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Association of a medial UKA and a Patellofemoral Arthroplasty: is it possible?
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so-called Marie-Antoinette effect (Guillotine
effect of the femur on the ACL when the knee
is coming in extension) that may compromise
theACLsurvival over the time. The osteophytes
are also removed from the medial aspect of the
femur.
Femoral preparation
of the patella-femoral
implant
The knee still in flexion, after drilling the
femur, an intra-medullary road is inserted into
the femoral canal. This guide is used to perform
the anterior femoral cut. First the rotation
should be determined according to the
Whiteside line and the posterior-condyle.
Second, the thickness of the anterior femoral
cut is determinate on the guide, which is then
securely fixed on the femur using four screwed
pins. The anterior cut is then done. The next
step is the determination of the size of the
femoral implant. The guide should be positioned
in the axis of the cut, slightly lateralized and
the two distal parts of the guide in contact with
the trochlear groove. It’s important to conserve
3 to 5mm of bone on each side of the implant to
limit the contact with the soft tissues. The guide
is then securely fixed on the femur and a
dedicated bur is placed into the milling rails of
the guide, starting with the central one and then
taking care of each rail on the medial and lateral
side of the guide alternatively. After the milling,
the finishing holes guide is inserted in the
previously milled area and the final holes are
drilled for the pegs of the final implant. The
femoral trial part of the PFJ is then inserted and
leave in place until the final trials.
Medial UKA
The medial UKA is then performed using an
extra-medullary technique to perform the
proximal tibial and the distal femoral cuts. The
sagittal cut of the tibia is then done respecting
the medial aspect of the ACL. The femoral size
is determinate using the femoral finishing
guide. It’s important at this step to make sure
that there is no contact between the two femoral
implants. The femoral preparation is then
realized taking a great care in the femoral
implant rotation.
Trials are insertedwith aminimumpolyethylene
thickness of 8mm and a targeted thickness of
9mm.
Patella
The knee in extension, the patella is then
prepared using a standard patellar clamp. The
patellar button should be positioned as medial
as possible. In case of remaining bone on the
lateral aspect of the patella, a lateral facetectomy
is performed. In case of history of chronic
patellar lateral subluxation, a partial lateral
retinaculum release can be performed from
inside. Final trials are then done with all
implants in place. The patellar tracking is
controlled as well as the stability of the knee.
Cementing technique
One dose of cement is used and all the
components are cemented in the same time. We
do cement first the tibial plateau the knee in
flexion, then the femoral component of the
UKA. Remnants of cement are removed
specially at the posterior aspect of the knee on
the tibial side and the polyethylene is inserted.
The knee is then brought at 30° of extension
and the femoral part of the PFJ is cemented and
finally, the patellar button, the knee in extension.
During the curing of the cement, it is important
to maintain a pressure in the axis of the lover
limb as well as a pressure on the femoral part of
the PFJ, the knee at 30 to 40° and not in full
extension to avoid any inversion of the slope
related to an excessive pressure on the anterior
aspect of the tibia.
Post-operative course
Postoperative rehabilitation protocols included
immediate weight bearing protected by crutches