The osteoporotic bone of an elderly lady is very different from the tough, growing bone of a child. Therefore, greater energy is required to produce a hip or pelvic fracture in a child, and many of these injuries occur as the result of high-speed motor vehicle accidents. Patient age, size, and skeletal maturity also contribute to the various fracture patterns with an example being trochanteric fractures, which tend to occur as a result of “bumper” injuries in children aged 6-7 years, the age when the greater trochanter is at the level of a car bumper (Fig. 12-1
It is misleading to apply the mass of information about adult fractures to children, and the small number of papers that relate specifically to children present widely varying statistics that are almost impossible to compare. If this were a more common injury, perhaps we would all know more about the best methods of treatment.
“We can be absolutely certain only about things we do not understand”
Figure 12-1 Age determines the site of a bumper fracture.
“Pelvic fractures may be accompanied by genitourinary and/or gastrointestinal injury”
Figure 12-2 This child was run over by a truck. Cystogram and retrograde urethrogram show complete disruption of the urethra (arrows) and elevation of the bladder. Always remember to check for GI and GU injuries when the pelvis is fractured.
Occasionally a child will fall from a counter top or the back of a couch and strike the floor in just the right way, sustaining an isolated sub- or inter-trochanteric femur fracture. However, more commonly, hip and pelvis fractures in children are the result of high-energy mechanisms and are associated with other injuries. In these cases the initial exam needs to concentrate on identifying any life-threatening injuries including head, spine, thoracic, abdominal, pelvic, neurologic, and vascular trauma. A coordinated plan to care for each injury must be established. The hip exam itself must be gentle to avoid further disruption of blood supply (especially femoral neck).
Pelvic fractures may be accompanied by genitourinary and/or gastrointestinal injury. It is important to look for blood at the urethral meatus, and check for hematuria; a retrograde urethrogram/cystogram should be obtained if clinically indicated (Fig. 12-2
). Abdominal, vaginal, and rectal exams are performed by or together with the general surgery team; blood at the anus suggests injury to the lower GI tract, which can contaminate a pelvic fracture and which can be problematic if missed. The rectal exam can also identify a displaced prostate, indicating transection of the urethra.
Instability of the pelvis can often be felt with a compression test, testing for both lateral and anteroposterior instability. This test should
not be repeated by multiple examiners as there is risk for compounding the damage already done by the fracture. Feel the pulses and test active movements in both legs. Subtle neurologic injuries are easily missed—always test sacral sensation. When the SI joint is dislocated, the lumbosacral trunk, superior gluteal nerve, and obturator nerve are at risk. However, as will be described later, children rarely have true SI joint disruption; typically they fracture through the physis adjacent to the SI joint. Sacral fractures can rupture the sacral roots, or the foramina can be compressed causing compression of the sacral roots.
In the field, prior to arrival at the hospital, hemorrhage from a pelvic fracture can often be partially controlled by binding the pelvis with a sheet wrapped tightly around the patient at the level of the AIIS. This will close down fractures and tamponade the bleeding during transport or until further treatment can be rendered.
Extraperitoneal hemorrhage to some degree is common and in most cases is allowed to tamponade with blood transfusion given as needed. In a few instances, bleeding can be massive and well concealed. An arteriogram may be required to identify the site of bleeding, and coils can be placed by the interventional radiologist.
Reading Pelvic X-rays
The pelvis is a very complex three-dimensional structure, and analyzing films can be difficult. Fractures are difficult to see and can occur through growth areas such as the tri-radiate cartilage, which makes x-ray interpretation difficult.
The ischio-pubic synchondrosis is even more puzzling, and may mimic a fracture (Fig. 12-3
). This syndesmosis often fuses asymmetrically, making interpretation difficult. Further complexity is added by Ogden’s noting that in very rare instances this syndesmosis can be the site of a stress fracture in a young jogger.
Dislocation is more common than femoral neck fracture in childhood, and fortunately carries far fewer risks for complications than does adult dislocation (Fig. 12-4
). This is likely due to hip joint laxity in the child as well as the fact that the acetabular growth cartilage (adjacent to labrum) is not yet ossified, with the true socket not as deep as in the fully ossified adult. The hip of a child under the age of 5 is usually dislocated by a fall with minimal trauma. As age increases, the degree of trauma required to dislocate the hip escalates (age 6-10—athletic injuries, automobile accidents thereafter). A more violent dislocation is more likely to be associated with fracture of the acetabulum or femur and sciatic nerve damage.
Figure 12-3 Top. In this young child, note the ischium and pubis beginning to fuse. Bottom. This is the same child 3 years later; the synchondroses had an almost expansile appearance. This is a normal finding and should not be confused with a fracture. These synchondroses may close asymmetrically, adding further confusion.
Figure 12-4 This child dislocated his hip during a simple slip and fall. Reduction was easy and protected with a hip spica for 4 weeks.
Table 12-1 Hip Dislocations
Hip extended abducted and externally rotated
Hip short, flexed, and internally rotated
Hip flexed, abducted, and externally rotated
Figure 12-5 MVA resulting in a proximal femur fracture and posterior hip dislocation with acetabular fragments.
Figure 12-6 Complications recognized after reduction. An acetabular fragment or avulsion from the femoral head may block complete reduction. A Type I injury to the physis may become evident.
A recent traumatic dislocation can hardly be confused with a long-standing paralytic dislocation for which the treatment is entirely different. On the other hand, recurrent dislocation of the hip in Down syndrome may be confusing. The bone looks normal, and only the appearance of the face clarifies the diagnosis.
The femoral head can be dislocated either anteriorly or posteriorly, or rarely into the obturator foramen (Table 12-1
). A hip is most commonly dislocated posteriorly (Fig. 12-5
) causing the limb to be held in a shortened, flexed, adducted, and internally rotated position. Anterior dislocations cause the limb to extend, abduct, and externally rotate. Traumatic obturator dislocations (or intrapelvic dislocations) are very rare in children but have been reported. The hip tends to be held in flexion, abduction and external rotation, but this is more variable.
Although complications are unusual, during a reduction maneuver an unrecognized proximal femoral epiphyseal separation may become apparent. In such a case the neck, not the head, reduces into the acetabulum. Such a circumstance mandates open reduction and pinning.
A trapped intra-articular fragment can easily be missed if a post-reduction CT study is not obtained (Fig. 12-7
). A fragment in the joint can be removed arthroscopically or through an arthrotomy where fixation can be performed if the fragment is large. This can be a posterior acetabular rim fragment, the ligamentum teres with an avulsed head fragment, or both.
The overall incidence of AVN in the literature is 10% or less. Delayed reduction and severe injury are the most important causes. Recurrent dislocation of the hip is a rare sequel to traumatic dislocation.
Figure 12-7 Following reduction, a widened joint space (arrows) is indicative of a fragment in the joint. This was varified with a post-reduction CT.
“A trapped intra-articular fragment can easily be missed if a post-reduction CT study is not obtained”
Figure 12-8 The adult has intraosseus vessels that supply the femoral head. Children with open physes have a more tenuous blood supply as vessels do not cross the physis.
Voluntary Dislocation of the Hip
Some teenaged girls complain that they can feel the hip dislocate. The usual cause is a snapping hip, in which the tensor fascia lata jumps across the greater trochanter as the girl rotates her hip. Once learned, some teenagers seem to have a morbid preoccupation with repeating the maneuver. Some very convincingly impress the neophyte examiner as being a dislocation. Treatment is by stretching (physical therapy) and only very, very rarely surgery (incision in tensor fascia). A rare cause is a true voluntary dislocation, a condition described by Broudy and Scott.