Varus migration of PCA stems

Forty-seven patients with cementless, porous-coated anatomic hip replacements were evaluated after a minimum 2-year follow up with specific attention to varus migration of the stem. A cadaver study was done to define a relationship between projected size of the lesser trochanter seen radiographically, rotation of the femur, and stem position. Seven (15%) of the stems migrated into varus with the distal tip moving laterally. Thigh pain occurred in patients with varus migration and those with no change in stem position. A lower percent canal fill was seen on the lateral radiograph (P < .001) and larger average width of radiodense lines in zone 1 superolateral, and zone 6, midstem medial (P < .005) in the patients with varus migration. Poor distal stability associated with a lower percent canal fill at the stem tip seen on the lateral radiograph may result in varus migration.