Modular Neck Stem

In total hip arthroplasty (THA), proximal modularity plays an important role in primary and revision hip arthroplasty. Furthermore, the new modularity of the neck and stem (distal modularity) has the advantage that leg length, offset, and anteroposterior torsion can be independently corrected. This is especially necessary to manage acetabular dysplasia and the associated complex geometry of the femur in Japan. A fixed neck-type prosthesis alone causes many intraoperative impingement problems for dysplasia deformities, and a changeable neck stem could be used for femoral arthroplasty up to 47° in Japanese patients with severe anteversion. Furthermore, we reported that using a neck-changeable stem prosthesis is useful to obtain a larger range of motion (ROM), appropriate offset, and correct leg length [1, 2].