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Hallux valgus- Basal metatarsal osteotomy (opening wedge) using the Arthrex LPS open wedge system

    Overview

    Learn the Hallux valgus: Basal metatarsal osteotomy (opening wedge) using the Arthrex LPS open wedge system 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: Basal metatarsal osteotomy (opening wedge) using the Arthrex LPS open wedge system surgical procedure.
    The basal metatarsal osteotomy of the first ray is an operation for moderate to severe Hallux Valgus deformity which can be technically challenging.
    The choice of an opening wedge osteotomy (as demonstrated in this technique) avoids the shortening of the 1st Ray which can occur with the use of a closing wedge osteotomy, but careful soft tissue balancing is required with the opening wedge.
    Though the inter-metatarsal angle is well corrected (as long as an appropriately large size of open wedge plate is selected) inevitably the distal metatarsal articular angle (DMAA) is pushed into valgus which means almost always an Akin osteotomy is also required. This is also required to address pronation of the hallux which can be marked with larger deformities. Other procedures are always required to rebalance the soft tissues in particular a modified McBrides procedure and medial capsular plication and on occasion careful Z-lengthening of the extensor tendons to the Hallux.
    Alternate operations for severe deformities are commonly either corrective first MTP fusions or a Lapidus procedure.
    The Arthrex LPS open wedge plate is probably the lowest profile plate on the market and plate irritation is as a result rare. This version is non-locking and as such not well suited to softer bone (though a less low profile locking plate is available).


    Indications

    INDICATIONS:
    -The indication for a Basal metatarsal osteotomy is most commonly a moderate to severe Hallux Valgus deformity. Whatever type of osteotomy is used these are usually more involved and testing operations than the correction of mild or moderate deformity.
    -The Basal osteotomy of course does not need to be restricted to just larger deformities and most opening wedge plating systems will contain smaller sized open wedges for these cases.
    SYMPTOMS & ASSESSMENT:
    Patients with symptomatic Hallux Valgus will have pain predominantly from the medial eminence. Pain is classically when in shoe-wear (or more specifically tighter fitting shoe-wear) though will persist for a while when shoes have been removed.
    If there is a proportion of pain from the hallux independent of shoe-wear, or perhaps pain is actually reduced in shoe-wear despite a bunion being being present , then first Metatarso-phalangeal (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 Hallux Valgus with an arthritic joint. It should be understood that more minor degrees of 1st MTP osteoarthritis would not preclude using a Basal metatarsal osteotomy and preserving the 1st MTP joint with a debridement or cheilectomy as appropriate . There are 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 (see paper by Bock et in the results section).
    Pain from other areas of the forefoot should be specifically questioned about. A first ray defunctioned by Hallux Valgus may lead to transfer metatarsalgia from the 2nd or 3rd metatarsals and Mortons neuromas are a common forefoot pathology that may co-exist with a bunion.
    In examining the patient the range of movement of the 1st MTP joint 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 either to arthritis or abnormal joint alignment caused by the deformity.
    It is worth noting if pronation of the MTP joint is present. If this is significant an Akin osteotomy may be required to correct this element of the deformity. Also any significant Hallux Interphalangeus should be identified and correction also by Akin osteotomy considered. A definitive decision on this is usually made at the time of operation. 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(see operative technique).
    One should also make an assessment of the nature of the soft tissues, by how passively correctable the deformity is. Large deformities with stiff soft tissues are harder to correct than ones with lax soft tissues which will allow easy correction passively.
    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 are painful on direct plantar compression. A Mortons’ neuroma will often yield pain on compressing through the 2/3 or 3/4 web spaces and lesser toe deformities may impinge in shoe-wear dorsally or produce plantar metatarsal head pain. Associated deformities of the lesser toes should also be examined for and corrected if symptomatic.
    A rare condition 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 examination finding).
    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).
    In most cases whether to proceed with surgical treatment should be determined by the level of symptoms experienced by a patient.
    INVESTIGATION:
    Weight bearing AP & Lateral X-rays should be performed on all patients having surgery.
    The first question is whether there is significant arthritic change , to the extent that a fusion rather than an osteotomy should be considered.
    The 1/2 inter-metatarsal angle determines whether the deformity is mild , moderate or severe from the perspective of planning which type of osteotomy is likely to be required to produce an adequate correction of the deformity.
    As a rule of thumb if both sesamoids are “uncovered” and not underneath the first metatarsal head on an A-P X-Ray then it is a severe deformity. If using this means of assessment(and also if measuring the 1/2 inter-metatarsal angle) one catch to be aware of is that if all the metatarsals have a varus angulation then the 1/2 angle will not measure as being large even in a severe looking deformity (aesthetically) and also the 1st metatarsal may not sit “off” both sesamoids.
    When assessing the foot radiographically be wary of the distal metatarsal articular angle(DMAA). If this is significantly into valgus (in other words if the joint surface sits at a significant valgus angle relative to the long axis of the metatarsal) then a basal opening wedge osteotomy will further increase this aspect of the deformity (whilst concurrently reducing the inter-metatarsal angle) .This will make correction of the Hallux Valgus (HV) angle more challenging. As a minimum an Akin osteotomy under these circumstances (or the addition of a distal metatarsal osteotomy) is likely to be required. More comprehensive soft tissue releases involving the Extensor Hallucis Longus and Brevis tendons may also be required.
    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 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.
    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 other designs of basal osteotomy described , in particular cresentic , basal chevron and a laterally based closing wedge. The most straightforward technically is certainly the opening wedge described but appropriate implant choice is cruical. There are significant variations in terms of the bulk of the implant as well as whether the screws are locking or not.
    Any symptomatic arthritic change should make one consider a corrective fusion, whose effects can be equally dramatic with respect to deformity correction(see the imaging section for 1st MTP fusion). This is a considerably more straightforward operation. Even in the absence of arthritic change a corrective fusion is legitimate treatment for a severe Hallux Valgus deformity in an appropriate patient (see 1st MTP joint fusion technique).
    In the presence of a hyper-mobile 1st Metatarso-cuneiform joint one may also consider a Lapidus procedure.
    CONTRAINDICATIONS:
    In a symptomatic Pes Planus with 1st Metatarso-cuneiform hyper-mobility consider a Lapidus procedure instead.
    Conditions or medications effecting soft tissue or bone healing need to be optimised prior to surgery ( and smoking avoided or minimised post-surgery).
    Patients with impaired neurological function (in whom fusion is more reliable)
    Juvenile deformity with open growth plates
    In patients with Hallux Valgus and moderate to severe joint disease (degenerate or inflammatory) an MTP fusion is likely to be required.

