Wednesday, 22 October 2014
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Firm hopes to improve knee replacements with robots

A British firm is hoping to speed up and improve recovery from knee-replacement operations by combining personalised implants with robot-assisted surgery.

Stanmore Implants Worldwide has developed a process that uses a patient’s CT scan data to build a bespoke knee implant and to help program a robotic arm that can help surgeons improve the accuracy of the operation.

Both personalised implants and robot-assisted procedures are well established. But Stanmore claims its system led to the world’s first operation combining the two in an integrated process in July last year.

The company hopes that its ‘Savile Row’ procedure will dramatically increase the number of patients that have just part of their knee removed instead of the whole joint.

This kind of ‘unicondylar’ knee replacement, which is only performed in around 10 per cent of cases, tends to lead to faster recovery and improved function compared with more invasive traditional techniques.

‘There’s evidence to show more than 40 per cent of knees could by unicondylar knees if we had accuracy and reproducibility in unicondylar surgery,’ Graeme Brookes, Stanmore’s managing director for integrated technologies, told The Engineer.

‘The less tissue you remove and the more of the natural knee you leave behind, the more natural the knee feels after surgery. There’s evidence to show unicondylar patients have better functionality because all the ligaments are intact.’

Fewer complications

Unicondylar operations are cheaper because they are smaller operations that tend to have fewer complications and require a shorter hospital stay.

More accurate surgery could also lengthen the lifetime of the implant and reduce the number of repeat procedures needed.

Robot-assisted operations replace hand saws and metal jigs with an electronic instrument that a surgeon can only move within a limited area to prevent accidental damage to tissue, becoming more resistant to movement as it reaches the edges of the area.

Justin Cobb, professor of orthopaedic surgery at Imperial College London and orthopaedic surgeon at Charing Cross Hospital, has carried out more than 10 operations using the Stanmore system since last July.

He said the new process would give surgeons the confidence to carry out more unicondylar procedures, which tended to be less forgiving of surgical error.

‘It sets you free to do what you want as a surgeon,’ he told The Engineer. ‘The robot allows you to sculpt any shape you want. You’re only limited by what you design before you start. You can be confident of sculpting exactly the right shape to fit the implant in exactly the right place.’

Operational plans

Stanmore said this technique has only previously been used with off-the-shelf implants but that its personalised implants cost little or no more to produce. It plans to carry out several hundred more operations over the next year.

Surgeons using the Stanmore process can review and approve each implant before it is produced using computer-assisted manufacturing techniques. The design of the knee implant was licensed from Imperial Innovations based on IP from Imperial.

The company is now looking at the possibility of using the process for other joint-replacement operations such as for hips and shoulders, and is also considering its use in replacing cancerous bone tissue with metal implants.

Cobb said that until now personalised joint implants hadn’t really taken off but that robot-assisted surgery could change that. ‘There’s no point having something perfectly made but put in less than perfectly.’


Readers' comments (3)

  • I had a unicondylar prosthesis fitted to my right knee joint about 7 to 8 years ago. It's always behaved pretty well, little differently than I recall my original knee joint behaving, although I don't try and kneel down on a hard surface. Any restriction of movement is to do with my left knee joint, which hasn't had any replacement, and it is out of vertical alignment.

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  • Is there any chance the Stanmore process will be exported to the States in the next few years or is this strictly a UK operation?
    I really would prefer a partial knee replacement, since it is only the inside knuckle that has been damaged by miniscus tears.

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  • Mako Surgical (United States) holds the worldwide patents for haptic robotic orthopedic surgery through US patents and worldwide exclusive license granted by Immersion Corp. While the Stanmore approach is interesting, how do they propose to work around MAKO's moat?

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