Summary Pelvis Fractures in the pediatric population are uncommon injuries that are usually associated with high-energy trauma and are often associated with CNS and abdominal visceral injury. Diagnosis is made with plain radiographs of the pelvis. CT studies may be required in the setting of occult fractures. Treatment may be nonoperative or operative depending on the location of fracture, presence of pelvic ring instability, and degree of fracture displacement. Epidemiology Incidence uncommon, only 1-2% of all pediatric fractures acetabular fractures only 1-15% of pediatric pelvic fractures Demographics avulsion injuries almost exclusively in adolescent patients Etiology Pathophysiology mechanism of injury pelvic ring injuries high energy trauma automobile accidents motor vehicle-pedestrian injury apophyseal avulsions low energy trauma (apophyseal avulsions) pathophysiology apophyseal avulsion avulsion injury occurs from the disruption of tendon origin on the pelvis during "explosive" type activities (ie. jumping, sprinting) pathoanatomy apophyseal avulsion ischial avulsion (54%) hamstrings and adductors AIIS avulsion (22%) rectus femoris ASIS avulsion (19%) sartorius pubic symphysis (3%) abdominal muscles iliac crest (1%) abdominal muscles lesser trochanter iliopsoas pelvic ring differs from adult pelvic ring injuries higher incidence of lateral compression injuries than adults, who are more commonly AP compression injuries higher rate of single-bone pelvic ring fractures increased bony elasticity cartilage able to absorb more energy SI joint/symphysis pubis more elastic thick periosteum apparent dislocations (symphyseal, SI) may have a periosteal tube that heals like a fracture lower rate of hemorrhage secondary to smaller vessels, which are more capable of vasoconstriction injuries less commonly increase pelvic volume acetabular fractures more common after triradiate closure differs from adult triradiate cartilage injury may cause growth arrest and lead to deformity fractures into triradiate cartilage occur with less force than adult acetabular fractures transverse fracture pattern more common than both column Associated conditions CNS and abdominal visceral injury high rate (> 50%) in traumatic pelvic injuries presumed secondary to the higher energy required to create a fracture in a more elastic pelvis femoral head fractures/dislocations associated with acetabular fractures GU injury increased rate with Torode Type IV fractures life-threatening hemorrhage Anatomy Osteology pelvis undergoes endochondral ossification (like long bones) at 3 primary ossification centers ilium appears at 9 weeks ischium appears at 16 weeks pubis appears at 20 weeks all meet and fuse at 12 in girls and 14 in boys acetabular growth enlargement is a result of interstitial growth within the triradiate cartilage concavity is a response to pressure from the femoral head depth of acetabulum results from interstitial growth in acetabular cartilage appositional growth in the periphery of cartilage periosteal new bone formation at acetabular margin 3 secondary ossification centers of the acetabulum appear at 8-9 and fuse at 17-18 os acetabuli (OA) forms the anterior wall acetabular epiphysis (AE) forms superior acetabulum secondary ossification center of ischium (SCI) forms the posterior wall other secondary ossification centers (of the pelvis) iliac crest appears at 13-15 fuses at 15-17 used in Risser sign ischial apophysis appears at 15-17 fuses at 19-25 anterior inferior iliac spine appears at 14 fuses at 16 pubic tubercle angle of the pubis ischial spine lateral wing of the sacrum Classification Tile Classification Type A Stable injuries (rotationally & vertically) Type B Rotationally unstable Vertically stable Type C Unstable rotationally & vertically Torode/Zieg Classification (pediatric pelvic ring) Type I Avulsion injuries Type II Fractures of the iliac wing Type III Fractures of the ring with no segmental instability Type IV Fracture of the ring with segmental instability Bucholz Classification (pediatric acetabulum) Shearing Salter Harris I or II Blow to pubis/ischial ramus/proximal femur leads to injury at interface of 2 superior arms of triradiate cartilage and metaphyses of ilium. A triangular medial metaphyseal fragment (Thurston-Holland fragment) is often seen in SH II injuries. Crushing/Impaction Salter Harris V Difficult to see on initial radiographs May detect narrowing of triradiate space. Leads to premature triradiate cartilage closure. The earlier the closure, the greater the eventual deformity. Presentation History pelvic ring fractures often occur secondary to motor vehicle accidents or when a pedestrian is struck by a motor vehicle pelvic avulsion injuries often occur