A Closer Look At The Use Of Interference Screws For Lateral Ankle Stabilization

Erigena Baze, DPM, Danielle N. Butto and Lawrence DiDomenico, DPM

Keys To Performing The Split Peroneus Brevis Tendon Technique

Prior to surgery, patients have received a diagnosis of a functional or mechanical instability involving the ankle joint and subtalar joint. The ligaments involved typically include the anterior talofibular and the calcaneofibular ligaments. With a mechanical instability, the patient would have had a positive ankle stress test (anterior drawer and talar tilt) and/or advanced imaging that demonstrates ruptures of the lateral collateral ligaments.

   After ensuring supine positioning of the patient, apply a mid-thigh tourniquet. One may obtain intraoperative stress views consisting of the talar tilt test and anterior drawer test to verify the amount of ankle instability.

   Make an incision over the peroneal tendons, beginning approximately 6 to 8 cm proximal to the distal tip of the fibula and extending distally toward the base of the fifth metatarsal. Deepen the incision through the same plane. Perform sharp and blunt dissection, but be sure to avoid all neurovascular structures.

   Dissect the tissues down to the peroneal tendon sheath. Incise the sheath and identify the peroneus longus and brevis tendons. Split the peroneal brevis tendon with fiber wire. Cut the anterior one-third to one-half of the brevis tendon (split portion) proximally. This will be available for the ligament replacement graft. Proceed to make a periosteal incision over the anterior aspect of the distal fibula at the level of the ankle joint, creating a periosteal flap. This will be another form of fixation at the end of the procedure prior to securing the tendon to the bone during closing.

   Using a 4.5 mm drill, create an osseous tunnel in the mid-portion of the distal fibula, aiming from proximal anterior to posterior inferior of the fibula. It is imperative that this drill is centrally located in order to prevent stress on the cortices of the fibula.
Proceed to apply a whipstitch to the free end of the brevis tendon. Pass the tendon in an anterior to posterior direction through the fibula. Make a small incision through the soft tissues superior to the calcaneus. Introduce a guide wire through the central dorsal aspect of the calcaneus and create a channel from a dorsal to plantar direction in the mid-portion of the calcaneus. Confirm the central placement of the guide wire through the calcaneus under fluoroscopy with a lateral and a calcaneal axial view.

   Then use a cannulated drill to drill over the guide wire to the expected length of the interference screw. Place the tendon graft end along with the whipstitch over the remaining peroneal brevis and peroneal longus tendon. Then insert the whipstitch into the guide wire and pull the guide wire from the plantar aspect of the foot, leaving the fiber wire to exit the plantar soft tissues of the calcaneus.

   At this time, place the ankle into a neutral position at 90 degrees to the leg and insert the peroneal brevis tendon graft into the osseous calcaneal tunnel. Proceed to insert a smaller guide wire from the superior calcaneus into the osseous tunnel and exiting the plantar skin along with the fiber wire.

   At this time, the surgical assistant is holding the ankle at a neutral position 90 degrees to the leg and is pulling the fiber wire firmly to the desired physiologic tension. Once you confirm the position and are happy with the tension, insert a cannulated interference screw from a superior to inferior direction in the mid-body of the calcaneus. While inserting the absorbable screw into the calcaneus, one should appreciate a positive “squeak sign,” which indicates good bone and tendon purchase.

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