LIVRE JDG 2010

source of confusion when comparing results

from different studies. The anatomic axis

unites the apex of the lateral epicondyle with

the apex of the medial epicondyle, whereas the

surgical axis unites the femoral insertions of

the lateral collateral and the medial collateral

ligaments [10]. The latter does not insert on

the apex of the medial epicondyle but rather

immediately posterior to it, at the level of a

slight depression or sulcus.

In total knee arthroscopy, the surgical transepi-

condylar axis is generally used because it

appears to be better reproducible and because

it corresponds to tibial mechanical alignment

and to the ideal axis around which knee

flexion and extension occur [1, 10-12].

Actually, the use of this axis has also attracted

criticism too [13] since it does not appear to be

equidistant to the distal and posterior condylar

surfaces, and so does not constitute the real

center of rotation of the knee during flexion:

the anatomy and biomechanics of the distal

femur are much more complex, and positio-

ning of the femoral component according to

this axis would represent only a compromise.

Other Authors maintain that, owing to the

considerable variability of the transepicondy-

lar axis and the even greater variability of the

anteroposterior axis, preoperative computed

tomography (CT) should be performed to eva-

luate the real femoral rotational alignment and

to aid in accurate bone cutting [14].

In their 2007 study, Hanada and Whiteside

[15] stated that bone landmarks are more

reliable than tensioned gaps for alignment and

balancing of flexion and extension spaces, the

suggestion being that to avert gross error in

femoral positioning, the surgeon should take

into account several parameters: ligament

balance, flexion and extension space, the ante-

roposterior and transepicondylar axis, distal

and posterior condylar wear, and varus-valgus

and recurved and procurved deviations of the

femur and the tibia.

We know that the average space between the

medial epicondyle and the articular rim is 3cm,

whereas that of the lateral epicondyle is 2.5cm.

The most commonly used methods for placing

a femoral posterior cut and for determining

femoral rotation according to anatomic land-

marks is the posterior condyles, the anteropos-

terior axis (Whiteside line), and the transepi-

condylar axis.

Generally, the instrumentarium for knee joint

replacement is such that bone cuts are predefi-

ned by component thickness. The femoral cut

is therefore made, after having selected the

varus-valgus, using an intramedullary guide

with jigs placed on the joint surface. In knee

joint arthrosis, however, we can very often

encounter deterioration of femoral surface, so

that basing the choice solely on the instrumen-

tarium, the bone cuts will be excessive, since

the jigs refer to a normal knee (i.e., a knee with

completely intact cartilage): so, to not take in

count this situation will lead to a certain rising

of the joint line.

Tibial resection, which does not influence the

joint line level, can normally be carried out

perpendicularly to the tibial load axis, attemp-

ting to cut a thickness equal to that of the pros-

thesis (metal backed – minimum polyethylene

insert). Regarding the tibial slope, to reprodu-

ce the lateral one might have more advantages

over the medial one in terms of restoration of

the natural slope [16].

The surgical approach we use is not based on

conventional jigs; instead, we cut the bone star-

ting from the joint surface and then size the

femoral cut needed to re-establish joint line

height. The first step entails placing a very

conservative distal femoral cut (fig. 1), then the

tibial cut. This does not disrupt joint biomecha-

nics but it does influence both flexion and

extension spaces, so that we can proceed more

aggressively to obtain an extension space that

will be adequate for implantation of the smaller

insert thickness of the prosthesis. Then, we

attempt to reach the correct ligament balancing

in extension (fig. 2). After that, we return to

flexion to make the posterior femoral cut in

order to obtain the same flexion space and to

maintain or re-establish the posterior condylar

offset, thus cutting as little as necessary. This is

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