Radiographic comparison of diaphyseal grit blasted with smooth surface stems by matched pair analysis

A matched pair comparison of two groups of 42 patients who had a total hip arthroplasty with uncemented fixation of the femoral stem with proximal por ous coating and distal grit blasting were compared with a stem of identical design except with diaphyseal smooth surfaces. Radiographic analysis was d one to determine differences in fixation and bone remodeling at the 2-year followup, and these results were compared with clinical results, The method used for measuring cortical thickness was semiquantitative, with measureme nts done at 15 1-cm increments beginning at 3 cm distal to the midlesser tr ochanter, This study determined whether, with an identical stem design, dia physeal biologic fixation, rather than mechanical fixation,, would pro,ide better fixation without significant stress shielding differences. Seven per cent of grit blasted stems had radiolucent lines in Gruen Zones 3 to 5, com pared with 79% of smooth stems. The smooth stem was on average one size lar ger so the stress shielding was not different between matched pairs, There was a distinct pattern of adaptive remodeling that occurred in the femur wi th both stem surfaces. Bone loss was greatest in the proximal medial and pr oximal posterior bone and occurred along the entire anterior cortex. Bone t hickening occurred in the distal medial and posterior cortices and extended below the tip of the prosthesis.