Anatomic Porous Replacement hip arthroplasty: first 100 consecutive cases.

One hundred consecutive Anatomic Porous Replacement (Intermedics Orthopaedics, Austin, TX) hip replacements were followed for 4 years. Eighty percent of patients had bone ingrowth fixation, 14% stable fibrous, and 6% unstable fibrous (loose) with 4% revised. Only two hips changed fixation grade after 2 years. Bone remodeling showed cancellous hypertrophy of the cortex, usually along the lateral cortex, and 7% had stress shielding (atrophy) of the proximal cortices. Adaptive bone remodeling almost always occurred in type B and C bone. Bone remodeling was statistically related to bone type, prosthetic fill, stem-bone ratio, and collar loading. We concluded that proximal bone ingrowth fixation with proximal load transfer provides good clinical results and excellent bone remodeling. Also, collar loading improves bone response. To expand this fixation in a predictable fashion to all type B and some type C bone requires geometry changes, which have been accomplished in the Anatomic Porous Replacement II.