J Korean Orthop Assoc.  2001 Jun;36(3):279-286.

Biomechanical Analysis of Proximal Fitting-Distal Filling Stem and Proximal Fitting- Distal Tapered Stem in Cementless Hip Prosthesis: A 3 Dimensional Finite Element Study

Affiliations
  • 1Department of Orthopaedic Surgery College of Medicine, Ansan Hospital, ansan, korea.
  • 2Department of Orthopaedic Surgery Mechanical Engineering, Korea University, ansan, korea.

Abstract

PURPOSE
This study was undertaken to compare the initial micromotion and stress shielding of a "fit and fill" stem to a "proximal fitting and distal tapered" stem in the early postoperative period using the load simulating single leg stance and stair climbing.
MATERIALS AND METHODS
Using the data from 3-D human CT scan, authors developed two types of 3-dimensional finite element total hip replacement model of proximal femur, which were inserted with a "fit and fill" stem and a "proximal fitting and distal tapered" stem. The constructions of stems were based on the OmnifitTM stem (about 13,000 element & 20,000 nodes). We compared micromotion, maximal principal stress and strain energy of each stems.
RESULTS
The results indicate that micromotion in a fit and fill stem were slightly lower than that of a tapered stem, especially in stair climbing over that in the single leg stance. The maximum principal stress on the cortex of femur was slightly higher in a tapered stem in the case of single leg stance, and 2 times higher in the case of stair climbing. Strain energy also was much higher in a tapered stem in both single leg stance and stair climbing gait.
CONCLUSION
These findings indicate that a tapered stem design could provide more favorable biomechanical benefits rather than a fit & fill stem after cementless total hip replacement.

Keyword

Cementless total hip replacement; Micromotion; Stress distribution; Stress shielding; Proximal fitting-distal filling stem; Proximal fitting-distal tapered stem; 3-D finite element models
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