Paul Hamilton and Sam Singh
SURGICAL MANAGEMENT
The primary indication for an Akin osteotomy is hallux valgus interphalangeus or in cases where residual hallux valgus causes pressure on the second toe on the load stimulation test. It is most commonly used to accompany a scarf or chevron osteotomy. An isolated Akin is contraindicated in the treatment of hallux valgus. We use a proximal medial closing wedge osteotomy that is fixed by a varisation screw (Depuy, Warsaw, IN).
The osteotomy is fashioned within metaphyseal cancellous bone, ensuring excellent cancellous healing. The osteotomy, by being close to the apex of the deformity at the interphalangeal joint, allows for more powerful correction.
TECHNIQUES
AKIN OSTEOTOMY
We describe an eight-step method for performing the Akin osteotomy.
The exposure is performed usually as an extension to the midline longitudinal incision from the metatarsal osteotomy. If performed as an isolated procedure, the exposure must allow visualization of the metatarsophalangeal joint proximally and the shaft of the proximal phalanx distally. The exposure of the shaft of the phalanx may require excision of overlying fatty tissue.
After dissecting directly onto bone, complete the exposure by periosteal elevation above and below the phalanx. Place two small pointed retractors above and below the phalanx to protect the extensor and flexor tendons (TECH FIG 1A).
Position a 1-mm Kirschner wire in the midportion of the phalanx in the sagittal plane approximately 3 mm distal to the phalangeal flare (TECH FIG 1B).
Traction on the big toe allows us to visualize the joint to ensure the wire is not intra-articular (TECH FIG 2A).
Remove the Kirschner wire and mark the hole (TECH FIG 2B).
TECH FIG 1 • A. Incision is made directly to bone with subperiosteal dissection above and below the proximal phalanx. B. Kirschner wire position on proximal phalanx parallel to phalangeal base.
TECH FIG 2 • A. The joint is checked to confirm the Kirschner wire has not penetrated the articular surface. B. The Kirschner wire position is marked.
TECH FIG 3 • A. The osteotomy is performed parallel to the phalangeal base. B. The second cut is performed to produce a small sliver of bone.
Make the proximal cut parallel to the phalangeal base (TECH FIG 3A). To maintain control of the osteotomy, score the lateral cortex but do not penetrate it with the saw blade, thus allowing it to act as a hinge. Perform the second osteotomy to produce a wafer of bone with the apex laterally (TECH FIG 3B). When removed it should look like a fine slice of lemon. Use direct pressure to close the wedge. This “greensticks” the intact but weakened lateral cortex.
TECH FIG 4 • The staple is marked with a pen.
Select the varisation staple (usually 8 mm; 10 mm in larger feet) and mark the tip of the distal end with a pen (TECH FIG 4).
Place the staple in position with the osteotomy compressed. Check that it is on the midportion of the phalanx in the sagittal plane (TECH FIG 5A). The distal staple leaves an ink mark; drill this mark with a 1-mm Kirschner wire (TECH FIG 5B) and then mark the hole. The position for the staple can then be identified by the two bone marks.
While maintaining compression, insert the staple in the predrilled holes. Check for stability of the fixation (TECH FIG 5C), and again axial traction confirms the staple is not in the joint.
Close the wound in layers with continuous Monocryl to skin, and apply a forefoot bandage to maintain the correction.
TECH FIG 5 • A. The osteotomy is compressed and the marked staple is placed in the correct position. B. The distal mark is then drilled with a Kirschner wire. C. The staple is inserted with the osteotomy compressed.
POSTOPERATIVE CARE
See Chapter FA-7 on scarf osteotomy.
OUTCOMES
The most common indication for an Akin osteotomy is in combination with a metatarsal osteotomy for hallux valgus. Outcomes are therefore reported together with satisfaction rates at between 85% and 95%.1,2,4 Very few studies have concentrated solely on the Akin.
COMPLICATIONS
Complications of this osteotomy are rare3 but can include nonunion, nerve damage, infection, displacement of the osteotomy, and overcorrection or undercorrection. Failure to recognize propagation of the lateral cortex may increase the risk of subsequent displacement.
REFERENCES
· Frey C, Jahss M, Kummer FJ. The Akin procedure: an analysis of results. Foot Ankle 1991;12:1–6.
· Garrido IM, Rubio ER, Bosch MN, et al. Scarf and Akin osteotomies for moderate and severe hallux valgus: clinical and radiographic results. Foot Ankle Surg 2008;14:194–203.
· Hammel E, Abi Chala ML, Wagner T. Complications of first ray osteotomies: a consecutive series of 475 feet with first metatarsal Scarf osteotomy and first phalanx osteotomy. Rev Chir Orthop Reparatrice Appar Mot 2007;93:710–719.
· Mitchell LA, Baxter DE. A Chevron-Akin double osteotomy for correction of hallux valgus. Foot Ankle 1991;12:7–14.