LIVRE JDG 2012

Deepening Trochleoplasty: the Lyon Procedure

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proximally into the muscle belly. After

inspection, the patella is retracted laterally,

providing adequate trochlear exposure.

Before starting the osseous procedure, the

synovium must be removed from the edge of

the trochlea. It is incised with a scalpel on the

cartilage edge and a periosteal elevator is used

to retract it away from the trochlear edge.

Trochlear planning

A line deviating 3 to 6 degrees laterally is

drawn proximally from the intercondylar notch

representing the bottom of the new groove. The

lateral margins are also drawn from the

intercondylar notch through the

sulcus

terminalis

of each condyle. The proximal part

of the new groove can be positioned according

to the TT-TG value in order to correct a possible

malalignment (fig. 2).

Bone removal

A strip of cortical bone (corresponding to the

amount of the bump) from the anterior femoral

cortex till the cartilage edge must be removed,

using a thin osteotome. This creates the access

to the under surface of the trochlea and

constitutes the first step to bring the new

trochlea to a normal position (not prominent)

and eliminate the bump.

The cancellous bone that lies under the trochlear

cartilage must also be removed to reshape and

reposition the new trochlea. Osteotomes and

curettes are helpful in the procedure, but a drill

with a specific depth guide is used for this

purpose. This depth guide is set to allow bone

removal from the cartilage undersurface

producing a uniform cartilage-bone shell of 5

millimeters. It avoids cartilage damage and

thermal necrosis which could result from

excessive bone removal (fig. 3). The shell

produced must be sufficiently compliant to

allow modeling. Without the guide, bone must

be removed especially from where the new

planned sulcus will lie. All bone that projects

beyond the anterior femoral cortex should be

removed (fig. 4).

Fig. 2 : The new trochlea is planned over the native

one. The central line deviating slightly laterally

represents the bottom of the groove. Note that

cortical bone has already been removed from the

osteochondral edge.

Fig. 3 : Cancellous bone removal with a drill and a

specific guide.