Mastering The Akin Osteotomy
One should not perform an isolated Akin to correct for a bunion deformity when there is significant medial deviation of the first metatarsal (metatarsus primus adductus), meaning an “increased” intermetatarsal angle. Performing an isolated Akin in this circumstance would be a considered a cheater’s Akin, especially with larger intermetatarsal angles. Similarly, adding a McBride (exostectomy and adductor release) to an Akin in these same circumstances doesn’t particularly justify the combination procedures. Of course, there are clinical situations (age, weightbearing requirements, bone stock, etc.) in which surgeons utilize these procedures but, in general, one should avoid the cheater’s Akin as a primary means of correction.
When To Add An Adjunctive Akin
The main goal of bunion surgery, from a positional standpoint, is to realign the first metatarsophalangeal joint (MPJ). This means creating a congruent joint where the midline of the osseous structures crosses the midline of the joint. With realignment of the first ray (and the cartilage on the first metatarsophalangeal joint), the weightbearing forces should pass through or near the center of the joint. This requires the big toe to be relatively well aligned with the underlying joint.
Many patients, especially women, seem to want the big toe to be perfectly straight. In my experience, a perfectly straight big toe does not function as well as a toe that is slightly abducted. Also, surgeons need to consider the spacing of the toes in the perspective of the entire foot to balance the overall “look” of the foot. It is my opinion that balancing the big toe to the foot is akin to balancing the nose to the face.
One can add the Akin procedure to a distal metatarsal osteotomy bunionectomy and/or a Lapidus bunionectomy.3,4
Unless there is obvious intrinsic deformity of the proximal phalanx, one should consider the Akin after performing the metatarsal correction. If the toe is still deviated (provided the metatarsal correction was adequate), then perform the Akin procedure. Keep in mind that one can achieve additional positional correction with capsule closure of the metatarsophalangeal joint.
Should You Perform A Proximal, Midshaft Or Distal Akin?
Theoretically, the surgeon would determine the location of where to perform the Akin procedure by identifying where the level of deformity is located within the proximal phalanx. Accomplish this by drawing a line bisecting the medullary shaft and compare that to a line that is perpendicular to the joint line of the articular side of the phalanx. The three options are: proximal, midshaft or distal.
In the rare exception of a severe intrinsic deformity of the hallux at the distal or proximal side, it is my experience that a midshaft oblique osteotomy that extends into a metaphysis is the best method of correction. In most cases, the osteotomy is an adjunct to the bunion correction so theoretically, extreme degrees of deformity correction are not necessary and center of rotation of angulation (CORA) corrections of such a small bone are unnecessary in clinical practice.
Most commonly, surgeons will perform wedge osteotomies of the proximal phalanx of the hallux with a lateral hinge. The benefits of the hinge are to act a single point of fixation when one combines this with another fixation source (i.e., screw, wire, staple). Through and through osteotomies can be beneficial to “dial” in the correction when the surgeon performs these in the transverse plane. Intraoperative fluoroscopy is extremely helpful to assess that the first MPJ and the hallux interphalangeal joints are parallel.
A Step-By-Step Guide To Effective Fixation For An Akin
There are several methods to fixate an Akin osteotomy and one can typically determine the best method by the orientation and location of the osteotomy.5