Hydroxyapatite fully coated conic hip prosthetic stem: a long term animal study

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Histology

Background:

• Hydroxyapatite coatings enhance osseointegration of orthopedic implants.
• Understanding the long-term effects of fully coated prosthetic stems is crucial for clinical success.

Purpose of the Study:

• To evaluate the long-term (1-year) results of a hydroxyapatite-coated prosthetic stem in an animal model.
• To assess the influence of initial bone-prosthesis contact on implant osseointegration.

Main Methods:

• Six sheep underwent arthroplasty with a fully hydroxyapatite-coated femoral stem and cemented polyethylene cup.
• Femurs were harvested after 12 months and processed for undecalcified cross-sectioning.
• Histological and histomorphometric analyses were performed on sections based on initial bone-prosthesis gap (0-2mm, >2mm).

Main Results:

• Extensive direct bone-hydroxyapatite coating contact was observed in areas with initial full bone contact.
• Reduced bone-prosthesis contact occurred with initial gaps of 0-2mm.
• No bone-prosthesis contact was achieved with initial gaps greater than 2mm.
• No delamination of the hydroxyapatite coating was observed.

Conclusions:

• A conic femoral stem fully coated with hydroxyapatite demonstrates excellent histological and histomorphometric results at one year.
• Initial bone-prosthesis contact is a significant factor in achieving successful prosthesis osteointegration.
• An initial gap exceeding 2mm prevents direct bone-to-implant contact.