The Influence of the Hip Joint Prosthesis Construction and Material Properties on Bone Remodeling

The hip joint is a strongly loaded joint and highly vulnerable to any diseases and pathological changes related to loading conditions (Wall, 2002). Improper load distribution in the hip joint leads to its pathological changes that consist in anomalous growth of the acetabulum and femur. In the most drastic clinical cases the only way of treatment is to replace the natural degenerated joint with an artificial one. An artificial cup, imitating the natural acetabulum, and stem, which is inserted into the femur, are the components of the artificial hip joint. The development of hip prostheses began in the late 19 century and continues to be an active area of bioengineering at the present time. The first hip prosthesis consisted of an ivory ball and cup held in place with a cement filler material made of colophony, pumice and gypsum (Maher, 2000). In the next years prosthesis materials and designs were evolving. The materials for stems were more and more biocompatible (stainless steel, recently titanium alloys) and the cups were made of polyethylene or ceramics. In the recent years bipolar acetabulum prostheses have been very popular and widely utilised in the hip joint alloplasty. The constructions of prostheses and technique of implantation have been also developing. The hip prostheses, with or without collar, have been implanted into the femur with usage of special cement or press-fitted without cement. In order to ensure better biofixation of implant and consequently minimise the risk of its loosening the proximal part of stem is roughened with titanium or hydroxyapatite coating (Moroni i in., 1994).