Abstract
Clearly uncemented hip stems are becoming more popular. They are working relatively well and avoiding the step of cementation is easier and much quicker. However, this speaker feels that well designed femoral stems with 25–30 years of proven successful fixation are perfectly good for elderly patients with 10, 15, and 20 year life expectancies. They are good for several reasons. They seal off bleeding from the femur essentially completely—particularly helpful in high anticoagulation patients. Also, addition of antibiotic cement would be expected to have a lower infection rate, and cases of gross osteopenia can be less likely to have fractures or undesired subsidence.
There are a few basic points which can make a big difference in the quality of hip stem cementation. These points are: (1) After ordinary broaching, loose, mechanically incompetent bone needs to be removed. This is well done with canal brushes and large angled curettes. (2) The canal must be plugged distally a centimeter or two beyond the tip of the femoral prosthesis. (3) The femoral cavity needs to be as dry as possible at the time of cement introduction. This is one of the more difficult tasks to achieve perfectly. First is pulse lavage with an intramedullary nozzle. Next, I use epinephrine soaked sponges pulled completely out to length and introduced to fill the cavity completely—filling retrograde and packing tightly. Shortly before the cement is to be introduced, the epi sponges are changed to dry ones with the same type of firm, retrograde filling. The canal is commonly dried twice occasionally three times.
Cement introduction: (1) A cement gun with long intramedullary nozzle is mandatory. (2) The cement must not be too runny, i.e. of too low a viscosity. You will have more trouble maintaining pressurisation with liquid runny cement, and you risk bleeding from the bone into the cement cavity significantly compromising the cementation. (3) The cement must be introduced retrograde with complete filling i.e. no voids, and not running out of cement to inject before the tip of the nozzle has reached the introitus, the entry point to the femoral cavity. Otherwise you wind up pulling out the nozzle itself out, leaving a void. (4) “Pressurisers,” that is, almost all that I have seen, do not really facilitate pressurisation. Once the canal is completely full with cement and the cement is getting stiffer, pressurisation by pushing at the introitus using your thumb over a lap pad creates tremendous pressurisation that can push cement beyond most cement plugs!
Introducing the femoral component: (1) Last, the femoral component is introduced rather slowly so that one maintains constant pressurisation by virtue of the volume displacement as the component goes to its proper level. Ideally the femoral component reaches its proper level just before the cement is really hard. You really can do this as you get the component 0.5 to1.0 cm. from the final level and impact it slowly as the cement comes to nearly complete hardness.
The two worst things you can do—
- 1.
Have the prosthesis reach its desired level with the cement relatively runny and have the bone bleed into the cement and degrade the quality of the cement interdigitation.
- 2.
Being too slow getting the prosthesis down to the desired level and having it stuck to high.
Consistent, optimum cementation of the femoral component is difficult, but achievable and worth it! You have a component with good stress transfer, no undesired proximal stress shielding like some porous implants have; less bleeding from the canal; good 20+ year fixation, etc., etc.
