[Dimensions of the lateral condyle in non-arthritic valgus knees. A cadaver study].

PURPOSE OF THE STUDY

Although the valgus slope of the femoral condyles seen in valgus knee is thought to be due to hypoplasia of the lateral femoral condyle, this fact has not been proved. The aim of this study was therefore to evaluate the difference between the size of the lateral femoral condyle of neutral and valgus knees.

MATERIAL AND METHODS

There were 41 non-arthritics lower limbs taken from 27 caucasians donors. Angular measurements were taken with respect to the mechanical axis of the bones. Femurs were then isolated from the tibia, all soft tissue was removed with respect to the articular cartilage. An osteometric system developed for this study allowed each femur to be precisely photographed in perpendicular planes. Each femur was mounted on the osteometric system. The dimensions (depth and height) of each lateral femoral condyle were obtained using direct measurements from standardized photographs. Knees were considered neutral when the tibiofemoral mechanical angle (TFMA) was between 181 degrees and 176.6 degrees and considered valgus when over 181 degrees. To be compared, measurements were related to the transepicondylar width of each femur. The related dimensions were then compared for both categories of knees (valgus and neutral). There were 18 valgus knees (mean TFMA 182.7 degrees +/- 0.8) and 23 neutral knees (mean TFMA 179.1 degrees +/- 1.6). A validation for the technique was performed by measuring six points on a same femur by the same person seven times. This revealed standard deviations of 0.7 millimeters which was small enough for our purpose. The relationships between the related measurements were analyzed using the Mann & Whitney U test. Significance was accepted at a P value of less than 0.05.

RESULTS

The related depth of the lateral femoral condyle was bigger for valgus knees 32.0 (+/- 2.5) than for the neutral knees 30.5 (+/- 2.0). The related heights of the lateral femoral condyle were about equal 28.7 (+/- 1.8).

DISCUSSION

Using a population of non arthritic knees, our data demonstrated that the lateral femoral condyle is thicker in valgus knees compared to neutral knees, thus in contradiction with the most common view. We suggest that in fixed valgus knees, beside arthritic wear, there is no deficiency of the posterior lateral condyle of the femur.