    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 or inter-metatarsal )for analgesia
    High speed saw & wire driver
    Lambotts osteotomes
    On table X-ray to be available.

    Operation

    The initial steps are as for a scarf osteotomy, with a lateral release, medial approach to the metatarsophalangeal joint and removal of exostosis (1, which has already occurred in this case). The exostosis needs to be saved and used as graft into the opening wedge osteotomy site.
    With a severe deformity the medial capsule can become very attenuated and deficient. It needs to be carefully dissected during the exposure and preserved as its repair is a key part of stabilising the joint and maintaining correction at the MTP joint.
    The exposure needs to be just a little more proximal than for a Scarf osteotomy, revealing the full extent of the metatarsal flare (3). The chosen implant (a minimum of 5mm plate for larger intermetatarsal angles) is offered against the bone to plan the position of the osteotomy (2). One should plan the cut to allow as much of the plate to sit flush on the bone as possible. Avoid dorsal prominence of the plate in particular. The cut should also be placed so that the proximal screws to fix the plate do not breach the MTC joint.
    The Arthrex plate(shown) is very malleable which means that as the screws are driven home it will largely contour to the bone surface. It is also a very low profile and small implant (compared to some others). A big advantage is its very low profile and that it is rarely prominent even when used on small feet.
    The screw threads however do not anchor well into osteopenic bone though for this situation a locking version of the plate exists (though is not and this version in this technique is not a locking plate(though one does exist).

    A simple straight cut is performed with the saw(1) , the soft tissues being protected dorsally and plantarwards with Homans’ retractors.
    The cut should leave the deep lateral cortex intact but weakened and deformable. The best way to achieve this is by making lighter cuts of short duration once across to the lateral cortex. After each saw pass an osteotome can be inserted and an attempt made at levering open a medial gap.

    A set of three osteotomes are supplied to sequentially mobilise the basal osteotomy by tapping them consecutively into the osteotomy gap.

    The second osteotome gently hammered into place.

    No more osteotomes are required once the number three is reached. Sometimes only two osteotomes are required to produce enough mobility at the osteotomy site. A bit of very controlled levering is usually needed to mobilise the bone ends adequately.
    The net stage is insertion of the plate which can be a little fiddly. A second pair of hands to hold the osteotomy open( by “bending” the first ray through the cut ) are useful. Using a small Lambotts osteotome at the inferior margin of the osteotomy to lever it open whilst inserting the plate often works. Drilling a 1.6mm K wire into the distal metatarsal just beyond the osteotomy and using it as a joy-stick can also work. A small laminar spreader tends to get in the way of inserting the plate despite opening the gap well.
    It is important that when the plate is placed that it is not allowed to sit proud , in particular dorsally.
    The size of opening wedge chosen is always a best guess and should be related to the size of deformity and size of metatarsal. A 5mm open wedge plate is a good starting point.

