Feeling needy? Stellenbosch lecturer designs tailor-made joints to ease arthritis

A lecturer at Stellenbosch University has found a way to create knee implants that fit patients with arthritis like a glove.

His work could end up helping millions of patients over the next decade.

“People whose knees have been affected by osteoarthritis‚ also known as the ‘wear and tear’ arthritis‚ often have to get knee implants to repair the damage. But if a knee implant does not fit the specific individual‚ it could lead to soft tissue damage‚ collapsing of the underlying bone‚ loosening of the implant and an increased likelihood of joint pain after an operation‚” the university said in a statement on Thursday.

Dr Johan van der Merwe‚ a lecturer in the department of mechanical and mechatronic engineering at Stellenbosch‚ added: “One possible solution is to design implants that are patient-specific‚ anatomically accurate‚ reproduce normal knee motion and are ultimately repeatable.”

Van der Merwe‚ who is also a member of the Biomedical Engineering Research Group in the department‚ developed a semi-automated method of generating patient-specific implant components.

“Replacing or repairing only the damaged part may result in faster recovery‚ improved post-operative joint movement‚ retains as much of the joint’s natural anatomy as possible and is done at a lower cost‚” he said.

“But designing patient-specific Unicompartmental Knee Replacements ultimately rely on a technician’s interpretation and skill in order to consistently reproduce healthy knee shapes. This is a difficult problem – what is considered healthy for one patient might not be the same for another.”

Van der Merwe said current standardised implants often did not match the shape of an individual patient’s knee‚ which may require surgeons to “make the patient fit the implant”.

Van der Merwe developed a model based on healthy knees‚ which could then be used to estimate the healthy shape of damaged parts on a patient’s knee.

Armed with this data‚ Van der Merwe wrote a semi-automated design programme that fits smooth surfaces onto the estimated healthy shape to create implants ready for computer-assisted manufacturing.

“The method proved able to repeatedly generate anatomically compatible implant shapes. We hope that the design could therefore facilitate the restoration of more normal joint function after an operation‚” he said.

Van der Merwe said customised implants could cut down operating and recovery times.

“Implants with a better fit and‚ in our case‚ more natural shape‚ could potentially also improve movement of the joint after an operation.”

Van der Merwe said his innovation could benefit people in their 50s and early 60s who suffer from osteoarthritis. His implant is ready for preliminary clinical testing.

More than three million knee replacement surgeries will be done over the next decade or so. Current knee replacements usually last for 10 years.