CONVENTIONAL TOTAL HIP REPLACEMENT
CONTENTS
1 Definition
Conventional Total Hip prosthesis is called so by many surgeons because it is a model that has been used in the majority (75-95%) of all total hip operations in the past. There are many different models of this total hip device, all have in common:
cemented cup and cemented stem
polyethylene cup articulating against metallic ball component
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Conventional total hip on this x-ray picture shows a polyethylene cup (darker semicircular area) placed between the outer cement layer (white area on the outside of cup) and the metallic femoral ball (round white disc. The metallic (white) ball is positioned symmetrically inside the cup, the darker semicircular area around the ball is equally thick on places. The whole shaft component is well seen: the stem (white) is placed inside the thighbone's marrow cavity, well enshrouded in a (less white) bone cement layer. The bone cement, which has x-ray opaque substance added, is more white than the skeleton but less white than the metal that is shiningly white. The polyethylene cup is not opaque for x-rays, so it is in reality invisible. Its x-ray picture is made by the dark space between the outer bone cement layer and the inner metallic ball. This x-ray picture shows only "shadows", it is useful to remember this fact when you study a x-ray picture. You may compare it with the schematic picture of a cemented total hip (lower picture) which shows the "reality". (Sarmiento's titanium total hip) (click on the icon for a full size picture) |
2 History:
conventional total hip prostheses were developed and introduced in the early 1960's by the English surgeon Sir John Charnley. His model with the very small ball component (diameter only 22 mm) which is still in use, although modified, has the longest track record and very good results several years after the surgery (Table).
uncountable modifications (different diameters of the ball component ranging from 22 to 32 mm, different forms of the shaft, etc.) have been introduced on the market since then.
3 Advantages of the conventional total hip prosthesis
cheep,
technically more easy to fit into the skeleton
immediate weight bearing
the surgeons have had the longest experience with just this method
cup components made from the modern cross-linked polyethylene (if they appear to be really wear-resistant) might improve the results furthermore
4 Disadvantages:
the cement ages and disintegrates successively, theoretically "the cement disease" will ensue eventually
the polyethylene will wear off and the particles will produce "polyethylene disease", osteolysis
5 For whom:
The use of conventional total hip prosthesis in different countries depends on culture. In some countries (England, Sweden) about 75% of all total hip devices still in use are the conventional cemented total hip, even in younger patients.
The conventional total hip prostheses have been recommended to older patients because these patients are
less active and will not wear the polyethylene component too much
have shorter life expectancy so that the conventional total hip will survive older patients
6 Results:
There is a well documented report on the results of 2 000 total hip operations done with the original model of Charnley total hip prosthesis between 1969 to 1971 on the Mayo Clinic in the USA. (Berry 2002).
These patients were followed for 25 years. The results in this statistics were achieved with the "old" operation methods, with the old techniques for the use of bone cement, etc.
| YEARS AFTER THE OPERATION | % STILL IN USE |
| 10 YEARS | 92 % |
| 25 YEARS | 77,5 % |
Not bad!
For more details about Berry and colleagues report CLICK HERE
The results achieved with all other models of total hip prostheses should be compared against this comprehensive and reliable statistics.
References:
Berry D et al: J Bone Joint Surg-Am, 2002; 84-A: 171- 177
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