Biological / cement-free fixation

When an artificial joint is cemented, this is, as previously mentioned, a fixation with dead material (similar to Araldite glue). This kind of fixation involves additional risks, as some cement can enter the bloodstream during cementing and cause pulmonary embolisms of various degrees.

From a mechanical standpoint, all dead material is subject to fatigue and will break sooner or later. Consequently, the joint will loosen.

With a cement-free joint, the bone directly grows onto the implant, creating a biological fixation that can adjust to the load level over the years and – as all other bones do – regularly renew itself. The aging process seen in dead cement does not take place. As a result, an X-ray image of an uncemented implant may look almost the same after 20 years of wear as it did shortly after surgery.

With a cement free fixation, the bone grows onto the implant surface (Hydroxyapatite coating) When an artificial joint

Ingrowing spongy bone (trabeculae)

What a cemented hip joint can look like after just 10 years is shown in the following image. Note that the left side of the bone next to the artificial joint has already been largely eaten away!

Provided that the bone has sufficient load-bearing ability, the biological integration of a prosthesis is clearly superior to fixation with cement. It is important however for the patient to know that “the bone needs time” to really grow in. As a result, the new joint should only be subjected to moderate load in the first six weeks.

No change after 18 years

Osseointegrated prosthesis;(left) histological section, (right): x-ray