Chapter 17 The Comparative Analysis with Finite Element for Cemented Long- and Short-Stem Prosthetic Replacement in Elderly Patients with a Partial Marrow Type Ⅰ Intertrochanteric Fracture

摘要

Objective This study investigated the stress distribution in a femur after a cemented prosthetic replacement surgery in elderly patients with a partial marrow type Ⅰ intertrochanteric fracture and compared the differences in stress distribution between a long- and short-stem prosthetic replacement. Methods A spiral computed tomography (CT) scan was used on the volunteer's right femur to obtain image data, which were processed with the Mimics software and the modeling software to reconstruct a three-dimensional model of the femur. On this basis, the three-dimensional physical models for a partial marrow type intertrochanteric fracture, long- and short-stem femoral prostheses, and the mantle layer of cement were established. Finally, the three-dimensional finite element models of the long- and short-stem femoral prostheses as a treatment of an intertrochanteric fracture were established using the software for finite element analysis, and the biomechanical analysis was implemented for the models. Results The stress distribution in the femur after the cemented long- or short-stem prosthetic replacement did not change significantly; it still gradually increased from the proximal end to the distal end, reaching the peak value at the lower 1/3 of the medial and lateral junction, and then decreased to the end. Although a stress concentration zone formed in the medial and lateral end of the bone cement-prosthetic stem interface in the short-stem prosthesis, which had a lateral peak value of 15.3 MPa, it did not exceed the fatigue strength of the bone cement. Alternatively, a stress concentration zone formed in the distal medial and lateral end of the bone cement-prosthetic stem interface and the medial middle part of the shaft in the long-stem prosthesis, which showed a peak value that was also lower than the fatigue strength of the bone cement. No significant stress concentration zones were found in the femoral calcar reconstructed by bone cement. Conclusion The stress distribution in the femur did not change significantly after cemented long- and short-stem prosthetic replacements were used for elderly patients with a partial marrow type Ⅰ intertrochanteric fracture. The probability of loosening of the cemented long-stem prosthesis was comparable to that of the short-stem prosthesis, but the latter may be more suitable for treating elderly patients with a partial marrow type Ⅰ intertrochanteric fracture due to the shorter surgery time, minor trauma, and fewer complications.