Article

Hip dislocation is one of the most frequent complications of total
hip replacement. The direction of dislocation matters.
Most dislocations are
posterior; anterior dislocation remains rare and its treatment is controversial.
OBJECTIVES: To clinically and radiologically evaluate the outcomes of the
conservative (orthopaedic without revision surgery) treatment of anterior hip
dislocations after total hip replacement by immobilisation of the hip in 45
degrees flexion, 10 to 20 degrees abduction and neutral rotation (deck chair
position). Between 1997 and 2007, 19 patients (11 women, 7
men), aged between 36 and 89 years old (average age 64.6 years), operated on for
hip osteoarthritis using a posterolateral approach, presented with anterior
dislocation of their cemented total hip arthroplasty. Instability during
extension associated with external rotation was noted at surgery in eight cases.
Ten dislocations occurred in the immediate postoperative period (within 48 hours)
and nine within an average postoperative delay of 39 days (6-82). After reduction
of the dislocation by closed manipulation, the patients were treated by
immobilisation in the deck chair position for an average of 2 weeks (10-21 days).
Radiological and functional assessment (based on the Merle d'Aubigne score [PMA])
was performed on average at 4 years after surgery. The inclination of the cup in
the frontal plane and any lengthening of the operated extremity were measured on
an AP pelvic plain film with the patient in the standing position. Cup and
femoral stem anteversion were calculated by CT-scan in 16 cases. RESULTS: At the
last follow-up, four patients had had recurrent anterior dislocations (one
patient had had two dislocations). They were again treated with immobilisation in
the deck chair position for two weeks without further recurrence. None of the
patients underwent revision surgery on the temporarily unstable operated hip.
Thirteen patients had no pain and eleven had an unlimited walking perimeter. The
final average PMA score was 16 (12-18). The patients who presented with one or
two recurrences had a PMA of 18 in the final follow-up. Six patients presented
with at least 5 mm of shortening (average: 10 mm, maximum 25 mm) with one case of
10 mm of lengthening. The average cup inclination angle in frontal plane views
was 48 degrees (40-57 degrees). It was more than 50 degrees in seven cases. The
average cup anteversion in CT-scan was 30 degrees (14-60 degrees). The average
femoral anteversion in CT-scan was 24 degrees (3-52 degrees). A total of 12
implants (eight cups and four femoral stems) had at least 25 degrees excessive
anteversion on CT-scan assessment. CONCLUSION:
Anterior dislocation
after total hip replacement is associated with approximately 10 degrees of
excessive femoral and acetabular anteversion respectively. Nevertheless,
correction of these architectural anomalies is not necessary because
immobilisation in the deck chair position for 2 weeks effectively prevents
recurrence and results in satisfactory medium-term functional results.

Langue : FRANCAIS