Stem curvature and load angle influence the initial relative bone-implant motion of cementless femoral stems

✍ Scribed by Aivars Berzins; Dr. Dale R. Sumner; Thomas P. Andriacchi; Jorge O. Galante

• Book ID: 102911414
• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 990 KB
• Volume: 11
• Category: Article
• ISSN: 0736-0266
• DOI: 10.1002/jor.1100110518

✦ Synopsis

Abstract

A 6 df measurement system was used to investigate the initial relative bone‐implant motion of two types of cementless total hip replacement femoral components—a straight stem and a curved stem. Five pairs of fresh frozen femurs from human cadavers were tested with loads applied to the femoral head at angles characteristic of level walking, stair‐climbing, and rising from a chair. The most important findings were that (a) the resultant proximal translations were twice as high with the straight stem as with the curved stem at load angles encountered in stair‐climbing and rising from a chair, (b) both stem types had more motion at load angles encountered in stair‐climbing and rising from a chair than in level walking, with the increases ranging from 3 to 14‐fold, (c) there was as much as 66‐fold more motion distally than proximally, and (d) the amount of interface motion varied by 5‐fold between the medial and lateral surfaces of the distal part of the implant because of the combined effects of translation and rotation. The amount of initial bone‐implant motion of the femoral component was found to be particularly sensitive to off‐axis loading; this suggests that stair‐climbing and rising from a chair should be avoided in the early postoperative period when a cementless porous‐coated femoral stem has been used.