Review Question - QID 1197

Osteolysis is the histiocytic response by macrophages to wear debris particles, which are often less than 1 micron in size.

Osteolysis is a particle-induced biological process occurring at the bone-metal or bone-cement interface around total joints resulting in rapidly expanding focal lesions that may or may not cause loosening. Its slower counterpart, aseptic loosening, involves the identical biological process. Wear particles generated within the joint space are phagocytosed and stored within cells in the joint capsule. Sub-micron particles are retained within macrophages and are implicated in osteolysis. 

Campbell et al. described an isolation method to recover ultra-high-molecular-weight polyethylene (UHMWPE) particles from tissues around failed total hip replacements. This process yielded particles that had rounded or elongated shapes. Additionally, the majority of particles isolated were reported to be submicron in size.

Mckellop reviews four topics in wear including Modes, Mechanisms, Damage and Debris. Four Modes that creates debris are described. Wear Mode 1 occurs when the two bearing surfaces are articulating against each other in the manner intended by the implant designer. Mode 2 occurs when a bearing surface articulates against a non-bearing surface. Mode 3 occurs when third-body abrasive particles have become entrapped between the two bearing surfaces, and Mode 4 occurs when two non-bearing surfaces are wearing against each other.

Incorrect Answers:
As reported by Campbell et al. the majority of particles recovered from prosthetic joints with osteolysis were submicron in size. Answer choices 2, 3, & 4 contain values greater than a micron and are therefore incorrect.