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Hallux valgus- Chevron Osteotomy

    Overview

    Learn the Hallux valgus: Chevron 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: Chevron Osteotomy surgical procedure.
    Patients with symptomatic Hallux Valgus will have pain predominantly from the medial eminence (though of course not all patients are symptomatic). Pain is classically when in shoe-wear (or more specifically tighter fitting shoe-wear). Surgery in the majority of cases is indicated for pain.
    With regards to radiographic criteria a mild Hallux Valgus could be said to be a Hallux Valgus angle (the degree of lateral angulation of the hallux relative to the first ray ) of less than 2o degrees and an inter-metatarsal (IM) angle of less than 11 degrees. A moderate deformity displays a Hallux Valgus angle of 20 to 40 degrees and an Inter-metatarsal angle of 11-18 degrees. A severe deformity a Hallux Valgus angle in excess of 4o degrees and inter-metatarsal angle over 18 degrees.
    The Chevron osteotomy is a distal diaphyseal osteotomy which is used for correcting smaller Hallux Valgus deformities and is most successfully used to correct IM angles of less than 15 degrees.
    There is debate about the risk of avascular necrosis if the operation is combined with a formal open lateral release. A more limited transarticular lateral soft tissue release can be performed through the medial joint approach and this is usually required to mobilise the osteotomy adequately.



