A Mathematical Evaluation of the Effects of the Head and Neck Diameter on the Arc of Motion and the Implications in Total Hip Arthroplasty

Both classical THA and the dual mobility systems achieve greater AOM than an anatomical normal hip. As the head diameter increases, the AOM and the JD increases. Increases in head size improve range of motion; however, head sizes over 36-40 mm gain little regarding component stability. The more durable and thinner modern polyethylene liners allow for larger conventional femoral heads. When considering between a classical THA or a dual mobility system, the minimal gains with increasing the head size in using a dual mobility system may be far outweighed by the increase in directional stability offered by the large head THA with highwall liners.