Latest News

Special 'off loader' for early knee arthritis

Update: April 2012

Professor James Richardson from Oswestry's Robert Jones and Agnes Hunt Orthopaedic Hospital (RJAH) learned of a special 'off-loader' for early knee arthritis called the Kinespring in 2009. Off-loading one side of the knee is a common strategy when the arthritis is affecting one side (compartment) of the joint between femur and tibia in the knee.

Osteotomy is one option when the lower limb has an existing malalignment (varus or valgus). This is an operation where the bone above or below the knee is divided to allow an opening wedge of new bone to form and a new alignment of the limb to be set. Now methods of fixation with locking screw plates and new bone graft substitutes appear to help in getting predictable results.

Use of an external brace can also help to move some load across from one compartment, but this is not easy to wear and the amount of load transferred is relatively small. External fixators have been also used to distract the joint and ‘give it a rest’ but this is not widely adopted.

Professor Richardson had been working on a design of a device that spans the knee under the skin with Dr Jan Herman Kuiper when Moximed demonstrated their device, the Kinespring, to him. The device runs across the knee from femur to tibia on the inside of the knee. It was a natural progression to use this device, even though it is new and seems unusual to most surgeons. A clinical trial had already been run in Australia, showing good pain relief. A European trial was being initiated and Oswestry was invited to join this trial.

The main concern with a device so close to the surface is the development of an infection around the implant. It has however an advantage of not being inside the knee joint so if an infection should develop then it can hopefully be managed successfully with antibiotics and removal of the device.

Patients who may benefit are those with painful early arthritis of the knee where the alignment of the lower limb is good, and so an osteotomy may not be appropriate.

Professor Richardson travelled to Ghent to study and be trained in the surgical technique together with Dr Frederik Almquist and Professor Rene Verdonk. The procedure takes less than an hour and although a short rest of two weeks is important to allow wound healing, rehabilitation is relatively speedy compared to an osteotomy. Two patients who wished to joint the study had their operation last year and are making good progress. No further patients will be treated at Oswestry until the study is complete. Early results are very encouraging with symptoms improving as much as following an ostetomy.

It is surprising how much the patients have improved, considering the amount of load the device shares from the knee is only small. Its main benefit may be in holding the knee joint surfaces apart when the knee is at rest, an aspect that could usefully be researched further. The off-loader may in future be a useful addition to autologous chondrocyte implantation with or without meniscal transplantation.

This technique is new and so no promises or expectations of its benefits can be made. It is experimental but it is only by trying new things that progress can be made. This device does have the advantage of being removable and unlike a knee replacement does not commit the patient to repeated revision of knee replacement. It does carry a significant risk of infection and should this happen then a future knee replacement might be at risk. There are also small metal bearings in the device and these could fail, or the spring could fail.

Knee replacement has disappointing function in some patients and carries significant complications. One particular problem is that having started on the line of joint replacement then the patient is generally committed to continuing with further joint replacements should there be a problem. This off-loader device is a welcome addition to the options for treating arthritis in the knee in younger patients. However, it should not be forgotten that avoiding surgery, maintaining knee movement and above all the use of diet to control overweight remain the safest options to help young patients with knee arthritis.

Future Meetings
The Oscell team contributes to and learns from international meetings on cartilage healing. The Institute of Orthopaedics and Keele University and the RJAH trust support the costs of these meetings. We are soon to go to the International Cartilage Repair Society meeting in Canada and will report back on what we have learnt!

We hope the update has been useful.