Effects of osteotomies around the knee on cartilage glycosaminoglycan content using dGEMRIC non-invasive imaging

Medial compartment osteoarthritis (OA) of the knee is an invalidating disorder
and leads to pain, decreased range of motion and inactivity. Underlying cause
is degeneration- and subsequent loss of weight bearing capacity of knee
cartilage. Two procedures aiming at maintaining original cartilage are the high
tibial osteotomy (HTO) and the femur osteotomy. These procedures have proven to
be effective in treating medial compartment OA of the knee in various clinical
trials. However, effects of this procedure on cartilage quality are not known.
Recently, a new technique has been developed which enables analysing changes in
cartilage composition in vivo: the dGEMRIC. The dGEMRIC-technique is based on
distribution of negatively charged contrast agent Gadolinium (Gd(DPTA)2)
between the glycosaminoglycans in the knee cartilage. The T1-signal reflects
the gadolinium uptake by the proteoglycans of the knee and thus provides us
with an indicative parameter of the cartilage quality. Visualising changes in
cartilage composition non-invasively will lead to greater understanding of the
effect of such an operation on knee cartilage metabolism. Knowledge gained
through the current pilotstudy can be applied in a study involving a greater
number of patients.

Primary objective: Evaluate changes in cartilage glycosaminoglycan content
using dGEMRIC, in patients with osteoarthritis of the knee undergoing axial
correction (HTO, femur osteotomy)
Secondary objective: Correlate quantitative MRI data to subjective symptom
scores (KOOS, WOMAC, VAS, Knee Society Score)

All patients that are included in this study will receive their regularly
planned operative treatment, as well as pre- and postoperative visits and
radiographs. In addition, patients will receive an MRI scan with dGEMRIC
settings before and 9 months after the surgical procedure, after removal of
orthopaedic hardware. They will further receive questionnaires (VAS, WOMAC,
KOOS, Knee Society Scale) before the surgical procedure and at 6,12, and 24
months after the surgical procedure.
The T1 values will be calculated as the average T1 signal of a region of
interest (ROI) consisting of 40-60 pixels. These averages will be compared
before and after treatment. Further, distances will be measured between center
of biomechanical axis (using X-rays) and the center of worst affected ROI (on
dGEMRIC). Also, associations of dGEMRIC scores (average T1 values) with KOOS,
Knee Society and VAS scores will be analysed.

In addition to their regular treatment, patients participating in this study
will undergo two MRI scans of their knee. Performing these scans will take
about 4 hours in total. The second MRI scan will be performed 9 months after
the initial operative procedure, after removal of orthopaedic hardware
(procedure in daycare; burden: +/- 1 day).
Further, patients are asked to fill out questionnaires before- and after their
surgical treatment. Filling out these questionnaires will take around 20
minutes per time moment (4 in total).
Risks associated with the MRI scan are the very infrequently occuring allergic
reactions to the contrast agent, which is used to depict the cartilage. Risks
related to removal of orthopaedic hardware are uncommon (infection, bleeding),
as well as risks associated with anesthesia (allergic reaction, dental damage,
paresthesia).