Exciting new developments in shoulder replacement surgery
Bioengineers in London are to investigate the effectiveness of a new type of shoulder replacement which could potentially improve the quality of life for thousands of arthritis sufferers in the UK.
The “Grammont reversed implant” is increasingly widely used by surgeons in people with severe arthritis who need a new shoulder joint. But although it appears to be very effective in the short-term, little is known about how long the prosthesis may last.
Now a team at Imperial College’s mechanical engineering department have been awarded two years of funding of almost £110,000 from the Arthritis Research Campaign to understand why the Grammont implant appears to be so well fixed in the bone, and to evaluate if this fixation is likely to lasting the long term.
In shoulder replacement surgery a metal head and stem replaces the upper part of the arm bone (the humerus), with a plastic cup fitted into the shoulder blade (the scapula) if needed.
Although shoulder replacement surgery can reduce severe pain, which restricts movement and use of the shoulder, many patients fail to get back all the movement they had before the operation, and the implant can also become loose.
If replacement joint is not securely attached (or constrained) the shoulder can dislocate. Conversely, if the implant is too securely attached, it leads to loosening. And for those arthritis patients whose rotator cuff muscle (the strong group of muscles in the shoulder which effectively holds the implant in place) is damaged, the surgical outlook is extremely bleak.
The Grammont reversed implant, which was designed especially for this group of patients, is now also being used more widely by surgeons in the UK on all patients who need shoulder replacements, because in the short-term at least, it appears to be highly effective. It is so-called because it is the reverse of the standard implant, with the ball in the scapula bone, and the cup or socket in the humeral bone.
“The Grammont implant seems to give almost amazing results,” explained principal investigator Dr Ulrich Hansen. “Some surgeons are so excited about it that the use it for shoulder conditions for which it was not originally designed.
“It may be that this implant offers a step change in shoulder implant development. However, for the overall group of patients it is an unproven and not very well understood implant, and its general use could prove a disaster. Using lab tests and computer techniques, our project aims to understand how this implant works, and so provide confidence in its wider use. Alternately it may warn surgeons as soon as possible that it should not be used as a standard implant.”
