Abstract
The theory of early prosthetic loosening states that loosening is initiated during or shortly after surgery, and that the subsequent progression of loosening is affected by biomechanical factors and periprosthetic fluid pressure fluctuations. Later and secondary to loosening, wear particles may affect the progression of loosening. The loosening may increase subclinically for a long period of time and may, when detected, be misinterpreted as a late occurrence of loosening. This concise overview presents the essential features of this theory as applied to hip replacements. Aspects discussed are insufficient initial fixation, early loss of fixation, biomechanical factors, periprosthetic fluid pressure fluctuations, periprosthetic osteolysis, and wear particles.