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Hallux valgus- Akin osteotomy

    Overview

    Learn the Hallux valgus: Akin osteotomy surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Hallux valgus: Akin osteotomy surgical procedure.
    The Akin osteotomy is a straight-forward , commonly performed and highly effective way to improve the alignment of the Hallux.
    Most often it is performed as part of a Hallux Valgus correction but on occasion it may be used to treat an isolated and symptomatic Hallux Interphalangeus deformity.

    Indications

    INDICATIONS.
    -Symptomatic Hallux Interphalangeus
    -As part of optimising correction during Hallux Valgus surgery
    -As an alternative to full Hallux Valgus correction
    SYMPTOMS & ASSESSMENT.
    Although Hallux Interphalangeus is not common it is rare for patients to present soley with an isolated and symptomatic Hallux Interphalangeus deformity. This will produce local discomfort in shoes from the dorso-medial aspect of the Inter-phalangeal joint of the Hallux. There may also be local pressure upon the second toe , with or without a deformity of the second toe. Such a case is shown in the clinical pictures at the end of the operative technique section.
    Most commonly an Akin is indicated during Hallux Valgus correction ,following the metatarsal osteotomy , when a capsular stay suture proves inadequate to prevent the MTP joint valgus deformity recurring or the MTP joint maltracks into valgus during testing of the joint range of movement. This may be due to inadequate correction of the Distal Metatarsal Articular Angle(DMAA) or simply due to the resistance of the deformity. It is required in most cases of an opening wedge Basal osteotomy (which worsens the DMAA) , frequently after a Scarf osteotomy and perhaps least frequently after a distal Chevron osteotomy.
    Also in the context of Hallux valgus surgery , even if there is no tendency to valgus drift of the toe a moderate or severe Interphalangeus can spoil the cosmetic effect of the correction . A small degree of interphalangeus however does leave a more naturalistic appearance to the toe and facilitate a narrower toe fitting to a shoe which needs to be considered if the Akin is being used purely for cosmesis.
    An Akin may be indicated when the primary issue is with a hammer or claw second toe which if corrected at the MTP level would have no space to sit down into , either due to a co-existant Hallux interphalangeus or an asymptomatic Hallux valgus.
    One variation on the theme of the Akin is the Moberg osteotomy , used to improve MTP dorsiflexion as part of joint debridement in the more sporting patient.
    In all cases the examination of the forefoot should include assessement for other common forefoot pathologies such as metatarsalgia, Mortons neuroma, degenerative change and Hallux Valgus.
    INVESTIGATION.
    X-Ray : An AP & lateral projection is adequate for the assessment of the Interphalangeus
    Additional imaging may be required according to other suspected pathologies.
    CONTRAINDICATIONS.
    No specific ones. Conditions which compromise soft tissue and bone healing need to be optimised.

    Setup

    General or Regional anaesthetic
    Antibiotics & LMW Heparin on induction
    Laminar flow theatre if available
    Ankle tourniquet
    Patient supine
    Pre/post operative Nerve block (popliteal and / or inter-metatarsal )for analgesia
    High speed saw & wire driver / drill
    Lambotts osteotomes

    Operation

    The incision for the Akin osteotomy is performed in the midline ,medially of the proximal phalanx. Distally it needs to extend close to the inter-phalangeal joint. It is usually run on in the line of the approach for hallux valgus correction. The Dorso-medial cutaneous nerve needs to be identified in the proximal part of the wound and mobilised if this is part of a Hallux Valgus correction. This may sometimes inconveniently cross from dorsal to a more plantar position.
    A subperiosteal dissection is needed to expose the proximal half of the proximal phalanx. The flexor & extensor tendons should be carefully defined to allow a Homans retractor to be placed both plantarwards and dorsally(3) to elevate them clear of the bone.
    The MTP capsular attachments to the base of the proximal phalanx (1,4) should be left attached during this subperiosteal dissection . This allows a robust capsular correction during closure. This is a key element of any Hallux Vagus correction, as seen here with a scarf osteotomy,(2).
    Even if not being performed as part of a Hallux Valgus correction the capsule still needs to be closed under appropriate tension and its attachments to the base of the proximal phalanx should always be left intact.

    The staples are on most sets are 8 and 10 mm widths and a straight(seen here) as well as an oblique profile staple. The depth of the staples are all the same. The size required is determined by offering the staple against the phalanx.
    Staples are only one way to fix the osteotomy. A single mini-fragment oblique screw could also be used and some describe the use of threaded K-wires or intra-osseous sutures.

    The position for the Akin Osteotomy should ideally be within the metaphyseal flare at the base of the proximal phalanx(3). However it should be remembered that the articular surface of the phalanx is relatively concave. Enough bone therefore needs to be left proximally to ensure that the fixing staple does not breach the joint. It is not uncommon to place the cut closer to the metaphyseal/diaphyseal junction to accommodate this need.
    A smaller saw blade (narrower, thinner and shorter) than is used for a 1st metatarsal osteotomy will usually be required.
    The saw should be angled at right angles to the long axis of the bone and kept in the midline of the bone when cutting from medial to lateral. Too much dorsal or plantar angulation risks injuring the Flexor and extensor tendons (though the Homans retractors are minimising the risk).
    Once the far cortex (and lateral resistance) is reached smaller ,probing cuts should be made with the saw, the objective being to weaken rather than fully divide the lateral cortex.