during sporting activities such as sprinting, jumping or kicking Symptoms pain inability to bear weight hemodynamic instability Physical exam primary exam as in all trauma patients, initial evaluation should include ABC's followed by primary and secondary surveys inspection important to thoroughly complete a rectal/genitourinary evaluation in polytrauma patient to rule out open injury log roll to inspect for soft-tissue contusions and ecchymosis palpation ASIS, iliac crests, SI joints, and pubic symphysis provocative tests posteriorly directed pressure on the iliac crests produces pain at the fracture site compressing pelvic ring at iliac crests causes pain excessive mobility indicative of a serious pelvic injury Imaging Radiographs recommended views AP pelvis Judet views 45 degree internal and external oblique views, to better evaluate the acetabulum inlet/outlet views 35 degree caudal and cranial tilt views, to better evaluate the integrity of the pelvic ring sensitivity plain radiographs will miss ~50% of all pediatric pelvic fractures CT may be necessary as 50% of all pelvic fractures may be missed on a plain AP pelvis indications negative plain films with increased suspicion when tenderness is present over the SI joints preoperative planning concomitant spine injury findings can delineate complicated fracture patterns MRI indications occasionally required to detect apophyseal avulsion injuries Treatment Nonoperative protected weight bearing followed by therapy indications pelvic ring dislocations of symphysis and SI joint have a potential for periosteal healing Type I Avulsion Injuries with < 2 cm displacement Type II Iliac Wing Fractures with < 2 cm displacement Type III pelvic ring fractures without segmental instability acetabulum minimally displaced fractures as these are relatively stable need close follow-up until skeletal maturity to detect premature triradiate closure technique for types I and II protected weight bearing for 2-4 weeks stretching and strengthening 4-8 weeks return to sport and activity after 8 weeks when asymptomatic type III weight bearing as tolerated for 6 weeks bedrest indications Type IV pelvic ring with instability AND < 2 cm pelvic ring displacement Operative ORIF indications pelvic ring type I avulsion injuries with > 2-3 cm displacement type II iliac wing fractures with > 2-3 cm displacement type III pelvic ring with displaced acetabular fractures > 2mm type IV pelvic ring with instability acetabulum comminuted acetabular fracture when traction does not improve the position of fragments joint displacement >2mm joint incongruity intra-articular fragments joint instability (persistent medial subluxation or posterior subluxation) central fracture dislocation open fractures External fixation indications hemodynamic instability increased pelvic volume Pelvic arteriography indications continued hemodynamic instability evidence of pelvic hemorrhage Techniques ORIF approach ilioinguinal approach stoppa approach instrumentation physeal sparing when possible when not possible, smooth pins across physis (especially triradiate) x 4-6 weeks with early removal anterior pubic symphysis plating percutaneous SI screw fixation complications specific to treatment early triradiate closure outcomes older children and adolescents with unstable ring fractures may have an improved outcome with internal fixation Complications Death rare most often occur in association with head or visceral injury Pelvic fracture-associated hemorrhage rare see above under death Physeal cartilage injury progressive acetabular dysplasia with thickening of the medial acetabular wall giving rise to shallow acetabulum (lateral hip subluxation) hypoplastic hemipelvis premature closure of triradiate cartilage/growth arrest (<5%) risk factors < 10 old at time of injury as the growth potential of the physis decreases with age, the younger the patient is at the time of injury, the more severe the growth disturbance will be Bucholz crushing type (SH V) treatment reconstruction with physeal bar excision premature triradiate closure can still occur in spite of bar excision late reconstruction with pelvic osteotomy Leg length discrepancy risk factors unstable fracture when vertical displacement of the hemipelvis is >2 cm Malunion/nonunion incidence rare treatment malunion well tolerated due to increased remodeling potential of young children Neurovascular injury Heterotopic ossification Osteonecrosis of the femoral head risk factors acetabular fractures and hip dislocation Degenerative joint disease of the hip risk factors patients with displaced acetabular fractures Prognosis Complications are rare Need for operative intervention increases after the closure of triradiate cartilage