LIVRE JDG 2010

For this purpose the epicondylar line was first

determined by connecting the most prominent

point of the lateral epicondyle (A) with the dee-

pest point of the medial epicondylar sulcus (B),

and distance AB was determined as the width

between these anatomic points. [12] Next the

most posterior point of the lateral (C) and

medial condyle (D) was determined perpendi-

cular to the epicondylar line, and the distance

between both (CD) was measured parallel to

the epicondylar line. Likewise, the most ante-

rior point of the lateral (E) and medial trochlea

(F) was defined perpendicular to the epicondy-

lar line, and the distance between both points

was measured parallel to the epicondylar line

(EF). The height of the lateral femoral condyle

(CE) was measured perpendicular to epicondy-

lar line between the most posterior condylar

ral condyle. The height of the medial femoral

condyle (DF) was measured perpendicular to

the epicondylar line between the most posterior

condylar (D) and anterior trochlear point (F) on

the medial condyle. The femoral aspect ratio as

an indicator of relative femoral width was defi-

ned as AB/CE. All patients were ranked accor-

ding to the height of the lateral condyle (CE) as

small (nrs. 1 to 250), intermediate (nrs. 251 to

500), or large (nrs. 501 to 1000).

The preoperative full leg radiographs were

taken with the patients in bipodal stance, the

knees in maximal extension and feet in neutral

rotation. These radiographs were calibrated

and care was taken to include the whole pelvis

in order to be able to measure the pelvis

width, which was defined as the distance bet-

ween the two anterior superior iliac spinae.

On the same radiographs we measured the

total length of the femur between the most

proximal part of the femoral head and the cen-

ter of the intercondylar notch. The length of

the tibia was measured between the most

proximal point of the sulcus between the emi-

nentiae intercondylaris and the tibiotalar joint

line at the mediolateral centre of the ankle.

The total leg length was defined as the sum of

the length of the femur and tibia. The mor-

photype of the patient was determined by the

ratio: pelvis width/total leg length.

Patients with a high ratio (wide pelvis/short legs)

were defined as endomorph, patients with an

intermediate ratio as mesomorph, and patients

with a low ratio as ectomorph (narrow pel-

vis/long legs). Patients were classified using the

observed tertiles; the 33% patients with the

highest ratio were considered as endomorph, the

33% patients with the lowest ratio as ectomorph,

and the middle 33% as mesomorph (fig. 2).

The postoperative CT scans were used to

determine the tibial geometry. CT slices were

taken every 2 millimeters, which allowed us to

determine the exact tibial resection level for

each specific case, upon which the surgeon

had based the tibial sizing. Only the slice just

distal to the metal base plate was therefore

analyzed. Cement intrusion into the tibial bone

was frequently noted as this level. The follo-

wing tibial measurements were taken: medio-

lateral width of the tibial surface (AB), antero-

posterior length of the lateral tibial condyle

(CD), and anteroposterior length of the medial

tibial condyle (EF).

For this purpose a tangential line was first

drawn along the posterior tibial margin, and a

second line parallel to this, at the level halfway

to the most anterior tibial margin. The distan-

ce between the intersection points of this

second line with the lateral (A) and medial

cortex (B) was defined as the tibial width

(AB). Next a line perpendicular to line AB was

drawn at 25% and another one at 75% of the

tibial width, to determine the anteroposterior

length of the lateral (CD) and medial (EF)

tibial condyle.

All tibia’s were ranked according to the

mediolateral width (AB) as small (nr. 1 to

250), intermediate (nr. 251 to 500), or large

(nr. 501 to 1000).

All radiographic and CT measurements were

digital. In 64 cases the quality of the CT-scans

was insufficient for adequate measurements,

and in 43 cases the quality of the full leg radio-

graphs did not allow adequate measurements,

and these were therefore excluded from the

respective analysis.

THE INFLUENCE OF MORPHOTYPE AND GENDER ON THE SHAPE OF THE KNEE IN TKA PATIENTS

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