Pre-operative templating by use of MRI in primary total knee replacement

Templating is generally recommended prior to total knee replacement. The aim is
to predict the bone stock; and the size and mechanical axis of the implant,
which theoretically would reduce the operation time and complication rate.
Several studies confirmed that there is a lack of reliability of the current
pre-operative template system, by use of radiographics, with a relatively low
percentage correlating with the exact size of the implanted prosthesis.

Because of the incapacity to predict the exact size of the implanted prosthesis
with the present templating method, a new template system has been developed:
the Signature* Personalized Patient Care (Biomet, Warshaw, IN). This system
utilizes patient specific femoral and tibial positioning guides, developed from
Magnetic Resonance Imaging (MRI). In combination with this template system, the
Signature* Personalized Patient Care contains a new developed jig, using rapid
prototyping, which could be used per-operatively in a total knee replacement
procedure using the Vanguard® Complete Knee System.

The purpose of this study is to evaluate the accuracy and the reliability of
the new template system in total knee replacement by use of MRI in comparison
with the conventional template method by use of radiographs.

A pilot study of 10 patients is undertaken. If the pilot shows acceptable
results, a new study protocol will be written. In that future study, we want to
include more patients that will undergo the complete Signature* Personalized
Patient Care protocol consisting of the MRI-template method combined with rapid
prototyping to produce extramedullary alignment jigs for guidance during the
operation. This new protocol will be compared with the conventional preplanning
and operative protocol.

Eligible patients will be asked to sign an informed consent. The patients will
be contacted through the following procedure: A research form is presented to
the patient by mail, one week before pre-operative consultation. This
pre-operative consultation will be approximately two or three weeks before
surgery (so called *knee-carrousel*). During this consultation, patients will
get the chance to obtain more information about the study. If informed consent
is obtained, an appointment for a pre-operative MRI will be arranged.
Radiographs of the knee have already been performed during the standard
protocol.

The knee replacement will be done by an independent surgeon. The surgeon will
be blinded for the study participation of the patient. Patient data will be
coded on radiographs and MRI-scans to prevent observer bias. Two independent
observers will template the pre-operative MRI and use the conventional
templating method for the first time after randomization of these data. They
are blinded for surgical technique and per-operative results. Two weeks after
the first templating, the observers will repeat both templating methods. When
the target of included patients is reached, the researcher will evaluate the
template data of both observers by the operation records and post-operative
radiographs. The post-operative score consist of the femoral and tibial size,
by use of the following three-scale score: too small (undersized), correct, or
too big (oversized).

The patient will undergo one MRI-scan pre-operative. No disadvantages for the
patients are expected, because patients with a contra-indication for a MRI-scan
will be excluded from the study.