//

First MTP Fusion-Crossed screws technique

    Overview

    Learn the First MTP Fusion-Crossed screws technique surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the First MTP Fusion-Crossed screws technique surgical procedure.
    A 1st MTP (metatarsophalangeal ) joint fusion is a highly versatile operation both in terms of the conditions which can be treated as well as in terms of the function possible after successful fusion.
    A union rate of 90% plus is recorded in most series using current techniques. Success defined in terms of patient satisfaction rates though can be slightly lower than those of radiographic union of the fusion.
    The keys to operative success are careful joint preparation, positioning and appropriate fixation as well as appropriate patient selection and expectation management.
    There are various ways of fixing the fusion, most commonly a single axial compressive screw combined with a dorsal neutralising or compression plate. The technique detailed in this operation is a “crossed-screws” technique which differs only in the final mode of fixation.
    Similar techniques shown on OrthOracle are the use of Coughlin reamers for the joint preparation
    https://www.orthoracle.com/library/first-mtp-fusion-coughlin-reamer-preparation-and-orthosolutions-cannulated-4mm-screws/
    also detailed on the platform is corrective MTP fusion of a hallux varus using a Stryker Anchorage plate
    https://www.orthoracle.com/library/hallux-varus-correction-stryker-anchorage-mtp-arthrodesis-plate/
    and the technique of bone block distraction MTP fusion for a short first ray
    https://www.orthoracle.com/library/bone-block-first-mtp-fusion-using-the-wright-ortholoc-plate/


    Indications

    INDICATIONS :
    -For end stage and symptomatic degenerative First MTP(Metatarsophalangeal ) arthritis (whatever the cause)
    -As a salvage operation after failed first MTP joint debridement with severe pain
    -As a salvage operation after failed first MTP joint replacement ( usually using a bone block technique)
    -For salvage after recurrent Hallux Valgus ( consider also a Lapidus operation ) or to treat Hallux Varus
    -As a primary corrective operation in severe Hallux Valgus deformity
    -As a primary corrective operation for Hallux Valgus in the neurological patient
    -As a two stage procedure for an infected joint replacement or an infected MTP non-union.
    SYMPTOMS & ASSESSMENT:
    Patients who will be much improved by an MTP fusion will in most cases have severe pain , well localised to the level of the Metatarso-phalangeal (MTP) joint , and advanced arthritic change or joint destruction. Pain is often improved to an extent when in appropriately supportive shoes.
    Pain is likely to be restricting the patients function significantly from their pre-arthritic state, whatever this was. There are no absolutes in determining which patients may benefit from a lesser operation (such as an MTP joint debridement) . Symptomatically though persistent pain at rest and in bed are often indicators of an advanced arthritis likely to need fusion.
    On examination joint movement will be very limited and likely to be painful through the range of movement in severe arthritis. In more moderate disease pain occurs at the end of range mainly. I would however rate the reduction in range of movement as being a less important consideration than the level of pain being experienced in deceiding whether a fusion is an appropriate intervention. The rank of importance in considering whether to fuse or not is foremost the level of pain , next the level of radio-graphic arthritic change and least important in fact the reduction in range of movement. Different surgeons opinions on this weighting may vary.
    Prominent osteophytes around the joint , producing additional pain from impingement when in shoes are common, and will be debrided at the time of a fusion . When examining the first ray it is important to examine also the inter-phalangeal joint of the hallux, which will be called into play more following fusion. If it hyper-extends significantly pre-operatively then in a female (or broad-minded male) the wearing of high heels will not be a problem.
    If there is symptomatic degenerative change at the inter-phalangeal joint too then consider intercurrent joint debridement here or possibly an MTP joint replacement. This is not a common occurrence fortunately.
    Be aware of a sub-group of patients with advanced MTP arthritis and significant hypertrophic bony exostoses around the joint who have very minimal pain. They present with dorsal impingement and severe arthritis but minimal or no arthritic pain. These simply require debridement of the dorsal exostoses and rarely require fusion.
    Patients who are keen to return to sporting activity , including running , should have no real concerns following big toe fusion. Following an ankle fusion subtalar and possibly midfoot arthritis will in the majority of patients ensue. There is no clear correlation with what occurs in the first ray after MTP fusion. In other words the remaining inter-phalangeal joint of the Hallux is only exceptionally effected after the fusion.
    The classification system of Coughlin is probably the most adopted for grading Hallux Rigidus and is worthy of fuller review (see results section). It combines an assessment of range of movement, plain X-ray features, the nature and frequency of pain as well as when during the range of joint movement pain occurs. In this it certainly identifies the aspects of an arthritic joint can that can be measured but lacks a weighting to the relative importance of these features in determining appropriate treatment.
    INVESTIGATIONS:
    In most patients with arthritic change an AP and Lateral weight-bearing X-Ray will suffice.
    X-Rays are in not especially prognostic and if the diagnosis is clear clinically and non-operative treatment being pursued then are not absolutely required.
    In patients being considered for an MTP joint debridement then an MRI gives a more objective assessment of the joint and also has the advantage of visualising the sesamoids well. It should be borne in mind however that more minor degrees of arthritic change may well not be identified even by MRI.
    NON-OPERATIVE ALTERNATIVES:
    Activity modification and regular non-steroidal medication are likely to have been tried already by the patient.
    Injections of steroid and local anaesthetic will usually provide only short term relief in advanced cases of MTP arthritis . They have a role in calming acute flare-ups.
    Of most help for weight-bearing symptoms is the choice of appropriate shoe-wear. A stiff soled and “rocker-profile” sole should be advised. This may be a particular make such as an MBT or Fit-Flop shoe or simply a more traditional leather soled brogue with an appropriate sole.
    SURGICAL ALTERNATIVES:
    –First MTP debridement: See https://www.orthoracle.com/library/hallux-mis-cheilectomy/
    -First MTP debridement and Moberg procedure: See https://www.orthoracle.com/library/moberg-procedure/
    -First MTP replacement : Full joint replacements and hemiarthroplasties both exist. The Rotaglide MTP replacement is detailed at https://www.orthoracle.com/library/first-mtp-replacement/and the Cartiva joint replacement at https://www.orthoracle.com/library/cartiva-implant-1st-mtp-joint-arthritis/
    –Kellers excision arthroplasty: See https://www.orthoracle.com/library/kellers-arthroplasty/
    -First metatarsal osteotomy: Watermann, shortening Scarf and Youngswick are three examples of such realignment /joint space “creating” procedures. See https://www.orthoracle.com/library/youngswick-osteotomy/
    CONTRAINDICATIONS:
    Patients who are unlikely to co-operate with post-operative instructions. Examples would include patients with impaired mental faculties or any smokers who realistically will not abstain during the period required for bony union.
    Patients with poor vascular supply to the foot or factors leading to impaired soft tissue or bone healing need these factors to be optimised pre-operatively.