    The 5mm plate here is seated well and not dorsally prominent.
    The screws are self tapping once they have been drilled. A fair gap has been created but can be filled with previously removed exostosis.
    A key step is to ensure that the distal metatarsal shaft once displaced is not allowed to dorsiflex from neutral (and if anything should be fractionally plantar-flexed) to avoid de-functioning the first ray.
    Bone quality can be variable and a locking plate option is a useful bail-out if required. This is a decision to make early on prior to drilling as there is not much space for alternate holes if these have already been made for a non-locking plate.
    As you will find out yourself when the lateral cortex fractures the whole osteotomy becomes very unstable and holding reduction whilst inserting the plate can be a real challenge.
    Avoid this happening in the first place of course. When it does (as on occasion it will) you may find it helpful to insert a stoutish K wire into the distal fragment and use it as a joystick to help control the reduction.
    If a self retaining retractor is in use remove it. This will allow some additional soft tissue slack which also will help.
    This situation, is perhaps more easily dealt with if using a locking plate. Lock the plate into the stable proximal fragment as a first step ignoring the mobile distal fragment. Next reduce the mobile distal fragment onto it and fix. You will need to be careful that the drilled locking hole does not move with respect to the plate between the time of drilling and the moment of screw insertion or the reduction may displace (or the bone fracture). Until this screw is “locked in” this remains possible as the distal side of the osteotomy will be highly mobile .

    The appearance of the osteotomy after placement of the exostosis(1) as bone graft.
    Often more of a gap is left and generally there is no absolute need for additional bone. An appropriate graft substitute can be helpful here and should be considered especially when using a larger opening wedge which leaves a larger gap or when little exostosis has been resected.

    Almost invariably an Akin osteotomy is also required (2) as the DMAA is worsened by the opening wedge(no matter where it starts), which increases the tendency for the MTP joint to deform into valgus.
    If the Akin osteotomy does not produce adequate correction (followed by an initial attempt at capsular closure ) then turn your attention to the great toe extensors which will be undoubtedly very tight & a deforming force.
    Try initially a careful (an adequately long) Z-lengthening of the Extensor Hallucis Longus (EHL) tendon. If this does not allow easy and stable correction of the MTP joint deformity then carefully Z-lengthen the Extensor Hallucis Brevis (EHB) tendon also.
    At this stage re-tension the medial capsule appropriately with a single stay suture and once the deformity is corrected re-suture carefully the two extensors back to a functional tension. Patients tend to notice weakness of the great toe extensor so this is important.
    There is frequently a significant amount of medial skin and capsular tissue that needs removal after correction of a severe Hallux Valgus deformity before final closure in layers of the approach.

    Note the clinically widened 1/2 inter-metatarsal angle which has been well reduced post operatively ,together with the normal alignment of the hallux.

    Note the clinically widened 1/2 inter-metatarsal angle which has been well reduced post operatively, together with the normal alignment of the hallux. The difference is marked between the clinical pre and post op pictures.
    These particular images also demonstrate very well the re-alignment of the EHL tendon, which is key for a stable reduction, from a laterally placed deforming deforming force on the left hand image to a stabilising one on the right hand image. Here the tendon is centralised with respect to the MTP joint.

    The effect upon the DMAA(distal metatarsal articular angle) of the opening wedge is understandably to push the articular surface of the metatarsal further into valgus (whilst of course correcting the inter-metatarsal angle).
    The DMAA is marked on both the pre and post operative images. Its deforming effect has been accommodated here by the use of an Akin osteotomy.

    A good example of the significant correction of the inter-metatarsal angle that is possible using an adequately sized opening wedge plate.
    An Akin osteotomy has also been performed and the 2nd toe has been inter-currently corrected.
    Again the DMAA has been worsened.

    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 they haven’t achieved adequate range through the joint.
    Kellers bandage/post operative splint for 4 weeks
    Dressings to continue 24/7 until all wounds dry.
    If the EHL has been lengthened then supportive dorsal taping to the hallux for a total of 8 weeks will be required to reduce the chance of the toe “dropping”.
    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 the post-op shoe
    I advise fit-flops, Uggs, wider fit shoes 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

    Proximal opening wedge metatarsal osteotomy for correction of moderate to severe hallux valgus deformities using a locking plate.
    Int Orthop 2013. 37(9) :1765-1770. Badekas A, Georgiannos D, Lampridis V, Bosbinas I.
    107 feet followed up for a mean of 4 years. The most common size of open wedge plate used was a 5mm one.
    Preop the mean IMA was 16 degrees(range 12-22 ) and mean Hallux Valgus angle was almost 40. Post-op the mean IMA was almost 12 degrees and mean Hallux Valgus angle was 12 degrees.
    Recurrence rate of 2%, non-union of 2% , infection rate of 3%, 4% required metalware removal.
    Basal closing wedge osteotomy for correction of Hallux Valgus and metatarsus primus varus
    Foot & Ankle Intl.1999. 20(3): 171-77. Trnka HJ et al
    42 patients with feet 60 operated feet were followed up for a minimum of 10 years
    Almost 90% rated their outcome as good or excellent and just over 70% rated the cosmesis similarly.
    Pre-op hallux valgus angle mean was almost 40 degrees and IMA mean 16 degrees
    Post-op mean hallux valgus angle was almost 20 and IMA almost 7 degrees


    Reference

    • orthoracle.com

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