Prosthetic implants

Osseointegration and prosthetic implants from the Royal Free London

For some patients, fitting a prosthetic limb or body part in the traditional way, without any permanent attachment to the body, can be too difficult to manage. These patients may benefit from osseointegration – a relatively new method to permanently attach an artificial body part (the prosthesis) to the human body. 

Osseointegration, in the area of prosthetics, involves inserting an implant (accepted by the body as part of the bone) that allows artificial limbs and body parts to be permanently attached to it, much like a joint and fitting. The implant will not easily loosen, and the prosthesis becomes permanent.

Only titanium-based prosthetic implants are known to have this property although a similar effect can be obtained when a metal implant is coated with a special layer that mimics bone (such as hydroxyapatite). At the Royal Free London, our world class plastic surgery team are experienced in inserting osseointegrated implants in the head and neck region. We also work with colleagues who have experience of using prosthetic implants in the upper leg and torso area.

Reducing the infection risk in patients with osseointegration:

Achieving osseointegration of a metal implant in the bone is now a very well understood and reliable process. However, to allow a prosthetic implant to be useful for connecting an artificial limb or body part, part of the implant must stick out through the overlying skin so that the artificial limb or body part can be secured to it.

Having a piece of metal protruding permanently through the skin exposes the patient to some risk. Human skin has evolved over many millions of years as a barrier between the external environment and the human body; whenever that barrier is breached, there is a potential chance of infection. 

Currently, there are two ways that we reduce risk at the Royal Free Hospital, both involve developing a closer attachment between the skin and bone by:

  1. Thinning the soft tissues so that the skin attaches directly to the outside (the periosteum) of the underlying bone.
  2. Applying a skin graft directly to the outside of the bone immediately next to the implant. 

 

Both osseointegration approaches have been carried out with some success, but this appears to be partly dependent on the part of the body the implant is hosted by.

Which parts of the body can host a bone-anchored implant?

Bone-anchored implants have been used for attaching prostheses to nearly every part of the human body. They have been used as a basis for artificial eyes, noses, ears, hands, and even thigh and mouthparts. They have not been used to help prosthetic legs, yet, but work is being carried out to see if there are any advantages to bone-anchored implants for below knee amputees. 

What advantages are there with osseointegrated implants?

Using a permanent prosthesis lessens many of the problems associated with temporary methods of attachment, such as chafing and restricted movement – which lead up to 80% of prosthetic users to abandon their prosthesis within two years.

Direct skeletal attachment of the prosthesis, using osseointegration, feels much more “natural” and allows for less restricted movement. It is also much easier / convenient for patients to attach an osseointegrated prosthesis. Patients often report being able to “sense” the prosthesis in a way that they are unable to do with a conventional prosthesis. This is referred to as osseoperception.

What disadvantages are there with osseointegrated implants?

One problem with all types of bone-anchor is the need to undergo further plastic surgery after the initial surgery to remove the diseased part (eg after amputation of a limb). This means having to go through two or three additional plastic surgery procedures before the implant can be used as a bone-anchor. There is also some risk of infection at the prosthetic implant site. However, in most cases, patients only experience minor and superficial infections. Patients must also put up with a change in appearance of the treated part. There will be a piece of metal protruding from the skin – permanently. 

How can I find out whether I am suitable for osseointegration?

This kind of reconstructive surgery is provided by the NHS, based on need. If you are interested and would like to be considered for this type of plastic surgery, please ask your GP to send a referral letter to:

Mr Norbert Kang FRCS (Plast)
Department of Plastic Surgery

Royal Free Hospital
Pond Street
Hampstead
London NW3 2QG

An out-patient appointment will then be sent to you.