    Setup

    General or Regional anaesthetic.
    Antibiotics & LMW Heparin on induction.
    Laminar flow theatre.
    Thigh tourniquet (ankle tourniquet gets in the way of positioning the wire driver and drill during fixation).
    Patient supine.
    Intra-operative nerve block (popliteal ) for analgesia

    Operation – 1

    The position aimed for after a fusion of the first MTP, by any means, is that the toe should sit slightly off the ground at rest, whilst allowing easy ground contact by the plantar aspect of the distal phalanx with the heel and metatarsal heads also in a weight-bearing position.
    Here the interphalangeal joint of the hallux is extended

    The position aimed for after a fusion of the first MTP, by any means, is that the toe should sit slightly off the ground at rest, whilst allowing easy ground contact by the plantar aspect of the distal phalanx with the heel and metatarsal heads also in a weight-bearing position.
    Here the interphalangeal joint of the hallux is flexed and making contact with the ground .

    If the inter-phalangeal joint happens to hyper-extend beyond neutral then a significant heel rise is also possible (though not required for normal function including running).

    A medial mid-line skin incision is used. This needs to extend further distally than the usual incision for Hallux Valgus correction, almost to the level of the inter-phalangeal (IP) Joint(1).Proximally however a shorter exposure to the mid point of the metatarsal is sufficient(2). Overall the incision is shorter than that required for a Hallux Valgus correction.
    Sharp dissect just through the skin to the start of the fat layer. Next use a pair of tenotomy scissors and start looking for the Doso-medial cutaneous nerve.
    An acceptable alternate approach is a direct midline dorsal incision onto the joint.

    Identify the fascial layer beneath the fat in which the dorsomedial cutaneous nerve (2) sits, by blunt dissection, and avoid it.Once the nerve is identified define it and mobilise it by careful dissection and then reflect this whole layer dorsally . The capsule is then safely exposed and can be opened(1) .

