Comparison Between Hydroxyapatite And Porous Coated Cementless Total Hip Arthroplasty

Abstract

The modem history of joint artroplasty began with press-fit modes of fixation and moved into the cemented era initiated by the late Sir John Charnely. Then the pendulum swung back to the cementless and osseointegration concept. Fixation by press-fit, in which macro-geometrical features of the prosthesis are secured by direct hard-tissue apposition, usually resulted - in the long run - in the production of pseudosynoviallayer with later loosening. Porous coated implants were introduced during I970s as a potential solution to the problems of cement fixation. Needless to say the most commonly used porous coatings are either cobalt-based alloys or titanium alloys, which are manufactured either by sintering, diffusion bonding or plasma spraying. Prerequisites for bone ingrowth are initial stability, intimate contact and pore size ranging from I 00 - 400 J.Ull• Porous - coated hip arthroplasty has been advocated as being potentially superior for young patients, but the problems of stress shielding, thigh pain, osteolysis and metal ion toxicity remain as an area of concern. To improve bone ingrowth and in a trial to decrease porous coating side effects, hydroxyapatite coated prostheses were introduced in the mid 1980s. They are manufactured by plasma spraying with a coating thickness from 50 - I 00 u. In fact, better bone ingrowth was noticed with HA coated implants, biocompatibility, corrosion resistance and better results in young patients with avascular necrosis of the head of the femur but still there are concerns about the degradation of the HA coating; whether HA debris increase polyethylene wear or osteolysis.