Step 5

Place the anterior cutting guide onto the femoral condyles so that the flat surface is parallel to the anterior cortex of the femur.This is facilitated by the saddle of the guide which is placed in the notch of the femur. The two inferior skids provide a reference for placement against the posterior aspect of the condyles, although this cannot be seen easily with the limited incision that is generally used. A new smaller cutting block is being developed for smaller patients and minimally invasive incisions.

Step 6

The extra medullary guide rod and tower assist in obtaining accurate alignment. This should be in line with the anterior cortex of the lower 1/4 of the femur in the lateral saggital plane. A 3.2mm diameter hole is drilled into the intramedullary canal through the central drill guide of the cutting block and the Guide Rod inserted.

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Step 7

Final positioning of the femoral cutting block is confirmed with respect to rotation. Particular attention should be made to ensuring that there is 3-6º of external rotation of the block on the femur. Internal rotation will lead to maltracking and overload and should be avoided. When satisfactory alignment has been achieved the position of the block is fixed with two 3.2mm diameter pins. The lateral pin should be inserted first to prevent internal rotation of the block.The extra medullary tower is now unscrewed.

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Step 8

The height of the trochlea is assessed using the anterior reference indicator which measures the exit point of the anterior resection using the superior surface of the cutting block. The cut should pass just beneath the deepest part of the groove, exiting parallel to the anterior cortex.