What is a prosthesis?
The prosthesis is the replacement of a joint with an implant that reproduces its original motion, and that is as close as possible to its physiology.
The prosthesis treatment of osteoarthritis and certain types of ankle deformities may require the use of this technique.
The ankle is made of the peroneal and tibial articular surfaces that join in the foot, with those of the talus, generating the motion and providing the distribution of weight during walking.
When this delicate balance is compromised, for example, for the reasons mentioned above, it may be necessary to perform prosthesis surgery, to replace the degenerated articular surfaces, implanting a prosthetic ankle.
Each prosthetic design must find a point of contact between two antithetical concepts: joint congruency, necessary to replicate as much as possible the original anatomy; the constraint, that is the limitation of the components movement, in order to avoid instabilities.
In recent years the only reliable ‘marriage’ between these two concepts was guaranteed by mobile-bearing prostheses: implantations with a tibial component, a talus component and a polyethylene mobile insert placed between these two. (For more information and details, please visit the section called Mobile-bearing prosthesis).
This solution has reduced the historic and inconvenient bulkiness of first- and second-generation prostheses, providing even longer duration of the system.
The only limit: it is not always possible to restore complete movement in the patient as it would be with a physiological ankle.
Mobile-bearing prostheses are now an important and well-established fact, which I support and practice, but today a new and highly advanced technology available only to a few selected surgeons, “resurfacing”, is becoming increasingly popular or, as we say in Italian, “sta prendendo piede” (and who else if not an orthopaedic surgeon like me can properly use this metaphor!).
Resurfacing allows you to reproduce the original anatomy of the ankle, starting from two simple yet fundamental premises. First: the articular surfaces of the tibia and the talus are curved.
With resurfacing you can reduce the bone resection (surgical removal of a portion more or less extended of a bone) by making curved cuts, so respecting the natural curvature of the tibia and the talus.
In order to make this type of cuts is however necessary to do it from a lateral perspective. Here is the first big innovation of resurfacing: curved cuts to reproduce the original anatomy of the ankle, made on side (via an osteotomy of the fibula which will show the joint) to offer a direct view of the centre of the neo-articulation.
The second premise is that to reproduce the anatomy of the ankle is necessary to think of a prosthesis made up of two parts: the tibial articular surface and the talar one, thus excluding the balance given by the mobile insert, which is the central element of the mobile-bearing prosthesis.
In order for this to be possible, it is fundamental to use innovative materials, and advanced technology.
And this is the second big innovation of resurfacing : the use of Trabecular Metal ™. It is a material that comes from the processing of tantalum and allows to accurately reproduce the porosity and any other bio-mechanical characteristics of the bone tissue.
Trabecular Metal™ allows a bone reconstruction that is reliable enough to be recognized and accommodated by the body itself as real bone tissue. This feature guarantees a unique bone-ingrowth, both in terms of stability and healing times.
So, it is the Trabecular Metal™ and curved cuts that ensure that resurfacing allows an intrinsically stable prosthetic implant to treat the problem. And always these two characteristics allow you to let go of the third mobile element (the polyethylene insert): we are therefore talking about a fixed bearing prosthesis (with 2 components) which means greater movement for the neo-articulation but also generally faster recovery times.
I am now, in Italy, the surgeon who has performed the largest number of resurfacing operations and with longest follow-up*. It is a choice as much revolutionary as reliable that offers great benefits, but that is now possible only in selected clinical cases.
A lot of our patients come from all over Europe, Asia, Britain and America and we are proud to have treated so many successful resurfacing cases.
*Live surgery protesi di caviglia con la tecnica del resurfacing
* Controls the patients undergo after surgery