Hydroxyapatite and hip arthroplasty: Lessons learned from 34 years of clinical experience

Background: Hydroxyapatite (HA) coatings have been utilized in cementless total hip arthroplasty for over three decades to enhance biological fixation. Despite established clinical success, HA faces contemporary competition from ultra-porous surfaces and additive manufacturing technologies, necessitating a long-term evaluation of its efficacy and role in modern orthopedics.

Objective: This review aims to evaluate the experimental, histological, and clinical performance of HA coatings over a 30-year period, specifically analyzing long-term outcomes in young, active patients and assessing the transition toward ultra-porous materials.

Key Points: Histological data confirm that HA promotes osteoconduction and secondary biological fixation, creating a stable bone-implant interface without fibrous tissue interposition. In a prospective series of 273 primary implants in patients aged ≤50 years, the 29-year cumulative survival rate was 95.4% for femoral aseptic loosening. Radiographic analysis demonstrated confirmed bone ingrowth in 97.26% of cases at follow-up exceeding 20 years. While plasma-sprayed HA remains the standard for femoral stems, electrochemical deposition offers advantages for complex geometries. Emerging ultra-porous structures and 3D-printed titanium components show promise for acetabular revisions by facilitating bone ingrowth rather than just ongrowth, though long-term data are currently limited compared to HA.

Conclusion: HA coatings provide durable, long-term biological fixation and excellent clinical outcomes in high-demand patients. While newer ultra-porous technologies offer specialized advantages for complex reconstructions and acetabular revisions, HA remains a highly effective and reliable adjuvant for primary cementless hip arthroplasty.