Flexor Hallucis Longus Tendon Transfer VS Gastrocnemius Augmented Flexor Hallucis Longus Tendon Transfer in Management of Achilles Tendon Defect

The FHL tendon will be dissected and transected as far distally as possible. The FHL tendon will be transfixed by Krakow's suture being inserted into the distal 3 cm in the stump to ensure adequate length of the graft inserted within the bony tunnel in the calcaneus.A guide wire with eyelet will be inserted in the calcaneum just anterior to the native AT insertion by a distance 2 mm more than the half of the diameter of the transferred tendon to avoid blow up of the posterior wall of the tunnel. A tunnel will be drilled over the guide wire according to the tendon thickness, without penetrating the planter surface of the calcaneum. The threads at the end of FHL tendon suture will be passed through the eyelet of the guide wire. The tendon will be driven into the calcaneal bony tunnel by pulling the guide wire through the plantar aspect of the heel. Then the FHL tendon will be tenodesed into the bone tunnel using a interference screw of the same size or 1 mm larger than the bone tunnel.

The gastrocnemius tendon will be refixed to the calcaneal tuberosity using anchors. According to the size of the defect: If the size of the gap was 4-5 cm, an additional gastrocnemius turndown or V-Y flaps will be done. Turn down flap will be achieved by creating 2 cm wide and 5-6 cm long flap from the gastrocnemius tendon. The most distal 1 cm from the proximal stump will be secured along the lateral border of the flap to prevent its separation from the original stump during tensioning and fixation to the calcaneus. V-Y flap will be achieved by having inverted V-shaped incision in the distal part of the gastrocnemius starting proximally and extending the two limbs distally leaving the lateral 1 cm from the original tendon. Then carful advancement of the proximal AT stump distally to reach the calcaneal tuberosity. then Fixation will be achieved by suture anchors. If more than 5 cm gap, tenomyodesis of FHL through the proximal stump of Gastrocnemius muscle will be done.