Phantom limb pain (PLP) is the chronic experience of pain in the residual impression of a limb which persists following amputation, and is one of the most distressing consequences of amputation. The problem of PLP is large and pervasive in the lives of many amputees.
Phantom limb pain has thus far proved to respond poorly to the current range of pharmaceutical, surgical, and psychological treatments. One promising development, however, was Ramachandran’s mirror box that allowed amputees to view a reflection of their anatomical limb in the visual space occupied by their phantom limb. Ramachandran reported evidence that the mirror box induced vivid sensations of movements originating from patients’ phantom limbs, and in some cases relieved their PLP.
Hypothesising that other visual therapies may work in similar ways to Ramachandran’s box, in 2006 we built an Immersive Virtual Reality (IVR) system that attempted to reproduce the positive effects of the box without its physical limitations. This system provided an immersive stereoscopic visual representation of the amputee’s whole body and used electromagnetic tracking hardware to transpose the movements made by the intact anatomical limb into movements of a computer graphical “virtual limb” in the phenomenal space occupied by the phantom limb (see some examples of the 2006 system in use):
In a small-scale trial, five participants whose phantom limb pain had resisted all other forms of treatment used the IVR system on a weekly basis; four reported tangible reduction in their pain levels; two found they gained some control over their phantom limb’s position, being able to manoeuvre it into a more comfortable state; and one found that he was even able to exercise some control over the stump of his amputated limb, which had previously been paralysed for over twelve years. Given such a small study, it is clearly premature to make any profound claims about the effectiveness of the IVR therapy. However, it is difficult to ignore the potential of this approach as a non-invasive mechanism for reducing the considerable suffering of thousands of patients in the UK and millions worldwide.
Since our prototype of 2006, there have been astounding advances in technology: wearable immersive 3D displays, unencumbered tracking devices and powerful 3D graphics engines are now available as off-the-shelf consumer goods. Using this technology brings major advantages: it is cheap and robust enough to place in a patient’s home, and it can be suitably engineered to facilitate controlled experiments that will investigate the numerous variables involved in the therapy.
- Toby Howard and Steve Pettifer, "Virtual Reality Therapy games for Phantom Limb Pain rehabilitation", EPSRC Vacation Bursary, £2500, 2011.
- Steve Pettifer, Toby Howard, I Lieberman, "Virtual Environments for Treating Phantom Limb Pain", University of Manchester EPS Strategic Fund award, £10,000, 2011.
- Toby Howard and Steve Pettifer, "Virtual Environments for Phantom Limb Rehabilitation", EPSRC Vacation Bursary, £2500, 2010.
- Craig D. Murray and Steve Pettifer, "Virtual Reality as a Rehabilitative
- Technology for Phantom Limb Experience", £40,000, 2006.
Watch 'Virtually Painless', a short video from the Science Museum covering how the group's research gives hope to amputees suffering from phantom limb pain.