Chapter 3 The described preoperative surgical plan is very convenient: preoperat- ive markings are easily identified (popliteal crease, tibial medial condyle, midline of gastrocnemius muscle), both in the supine and prone position; the possibility of dissecting the flap in both positions is very important from the clinical point of view during reconstructive surgery because the position of the patient on the operatory table is not conditioned by the donor site. The great and small saphenous veins can be used as lateral and medial border of our flap. Identified preoperatively, clinically or with a doppler probe, they should be spared during dissection of the flap, while minor branches are ligated. The average length of the harvested flaps was about 13 cm, the average width approximately 8 cm. This allows us to obtain a flap of such dimensions to cover small, moderate and quite large soft tissue defects, centering the flap on the midline of the medial head of the gastrocnemius muscle, to include perforators. If the width of the flap is 4 cm or less, direct closure is almost always possible with no risk of compartimental syndrome. Perforators were present in all flaps, starting dissection 6 cm distally to the popliteal crease; this distance was chosen according to literature,2-4 correct also at the light of our results, since all perforators were found at 7 cm to 18 cm from the popliteal crease. So the advisable length of the flap should be 13 cm, in order to have 50% of probabilities to include two perforators, 30% to include one and 20% to include three perforators. As shown in figure 3.5 and 3.6, only 34.2% of perforators was found exactly on the MGML, but 87% (33 out of 38) was within 1 cm (medially or laterally) from that line. So in a flap 8 cm wide, we can identify an area 2 cm wide, the midline of which is MGML, where there is 90% of probabilities to find perforators. The average diameter of perforator arteries (0.5 mm) before entering fascia, where the surgeon begins intramuscular dissection, is acceptable according to literature.1 The intramuscular pathways of MSAPs followed two modalities. In 70% of cases perforators, once pierced the fascia, ran deeply within the muscle substance before reaching greater vessels, rendering dissection more difficult and aggressive. In 30% of specimens the running was immediately under- neath the fascia; in this case the muscular damage is minimal and dissection easier. (Fig.3.3, 3.4) In no cases the motor nerve to the gastrocnemius muscle could be found, 43
5. lay-out phd DEFINITIEF_digitaal2
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