    Indications

    INDICATIONS:
    Mild Hallux Valgus deformity ( as defined by the inter metatarsal angle on weight bearing X-rays) with minimal associated arthritic change.
    The presence of an abnormal distal metatarsal articular angle (DMAA) with the above level of deformity
    SYMPTOMS & EXAMINATION:
    Patients with symptomatic Hallux Valgus will have pain predominantly from the medial eminence (though of course not all patients are symptomatic). Pain is classically when in shoe-wear (or more specifically tighter fitting shoe-wear). A rare variant of pain is localised numbness/pain from the medial border of the Hallux due to compression of the dorso-medial cutaneous nerve (which if present should be clearly documented as a pre-existing symptom ).
    If there is a proportion of pain independent of shoe-wear, or perhaps pain is actually reduced in shoe-wear despite a bunion being being present , then first metatarsophalangeal (MTP) arthritis may be present. Depending on its severity this may preclude an osteotomy , a 1st MTP fusion being a more predictable way of treating the combination of increased inter-metatarsal angle with an arthritic joint. It should be understood that more minor degrees of 1st MTP osteoarthritis would not preclude using a Chevron osteotomy. There a no absolutes and this is something for discussion with the patient in detail.
    Patients with 1st MTP arthritis in whom the joint is being preserved should be aware that the joint will likely be stiffer post-operatively and over a period of time their arthritis will likely progress. Hallux Valgus correction is not known to stop this risk.
    Examining the patient the range of movement should be assessed .There should be a full (same as the other side) range of pain-free MTP movement from the joint. If the range is reduced it may be due to arthritis or abnormal joint alignment caused by the deformity (though this is more an issue with the severer Hallux Valgus deformities where a Basal osteotomy is likely to be used).
    It is worth noting if pronation of the MTP joint is present. If significant an Akin osteotomy may be required to correct this. Also any significant Hallux Interphalangeus should be identified and correction also by Akin osteotomy considered. An Akin osteotomy may also be required if during capsular closure there is a tendency for the MTP joint to continue deviating into valgus despite a stay stitch in the medial capsule.
    One should also make an assessment of the quality of the soft tissues, by how passively correctable the deformity is. A stiff soft tissue envelope will likely need a greater effort in surgical correction and with a slack soft tissue envelope. With the latter it can be easy at the time of capsular closure to over-correct the deformity and produce a Hallux Varus.
    Other sources of pain from the forefoot should be actively looked for in every case (whether complained of or not). Common inter-current pathologies are transfer metatarsalgia (mainly from 2nd, 3rd and 4th metatarsal heads where callosities are often associated and may be painful on direct plantar compression) , a Mortons’ neuroma (which will yield pain on compressing through the 2/3 or 3/4 web spaces) and lesser toe deformities which may impinge in shoe-wear or produce plantar metatarsal head pain.
    Occasionally if the patient is asymptomatic from the perspective of pain they may still wish surgical correction and this should be discussed carefully with them if it is to be undertaken. Some female patients will be very embarrassed by the feet that they have inherited and developed . This may be to the extent that they avoid activities which require the exposure of the naked foot in public (such as swimming or beach activities) .If the pros & cons of treatment are explained and they are realistic about the recovery time and willing to engage in active rehabilitation post-operatively then I would deem surgery appropriate (and no different ethically than cosmetic surgery to other areas).
    INVESTIGATION:
    Plain X-Ray.
    Weight bearing AP & Lateral X-rays should be performed on all patients having surgery. It is not though a requirement to make the diagnosis necessarily.
    In assessing X-Rays the first question is whether there is significant arthritic change , to the extent that a fusion rather than an osteotomy should be considered. It should be borne in mind that arthritic change from the sesamo-phalangeal articulations is not well imaged on plain X-ray (though this may present with well localised plantar pain).
    The 1/2 inter-metatarsal angle measured on X-Ray determines whether the deformity is mild , moderate or severe (from the perspective of planning which type of surgical procedure is likely to be required to effect an adequate correction of the deformity). When measuring the inter-metatarsal angle beware that it may appear erroneously low if all the metatarsals have a varus angulation. A measured moderate deformity under these circumstances (defined by the inter-metatarsal angle) may actually require a Basal osteotomy to correct it adequately. The clinical appearance of the deformity on weight-bearing and resistance to easy passive correction are also (softer) indicators that a Basal osteotomy may be required in these cases.
    With regards to radiographic criteria a mild Hallux Valgus could be said to be a Hallux Valgus angle (the degree of lateral angulation of the hallux relative to the first ray ) of less than 2o degrees and an inter-metatarsal (IM) angle of less than 11 degrees. A moderate deformity displays a Hallux Valgus angle of 20 to 40 degrees and an Inter-metatarsal angle of 11-18 degrees. A severe deformity a Hallux Valgus angle in excess of 4o degrees and inter-metatarsal angle over 18 degrees.
    The Chevron is most successfully used to correct IM angles of less than 15 degrees
    The distal metatarsal articular angle should be measured, and if abnormal (angled to any notable extent into Valgus relative to the long axis of the Metatarsal shaft) then it is likely to require correction by differential movement of the osteotomy . In addition an Akin osteotomy may be needed as the Hallux is at greater risk of deviating into Valgus even after correction of the inter-metatarsal angle.
    The relative lengths of all the metatarsals should also be noted. If there is significant transfer metatarsalgia effecting the lesser toes toes (associated with a relatively short 1st metatarsal ) then Weils osteotomies are likely to be required to these metatarsals (see Weils osteotomy operative technique).
    Mri.
    Has a role if sesamoid pathology or early degenerative change is suspected pre-operatively.
    Ultrasound.
    Will be indicated to diagnose inter-current neuromas pre-operatively.
    NON-OPERATIVE ALTERNATIVES:
    Wide fitting shoe-wear.
    Silicone spacers and toe splints will separate the digits but not effect the forefoot width in any corrective way.
    In flat feet a medial arch orthotic may reduce medial column loading and reduce the forces through the medial eminence. They however add extra volume into a shoe and so may tighten shoe-wear fit and increase pain in this way.
    SURGICAL ALTERNATIVES:
    There are a number of alternate diaphyseal osteotomies.
    CONTRAINDICATIONS:
    In a symptomatic Pes Planus with 1st Metatarso-cuneiform hyper-mobility consider a Lapidus procedure instead.
    Vascular compromise
    Neurological patients (in whom fusion is more reliable)
    Juvenile deformity with open growth plates

    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

    Medial, midline skin incision and definition of the dorso-medial cutaneous nerve.

    A medial midline skin incision(1), extended at most to mid point of metatarsal and phalynx. Scissors dissect fat layer (2) looking to define & display dorso-medial cutaneous nerve(3).Sharp dissect capsule (4)in the midline, initially going deeply through it at the level of the MTP joint.

    Horizontal capsulotomy and dorsal capsular release.
    Once the MTP joint is open use a McDonalds (1) to lever up the capsule and put the remaining calsular attachments to the metatarsal head under tension .This aids their identification prior to closely dissecting them off the bone in one continuous layer.

    Limited plantar capsular release, preserving plantar vessels to metatarsal neck.
    Again by stretching the soft tissue envelope using the McDonalds the capsular attachment to the metatarsal head/neck area is identified (1). This should be left intact, cutting it risks avascular problems with the metatarsal head.
    All capsular attachments to the base of the proximal phalanx should also be left intact.

