Extensively Porous Coated Femoral Stems in Total Hip Arthroplasty: Where Do We Stand Now?

Background: Porous coating on femoral stems is a critical feature in total hip arthroplasty (THA), which enables a secure, long-lasting and biological form of cement less fixation.The term "extensively coated" femoral stem in THA denotes a prosthesis, wherein the porous coating covers a substantial portion or even the entire surface of the implant.In this article, we comprehensively reviewed the current literature on the status of extensively porous coated femoral stem in different clinical scenarios.Materials and methods: A detailed search was performed using the databases "Embase", "Google Scholar", "PubMed", "Scopus" and "Web of Science" on August 1, 2024.Relevant manuscripts were identified using the inclusion and exclusion criteria.All clinical studies, including prospective or retrospective case series, comparative or noncomparative trials, randomized and nonrandomized studies discussing the role of extensively porous coated femoral stem in primary and revision THA, were considered for inclusion.Experimental or nonclinical studies, other review articles, editorials and opinions were excluded.Results: Overall, 9 manuscripts (6 studies on revision THA) were finally considered for the narrative review.Seven studies reported on functional outcome (patient reported outcome measures -PROM).Studies reported significant improvement in Harris hip score (HHS), satisfaction score (SF-12), Western Ontario and McMaster Universities Osteoarthritis (WOMAC) and University of California, Los Angeles (UCLA) scores.The reported complications with extensively porous coated stems include intraoperative femur fracture, thigh pain, infections, and heterotopic ossification.Studies have reported high survivorship rates with this prosthesis (ranging between 94.5 and 99.3%), with re-revision rates between 2.7 and 5%.The radiological osteointegration has been reported to range between 94 and 100%.In addition, studies have reported radiological parameters, including stem subsidence and stress shielding rates, which have remained fairly low.Hydroxyapatite (HA), metallic coatings (such as titanium or cobalt chrome alloys) and coatings with diverse biocompatible materials have been utilized as porous coated materials.Four generations of extensively porous coated femoral stems have been described.With each generation, more sophisticated coating techniques, improved stem geometry and incorporation of modern technological advancements (such as 3D printing, CAD-CAM technology) have been progressively included.Conclusion: Extensively porous-coated femoral stems have remained a durable and reliable option in complex primary and revision THA surgeries.They enhance the extent of osteointegration, resulting in improved longevity and better stabilization of the cement less prosthesis.With the sophistication of porous coating techniques, and incorporation of technological advancements, these stem designs have provided a long-term benchmark for the emerging versions of revision stems.