Patient Matched Osteotomy to Correct Angular Deformities in Knee Arthrosis

The use of osteotomies to correct angular deformities around the knee has been
a surgical option for delaying, and potentially preventing, the progression of
knee osteoarthritis, especially in younger and physically more active patients
in whom total knee arthroplasty is undesirable. Pre-operative digital osteotomy
planning has been shown to have a high inter-rater reliability, irrespective of
the user*s experience. This operative plan is precise, however the majority of
surgeons still rely upon relatively crude and ipso facto unreliable
intra-operative measurements to guide the operation, which may explain the
relatively poor results. Surgical navigation may improve accuracy but the
longer and more complex procedure may be associated with increased costs, and
complications, as has been the case in arthroplasty, where clinical benefit has
not been convincingly demonstrated. We propose to translate two technologies
that are already commercially available in arthroplasty into the field of
corrective osteotomy. Utilising standing radiographs and a pre-operative low
dose CT scan, the surgeon will plan deformity correction in three dimensions.
From this a 3D cutting block will be manufactured. If proved valid and
reliable, patient-matched cutting blocks offer a low-cost, straightforward
method of achieving a precise deformity correction. This will facilitate
further studies into the optimal degree of correction required to reduce, and
possibly prevent, progression of osteoarthritis in patients.

To assess the radiological, clinical, and functional outcome of osteotomies
around the knee using 3D CT planned patient-matched cutting blocks at three,
six and twelve months post-operatively.

A prospective multicentre study.

The surgeon will determine the desired angular correction with the aid of
standard radiographs and pre-operative three-dimensional CT-scan. The surgeon
will also specify the fixation device (plate and screws) used to stabilise the
osteotomy. Osteotomy will be carried out according to the local investigating
surgeon*s technique. The key difference in this study is that a patient-matched
cutting block will be used to assist positioning and angle of the saw cut, and
provide guidance on the degree of angular correction as per the pre-operative
plan.

The patient matched cutting block will only act to fine tune the bony cuts and
drill holes during surgery, rather than replacing the surgeon*s normal
operative skill and technique, which should minimise any potential risks. The
cutting block will be manufactured from nylon, which is known to be safe and
nontoxic. Two additional CT scans will be performed as part of the study
(pre-op and 3 months post-op), which will mean additional exposure to
radiation. However, the radiation dose will be small given that this will be
low dose and focussed on the proximal tibia. Subjects have to fill in
questionnaires at visits, taking about 4 x 15 min in total.
There is no direct benefit for the subjects, other than the expected, but
hypothetical, more precise deformity correction.