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Hallux valgus- Basal osteotomy using Arthrex Low Profile Locking Proximal Opening Wedge Osteotomy Plate

    Overview

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    Learn the Hallux valgus: Basal osteotomy using Arthrex Low Profile Locking Proximal Opening Wedge Osteotomy Plate 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 osteotomy using Arthrex Low Profile Locking Proximal Opening Wedge Osteotomy Plate surgical procedure.
    A basal metatarsal osteotomy of the first ray is an operation for moderate to severe Hallux Valgus deformity, and most commonly is either a medially based opening wedge or a laterally based closing wedge. Less commonly performed, and more technically challenging designs of osteotomy also exist, in particular the basal chevron and the cresentic basal osteotomy.
    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 angulated more into valgus which means almost always an Akin osteotomy, or distal metatarsal osteotomy, is also required. An Akin is often 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 (in common with most operations for Hallux Valgus correction) and on occasion careful Z-lengthening of the extensor tendons to the hallux.
    Some Surgeons will routinely combine a basal osteotomy with a distal metatarsal osteotomy to correct severe deformity, though I have not found the need if using the other techniques described.
    Alternate operations used for severe deformities are commonly either a corrective first MTP fusion or a Lapidus procedure, or in some peoples hands a Scarf osteotomy.
    Readers will also find these other OrthOracle surgical techniques give useful, alternative perspectives Scarf osteotomy , Lapidus fusion using the I.O. Fix implant (Extremity Medical) , First MTP Fusion :Coughlin reamer preparation and Orthosolutions Cannulated 4mm screws. ,First MTP Fusion-Crossed screws technique. First MTP Fusion (using Stryker Anchorage MTP arthrodesis plate )for Hallux Varus .

    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 procedures than the when correcting 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 producing a more predictable outcome with the combination of Hallux Valgus and 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. Arthritic symptoms if present may be exacerbated by the realignment of the MTP joint, on occasion severely.
    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 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 first thing to do is look at the weight-bearing appearance of the foot, which gives the most valid way of assessing the size of the deformity.
    In my own practice 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 to arthritis in which case a fusion procedure may be a more appropriate choice. Equally, abnormal joint alignment caused by the deformity may limit the range of an otherwise normal joint in which case a basal osteotomy
    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 Hallux Valgus 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.

    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 should 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 – 1


    On clinical assessment this appears a moderate to severe Hallux Valgus deformity.
    I make this assessment by looking at the line of the first metatarsal and referencing this to where I estimate the second metatarsal sits, in line with the second toe. In practical terms though the decision on degree of deformity is always made with the patient weightbearing.
    There is the starting of some under riding on the 2nd toe which has a minor deformity associated with it. There is little if any pronation of the great toe.

    The weight-bearing AP view does not show both sesamoids uncovered, though the DMAA already sits with a degree of valgus angulation.

    A more severe Hallux Valgus deformity, clearly demonstrating pronation of the hallux and more significant under-riding of the 2nd toe.

    The first step operatively, as with most hallux valgus procedures, is a modified McBride’s procedure.A sandbag is usually placed usefully under the ipsilateral buttock, to rotate the foot internally so that it sits at right-angles to the table surface. This position provides easiest access for the lateral release, which is the first step of the operation.
    The incision is placed in the first webspace but before the incision is made it is a useful exercise to gauge the tightness of the soft tissues by attempting correction of the hallux into a neutral position.
    Even with a reasonable degree of force applied to the toe there remains here a quite persistent hallux valgus here.

    I normally centre the first webspace incision just to the lateral side of the 1st MTP joint. Positioned like this it is more straightforward to get access to the joint and with less dissection required.
    On this occasion however I am centring the incision midway between the 1st & 2nd MTP joints. The 2nd toe deformity also requires correction and by using a more midline incision adequate access to both joints is possible through the one dorsal incision.

