Cause:Perhaps a genetic defect, autosomal dominant
Pathophys:Acetabular defect with shallow, vertically sloping roof and infolded glenoid; weight-bearing results in anteversion of femoral neck, which progresses to DJD and eventually to subluxation and/or dislocation
<5/1000 births; female/male = 8:1; winter incidence twice summer incidence by birthdays; positive family hx in 1/3; increased incidence in Mediterraneans and Scandinavians, in 1st borns, and 8 × incr if breech delivery
Sx:H/o breech delivery (12-20%). Limp
Si:In newborn, only finding may be positive subluxation provocation test (Barlow test; subluxation of femoral head with adduction and posterior pressure on femur); Ortolani test, relocates with a “clunk” w hips flexed 90° abducted and anterior pressure up on greater trochanters; telescopic femoral movement with hip at 90° (<1% false neg, 80% false pos). May have short leg unilaterally; asymmetric buttock folds; wide perineum; Hip abduction often is limited (normal is 90° at birth when hip flexed). Benefits of screening questionable given high spontaneous resolution rate, does not improve functional outcome (Peds 2006;117[3]:e557)
In walking child, limp and positive Trendelenburg’s test unilaterally
Adductor contractures; DJD
r/o similar hip dysfunctions caused by meningomyelocele and cerebral palsy adductor spasm/contractures
Xray:Ultrasound under 3 mo age since xray no help because no secondary center of ossification yet; reduces number of late-presenting cases (Int Orthop 2008;32:415; Orthop Clin N Am 2006;37:141); sens 89%, specif 97% (BMJ 2005;330:1413)
Radiographic screening at 3-5 mo fallen out of favor
Plain films will miss dx in 25%. Femoral epiphysis ossification center smaller, higher, and more lateral relative to acetabular center; acetabular roof obliquity pronounced, <30°; neck/shaft angle widened, ie, becomes more vertical
Occasionally CT with 3D reconstruction or even MRI, but need sedation to keep child still for test.
Rx:
All surgical and nonsurgical rx associated with AVN femoral head
<1 mo age: abduction splint or brace (Pavlok Harness) × weeks or months until xray shows improvement or can no longer dislocate. Watch for femoral nerve entrapment and assess quad strength at each check-up. Best to rx if any doubt; will have 80% false positive by clinical exam. Double diapering inadequate. 20-100% undergoing abduction tx will eventually require surgery (Can Med Assoc J 2001;164 [12]:1669); timing of initiation of treatment does not affect outcomes (Lancet 1990;336:1549)
Older child: spica cast in abduction after closed reduction; if over 2 and previous treatments failed, then open reduction; if over 4 consider acetabular procedure
Adult: wait until sx’s, then crutches, corset, decreased activity, then surgical total hip