Is Arthrodesis The Answer For A Severely Deformed Ankle?
Dissecting the lateral incision should reveal the distal fibula. Although many techniques for ankle arthrodesis may preserve the fibula, it is often necessary to resect it not only to gain access to the joint, but also because it is a large factor preventing reduction of the deformity. Once you have resected the fibula at an angle, you can insert lamina spreaders into the joint for removal of the cartilaginous surfaces.
Although the currettage method of joint preparation is very effective, you usually cannot employ this method in the malaligned ankle. Joint resection and extensive planning are often needed to restore alignment.
When resecting articular surfaces, be sure to consider both the sagittal and frontal planes. Be careful to avoid injuring the anterior and the posterior-medial neurovascular structures. Blunt dissection can easily facilitate freeing of the soft tissues from the anterior distal aspect of the tibia. This lessens the chances of neurovascular injury.
Medially, you usually want to leave the malleolus intact. Although you can remove it to facilitate joint access, it can lead to significant medial displacement of the foot in relation to the leg. This results from the tendency of the surgeon to align the medial surface of the talus with the medial border of the tibia. If you leave the malleolus intact, it not only helps in appropriate positioning, but increases the contact area for fusion.
It is at this point that you must consider the transverse plane. Fifteen degrees of external rotation is commonly accepted as the norm for transverse position. Often, you can evaluate this prior to surgery and match the surgical site to the contralateral limb.
It’s also important to address the sagittal and frontal plane for optimum position. The foot should be at a 90-degree angle to the leg or very slightly plantarflexed. Excessive dorsiflexion will reduce the chances of the knee fully extending during gait and excessive plantarflexion will cause the knee to hyperextend. The hindfoot should be neutral to slight valgus.
Other Pertinent Pointers
I often employ a Steinman pin directly from the plantar surface of the calcaneus into the tibia for temporary (or permanent) fixation. (Even in the subtalar joint that is left intact following ankle arthrodesis, there is little chance of degenerative changes simply from pin placement. In reality, any arthrofibrosis or degeneration results from fusion of the ankle joint itself. In the severely deformed ankle, the subtalar joint is already involved and may be autofused.) This technique is used by many surgeons and allows you to place internal or external fixation.
Although you may have given much consideration to choosing appropriate fixation in the preoperative phase, be aware that you may have to modify or completely change the fixation intra-operatively in the severely deformed ankle. In many ankles, such as those affected by rheumatoid arthritis and Charcot, I have found external fixation to provide significant advantages over purely internal fixation. Again, the choice of fixation is dependent upon one’s experience level, the given procedure and whether it is right for the patient. Postoperative care will not usually differ from that of the lesser deformed ankle undergoing arthrodesis.
Arthrodesis of the severely deformed ankle presents a significant challenge to the podiatric foot and ankle surgeon. However, if this procedure is performed correctly, it can provide the patient with decreased pain and increased function.
Dr. Burks is a Fellow of the American College of Foot and Ankle Surgeons. He is board certified in foot surgery and reconstructive rearfoot and ankle surgery. Dr. Burks practices in Little Rock, Arkansas.