A Closer Look At The Mini-Open Ankle Arthrodesis
- Volume 22 - Issue 1 - January 2009
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Debride the cartilage using a combination of osteotomes and curettes. Straight curettes can debride the cartilage along the anterior tibia and talus. One can use curved osteotomes to facilitate the removal of cartilage from the middle and posterior tibial plafond. Take care not to penetrate the posterior ankle capsule. One can use curved ring curettes for the remaining cartilage on the talus.
There is concern that removing cartilage along the posterior third of the talus can be difficult. I have found that the use of ring curettes allows safe and easy access to the posterior talus. After removing the cartilage, fenestrate the adjacent surfaces using a fish scale technique with an osteotome and mallet. Then position the talus within the ankle mortise and place temporary fixation wires. Check the position visually and via fluoroscopy.
Once you have achieved satisfactory alignment, place the screws. Three screws are preferable to stabilize the joint for arthrodesis. The surgeon has the option of using cannulated or solid screw fixation. The first screw is considered the “home run screw.” Place this screw from the posterior aspect of the tibia into the head and neck of the talus. Make the incision between the lateral Achilles tendon and the sural nerve. A good aiming position is the course of the first metatarsal. Use fluoroscopy to confirm the location of this screw. This screw is typically 60 to 70 mm in length.
Place the second screw from the lateral-distal tibia into the posterior-lateral aspect of the talus. The starting position of this screw is the reason for extending the anterior-lateral incision slightly more proximal. The third screw’s starting position is just proximal to the medial malleolus and extends inferior-lateral to the distal-lateral aspect of the talus. Both of these screws are approximately 40 to 45 mm in length.
A washer is recommended for the third screw in order to increase the surface area. When inserting the second and third screws, alternating tightening between the two screws will prevent any rotation of the talus. Fluoroscopy confirms the placement of the screws. Take care to avoid placement of the second or third screws into the subtalar joint.
Then pack the bone graft into the medial and lateral gutters and along any voids within the ankle. Close the incision by layers.
What You Should Know About Postoperative Care
Patients wear a non-weightbearing compression splint for two weeks. Follow this with the use of a non-weightbearing cast for an additional two weeks.
Obtain X-rays at the four-week post-op visit. If the patient’s pain is under control without tenderness to palpation or excessive swelling, and the radiographs are stable, place the patient in a weightbearing cast and allow him or her to bear weight as tolerated. Obtain X-rays every four weeks and keep the patient in a weightbearing cast until he or she achieves radiographic consolidation.
Most patients are out of the cast and into a cast boot at two and a half to three months after the surgery. If there is any doubt of joint stability, keep the patient in a cast. Once the patient is weightbearing in shoes, a rocker bottom shoe is recommended to help compensate due to the lack of ankle joint motion.
While the current literature is lacking with this technique, the limited studies have shown very favorable results. Paremain, et al., and Miller, et al., showed a 100 percent and 96.8 percent union rate at a mean time of six weeks and eight weeks respectively. 4-7
Dr. Grambart is the foot and ankle surgeon for Carle Clinic Association, Division of Orthopedics in Champaign, Ill. He is a clinical instructor at the University of Illinois School of Medicine. Dr. Grambart is a Fellow of the American College of Foot and Ankle Surgeons.
Dr. Burks is a Fellow of the American College of Foot and Ankle Surgeons, and is board-certified in foot and ankle surgery. He is in private practice in Little Rock, Ark.