    In Akin terms this is a fairly large wedge and is being used for a very large correction. The saw cut by itself , without any wedge , will remove bone. It is straight forward to remove more bone if required so better to start small with the wedge unless a large deformity is being corrected.
    A Lambotts osteotome is used to remove the medial wedge(2).

    For the osteotomy to be stable (which is preferable) a small proportion of the lateral cortex should be left intact .Probing cuts are made with the saw to avoid complete division of the lateral cortex but rather to weaken it. Regular attempts at correcting the toe through the osteotomy should then be made
    Care should also be taken to ensure that the lateral aspects of the osteotomy (both superiorly and inferiorly) are cut back to smooth surfaces without unevenness which could stop the osteotomy closing adequately.

    With the medial wedge removed and the osteotomy closed there should be good bone to bone contact.
    If the osteotomy fails to close then the points to re-inspect are the dorsal and plantar cortices to ensure they have been cut symmetrically without any areas of unevenness which will prevent good bone to bone contact at the osteotomy site.

    The varisation staple is mounted in its holder ready to be impacted.
    This can also easily (perhaps more easily) be inserted simply by being held in a needle holding forceps.
    The staple is offered up against the osteotomy and a useful additional step is to pre-drill holes for it with a 1mm K-wire.
    It is important to be careful of the direction of drilling. The staple needs to be directed away from the joint surface and therefore angled distally.

    The varisation staple has been impacted. It is important during this manoeuvre that the osteotomy is held compressed by an assistant. If the bone is hard it can be useful to pre-drill one or both of the entry points before impacting the staple with a 1mm K wire.
    The mid-point (in the saggittal plane)of the phalanx is chosen for fixation. The osteotomy should be stressed after implantation of the staple to ensure that fixation with a single staple is adequate(which it usually is). If still mobile a second staple can be added as additional fixation.
    The joint should be checked visually to ensure it has not been breached with the staple.
    Alternative forms of fixation are K-wires , simple bone sutures and screws .

    Pictures showing the appearance of the hallux before and after an Akin osteotomy.
    This is an unusual case where the sole pathology is a symptomatic Hallux Interphalangeus.

    This is again a severe hallux interphalangeus deformity. The deformity here clearly lies at the distal articular surface of the proximal phalanx.
    The X-rays show it is well corrected by removal of the medially based wedge of the Akin osteotomy. It is fixed with a varisation staple.

    This is a less severe hallux interphalangeus deformity.
    This is case where the issue is one of the second toe deformity which needs space to sit down into which is prevented by a combination of a mild and asymptomatic Hallux Valgus as well as the Hallux Interphalangeus.
    The X-rays show it is well corrected by removal of the medially based wedge of the Akin osteotomy.It is fixed in this case with a small compression staple .

    Post Operative

    Day-case or overnight stay
    LMW Heparin 2 weeks
    Weight bear using post operative shoe for 4 weeks
    Crutches likely required 1-2 weeks
    Imaging is by plain X-ray immediately post-operatively and at 4 weeks minimum.
    Despite care being taken re the staple may appear on plain X-ray angled into the joint. If there is any doubt then a CT of this area is indicated and early staple removal can be performed after bone union.
    Patient taught self-mobilisation of MTP from 1 week post op, both active and passive. A thera-band is useful for this .The key is achieving dorsi-flexion early. My routine is to suggest 20 -30 cycles of plantar/dorsi-flexion using & against the thera-band three times per day. Physio supervision from 4 weeks if havent achieved adequate range. If the Akin has been performed in isolation and the 1st MTP joint has not been opened then joint stiffness is not much of a risk.
    Kellers bandage/post operative splint for 4 weeks
    Dressings to continue 24/7 until all wounds dry
    From 4 weeks the patients should cleanse the foot twice a day, once in a salt water bath and once by bathing/showering
    Dressings , to medial wound , to continue for the first month once returned to normal shoe-wear.
    Appropriate shoe-wear fit is vital in the first month or so after post-op shoe
    I advise fit-flops , Uggs , wider fits or open sandals. Stiffer Heels ( platform or wedge ) are encouraged in women , from when comfortable , to promote MTP dorsi-flexion.
    Patients may static bike & swim from 4 weeks , Cross-train from 6 weeks and re-start light jogging on treadmill from 9 weeks .

    Recommended Reading

    A Chevron-Akin double osteotomy for correction of Hallux Valgus.
    Foot & Ankle Intl. 12. 1. 1991
    L A Mitchell, D E Baxter.
    24 feet were followed up for a mean of over 2 years. The mean pre-op Hallux Valgus angle of 27 Degrees was improved by a mean of 14 degrees. Patient satisfaction rates of 95% .
    2 patients suffered degenerative change due to intra-articular extension of the Akin osteotomy.
    Clinical outcome after Chevron–Akin double osteotomy versus isolated Chevron procedure: a prospective matched group analysis
    Archives of Orthopaedic and trauma surgery .2011.132. 1. 9-13
    P Lechler ,C Feldmann, F X Kock, J Schaumberger ,J Grifka, M Handel.
    72 patients with mild-to-moderate hallux valgus. 46 patients were treated with a Chevron ,the group having a mean hallux valgus angle of 27° .26 patients were treated with both Chevron and akin with a mean hallux valgus angle of 32°.
    Outcomes were assessed at a mean of 1.37 years for the Chevron (where the mean Hallux Valgus angle improved by 10.6 degrees) and 1.04 years for the Chevron and Akin (where the improvement was by 17.5 degrees mean). Slightly higher patient satisfaction in the combined osteotomy group.

    Reference

    • orthoracle.com

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