Explanation
The correct option is a. Kienböck's disease is the eponymous term for avascular necrosis (osteonecrosis) of the lunate bone. It is frequently associated with negative ulnar variance, which increases radiolunate contact stresses. The exact etiology is often multifactorial, involving mechanical, anatomic, and vascular factors leading to progressive lunate collapse, carpal instability, and severe wrist osteoarthritis if left untreated. Reference: Lichtman DM et al. Kienböck's Disease: Update on Silicone Replacement Arthroplasty. J Hand Surg Am. This is a high-yield Ortho mcq for board examinations.