THR: Subsidence

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- Discussion: - by definition, is a decrease of more than 5 mm in the verticle distance of the femoral stem; - subsidence of 1 mm or less is within limits of measurement; - subsidence of cement mass & stem or migration of stem into cement mass resulting in more distal position of collar or platform in relation to proximal surface of cement & femoral neck; - subsidence may not be noted unless relationship of stem & cement mass to proximal femur is carefully evaluated in serial x-rays; - stem may subside in cement, in which case there is usually frx of cement near tip of stem, or entire cement mass & stem may subside;