    The joint is opened with a long horizontal capsulotomy. Start at the level of the joint and as soon as the metatarsal head is seen insert a McDonalds retractor(1) and place the capsule under tension to aid its accurate dissection in two complete layers, one superior and one inferior.
    All capsular attachments in the immediate surgical field are dissected off the length of the proximal phalanx(2). This is different to the exposure used in Hallux Valgus where it is very important to keep the attachments to the base of the proximal phalanx intact to allow accurate balancing of the joint during closure. Proximally care needs to be taken to avoid the dors0-medial cutaneous nerve(3).
    It is never the less still important to avoid stripping the plantar soft-tissue attachments to the metatarsal neck which remain an important vascular supply.

    The proximal phalanx (1) needs to be carefully sub-periosteally dissected dorsally almost to the level of the Inter-phalangeal joint distally.This allows adequate clearance of the soft tissue for both guide wire and screw placement as well to get the fairly acute angle required with the small joint instruments.

    The head of the metatarsal is prepared first using appropriate sized bone nibblers. Best exposure for this step is usually gained by an assistant with Homans’ retractors inserted to the dorsal-lateral(1) and plantar-medial aspects of the metatarsal head, levering away the soft tissues.The head of the metatarsal is prepared first using appropriate sized bone nibblers. Best exposure for this step is usually gained by an assistant with Homans’ retractors inserted to the dorsal-lateral(1) and plantar-medial aspects of the metatarsal head, levering away the soft tissues. The larger the bone nibblers used generally the easier the preparation. On occasion the subchondral bone can be very dense and difficult to start into with any nibblers. An appropriately sized (4-5 mm) high speed bone burr is useful in such cases .Any dorsal(2), medial or lateral exostoses are also removed at this stage. The objective is to keep the head convex and congruent with the base of the phalanx, whilst getting the surface back to bleeding subchondral bone.
    If cysts are present these are best dealt with by curetting out then packing with bone removed during preparation. Cutting the whole articular surface back to the base of the deepest cyst during preparation risks shortening the first ray unnecessarily and is not required.
    It is also possible to perform the preparation using sized reamers for each side of the joint.

    The metatarsal head prepared back to healthy subchondral bone(1). The proximal phalanx has been exposed to the level of the DIP(distal interphalangeal) joint(2) , the plantar and medial capsular attachment(4) and the lateral margin of the MTP joint(3).

    The base of the proximal phalanx is delivered for preparation by fully plantar flexing the toe(2) whilst pushing the base of the phalanx medially with a carefully placed Homans retractor(1),resting directly upon the cortical bone.With the base of the phalanx thus exposed its bony margins can be defined by careful and limited sharp dissection of soft tissue attachments.
    It is worth at this stage inspecting the sesamoids from the inside of the joint and if bulky and degenerate these can be debulked with finer nibblers .They do not need to be debrided back to the level of the subchondral bone.

    Using a high speed 4-5mm burr (1) the base of the proximal phalanx is taken back to healthy sub-chondral bone. The surface should be left concave to allow congruent positioning with the convex metatarsal head.Care should be exercised at the most plantar aspect to avoid damage to the flexor apparatus. This is marked 2 and denoted by the yellow plantar based line.
    The phalanx tends not to bleed as readily as the metatarsal head once an appropriate depth of bone has been removed.
    It is important also to continually take note of the appearance of the bone surface, not just whether bleeding is occurring, otherwise it is easy to remove too much bone from the phalanx, shortening it needlessly.

    A 1.6 K wire(1) is a useful tool to micro-fracture any articular surface not bleeding sufficiently after an appropriate amount of preparation has occurred to the articular surface of the proximal phalanx.A balance needs to be struck in preparation of the proximal phalanx between exposing all subchondral bone and not removing so much bone that shortening of the toe becomes an issue.
    If using the fusion to correct a severe Hallux Valgus deformity then at this stage a lateral release may be required. It is often possible to perform this through the joint , after bone preparation , as opposed to through a separate dorsal incision.
    In correcting a severe Hallux Valgus it is useful for an assistant to reduce the inter-metatarsal angle by pushing the first metatarsal back towards the second metatarsal before the Hallux is reduced and then the K-Wire is driven across the joint. The soft tissue tension within the tendons of the Hallux will assist the reduction if appropriately positioned. A dorsal plate should always be used as part of the fixation when correcting a severe Hallux Valgus .

