Expert Insights On Performing The Akin Osteotomy
- Volume 23 - Issue 1 - January 2010
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Even with this data, determining the amount of bone to remove is often based on the surgeon’s judgment. If one does not remove enough bone, the great toe can remain abducted and if one removes too much of a wedge, this can result in a varus deformity. The variable is the intraoperative instability of the first metatarsophalangeal joint. This makes it difficult to determine if the amount of bone removed is enough or too much.
To reduce this potential source of error, I will align the joint, insert a temporary K-wire and extend it through the base of the proximal phalanx into the metatarsal head. Then balance the capsule and suture it for stability. Perform the Akin osteotomy by resecting the appropriate amount of bone and temporarily fixating it with another K-wire. If the position of the toe is satisfactory when the foot is loaded, proceed to fixate the osteotomy site and remove the K-wires. This technique gives a good idea of what you can expect to see postoperatively.
Why You Should Preserve The Lateral Hinge
Preserving the lateral hinge is paramount in performing the Akin procedure. The hinge provides a natural area of stability that complements the internal fixation. Avoidance of dissection laterally preserves the blood supply and ensures optimal healing.
Christensen determined that osteotomies with an intact hinge demonstrated superior stiffness in comparison to osteotomies without a hinge in first metatarsal osteotomies. Both groups had equal internal fixation.14 Boberg felt there was less chance of hinge failure when performing an oblique osteotomy as opposed to a transverse osteotomy.15
What About Monofilament Wire Or K-Wires For Fixation?
Although the great toe is not the primary weightbearing area of the foot, weightbearing forces occur through the great toe, especially at heel-off.16 This can cause an axial load across the hallux that displaces the distal portion of the proximal phalanx. The goal of fixation is to provide stability, prevent displacement and achieve appropriate healing. Fixation failure can result in postoperative pain, swelling, delayed healing, displacement and nonunion.
When it comes to the Akin osteotomy, surgeons have advocated many types of fixation, including tongue depressors, sutures, monofilament wire, Kirschner pins, staples and bone screws.
Monofilament wire. This type of fixation is probably the most common type surgeons use for the Akin osteotomy although they do not always use it correctly. Often surgeons insert 28-gauge wire in holes drilled only on the dorsal or dorsal medial aspect of the great toe. When the surgeon tightens the wire, it only compresses the dorsal medial surface of the osteotomy site. By itself, this fixation is not stable and does not resist axial load. Weightbearing results in dorsiflexion of the head of the proximal phalanx. Undoubtedly, this dorsal two-cortex technique is effective only if the intact lateral hinge remains intact.
If one uses monofilament wire, it should penetrate four cortices. Schlefman described a four-cortex horizontal wire loop technique for a distal Akin.10 Pass the wire from medial to lateral and then from lateral to medial prior to making the osteotomy. After retrieving the wire to the medial surface, perform the osteotomy, thin the cortex and tighten the wire.
Boberg advocated a four-cortex technique that used a vertical loop perpendicular to the plane of the osteotomy.15 He felt this would limit dorsiflexion of the distal phalanx. This technique also relies on an intact lateral hinge. Ideally, for greater stability, one should use another wire dorsal to plantar that is oriented 90 degrees to the first wire. Monofilament wire has the advantage of providing stability, has a low profile and does not need to be removed.