Description: Prosthesis for total hip replacement

AB - Dislocation of a hip prosthesis is a common complication in usual cases of hip prosthesis dislocation, the prosthetic femoral head comes out from either the natural acetabular cavity in a bipolar hemiarthroplasty or the prosthetic acetabulum in a total hip arthroplasty. Only a few cases of bipolar hip prosthesis dislocation due to dissociation between the polyethylene and inner head of the prosthesis have been reported. We describe a rare case of disassembly of the inner head from the bipolar outer prosthesis in an osteoarthritic acetabulum. A 72-year-old woman had undergone bipolar hemiarthroplasty due to fracture of the left femoral neck about 10 years previously. Recently, she sustained an injury after falling from a chair, and examinations revealed an unusual disassembly-dislocation of the bipolar hip prosthesis. We classified this failure in our patient as a type II failure, representing extreme varus position of the outer head in the acetabulum, dislocation of the inner head from the outer head, and a detached locking ring around the stem neck. This mechanism of failure as shown in our patient rarely occurs in the bipolar prosthesis of the self-centering system. Osteoarthritic change of the acetabulum would place the outer head in the varus position, increasing wear on the beveled rim by impinging the femoral stem neck and causing dislodgment of the inner locking ring and consequent disassembly-dislocation of the inner head.

Artificial Hip Joint - Hip Prosthesis - KLINIK am RING

Dislocation of a hip prosthesis is a common complication in usual cases of hip prosthesis dislocation, the prosthetic femoral head comes out from either the natural acetabular cavity in a bipolar hemiarthroplasty or the prosthetic acetabulum in a total hip arthroplasty. Only a few cases of bipolar hip prosthesis dislocation due to dissociation between the polyethylene and inner head of the prosthesis have been reported. We describe a rare case of disassembly of the inner head from the bipolar outer prosthesis in an osteoarthritic acetabulum. A 72-year-old woman had undergone bipolar hemiarthroplasty due to fracture of the left femoral neck about 10 years previously. Recently, she sustained an injury after falling from a chair, and examinations revealed an unusual disassembly-dislocation of the bipolar hip prosthesis. We classified this failure in our patient as a type II failure, representing extreme varus position of the outer head in the acetabulum, dislocation of the inner head from the outer head, and a detached locking ring around the stem neck. This mechanism of failure as shown in our patient rarely occurs in the bipolar prosthesis of the self-centering system. Osteoarthritic change of the acetabulum would place the outer head in the varus position, increasing wear on the beveled rim by impinging the femoral stem neck and causing dislodgment of the inner locking ring and consequent disassembly-dislocation of the inner head.


Bipolar hip prosthesis with free floating ring - …

Cemented versus uncemented femoral components in the ring hip prosthesis

There have been great advances in extending the life of an artificial joint. However most joints eventually loosen and will require replacement, but in many cases a primary hip replacement can last in the region of 15 years. In some cases the hip may loosen earlier. Younger patients must be aware that the primary hip replacement will fail within their life-time and that they will require revision hip surgery at some point in time.


Acetabular ring prosthesis with ..

Fracture of the femur including the greater trochanter can occur during insertion of the prosthesis. This problem is usually treated with fixation with cables and/or wires. Intra operative fractures range between 0.1-1.0% with cemented total hip replacements and is increased when using a cementless prosthesis (3-29%).

The Radiology Assistant : Hip - Arthroplasty

If a significant leg length discrepancy of greater than 2cms occurs this may be a reason for continued and unexplained pain following a total hip replacement. If there is a significant marked increase in leg length discrepancy then the patient may require revision of the total hip replacement. Significant leg length discrepancy may be associated with nerve palsies.

Acumed | Innovation With Purpose

It is always difficult for the surgeon to accurately equalise the leg lengths. Within the limits of surgical tolerance the more experienced and specialist hip surgeons have less leg length discrepancies as compared with trainee surgeons performing total hip replacements.