SURGICAL TREATMENT
| Structure of the knee joint |
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What is an arthrosis? How does a knee joint arthrosis develop? |
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Studies and research projects carried out by Sport Orthopedics in Bern |
| At Sport Orthopedics Bern, cementless hydroxylapatite-coated hip joint implants are used for hip joint replacement. The material composition of these artificial joints corresponds to the basic mineral composition of the bone matrix in the human body. |
Materials Used in a Biodynamic Hip Implant
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X-ray diffraction spectrum of the calcium hydroxylapatite, |
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 A: metal B: calcium hydroxylapatite C: bone tissue D: edullary space |
Chemical formula:Ca10(PO4)6(OH)2
Calcium hydroxylapatite is a calcium phosphate with a chemical composition corresponding to the basic mineral composition of the bone matrix in the human body. This is a very pure apatite ceramic.
Regular quality checks are carried out to guarantee a hydroxylapatite fraction of 98%. The remainder is tricalcium phosphate. It has been possible to reduce the amounts of trace elements to:
AS < 3ppm / Cd < 5 ppm / Hg < 5 ppm / Pb < 3 ppm
Crystallographic properties: 50 bis 70% crystalline phase.
Coating
Plasma spraying is the only reliable method for applying an apatite coating.
Several requirements must be met during this process:
- The titanium surface is bead coated to create a microscopic roughness that permits a strong adhesion of the coating and resistance to mechanical forces.
- The hydroxylapatite ceramic (HAC) coating has a peel strength of 35 Mpa.
- Use of ultrapure HAC powder with a controlled grain size.
- Complete control of numerous thermal engineering parameters and full automation of the manufacturing chain.
The HAC coating produced in this manner has a mean thickness of 155 µm (+/- 35 µm). This layer thickness represents a compromise between brittleness and premature resorption. The entire stem is coated.
- The coating of the entire stem ensures optimal biocompatibility and maximal osteointegration.
Bioactivity
Apatite ceramic is a bioactive material that very rapidly forms a strong bond with the bone. This bond is both chemical and cellular; the primary bond is formed by the union of two apatite phases.
This creation of new bone tissue within the framework of the bonding process is the expression of the osteoinductive properties of calcium hydroxylapatite.
Histological examination of tissue sections reveals.
- ...no formation of connective tissue between the implants and the bone
- ...the absence of an inflammatory or macrophage reaction.
- ...an osteoblastic response in both a centrifugal and centripetal direction.
