Today we are able to get consistently good results with cemented THA provided we use the right implants, employ modern cementing techniques with good quality cement and make the right patient selection.
Using modern 2nd or 3rd generation cement techniques the results on the femoral side are excellent in the older, lower demand patients.
Despite advances made with cement techniques on the cup side the long-term result of cemented cups has shown only slight improvement.
The results of cemented THA on the femoral and acetabular sides were moderate at best using 1st generation cement method of digital insertion and minimal bone preparation. Failures of 20% at 5 years (Amstutz 1976, Beckenbaugh & Ilstrup 1978) and 40% at 10 years (Stauffer 1982, Sutherland 1982) were reported.
Radiographic loosening rate was high but revision rate ranged widely from 3-20% because of variation in indication for revision.
Long standing loosening is typically associated with dramatic osteolysis and implant migration. A high proportion of failures were the result of poor cement fixation which resulted in implant loosening which in turn caused accelerated polyethylene wear and osteolysis.
Recognition of this problem led to improvement in cement technology and also method of cementation.
The modern form of cementation (2nd and 3rd generation) prescribes
- Thorough cleansing and drying of bone bed – pulsatile lavage and brushing
- Pressurization
- Use of stem centralizer to ensure an even cement mantle
- Reduction of cement porosity to increase cement strength by vacuum mixing and centrifugation.
With use of 2nd generation cementation the failure rate on the stem side has fallen dramatically. Harris (1990) reported a radiographic loosening rate of 2.9% and a revision rate of 1.9% at 11.2 years and Barrack (1992) 2 and 0% respectively.
Although the results on the femoral side improved substantially, the use of modern cementation has not led to equal improvement on the acetabular side. Harris & Mulroy (1990) whilst having a 3% loosening rate for the stem had 42% loosening of the cup at 10yrs. The failure to improve the result on the acetabular side is due to a number of factors including difficulty with ensuring adequate pressurization and the cancellous nature of acetabular bone.
Thus meticulous cementation technique is essential for success. Equally it should be recognized that cemented THA may not be suited for the young, heavy or active young person.
This slide shows the early failure at 3 years of a well performed hybrid THA done for a 110kg young male patient. As you can see the stem is obviously loose and there is major osteolysis, whilst the uncemented cup appears to be solidly fixed.
>> Read more...