    A relatively short skin incision can be used and this should be made at the level of the 1st MTP joint in the first web space.A very useful instrument to use at this stage is a small West’s type retractor as shown here. Once through the skin there is a good fat layer and this has already been blunt dissected away here, partly with scissors and partly with a dry swab, to reveal the underlying fascia over the 1st dorsal interosseous muscle.

    A knife is used to incise longitudinally the fascia overlying the fisrt dorsal imterosseous muscle, the fat having been blunt dissected away. Once through this a MacDonald’s or similar instrument can be used to move laterally the first dorsal interosseous (which is what is occurring in this image) to reveal the lateral aspects of the 1st metatarsal head and 1st MTP joint.

    A horizontal capsulotomy is made in the first web space, the object being to site this just above the lateral sesamoid.
    With a severe hallux valgus deformity sometimes both sesamoids can sit within the 1/2 intermetatarsal space and if this is the case the lateral sesamoid may sit fairly high up the side of the 1st metatarsal head.
    Once through the capsule with the capsulotomy there should be synovial fluid seen and it should be easy then to put a blunt instrument such as MacDonald’s into the joint and above the sesamoid to confirm the correct level is being incised. If this is not the case then choose a different spot, slightly higher or slightly lower and repeat a small horizontal capsulotomy. This is extended along the length of the sesamoid and it is useful to put a MacDonald’s on top of the sesamoid whilst dissecting the capsule off it.

    The proximal extent of this capsular release involves dissecting the abductor hallucis from its attachment to the sesamoid. This sharp dissection should not go beneath the level of the sesamoid as the plantar digital nerve does not sit far from here.
    At the distal extent of the sesamoid a vertical capsular incision is normally required to allow adequate mobilisation of the MTP joint. Before making this vertical capsular incision it is worth seeing if the MTP joint will now easily correct beyond a neutral position and certainly out of hallux valgus.
    In making this vertical capsular incision at the level of the MTP joint, it should be borne in mind that with a severe hallux valgus deformity often the extensor tendons are subluxed laterally and these are liable to be cut inadvertently if one wanders too far superiorly with this vertical capsular incision.
    For a clearer visual illustration of the steps involved in a modified McBride’s procedure refer to Lateral MTP joint release ( modified McBrides procedure)

    With the releases around the lateral sesamoid made, the joint is inspected by distraction through the sesamoid using a McDonalds as shown here.

    Following adequate release on the 1st MTP joint is easy to correct to neutral and should easily go beyond this as demonstrated in this slide.
    The first webspace incision can at this stage be closed using a 2.0 vicryl and 3.0 vicryl if no further work is required to the 2nd MTP joint.


    Attention is now turned to the medial aspect of the foot.
    Any sandbag that has been placed beneath the buttock to correct external rotation of the leg can now be removed. Having the foot sitting in a degree of external rotation is helpful when accessing the medial aspect of the foot.

    The longitudinal medial skin incision will be made in a midline position, centred halfway between the superior and inferior aspects of the 1st metatarsal and proximal phalanx of the hallux.It is useful for an assistant to hold the big toe in a corrected and neutral position when the skin incision is being made.

    Once through the skin fine tenotomy scissors are used to dissect the fat layer and in particular to identify the dorsomedial cutaneous nerve, and allow its dorsal mobilisation and avoidance.This sits somewhere usually in the dorsal aspect of the dissection and can be seen here with a small dissecting blade being used to further mobilise it from the underlying capsule. It is important that this is done under direct vision and a further manoeuvre which assists is putting the dorsal soft tissue envelope under some tension by lifting it which has been done here with Adson’s toothed forceps.