    The metatarsal head is “delivered” as the MTP joint is subluxed. Joint is inspected.
    The complete dorsal aspect of the metatarsal head (1) as well as medial aspect (2)should be exposed. Retraction is with the McDonalds and a Homans’ retractor. The head can now be inspected for any chondral lesions and these debrided/microfractured as required.

    The metatarsal head is “delivered” as the MTP joint is subluxed. Joint inspected.
    This is usually performed with a fairly minimal resection, the cut being made in the line of the metatarsal shaft.
    It is as much to produce a flat surface for the Chevron cut as anything.

    The medial eminence removed with a power saw.
    This demonstrates the small amount of bone removal required(1).
    This is largely to produce a flat surface that’s easier to cut into for the osteotomy.

    Mark the cut face of the metatarsal head prior to osteotomy.
    The bone of the midpoint of the cut metatarsal surface is marked with an indent made by the tip of a pair of forceps.


    The centrally placed indent which will be used to define the inferior limit of the osteotomy cuts.
    By adding this additional step it makes one less likely to wander too far plantar-wards with the power-saw cut. If the latter occurs the risk is one of fracture propagation directly into

    A vertical power saw cut is made across the metatarsal head/neck junction.
    The initial cut (1) is made vertically .It should not pass lower than the mark already made in the metatarsal head. It must pass out of the lateral aspect of the metatarsal head , the soft tissues being well retracted & protected by the Homans retractor.

    A second horizontal and plantar angulated osteotomy power saw cut is then made.
    The horizontal cut is angled plantarwards in a lateral direction so that when the osteotomised metatarsal head is moved laterally it is also directed into a functional, weight-bearing and plantar position.

    Completion of proximal extent of osteotomy cut may need to be with a transverse plantar located cut with osteotome or fine saw blade.
    With the vertical limb of the osteotomy completed this cut should not extend below the central point of the metatarsal head(2), as this risks propagating a fracture line through into the inferior aspect of the head during mobilisation of the osteotomy.
    The proximal and inferior aspect of the cut (1) may on occasion not exit through the plantar bone of the shaft, instead following the line of the metatarsal. A small additional vertical cut with a small saw blade may be required to complete the osteotomy if this occurs.
    Care should also be excercised to ensure that the proximal extent of the horizontal cut does not disrupt the plantar based vessels at the metatarsal neck.
    There are other designs of the chevron osteotomy that avoid this final step.

    Careful mobilisation of the osteotomy with Lambotts osteotomes and medial translation of head fragment.
    It is usual to need to “free up” the osteotomy once cut by tapping along the cuts with a fine Lambotts osteotome (not shown). Note the soft tissue attachments and blood supply to metatarsal head (2)are clearly still intact.
    If stubborn to move it may be necessary to release the soft tissues on the lateral aspect of the joint with a limited lateral release. This can easiest be done by going “over the top”of the metatarsal head and performing a limited sub-periosteal release. It can be done through the osteotomy too by carefully distracting through the vertical limb and incising the lateral capsule with a single vertical cut, but avoiding the plantar aspect and neurovascular bundle.
    It can also be useful to apply traction to the cut superior edge of the metatarsal with a sharp towel clip and counter pressure against the metatarsal head to aid its lateral displacement(not shown).

    Temporary fixation with reduction clamp and guide-wire insertion.
    Once mobilised the head fragment (2) can be directly translated and also rotated (if an abnormal DMAA is to be corrected). To achieve rotation through the osteotomy its dorsal and medial edges may need to be chamfered back. Space is tight for the reduction clamp(3) and smaller pointed tip clamps are also available.
    A guide-wire for screw fixation (1) is inserted. This should neither be positioned too far distally or laterally otherwise during over-drilling & screw insertion fracture may occur through this upper bone fragment and fixation may loosen.
    During over-drilling the guide-wire(not shown) one should ensure that the countersink on the proximal end of the drill has removed adequate bone to let the screw head seat down well. Visible bone should be removed by the counter-sink and if this doesn’t occur during direct in-line drilling work the dorsal cortex with the countersink using a circular motion of the drill after withdrawing it a small amount.
    Screw implantation should be done slowly and with attention being paid to the state of both the dorsal cortex and how well the osteotomy is compressing. If a fracture does occur through the hole this will happen slowly. As long as the screw has seated adequately to provide compression and is not prominent dorsally (and the construct is stable on stressing) then this should be left and the first 4-5 weeks of activity post-op kept minimal.
    If this is not the case it may be necessary to reposition another screw more proximally.

