One of the first questions I am often asked when fellow amputees and ‘normal’ people find out about ITAP is: ‘Can you run with that?’. As with most things in life, the answer is not a simple one!
Everyday movements impart various forces through the body that are borne by the skeleton. Obviously, for an implant attached prosthetic leg, ground impact and other forces will be conducted by the prosthetic into the skeleton via the implant/bone interface. Considerable effort and ingenuity is therefore expended by the designers of implants to ensure that their devices maximise the process of integrating themselves within the residual bone in the stump after surgical implantation (known as osseointegration). If the osseointegration reaches a suitably high quality then the implant should be sufficiently strongly attached to the bone to withstand the various forces encountered in everyday life. It is now thought that the process of osseointegration can be stimulated soon after surgery by gradually loading the implant with initially small but appropriately increasing forces during the course of the recipients rehab. This is exactly what I experienced in the months after my surgery, guided by the excellent physiotherapist that supervised my recovery. As I understand it, small forces initially stimulate the microscopic inclusion of bone into the adjacent surface of the implant, giving a ‘tight fit’, which continues into significant bone remodelling as the rehab forces increase, resulting in stronger overall bone to support the entire structure of the implant.
In order to protect their ‘investment’ in myself as a trial patient, I was advised by the ITAP designers that I should refrain from any high impact activities after my implantation. The forces experienced by a lower limb whilst running are likely to be considerably larger and at a higher rate of repetition than anything that would be generally experienced on a day to day basis and would definitely be considered high impact . For an implant to withstand these forces, the quality of integration between bone and implant would need to be proportionally higher than otherwise required and this would need to be combined with with additional overall bone strength. Some years ago now, I had a very gentle attempt at running and fortunately suffered no ill effects. As a result of this experience I speculated that it may be possible to run safely with an implant and the appropriate prosthetics, assuming the inherent springiness of a blade would provide some level of cushioning from the impact forces, and after gradually building up the intensity of exercise to allow the bone within the stump to cope with the forces involved via the process of remodelling.
After that significant preamble, I have finally come to the point of my post. Whilst trolling through my computer files recently I found a photograph I had taken some time ago of one of my follow up x-rays (three years post-op I think). The thickness of the bone where the implant emerges looked pretty impressive to me so I dug out a post-op x-ray for comparison (left = post-op, right = three years later).
Looking at the two images, the differences that three years of weight bearing use have wrought upon what remains of my femur are clear to behold. All the cycling, mountains and long walks appear to have had an effect – demonstrable evidence of the effect of bone remodelling.
Back to the question at hand; is it sensible to run with an implant? There’s still no definitive answer but I’d happily have another go, especially with appropriate prosthetics, now I’ve seen how my implant is embedded in the bone!