced apophyseal avulsions usually do well with non-operative care and rehabilitation. Unstable pelvic injuries, acetabular injuries, hip dislocations and femoral neck fractures carry outcome risk because they involve joint congruity, femoral-head perfusion, growth centres and associated trauma.

Poor prognosis. These features predict a worse outcome:

• Delayed hip reduction, nonconcentric reduction, or an associated femoral head or acetabular fracture
• Displaced Delbet I or II femoral neck fracture, poor reduction quality or unstable fixation
• Triradiate cartilage injury
• High-energy polytrauma
• Delayed diagnosis of apophyseal avulsion with nonunion

Paediatric pelvic ring fractures account for roughly 1 to 5 percent of all paediatric fractures and well under 1 percent of paediatric fractures involve the acetabulum or femoral neck. Traumatic hip dislocation in children is rare; in younger children it can follow low-energy trauma because of soft-tissue elasticity, whereas adolescents typically need high-energy mechanisms. These are uncommon injuries, so high-quality randomised data are scarce and most guidance derives from cohort studies, registries and expert consensus.

Registry evidence specific to paediatric pelvis and hip trauma is limited because implant survival registries (NJR, AOANJRR, AJRR, the Swedish and Norwegian registries) are built around arthroplasty rather than paediatric fracture fixation. Population-based trauma registries and large single-centre series therefore carry the epidemiological weight, and they consistently show that displacement, Delbet type, reduction quality and associated injuries — not geography — determine outcome.

Across all settings the common thread is the same: stabilise the child, classify the injury family, achieve prompt and accurate reduction of the hip and femoral neck, respect growth centres, and commit to long-term avascular-necrosis and growth surveillance. Where local expertise or imaging is lacking, early discussion and transfer beat repeated reduction or fixation attempts.

Because these injuries are rare, much of practice rests on cohort data and expert opinion rather than randomised trials. Several genuine areas of debate recur in vivas.