Factors Affecting the Design of the Head and Neck Segment of a Contemporary Total Hip Prosthesis

Anthropometric investigation of femoral sizes and femoral pelvic relationships was performed in a group of unilateral total hip arthroplasty patients. Standardized radiographs were used to perform the measurements. The non-operated, contralateral side was used as a standard for endosteal anatomy and the normal femoral pelvic relationship. Analysis of endosteal shape reveals a spectrum ranging from the stovepipe shape of the aged bone that has undergone diaphyseal expansion, to the trumpet shaped proximal femur found in younger patients. There is also a relationship between this shape and the relative varus or valgus position of the head and neck of the femur. Implants can be designed with head and neck geometry corresponding to these relationships. These implants would reconstruct normal anatomy more accurately. Cementless, acetabula placed in a more medial and proximal position should be matched to femoral components with longer neck-length options than cemented acetabular components.