Painful Chondral Delamination in Early-stage Osteonecrosis of the Femoral Head Precipitating Total Hip Arthroplasty.

Introduction: Aim and Background: Osteonecrosis of the femoral head (ONFH)/avascular necrosis of the femoral head (FH) is a debilitating clinical entity. Bisphosphonates (BPS) are beneficial for conservative/medical management, especially in the early stages. There is, however, a subset of patients with early ONFH who do not respond to BPS and continue to worsen clinically despite no radiological progression. This retrospective cross-sectional study offers a possible explanation for the inexplicable cause of the severe pain in patients with early ONFH from the gross pathological changes of the retrieved FH. Materials and Methods: A retrospective cross-sectional analysis was conducted on all patients who underwent THA for Early Ficat Arlet Stage Two by the senior surgeon following inadequate relief with BPS between August 2014 and February 2025. Gross intraoperative cartilage findings were graded as per Outerbridge Classification. Results: 116 patients (mean age 38.1 years) met the inclusion criteria. Cartilage changes observed were: softening in 37, partial thickness fissure in 30, full-thickness fissure in 17 and exposed subchondral bone in 32 FHs. Conclusion: Delamination of FH cartilage observed in retrieved FHs could explain the persistent pain in some patients with early ONFH unresponsive to medical therapy. Level of Evidence: Level III - retrospective cross-sectional study.