    Insertion of second guide wire stabilises the reduction and screw measurement is read off the initial wire which is then over-drilled.
    The reduction clamp (3) usually needs to be removed to allow access for over-drilling the guide wire. Prior to clamp removal I will often use a second parallel guide wire to maintain the reduction.
    This image demonstrates almost ¾ cm of translation which is as much as one is likely to wish to produce with a chevron osteotomy.
    The inferior aspect of the metatarsal head should be visualised to check the depth of the guide wire and a screw several mm shorter than measured wire inserted following over-drilling of the wire (again the depth being visually checked).
    The screw used will usually be a differential pitch type implant and the common lengths here are 16-20 mm. If as the screw is finally being driven home the osteotomy distracts (and its state during implant fixation should always be continually checked) then both the hole drilled has been incomplete (not through the plantar surface of the Metatarsal) and the screw has been too long for the hole drilled . Downsize the screw or re-drill the hole.

    Insertion of screw, removal of wires and chamfering of medial bone.
    After screw insertion the overhang of medial bone is removed
    It is also specifically worth removing the superior and medial edge of the cut bone which otherwise will leave a sharp edge.
    It is also not a bad thing to leave a little more inferior bone (seen here beneath the McDonalds retractor) to provide a small butress to medial seasamoid displacement/hallux varus.

    Remove of excess medial capsule and excise a V shaped plantar wedge of capsule.
    The capsular closure is as for Scarf osteotomy. Excess medial capsule is trimmed and then a plantar based V shaped wedge of capsule is excised (see next step).
    It is very important not to over-tighten the repair as over-correction and Hallux varus may easily result.
    This image shows a very well defined Abductor Hallucis tendon (1) blending into the medial capsule.

    Tighten the medial capsular closure and assess joint stability/tracking.
    For capsular closure initially a V shaped excision of capsule should occur from the inferior capsule as shown( this is a left foot not right as in the operation). Closure should then be with a 1 Vicryl suture running from plantar and proximal(1) to dorsal and distal(2) capsule. The suture is then sewn distal and plantar(3) before coming back proximally. It is tightened appropriately to ensure a stable soft tissue correction with full movement from the joint possible.

    A mild hallux valgus deformity, easily dealt with using a chevron osteotomy. The DMAA is broadly speaking normal.

    A complete reduction of the increased inter-metatarsal angle has been achieved using the chevron osteotomy. Here an Akin osteotomy has also been required. The joint looks over-reduced (even into slight varus). This is an immediate post-operative X-Ray with a bulky Kellers bandage. The next dressing applied (at 1 week post op) will need to correct this.

    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
    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 haven’t achieved adequate range.
    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 ,especially to medial wounds , to continue for the first month in 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. Swelling will be present for at least 4 months post-operatively. “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

    The Chevron Osteotomy for correction of Hallux Valgus: comparison after 2 and 5 year follow up.
    J Bone Joint Surg.2000. 82-A;1373-1378
    H.Trnka , A.Zembsch , M.E.Easley ,M.Salzer ,P.Ritschl ,M.S.Myerson.
    A cohort of 57 feet .
    IMA pre-op was 13 +/- 3 degrees & post-operatively 8+/- 3 degrees
    Outcome scores Excellent / good in over 8o% of patients
    Range of movement reduced slightly post-operatively by approximately 10 degrees
    Neither extent of correction nor results changed significantly over the study period
    Osteoarthritis developed in 14% by 2 years
    Hallux valgus and cartilage degeneration in the first metatarsophalageal joint.
    J Bone Joint Surg.2004.86-B;669-673
    P.Bock , K-H.Kristen , A.Kroner, A.Engel.
    265 MTP joints inspected at the time of Hallux valgus surgery in a group with a mean age of 54.2 years and with no symptoms or signs of Hallux Rigidus.
    Over 70% had some form of Cartilage lesion associated with the joint detected at the time of operation.

    Blood supply to the first metatarsal head and vessels at risk with a chevron osteotomy.
    J Bone Joint Surg.2007.89-A;2018-2022.
    J.J.G.Malal, J.Shaw-Dunn,C.S.Kumar.
    A dissection of 10 legs after injection of the arterial supply of the foot with ink-latex mixture.
    The aim was to provide guidance on the placement and orientation of osteotomy cuts with the objective of reducing the chance of injury of the blood supply to the metatarsal head.
    A long plantar limb is advised following identification of major inflow via the plantar-lateral aspect of the first metatarsal neck.

    Reference

    • orthoracle.com

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