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
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
knee is at rest, an aspect that could usefully be researched
further. The off-loader may in future be a useful addition to autologous
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.
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.