The FSL or ‘frangible surrogate limb’ is designed to mimic the behaviour of a human leg under the rapid loading experienced when you step on an anti-personnel landmine or when you are in a vehicle that has been hit by an IED.

By having bones that break at the same levels and in the same way as human bones and by taking measurements of the forces experienced, it provides invaluable information to both clinicians and engineers. This data will help in the development of systems to protect the lower limb for both mounted and dismounted personnel in areas in which landmines and buried IEDs may be found.

With its roots in Adelaide, Australia, the limb was developed initially to provide a comparison tool for anti-personnel landmine protection footwear. The big push for humanitarian demining in the 80s and 90s attracted a variety of potential footwear ideas.

At that time no validated test limb existed, so there was no clear way of comparing these footwear systems in a way that was clinically relevant – mechanical test limbs do not behave like flesh and bone. It was also the case that there were no obvious animal surrogates that would do the job. In some programmes cadavers and amputated human limbs were used.

Steve Holland, of SJH Projects, recalls the limbs he used with a surgeon colleague, saying: "They varied enormously and you can imagine that limbs amputated for health reasons are not of the highest quality".

The FSL has become a NATO approved tool for research into landmine footwear with upgrades being made to continually improve its biofidelity. Until now the limb was only available to a limited military research community. Having been witness to and contributing to its evolution, SJH Projects is pleased to be able to offer the FSL commercially.

In most vehicle underside blast tests the lower limb measurements are taken by crash test dummies. These steel limbs are robust and yield good numerical data but the correlation to the pattern of injury requires an educated interpretation.

As vehicle research matches the IED threat, the charges are getting larger and so damage and the need to replace crash test dummy limbs is not uncommon. This has seen the frangible limb find a role in such vehicle tests, although it can usually only be used once it can still work out more cost effective than replacing the mechanical limbs. Those who have tried will have found that insurance for crash test dummies for vehicle blast tests is hard to come by so the cost of such damage is usually underwritten by the customer.

The FSL has a knee joint bracket that allows it to directly replace the lower limb of a crash test dummy or to attach into other purpose built rigs for landmine research. The FSL can be X-rayed and go under a CT scan to provide images that match human lower leg bones.

It is fully expected that the limb will find other high speed impact applications and the technology behind it is already finding its way into other body parts.