Surgical system may extend life of shoulder implant

A Nottingham University surgeon believes to have found a solution for extending the life of an advanced shoulder implant designed for patients with torn rotator cuffs.

Dr Angus Wallace has introduced a newly designed implant and surgical instrumentation system dubbed Versatile, Anatomic and Inverse Optimised Stable (VAIOS) for shoulder replacement surgeries.

The system reportedly makes it possible for surgeons to choose between conventional or more advanced ‘inverse’ shoulder replacement surgeries in the operating theatre.

A conventional shoulder implant mimics anatomy by putting a socket on the shoulder blade and a ball on the arm. An inverse shoulder replacement is needed in cases where a rotator cuff tendon is damaged to the point that it cannot hold a ball on its socket. Patients with this find their shoulder will hunch up when they try to lift their arm.

An inverse shoulder implant will place a socket where the ball is normally located. A ball is then placed on the shoulder blade so the socket can move against it. Dr Wallace explained that articulation will mean the humerus, the arm bone, cannot ride up because it is stopped by the ball.

Previous inverse shoulder implant surgeries required copious amounts of specific instrumentation – meaning surgeons had to know before operating what procedural path they would take or else risk extending a patient’s time on the surgical table.

Dr Wallace said the VAIOS instrumentation kit includes a much smaller number of dedicated instruments – including the intramedullary jigs, Fukuda retractors and angled reamer driver – which fit into three instrument trays. More importantly, the inverse implant design has been optimised in a way that reduces notching to the border of the scapula – the bone that connects the arm to the collar.

‘It also involves less bone resection to the humerus, making revision surgery possible,’ he added.

Dr Wallace began working with colleague Garth Johnson, a professor of biomechanics, on the new inverse shoulder replacement with JRI Orthopaedics in November 2006.

‘Inverse shoulders had become popular for the treatment of patients with torn rotator cuffs and arthritis,’ he said. ‘Unfortunately current designs have significant problems leading to quite a high proportion developing early failure. We have developed a design that we believe addresses many of the problems that have previously resulted in early failure.’

In June 2007 Dr Wallace and Prof Johnson received funding from a government-funded Knowledge Transfer Partnership Grant and appointed a then Newcastle University engineering student Ian Flatters to work on the project under their supervision.

With support from JRI Orthopaedics, the system was completed in three years.

In April this year Dr Wallace inserted the first VAIOS shoulder replacement in Nottingham. Since then 21 VAIOS shoulder replacements have been inserted and are being followed up in Nottingham.