Vol 43 # 3 September 2011 - Kma.org.kw

September 2011
KUWAIT MEDICAL JOURNAL 235
Fig. 1: Anteroposterior radiograph of the pelvis, presenting perineal right hip dislocation with ipsilateral avulsion fracture of the greater and
lesser trochanter of the right femur before (a) and after (b) surgical procedure
The postoperative period was uneventful, with no
sign of infection. The patient was treated with skeletal
traction for five weeks, after which he was mobilized
in bed. Walking was not permitted till the contralateral
segmental fracture was healed. He started full weight
bearing four months after the injury (Fig. 2). He was
regularly followed up in the outpatient clinic and had
regular magnetic resonance imaging screening. Eight
months after the injury the patient started to complain
about right hip pain, at first only on putting weight
and later even when resting. Follow up radiographs
proved avascular necrosis of the femoral head (Fig. 3).
He was advised avoidance of strain and
weight bearing, physiotherapy, nonsteroidal antiinflammatory
drugs and close follow-up. In case
of deterioration, he might need further surgical
interference including core decompression and
vascularized bone graft.
DISCUSSION
Traumatic hip dislocation in children is rare. Under
the age of five years, it can occur following trivial
trauma. Canale and King [9] noted that in this age group,
the acetabulum is soft and pliable. Such an anatomical
situation and additional generalized joint laxity can
lead to hip dislocation after minimal trauma. If the hip
is properly reduced without delay, avascular necrosis
of the femoral head is an uncommon complication [9] .
Over the age of five years, the hip joint is stable
and considerable forces are necessary to provoke
dislocation [10] . Epstein [1] and Pringle [11] stated that
the most important factor producing anterior hip
dislocation is forcible abduction combined with
external rotation. This tends to force the femoral
head forward through the capsule, while as a result
of abduction, the femoral neck impinges upon the
acetabular rim and the head is levered out of its socket
through the anterior capsule. The occurrence of an
associated avulsion fracture of the greater trochanter
could be explained by the greater trochanter being
driven against the acetabular rim. This might become
detached as the head and neck of the femur move
forward and inward during dislocation [4] . The avulsion
fracture of the lesser trochanter could be explained on
the basis of traction between the ileopsoas muscle,
attached onto the lesser trochanter, and the proximal
femur which is displaced medially [12] . Closed
reduction of a fresh dislocation is usually effective.
Offierski [13] reported that closed reduction failed
in five out of 33 cases of traumatic hip dislocation,
while Canale and Manugian [14] reported failure in
nine out of 54 cases. Interposition of soft tissue and
osteo-cartilaginous loose bodies could be responsible.
Failure of closed reduction is an indication for
operative treatment [4,15,16] .
The surgical approach should be from the direction
of the dislocation. Anterior dislocations should be
approached anteriorly and posterior dislocations
posteriorly to preserve the blood supply in the posterior
or anterior capsule [17] .
Avascular necrosis is not common occurring
in 3 -15% of cases [8] . The incidence after anterior
dislocation in a large series is similar to that in posterior
dislocation [4] . It can occur or become evident between
three weeks and 28 months after the injury [18] . The
main blood supply for the femoral head runs through
the posterior capsule, and when the head dislocates
forward, the vessels distract or even tear because the
distance between the posterior capsule and the femoral
head is increased [4] .