Paediatric Pelvis and Hip Trauma

Paediatric pelvis and hip trauma ranges from common sports-related apophyseal avulsion to rare, high-risk injuries such as traumatic hip dislocation, acetabular fracture and paediatric femoral neck fracture. The child's pelvis has open physes, apophyses, thick periosteum, relatively elastic bone and important growth centres. These features change fracture patterns and complications.

The mechanism matters. Low-energy adolescent sprinting or kicking injury suggests apophyseal avulsion. 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. A low-energy femoral neck fracture, especially without a clear major trauma mechanism, should prompt assessment for tumour-like lesion, metabolic bone disease, endocrine disease, infection or non-accidental injury in the right clinical setting.

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The paediatric pelvis and hip contain multiple growth-related weak points. The triradiate cartilage contributes to acetabular growth and is important in acetabular trauma. The proximal femoral physis, femoral neck and greater trochanteric apophysis influence proximal femoral growth and alignment. Pelvic apophyses are traction sites for powerful muscles, so adolescent athletes can sustain avulsion fractures through the physis or apophysis before the tendon fails.

The femoral head blood supply is vulnerable in paediatric femoral neck fractures and traumatic hip dislocation. Displacement, fracture location, intracapsular pressure and reduction quality all contribute to AVN risk. This is why the same child who otherwise heals fractures well can have devastating sequelae after proximal femoral trauma.

Pelvic ring injuries occur when force overcomes ring elasticity and 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. In children, haemodynamic instability is often from associated injury rather than pelvic bleeding alone, but severe pelvic haemorrhage still occurs.

Traumatic hip dislocation occurs when 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. The longer the hip remains dislocated, the greater the concern for femoral-head perfusion and chondral injury.

Paediatric femoral neck fractures are uncommon but dangerous. The fracture line, displacement and treatment can compromise femoral-head perfusion, and poor reduction or inadequate fixation can produce nonunion or coxa vara. Apophyseal avulsions are traction injuries: the muscle-tendon unit pulls off an apophyseal fragment during sprinting, kicking or sudden eccentric contraction.

Start with primary survey, analgesia and immobilisation. In high-energy trauma, ask about mechanism, speed, height, crush, seatbelt, pedestrian impact, loss of consciousness, abdominal pain, urinary symptoms, perineal pain, neurological symptoms and pain in other limbs. Document haemodynamic status, abdominal findings, perineal bruising, blood at urethral meatus, rectal tone when indicated, lower-limb neurological function and distal perfusion.

For hip dislocation, document limb position and sciatic nerve function before reduction if this does not delay urgent care. For femoral neck fracture, avoid repeated painful movement. For 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.

Initial imaging usually includes AP pelvis in trauma, plus targeted hip and femur views if pain localises to the hip or proximal femur. CT is used for pelvic ring displacement, acetabular fracture, posterior wall injury, intra-articular fragments, post-reduction hip dislocation assessment and complex trauma planning. MRI is useful for occult injury, chondral injury, femoral-head perfusion concern, marrow oedema, labrum, soft tissue and occult femoral neck fracture.

In 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.

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

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Postoperative care must match stability and biology. Pelvic ring injuries need pain control, mobilisation planning, venous thromboembolism risk assessment in adolescents, skin care and associated injury care. Hip dislocation follow-up includes range, pain, weight-bearing progression and surveillance for AVN. Femoral neck fracture care requires protected weight-bearing, serial radiographs, monitoring for joint penetration or loss of fixation, and long-term review for AVN, coxa vara, nonunion and growth disturbance.

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 have outcome risk because they involve joint congruity, femoral-head perfusion, growth centres and associated trauma.

Poor prognostic features include delayed hip reduction, nonconcentric reduction, associated femoral head or acetabular fracture, displaced Delbet I or II femoral neck fracture, poor reduction quality, unstable fixation, triradiate cartilage injury, high-energy polytrauma and 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.