Proximal Phalangeal Osteotomy (Akin)

Abstract

In cases of mild residual hallux valgus following intraoperative correction or in patients who have hallux valgus interphalangeus, an Akin osteotomy is an effective procedure to correct either valgus or pronation deformity. This should not be routinely used as an isolated procedure in the absence of additional osteotomies or arthrodesis for correction of hallux valgus.

Key Words

Akin, hallux valgus interphalangeus, osteotomy, bunion

A commonly performed adjunctive procedure for correction of hallux valgus is an osteotomy of the proximal phalanx of the hallux that is performed in conjunction with other procedures. By itself, this procedure has few indications. When this osteotomy is performed alone, the incidence of recurrence of hallucal deformity is exceedingly high because the biomechanical deformity and imbalance around the metatarsophalangeal (MTP) joint is uncorrected. However, as an adjunctive procedure with other osteotomies for correction of hallux valgus, the closing wedge phalanx osteotomy’s outcome is predictable and reliable.

Although used predominantly for correction of symptomatic hallux valgus, this osteotomy is useful in conjunction with correction of a crossover second toe deformity, even when the hallux valgus is asymptomatic. The second toe is difficult if not impossible to realign if the hallux is abutting on it laterally, since there is no room to correct and position the toe without the hallux underriding the toe and causing recurrent deformity. In the elderly patient with second claw toe deformity secondary to hallux valgus, isolated Akin osteotomy in addition to correction of the second toe may be considered as opposed to a full reconstruction of the hallux deformity. Although long-term recurrence is likely, these patients are willing to wear accommodative shoes, and elimination of the second toe pain with minimal morbidity may be superior to a more formal reconstruction ( Fig. 3.1 ).

Correction of the mechanical axis of the hallux MTP joint is also important, for example, with an abnormal distal metatarsal articular angle. Correction of the MTP joint alignment abnormality with a biplanar osteotomy of the distal first metatarsal is preferable. However, with the addition of the phalangeal osteotomy, the hallux shortens slightly. As a result, tension on the extrinsic tendons decreases, and correction of the pronation is easier. Although the closing wedge phalanx osteotomy is of secondary importance, it does improve the cosmetic appearance of the toe. The phalangeal osteotomy is very useful to correct fixed pronation of the hallux. This deformity does not correct well with any osteotomy, and trying to pull the capsule using the capsulorrhaphy to correct the pronation will only increase tension on the joint and decrease range of motion, and is not to be recommended ( Fig. 3.2 ).

The traditional use of the phalangeal osteotomy is to function as an adjunctive procedure for the correction of hallux valgus. As discussed later, this osteotomy is performed in the metaphysis at the base of the proximal phalanx. However, a far more important use of the phalangeal osteotomy is the correction of hallux valgus interphalangeus (HVI) ( Figs. 3.3 and 3.4 ). Although HVI can be seen preoperatively, in some cases the deformity may become “unmasked” following metatarsal osteotomy or Lapidus procedure. With correction of the sesamoids and the rotational deformity of the MTP joint, the radiographic appearance of the phalanx will be altered. Therefore the surgeon should be prepared to perform an Akin osteotomy in all cases, as the deformity may not be noted until correction of the joint is complete. Other than an arthrodesis of the hallux interphalangeal (IP) joint, there is no method of correction other than an osteotomy through the distal portion of the proximal phalanx that will work.

The incision is made along the medial aspect of the proximal phalanx, extending from the capsule distally toward the IP joint, and the periosteum is split. The attachment of the capsule to the base of the proximal phalanx must be preserved to facilitate the capsulorrhaphy. After subperiosteal dissection, small retractors are inserted subcutaneously to expose the bone. Although rare, injury to the flexor hallucis longus (FHL) or the extensor hallucis longus (EHL) tendons from the oscillating saw has been reported and can be difficult to primarily repair, secondary to the soft tissue trauma. Therefore use of a Hohmann-type retractor is critical before making the osteotomy. Because supinating the hallux is usual, a biplanar osteotomy is generally performed, in addition to the closing wedge phalanx osteotomy. If fixation with suture is desired, two sets of pilot holes are now made on either side of the osteotomy with a Kirschner wire (K-wire). These are unicortical holes inserted at a 45-degree angle with respect to the plane of the phalanx. The proximal set is made in line with the medial aspect of the phalangeal shaft, and then the distal set is drilled more plantarward so that when the osteotomy is closed, the hallux is supinated and the two sets of holes line up with each other. The distal holes are approximately 2 mm inferior to the proximal holes ( Fig. 3.5 ).