17. ИИссттоорриияя ссооззддаанниияя ээннддооппррооттееззаа
CChhaarrnnlleeyy
11997744--55 -- нноожжккаа
RRoouunnddbbaacckk ппрриишшллаа
ннаа ссммееннуу FFllaattbbaacckk..
ЭЭттоо ууввееллииччииллоо
ппооввееррххннооссттьь
ккооннттааккттаа ммееттааллллаа сс
ццееммееннттоомм ии ууммеенньь--
шшииллоо рриисскк рраассккааллыы--
вваанниияя ммааннттииии ууггллааммии
нноожжккии
1975 г - переломный в развитии цементной техники
18. История ссооззддаанниияя ээннддооппррооттееззаа
CChhaarrnnlleeyy
1975 г - переломный в развитии цементной
техники, появление ее второго поколения
Качество цементной мантии - ключ к успеху.
1 - Необходимо создание дополнительного
давления в цементе
2 - Введено обязательное дистальное блокирование
(костные и синтетические пробки)
3 - Исследована важность создания дополнитель-
ного давления в цементной мантии и в
проксимальном отделе.
It is straight collarless design. The “Cobra” flange is a cement pressuriser and also centralises the stem in the thick cement mantle.
The small collar like design on a Charnley stem is not a real calcar loading device. It supports the cement pressurisation.
The cross section is rounded reducing cement stresses.
The wear rate of the small head is better and also enables to use thicker PE cups.
The reduced diameter neck increases the range of motion.
The material is a SS-alloy called ORTRON 90.
The theory of the smooth surface finish is similar to the polished philosophy reducing the stress between the stem and the cement mantle.
All these design features are the principles of Charnley’s low friction arthroplasty.
The main point of this philosophy that it is coming from the AO group which is very strong on the continental Europe. This is a collarless implant where the cement mantle was designed just to be a thin filler layer between the bone and the stem. The original design has a longitudinal grooves on the sides and the cross section is quite boxy. The original system used a 32mm head with a 14/16 taper. The idea behind the big head is a better stress distribution and a better postoperative hip stability.
This is a double tapered collarless stem, designed for a controlled sinking in a thick cement mantle.
The main feature of this stem is a highly polished surface which reduces the stresses between the cement and the implant. In this situation the permanent load will produce a - so called - cold flow of the PMMA. The stem is very slowly sinking in the cement mantle without causing any damage on the cement bone interface. This philosophy needs well designed cement centralisers to avoid cement crack at the tip of the stem.
The collared stems are working on a complete different way like all the others we mentioned before.
This stem is loading the femur on the proximal-medial part which is known as CALCAR. For this reason the instrumentation of any collared stem must provide a precise femoral neck cut to reach the ideal collar-bone contact.
Because of the principles of this philosophy this stem is unable to sink and there is a high risk of the distal stress shielding.
The collar is also expected to work as an umbrella to stop penetration of PE particles into the bone-cement interface.
The cross section of the original design is boxy.
Here is a very simple chart of the cemented hip philosophies.
If you see a cemented stem manufactured anywhere in the world you can fit it to one of these groups.
These are the differences between the collared and the collarless philosophy.
Don’t forget that all collarless designs are working on the same way!
When a collared stem is hanging on the calcar there is a steress shielding on the distal part which will cause tilting sooner or later.
If bone cement is mechanically the weakest of the materials in the hip joint then it is sensible to assume that the cement will be the most susceptible to failure due to overloading.
A cemented hip replacement design therefore will have the best chance for long life if it is designed to allow minimum cement stresses.
These are the products what we have to these philosophies.
The good news that we have candidate for each category, the bad news is that it is you task to sell them. Use the features and benefits of different philosophies and then differentiate our products!