    A horizontal capsulotomy is made through the medial aspect of the 1st MTP joint.
    Note again that the joint is being held in a corrected position whilst this is being done.
    Care should be taken when extending this deep incision proximally as the incision converges towards the dorsomedial cutaneous nerve

    Once the joint is open a MacDonald’s retractor is placed dorsally beneath the capsule and into the joint to put the joint capsule under tension which assists its release off its metatarsal head (proximal) attachments, superiorly, laterally and inferiorly.The first stage is a dorsal release and the capsule is carefully subperiosteally peeled all the way from this medial incision to the lateral aspect of the 1st metatarsal head (this stage is not shown).

    The MacDonald’s retractor is then placed beneath the metatarsal head and again the capsule placed under tension to assist its careful dissection off it’s metatarsal attachment.
    It is important in this step that the fat attached to the plantar aspect of the metatarsal head neck area is not incised and released. as this contains the blood supply to the metatarsal head. Releasing this is associated with a risk of developing avascular necrosis of the metatarsal head post-operatively.

    Once the capsule has been adequately released it should be straightforward to “deliver” the metatarsal head for complete inspection. The toe itself is subluxed laterally.
    It is an important step to inspect in particular for evidence of degenerative change and chondral lesions. If there are any loose chondral flaps these should be dissected back to a stable remnant and consideration given to microfracture the defect with a small 1mm k-wire.
    There is a recognised instance of post-surgical development of degenerative change within the 1st MTP joint and it is worth informing the patient immediately post-operatively if there has been some evidence of degenerative change seen at the time of surgical treatment.
    What is also worth noting on this slide is the clear demarcation between the 1st metatarsal head and the regional eminence.
    The next step is to resect the medial eminence. My own practice is whenever doing this to leave a small ridge of medial eminence still present, in particular in it’s plantar aspect. My reasoning is that a small ridge here provides some bony buttress against the tibial sesamoid to potentially minimise the risk of medial subluxation of the sesamoids post-surgery and developing post-surgical hallux varus. I don’t have any evidence to base this on but it is a small thing to do and potentially has value.

    Two Homans retractors are used, one to the plantar aspect of the MTP joint and the other to the lateral aspect of the first metatarsal head to project the local soft tissue.The medial eminence is resected using an appropriate power saw. Ideally this should have a small arc of travel so that it is easy to control the cut precisely. It is also important that the blade is relatively thin.


    The medial eminence is resected using an appropriate power saw. Following resection it is possible here just to see the slight ridge of medial eminence still present.

    A V-shaped section of capsule needs to be removed from the inferior capsular flap.This can occur either now or later just prior to closure.
    It needs to be approximately ½ cm in terms of the maximum base dimensions and it’s apex should be well above the sesamoid.

    The longitudinal skin incision is extended proximally. Subperiosteal dissection is used at the base of the 1st metatarsal, in particular it’s key to identify the location of the 1st MTC (Lisfranc) joint (1).Attention is now turned to the proximal aspect of the 1st metatarsal.
    It is possible to perform this operation with two separate longitudinal incisions. One dealing with the 1st MTP joint and one the basal aspect of the first ray. In my experience however these usually end up being so close together that there is little advantage in trying to perform the operation through 2 incisions.
    The objective is exposure of the metatarsal to allow visualisation of the appropriate position to make the osteotomy. There is usually a slight ridge and then indentation at the level of the joint and further clues to its exact location are given by moving the base of the metatarsal and looking for the point of articulation with the medial cuneiform.
    Assistance of identification of the base of the metatarsal is also given by the fact that the metaphyseal bone “flares” at this point. There are also longitudinal periosteal fibres here known as sharpeys fibre which guide the anatomical identification.

    The location of the plantar aspect of the 1st metatarsal base is confirmed by sliding a small Lambotts osteotome and thus also creating a channel for the homans protractors which will keep the soft tissue away from the power saw used imminently.

