Shoulder hemiarthroplasty is a surgical procedure in which only the damaged humeral head of the shoulder joint is replaced with a prosthetic implant. The shoulder functions as a ball-and-socket joint, with the humeral head (ball) fitting into the glenoid cavity of the scapula (socket). A smooth layer of articular cartilage normally protects this joint, allowing pain-free movement by reducing friction. When this cartilage is severely worn or the humeral head is damaged due to arthritis, injury, or overuse, patients often experience persistent pain and restricted mobility. In such cases, replacing just the humeral head with a metal prosthesis helps restore smoother articulation and shoulder function. Hemiarthroplasty may also be recommended for complex fractures, failed prior shoulder replacements, bone tumours, or avascular necrosis, where the blood supply to the bone has been compromised.