الفهرس 
Review of LiteratureOnly 14 pages are availabe for public view
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Abstract
Treatment of patients with displaced femoral neck fractures is a challenging and demanding task for orthopaedic surgeons. For decades, there has been an ongoing discussion about what is the optimal treatment for displaced femoral neck fractures 1.
Arthroplasty is a widely accepted treatment as it allows early mobilization of the patient and a better functional outcome 2.
Often hemiarthroplasty is the preferred treatment compared to total hip arthroplasty because of reduced dislocation rates, less complex surgery, shorter operation time, less blood loss, and lower initial costs 2.
The use of total hip arthroplasty as primary treatment for displaced femoral neck fracture is controversial. It has been reported that total hip arthroplasty has a higher rate of dislocation than hemiarthroplasty, the duration of surgery is longer and the perioperative blood loss is greater 3,4.
Back in the 1970s the dual mobility concept was invented in France by Prof. Gilles Bousquet, which consists of a combination of two apparent joints, one large unconstrained joint between the metal cup and the liner, and a smaller constrained joint between the liner and a standard metallic head that is attached to the femoral component 8.
The insert is mobile with respect to the metallic shell (large-diameter articulation) and captured and mobile with respect to the femoral head (small-diameter articulation) 8.
For that total hip arthroplasty with a dual mobility cup should increase the range of motion and provide very stable articulation and also is associated with lower rates of dislocation procedures compared to total hip arthroplasty with a conventional cup and can be better alternative to bipolar hemiarthroplasty9.
In our study we evaluated the clinical and functional outcome of dual mobility cup total hip arthroplasty versus bipolar hemiarthroplasty in the management of displaced fracture neck femur in elderly patients.
Bipolar prostheses are designed to have two articulations. The inner, low friction bearing is composed of a metal inner head and a polyethylene liner, while the outer bearing is composed of a metal outer head and an acetabulum. The bipolar movement should mainly occur at the inner bearing when the hip is moving in a small range and the polyethylene liner should absorb some impact stress of the hip during weight-bearing; thus, reducing friction between the outer head and accetabulum37
However, the main complication of bipolar hemiarthroplasty was dislocation mainly with patients with shallow acetabulum.
Compared with bipolar hemiarthroplasty, DMC THA has the advantage of adjusting the acetabular side so the stability is improved and lower dislocation risk is found.
A bipolar hemiarthroplasty should be carefully considered when the acetabulum tends to be shallow and a total hip replacement should be performed if necessary44.
In DMC THR The interposition of a mobile polyethylene component between the prosthetic head and the highly polished inner surface of the outer metal shell provides two bearings and allows increasing the effective head size. In such a system, the head is snapped into the mobile polyethylene component and no additional locking ring is mandatory. Increased range of motion (ROM) to impingement and therefore increased stability is expected25.
This study is a prospective randomized study, where 40 patients were conducted with fracture neck femur garden 3 and 4. Ethical approval was obtained prior to initiation of the study.
Patients were divided randomly onto two groups. group (A) 20 patients were treated with Dual Mobility Cup THR and group (B) 20 patients were treated with Bipolar Hemiarthroplasty.
All patients were treated with the same protocol: intra operative 3rd generation cephalosporin antibiotic for antimicrobial prophylaxis and continued for 3 days post operative, intra operative transemic acid is given intravenous and locally on the wound to decrease post operative blood loss, thromboembolic prophylaxis as oral anticoagulant is given to prevent DVT. The patients were allowed to stand on Day 1 after surgery when their general condition allowed it.
The presented study shows that DMC is superior when compared to BHA in treating fracture neck femur. Dual mobility total hip reduces the risk of dislocation, cause less impingement, decreases friction and wear. It also increases range of motion. The intervening polyethylene liner between the prosthetic head and outer metal shell provides two bearings, where motion preferentially occurs at the inner bearing and the outer bearing is engaged at the extremes of motion.
Dislocation after hip arthroplasty is a key issue. Compared to bipolar hemiarthroplasty, in our study the risk of dislocation was lower with DMC THA than bipolar HA (2 patients were dislocated) also, the reoperation rate was also lower in the DM-THA group, which can partly be explained by the decreased dislocation rate.
In this study, BHA showed the merits of a shorter operative time and less intra-operative blood loss, while DMC demonstrated a higher mean HHS. Both options revealed no significant differences in the blood transfusion, one-year mortality and infection rate.
Also, in this study we found significant difference in terms of HHS postoperatively at 6 months and I year in favor of DMC group. The HHS increased progressively over time with better functional outcome and less pain in DMC group.
In light of our results, the use of THA DMC did not seem to increase mortality, morbidity, or complications rate like infection or bleeding but it decreases dislocation rate and increase functional outcome when compared to BHA. Also, THA DMC is not affected by pelvic morphological factors which may lead to dislocation with BHA and doesn’t cause acetabular erosions. Therefore, THA DMC could be considered as primary treatment modality for displaced fracture neck of femur in elderly population especially in active healthy patients, patients with high risk of dislocation (previous hip operation, abductor weakness or with neuromuscular diseases). Also, patients with acetabular dysplasia (lateral central edge angle <25° or >39°) or arthritic joint (grades 3 or 4).