Department of Mechanical Engineering

Ortho-biomechanics cadaveric ultrasound

Ultrasound analysis of cadaveric bone

Ortho-biomechanics fracture stiffness

Direct measurement of fracture stiffness on a patient with a tibial fracture

Fracture fixation

Mechanics plays a very important role both in the ability to reduce and stabilise fractures and in the promotion of fracture healing.

Fracture healing is also a dynamic process in which the stiffness of a broken bone is gradually regained and it is important to understand how the stiffness of the fracture evolves during healing.

Fracture fixation devices must be sufficiently strong to withstand the loads applied to the healing bone without premature failure and also be flexible enough to permit some micromotion at the fracture site which is necessary for healing to progress. These requirements are sometimes contradictory and extensive testing of new implant designs is necessary to ensure that they perform as required under as realistic loading conditions as can be simulated in the laboratory.

Viewed in mechanical terms, fracture healing is a gradual evolution of the stiffness and strength of a broken bone to its unfractured values.

This process can take up to a year from the initial fracture and the rate of increase of stiffness determines not only the speed of healing but can also be predictive of whether the fracture will unite or whether a non-union will develop.

It is therefore important to be able to measure changes in fracture stiffness as healing proceeds and several techniques, including vibration, ultrasound transmission and attenuation and direct measurement of stiffness have been developed to do this.

The aim of these measurements is to enable the mechanical progression of healing to be monitored, define an end point of healing (not necessarily when the bone regains its pre-fracture stiffness and strength) when restricted or unrestricted loading of the fracture can be permitted and allow prediction of when the fracture is progressing towards a non-union.

Project Author(s) Dates
Distal radius locking plate screw configuration testing D Avis, Dr Tim Holsgrove, Samantha Wright, Jason Forder, Professor Tony Miles, 2013