    I choose the Arthrex locking basal plate by estimating the size of the opening wedge box required. Most severe hallux valgus deformities require a 5mm to 6mm opening wedge. There is also a trial wedge on the set which can be inserted into the osteotomy once it has been made, to better estimate the size of plate required. The issue with choosing the plate after the osteotomy has been made is that the plate can’t be used to assist with appropriate osteotomy placement
    If one is using the plate for smaller deformities a 4mm width of box may suffice. The larger the opening wedge used the greater the degree of varus angulation of the distal 1st metatarsal shaft and therefore the greater the degree of uniplanar correction achieved.
    For each mm of wedge approximately 3 degrees of correction of the inter-metatarsal angle can be expected.
    It should also be remembered that the more correction there is the more the distal metatarsal articular angle is placed into valgus which produces a deforming vector at the MTP joint. A further effect is the tightening of the medial soft tissue envelope the greater the size of wedge used.

    This shows the dimensions of the 5.5mm opening wedge plate.
    I tend to use a 5mm-6mm plate for most deformity but on occasion for a smaller or more flexible deformity will use a 4mm plate.
    The Arthrex basal plates in fact come with a range from 2mm to 7mm.
    Each mm of wedge can be expected to result in 3 degrees of correction with the plate appropriately positioned.
    The locking screws have a 3mm diameter.

    Operation – 2

    The kit required from the first tray is:
    Drill
    Locking guide
    Depth gauge
    Screw driver shaft

    The kit required from the second tray is:
    Mini joint distractor A
    BB tack B
    Trial wedge (not shown)
    Screw driver handle C

    The basal plate is offered up to the metatarsal initially, the purpose of this being to plan, and mark, were the osteotomy will sit.The location of the osteotomy should be in metaphyseal bone (which heals relatively rapidly) or the metaphyseal/diaphyseal junction.
    The proximal part of the plate also needs to be located distally enough to ensure that the proximal screws do not breach the 1st MTC joint.

    Here the plate is appropriately located. The 1st MTC joint can be clearly seen proximal to the plate (1).
    A knife is being used to mark the position of the osteotomy which is being made at the midpoint of the box section of the plate.
    Note, the Arthrex official technique involves estimating the position for the osteotomy cut without the plate and then inserting a trial wedge to determine the box size before choosing the appropriate implant.

    Homans retractors (1) have been placed superiorly and inferiorly to elevate the soft tissues away from the osteotomy cut. An appropriately sized blade of narrow dimensions (10mm width by 2mm thickness) is used to make the osteotomy.
    This is a critical step in the operation and needs to be concentrated on. Before starting to cut one should be clear on the orientation of the cut. The long axis of the metatarsal needs to be identified and the saw cut should be at 90 degrees to this long axis.
    In making the saw cut the objective is also to leave some of the lateral cortex intact, which provides innate stability to the osteotomy as it is opened. If one cuts all the way through then what should be a straightforward step in the operation becomes unnecessarily problematic for the surgeon.
    Probing cuts should be made once 50% of the osteotomy has been completed. One should also pay attention to the superior and inferior aspects of the osteotomy to make sure that as one is progressing across the whole width of the metatarsal. These aspects of the bone are also routinely divided and these parts of the saw cuts need to be directly visualised to minimise the chance of damaging the immediately adjacent soft tissues.
    Once one has made contact with the far, lateral cortex, my recommendation is that the saw blade is removed and manual pressure is applied at the level of the MTP joint to identify whether there is some mobility at the osteotomy site.


    With the saw blade removed it should be possible to demonstrate some movement at the osteotomy site at this stage, though not full required movement.
    Pressure on the metatarsal neck/head area (1) will give a degree of lever arm advantage and allow movement at the osteotomy, if there is any to be seen.
    Once there is some movement inducible here by valgus pressure being applied to the MTP joint this is when to stop cutting with a saw and to procedure to the next stage of inserting osteotomes to gradually widen the osteotomy.

    There are three osteotomes which are sequentially introduced into the osteotomy gap. They should be gently tapped in using a toffee hammer, into the central part of the osteotomy.
    These osteotomes come on the set. Here the first two have already been inserted.

