A NEW TYPE OF HIP JOINT….
Hip joint replacement has come a long way after it was first done in 1970….
From smaller size heads and cemented prosthesis we have now come to larger heads and cementless prosthesis. Ceramic Heads gave replaced cobalt-chrome heads. But there are few issues which have always troubled HIP- REPLACEMENT patients.
1. Post Operative Dislocation
2. Range Of Movement(i.e. not sitting cross legged)
These two issues have been very well addressed to by a new Hip Joint…THE DUAL MOBILITY HIP JOINT.
What is Dual Mobility ?
- Metalback shell fixed to acetabulum with highly polished inner surface
- Prosthesis head articulates within a retentive polyethylene (A)
- Polyethylene is like a large head and free to move in metalback shell in a NON RETENTIVE way
Why have Dual Mobility?
- Improve prosthetic stability, significantly reduce the risk of dislocation – increased jump gap
- Increase amplitude of movement before impingement
- To reduce wear
- To reduce shear forces at the bone interface which contribute to implant loosening
How do we get increased range of motion with Dual Mobility?
- 1st mobility, head moves in liner
- 2nd liner moves within the shell
RANGE OF MOTION:
It has been demonstrated that dual mobility cups have a stability advantage over standard hemispherical cups
- Fractured neck of femur
Primary hip replacements:
- Elderly patients (> 55)
- Non compliant patients (dementia, alcohol..)
- Joint laxity (neuro muscular disorders, cerebral palsy, age)
- Dysplasia & congenital dislocations
- Rheumatoid Arthritis
- Revisions due to any reason(ostelytic loosening, periprosthetic fractures etc)
- For dislocations because many dislocations become recurrent
- Extensive clinical history (>30 years)