Total Hip Arthroplasty for Neglected Pathological Femoral Neck Fracture in a Young Patient with Autoimmune Polyglandular Syndrome.

Introduction: Neglected pathological femoral neck fractures in young patients are rare and present significant surgical challenges, particularly in the presence of systemic metabolic disorders such as autoimmune polyglandular syndrome (APS). Poor bone quality, impaired healing potential, and endocrine instability complicate management, often limiting the success of head-preserving procedures. Purpose: The purpose of the study was to describe the surgical decision-making, technical considerations, and early outcomes of total hip arthroplasty (THA) in a young patient with a neglected pathological femoral neck fracture associated with APS. Materials and Methods: A 34-year-old male with a history of Type 1 diabetes mellitus, hypoparathyroidism, and hypocalcemia presented 4 months after a trivial trauma with a displaced transcervical left femoral neck fracture. Imaging revealed non-union, mild femoral head resorption, and severe osteoporosis. After multidisciplinary endocrine optimization, THA was performed through a posterior approach. A cementless multihole acetabular cup with screw fixation, a cemented congenital dislocation of the hip femoral stem, and a dual mobility articulation system were utilised to address poor bone quality, narrow canal morphology, and instability risk. Results: The patient remained hemodynamically stable postoperatively, with transient hyperglycemia managed with insulin infusion. Radiographs demonstrated well-positioned and stable components with restoration of limb length and offset. Pain relief was achieved early. Due to compromised bone quality, weight-bearing was progressed gradually, with full weight-bearing initiated at 4 weeks. Preoperatively, the patient had severe pain and functional limitation, with a Harris Hip score (HHS) of 25/100. At 3 months, the HHS was 78/100, improving to 90/100 at 6 months. Conclusion: This case highlights the feasibility of an individualized THA approach for the management of a neglected pathological femoral neck fracture in a young patient with APS and severe osteoporosis. Satisfactory early clinical, radiographic, and functional outcomes were observed; however, longer follow-up and further studies are required to determine the durability and generalizability of this treatment strategy.