    The third osteotome is inserted between the other two, I tend to make the third osteotome the smallest of the three. The other two osteotomes have broader surface to them and this technique seems to work well.

    Once the central osteotome has been tapped home adequately the other two osteotomes are used to gently distract the osteotomy site.One should note slightly more controlled movement at the site than was present previously
    Too much distraction risks fracturing lateral cortex and should be avoided.

    It is not bad practice to walk an osteotome around the superior and inferior aspect of the osteotomy, gently tapping.
    You should be also looking to make a judgement in terms of how far the osteotome is proceeding into the metatarsal and this distance should be broadly comparable both to the superior and the inferior extent of the osteotomy.

    It is not bad practice to walk an osteotome around the superior and inferior aspect of the osteotomy, gently tapping.
    You should be also looking to make a judgement in terms of how far the osteotome is proceeding into the metatarsal and this distance should be broadly comparable both to the superior and the inferior extent of the osteotomy.
    Enough of a bone cut has been made when the osteotomy moves relatively easily medio-laterally but is axially stable and closes acurately medially when not loaded.

    Before the osteotomy is definitively displaced and the plate inserted, I would suggest getting the chosen plates and the locking drill guide assembled and also mounting the appropriate drill bit and also having the osteotomes and screwdriver to hand.


    Screw the drill guide into a proximal hole on the plate, to assist with plate insertion.This needs to be accurately done, or the hole drilled will not allow the head of the locking screw to
    The reason for assembling all the tools required for plate insertion and fixation is that one wants to be able to proceed rapidly with this step, with a minimum of movement and fiddling around with the osteotomy.
    The osteotomy remains at risk of breaking until the plate is well fixed. If the osteotomy does break during insertion again this destabilises the situation and is best avoided.


    There are various ways to distract the osteotomy and the set does come with a mini joint distractor ( like a small laminar spreader).
    I have usually found it easier simply to manually apply a varus force far enough away from the osteotomy, to give some lever arm advantage. Here I am applying appropriate pressure at the level of the metatarsal head/neck. The osteotomy has opened up easily following the careful previous steps in preparation.

    Distract the osteotomy with your preferred technique and manoeuvre the basal plate into the gap, using the locking guide already on the plate to assist this process.The pressure applied in the previous step on the metatarsal neck needs to continue whilst the plate is being inserted.
    What this slide also shows is that the initial point of insertion is slightly too superior. The plate is in no way malleable and what is shown here is that the distal screw holes sit off the superior aspect of the 1st metatarsal and will both be prominent if the plate is not repositioned. This will also lead to inferior purchase of these two screws unless corrected.

    The plate is seen here appropriately positioned which is straightforward to do by repeating the previous steps.
    Arthrex supply a ball-ended wire, the BB tack, that can be drilled into holes on the plate at this stage to stabilise the implant temporarily.
    This is however an additional step and alternatively the plate can be carfully held in its reduced position until fixed with at least one screw either side of the osteotomy.

    Once an appropriate position has been achieved it is a good idea to hold this and not let go until the plate is finally definitively fixed. This is the reason for having all of your instruments to hand prior to starting the manoeuvre.
    Note as well that the inferior limb of the proximal part of the plate sits appropriately on the bone and this screw will also have good purchase. If the plate is too far translated inferiorly, which can occur if one is avoiding dorsal prominence of the plate, then this inferior hole can be suboptimal and again the plate would need to be repositioned.

    Following drilling and measuring at the standard fashion an appropriate sized locking screw is chosen. Fix the stable proximal end with the first screw.

    The locking screw is screwed home using the torque limiting screwdriver which is included on the set, which is a nice piece of kit.

    Torque limiting screwdriver has a collar that needs to be engaged.

    The instructions for use are usefully etched on the underside.

    With fixation proximally and distally the construct is temporarily stable enough to release hold on the plate.
    Each screw held is drilled using the guide supplied. Note that the box sits well seated within the osteotomy here. There is a fair sized gap left and this should be filled using the previously removed exostosis.

