1. Proc Inst Mech Eng H. 2013 Jan;227(1):78-86. doi: 10.1177/0954411912454368.

The biomechanics of three different fracture fixation implants for distal femur 
repair in the presence of a tumor-like defect.

Ahmadi S(1), Shah S, Wunder JS, Schemitsch EH, Ferguson PC, Zdero R.

Author information:
(1)Division of Orthopaedic Surgery, University of Arkansas for Medical Sciences, 
AR, USA.

The femur is the most common long bone involved in metastatic disease. There is 
consensus about treating diaphyseal and epiphyseal metastatic lesions. However, 
the choice of device for optimal fixation for distal femur metaphyseal 
metastatic lesion remains unclear. This study compared the mechanical stiffness 
and strength of three different fixation methods. In 15 synthetic femurs, a 
spherical tumor-like defect was created in the lateral metaphyseal region, 
occupying 50% of the circumference of the bone. The defect was filled with bone 
cement and fixed with one of three methods: Group 1 (retrograde nail), Group 2 
(lateral locking plate), and Group 3 (lateral nonlocking periarticular plate). 
Constructs were tested for mechanical stiffness and strength. There were no 
differences between groups for axial stiffness (Group 1, 1280 +/- 112 N/mm; 
Group 2, 1422 +/- 117 N/mm; and Group 3, 1403 +/- 122N/mm; p = 0.157) and offset 
torsional strength (Group 1, 1696 +/- 628N; Group 2, 1771 +/- 290N; and Group 3, 
1599 +/- 253 N; p = 0.816). In the coronal plane, Group 2 (296 +/- 17 N/mm) had 
a higher stiffness than Group 1 (263 +/- 17N/mm; p = 0.018). In the sagittal 
plane, Group 1 (315 +/- 9 N/mm) had a higher stiffness than Group 3 (285 +/- 19 
N/mm; p = 0.028). For offset torsional stiffness, Group 1 (256 +/- 23 N/mm) had 
a higher value than Group 3 (218 +/- 16 N/mm; p = 0.038). Group 1 had equivalent 
performance to both plating groups in two test modes, and it was superior to 
Group 3 in two other test modes. Since a retrograde nail (i.e. Group 1) would 
require less soft-tissue stripping in a clinical context, it may be the optimal 
choice for tumor-like defects in the distal femur.

DOI: 10.1177/0954411912454368
PMID: 23516958 [Indexed for MEDLINE]