Endoprosthetic

An endoprosthetic, or endoprosthesis, is an artificial device implanted inside the body to replace a damaged natural structure, most commonly a joint or segment of bone. Endoprostheses are used to restore alignment, stability, and function after disease or injury and are distinct from external prostheses (limbs that attach outside the body) or from allografts and osteosynthetic implants. In orthopedics, the term typically refers to artificial joints such as hip and knee replacements, but it can also describe implants that replace portions of the femur, tibia, humerus, or pelvis. Endoprostheses may be cemented to bone with bone cement or designed for press-fit fixation (cementless); many incorporate modular components and porous surfaces to encourage osseointegration.

Materials include metals (titanium and cobalt-chromium alloys), polymers (ultra-high-molecular-weight polyethylene), and ceramics, often combined in a bearing couple. Implants may be fixed with bone cement, press-fit fixation, or both (hybrid). Design features aim to emulate natural joint motion while reducing wear and preserving surrounding tissue.

Surgical indications include severe osteoarthritis, post-traumatic joint damage, malignancy with resection of bone, and failed previous arthroplasty. Postoperative rehabilitation and activity levels depend on the specific joint replaced, implant type, and patient factors.

Common complications include infection, prosthetic loosening or wear, dislocation (for certain joints), periprosthetic fracture, and mechanical failure. Modern endoprostheses have improved longevity, with functional outcomes generally favorable for many patients, though revision surgery may be required over time.