    Once all four screws have been inserted under the correct torque the osteotomy is packed with morcelised bone from the exostosis.In preparing the exostosis I tend not to discard any of the chondral surface but morcelise the whole and in doing this there is usually enough bone to adequately fill the osteotomy gap.
    Various bone substitutes and processed allografts are also available if required.

    At this stage some assessment is made of the likely adequacy of correction.
    In most cases, though not all cases, an Akin osteotomy is also required.
    If one is fighting to hold the 1st MTP in a neutral position, then an Akin osteotomy will definitely be required. If however at this point, the MTP joint seems reasonably happy in a neutral position it may just be worth placing a single closure suture in the capsule (see later) and if this allows stable reduction of the joint and normal tracking of the joint then closure could proceed at this point.
    With a larger hallux valgus deformity however, being able to close at this stage is very unusual.

    The first step for an Akin is to follow the dorsomedial cutaneous nerve which is sitting in the superior fat layer and using tenotomy scissors to trace this distally such that it can be avoidedSubperiosteal dissection proceeds both superiorly and inferiorly, sticking to the metaphyseal/diaphyseal junction at the base of the proximal phalanx. It is absolutely key at this point that the capsular attachments to the base of the proximal phalanx (1) are not released off the base of the proximal phalanx. The capsular closure is also a key part in final stabily correcting the hallux valgus deformity.

    Operation – 3

    A Homans retractor is placed both superiorly and inferiorly at the metaphyseal/diaphyseal junction at the base of the proximal phalanx, following subperiosteal dissection. Soft tissues are elevated to avoid damage when the osteotomy is cut in the next step.
    The toe itself should be held and stabilised at this point by an assistant and ideally held in a corrected position so the surgeon has a good idea of the line he is taking with his osteotomy.

    A smaller saw blade is used for the akin osteotomy than for the basal osteotomy. The point at which the osteotomy is made is again at the metaphyseal/diaphyseal junction.It should be appreciated that the articular surface at the base of the proximal phalanx is quite concave and both the osteotomy and also the staple used to fix the osteotomy are at risk of breaching the joint unless care is taken with placement of the cut.
    The osteotomy cut is made at a right angle to the long axis of the proximal phalanx. Probing cuts should be made as one crosses the bone and one should aim to leave the lateral cortex intact and not plunge through it under any circumstances.
    On the plantar aspect the neurovascular bundle and also the flexor mechanism to the great toe is at risk. Dorsally the extensor tendons are at risk if care is not taken.

    A relatively small slither of bone is normally all that is required. The saw blade itself removes bone simply in the making of the cut. Even a relatively small akin osteotomy wedge cut as shown here will once removed lead to reasonably sized gap that needs to close.
    Attention should be paid to the most superior and also most inferior parts of the osteotomy and if the osteotomy fails to close these are the areas that should be looked to first and a small amount of feathering maybe required with the saw in these areas to get good congruent closure of the osteotomy.

    A fairly typical appearance of the akin osteotomy following bone removal.

    An estimate is made of the size of the staple required to fix the Akin. In a small foot use an 8mm interaxis staple and in a more standard sized foot a 10mm interaxis staple.With the osteotomy closed (or largely closed as shown here) I offer the staple to the base of the proximal phalanx and will pre-drill the holes for the staples using a 1mm guidewire.
    In positioning the proximal guidewire hole, it is important that the staple is angled distal to the joint rather than towards the joint.
    The staple is pushed onto the bone first of all to mark the periosteum, and then removed.

    The hole made by the staple is drilled to the other side of the phalangeal cortex using a 1mm guidewire.

    The staple is engaged in the proximal drill hole, the osteotomy at this point does need to be fully closed before the distal drill hole is marked and then drilled.

    Here a distal hole is being drilled with a 1mm guide wire.

