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Table 2 Comparison of length normalized 3D loading-measurement system mean stiffness (K3DN) results to published conventional test machine load-measurement system stiffness (KH) results of intact equine radii. Differences in testing protocols are listed in the table. To be able to directly compare our 50 mm test segment stiffness (K3D) results, they were normalized to comparable values for test segment lengths used by Hanson et al. [1] by multiplying K3D by the ratio of test segment lengths: for axial and torsion (50 mm/150 mm), and for bending (50 mm/11.5 mm) and (50 mm/101 mm) to produce a range of K3DN values within which KH should lie.

From: Development of an in vitro three dimensional loading-measurement system for long bone fixation under multiple loading conditions: a technical description


Mean stiffness (K) of intact equine radius


Axial Compression (N/mm)

+/-Torsion (Nm/deg)

CrCa Bend (Nm/deg)

LM Bend (Nm/deg)

Measured using: 3D unconstrained fixtures

(3D optical) 34 cm test section 4-point bend, force applied on steel extensions to potted radius ends

3D optical tracking of the 50 mm test segment ends

K 3D (50 mm test segment)





K 3DN (150 mm axial & torsion segment)

(11.5 to 101 mm uniform bend segment)



4378 to 504

7305 to 840

Measured using: Constrained axial compression and torsion fixtures

(Hanson et al.) 1.15 cm test section 4-point bend (10.1 cm between outer force applicators), force applied directly on bone.

Test machine ram displacement

K H (150 mm axial & torsion segment)

(11.5 mm between inner, 101 mm between outer 4-point bend force application points)