    The definitive staple is inserted simply using a needle holder which is gently tapped home by an assistant whilst the surgeon holds the osteotomy in a reduced position.There is an impactor on the set which is used to fully tap it home.
    Once the staple has been impacted it is important to distract the MTP joint and directly visualise the joint surface. The staple can on occasion breach the joint, which by its nature is concave in the proximal phalanx. If this occurs the staple should be re-sited.

    A single trial suture is placed into the medial capsule, tightening it, to test joint stability and tracking following the Akin osteotomy.The standard design of “box” stitch is used, starting plantar proximal (PP), to dorsal distal (DD), to plantar distal (PD) and finishing plantar proximal(PP) which is then tied under appropriate tension.

    Despite the akin osteotomy in this case the 1st MTP joint still has a tendency towards valgus angulation. This is even with a trial suture placed into the capsule (not shown here).
    It is evident that the issue is a significantly tight EHL tendon(1) which remains a deforming force, and should be fractionally lengthened. It is not a common step to need to take but the surgeon should not avoid it rather than try to compensate with an overly tight medial capsular closure. The soft tissues should be properly balanced before the capsular closure is undertaken.

    A standard Z-lengthening is performed under direct vision, ensuring two equally thick halves of the tendon result and the lengthening is over an adequate length (better too long than too short a z is produced).

    The tissues plantar to the EHL, and n particular the extensor hallucis brevis, should be left intact.

    The fractional lengthening of the tendon is evident at A.
    This should now allow a stable initial closure of the capsule with a single capsular suture.

    The capsule is closed with a single corrective 1 Vicryl suture initially and at this point the EHL tendon repaired under appropriate tension using interrupted 2.0 Vicryl sutures. The EHL should be retensioned to allow the hallux to sit well aligned in the sagittal plane with the other toes. Care should be taken not to leave the tendon slack and defunction it.

    Further interrupted 1 Vicryl capsular sutures are placed, being careful to balance the position of the hallux and also not over-correct into varus.

    The deformity is well corrected and joint stably reduced, with a full range of movement, following a single plicating capsular suture.
    2 or 3 more interrupted capsular sutures are then placed.

    After the significant degree of displacement of the achieved in correcting a severe deformity using a basal osteotomy there is inevitably much redundant medial soft tissue at the level of the MTP joint.
    A generous ellipse of just the skin from the plantar aspect of the wound is excised, and the dorsal flap of skin is advanced inferiorly into the defect created. Care must be taken in excising the plantar skin as the digital nerve will be in close proximity. Just the skin is excised, not the underlying tissue.

    Soft tissue closure, following excision of excess medial skin, is with 2.0 & 3.0 Vicryl.

    A more severe Hallux Valgus deformity, with both sesamoids being uncovered.
    The joint itself looks minimally arthritic, though only a small lateral portion can be assessed given the MTP joint subluxation.
    If the inter-metatarsal angle where measured here however it would be relatively modest, considering the degree of the deformity, as the second metatarsal also has a varus angulation. This has the effect of reducing the size of the measured gap.
    The second MTP joint has dislocated dorsally.

    In this case a corrective MTP fusion has been used, and a Weils with soft correction for the chronically dislocated 2nd MTP joint.
    I would more usually utilise a robust dorsal plate when correcting such a deformity, where initially the soft tissues can exert a residual deforming force into valgus.

    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

    Hallux Valgus and cartilage degeneration in the first metatarsophalangeal joint.
    P.Bock, K-H. Kristen, A. Kroner, A. Engel. J Bone Joint Surg. 2004. 86-B(5):669-673
    An intra-operative observational study of chondral lesions within the 1st MTP joint (including the sesamo-phalangeal articulations)seen at time of corrective Hallux Valgus surgery. Almost 70% of 265 1st MTP joints displayed some degree of lesion, the severity of which correlated with the severity of the pre-surgical deformity.

    Reference

    • orthoracle.com

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