    An initial guide wire is placed across the joint to allow accurate positioning prior to fixation. A K wire from the cannulated screw set is drilled from distal and dorsally and angled just lateral of the midline axis of the toe in a proximal direction.It is really important that once the joint is positioned appropriately (see following slides) that it is both stable and also has excellent bone to bone surface contact. If contact is not good then remove the temporary wire, inspect both sides of the joint and remove any prominent areas of bone that may be hindering congruent seating of the joint.
    The joint must both be in an appropriate functional position as well as having excellent bone to bone contact.
    Spend time on achieving this.
    A final point on this stage of the operation is that if the objective is correction of a Hallux Valgus deformity then it is useful to have an assistant put laterally directed pressure on the medial eminence , reducing the inter-metatarsal angle, before the K Wire is advanced across the joint. With a mobile MTP joint this will allow acute correction of both the Hallux Valgus and the inter-metatarsal angles.
    You can see on-table X-Ray images of this technique in the post-operative images at the end of this operation.

    To determine the correct amount of dorsi-flexion to place the MTP joint into for fusion a sterile flat surface is placed under the sole of the foot. The heel (1) and the plantar aspect of the MTP joint (2) when in contact should allow the tip of the distal phalanx (3) to make easy contact as well.If it does not the first ray is de-functioned and excess weight passes through the lesser metatarsals which may become painful.
    Getting the balance right is a matter of experience too. Following surgery for a number of months swelling will effectively lift the whole medial boarder of the foot off the ground so this carefully positioned toe may not be back into this “on-table” functional position for several months post-operatively.
    The foot should be at right angles to the tibia and weight-bearing simulated by loading the foot in this position when a decision on position is being made.
    The exact position of dorsi-flexion is also determined by the relative lengths of the proximal and distal Phalanges and the mobility of the inter-phalangeal joint.

    Correctly positioned the distal phalynx sits just off the flat surface. If too dorsiflexed the dorsal surface of the toe will rub on shoewear and may not be able to contact the ground , thus defunctioning the hallux.
    The practical effect of this is most patients will be to overload the second and other metatarsals , leading to transfer metatarsalgia (plantar pain from the lesser metatarsal heads during weight-bearing). A revision MTP fusion then looms.
    If too plantar angulated the first ray will be painful and non-functional and again transfer metatarsal pain can occur.

    Attention also needs to be paid to the medio-lateral position of the hallux during the temporary K-wiring. Some clearance between it and the second toe is preferable.

    Prior to placing the second ( and proximal to distal ) guide wire raise the foot upon a well padded sterile bowl(1).This positioning allows the easiest access for use of drill and wire driver.

    The proximal to distal guide wire should be drilled into position to avoid the other wire. Place it either plantar or dorsal to the initial wire.
    The best entry point is just towards the plantar aspect of the junction of the metatarsal head and neck

    The two guide wires should be placed to allow the easy passage of two screws. One placed more plantar and one more dorsally.The distal screw(2) needs to be placed fairly far distally along the proximal phalanx to allow enough purchase for the screw. If placed to proximal and close to the joint the phalanx is at risk of fracturing as the screw is driven home , losing compression. The distal wire/screw should also not be angled too far laterally as this will not give adequate purchase in the metatarsal head.

    Once the wires are placed the screw lengths can be checked. They are usually in the range of 30-40mm depending upon size of foot & screw position.Screw length being measured.

    Over-drill the proximal guide wire with the cannulated drill. If significant resistance is encountered in this step it means the non-drilled wire is too close and should be backed out and repositioned.If bone quality is good it may be necessary to tap the drilled bone as well.

    Counter-sink the proximal screw head. This is an important step to avoid the screw head causing irritation in shoewear.
    This can also simply be done with a bone nibbler to create space for the screw head.
    Certain cases can be more reliably fixed with an appropriate sized dorsal plate rather than a second distal to proximal screw. Examples would be cases of severe deformity being corrected, poor bone quality (for example a Rheumatoid patient ) and large adult male feet.
    Is is a good idea to have a dorsal plate available anyway for those occasional circumstances where the crossed screws do not provide adequate stability or compression of the fusion on table.

    Insert the first 4.0mm partially-threaded cannulated screw, from proximal to distal. During insertion it is important to manually hold the MTP in a corrected position as rotational malalignment can occur.
    2 screws are always required for adequate compression and also rotational stability.
    The standard fixation is using a partially threaded cancellous screw used in compressive mode. If the screw is not suitably compressive or has inadequate bone purchase then options include using a fully threaded screw, upsizing the screw diameter or using a dorsal plate in addition to a single axial screw.

    The distal to proximal wire should now be overdrilled.The orientation of the wires/screws demonstrating that they have been be positioned in different horizontal planes to minimise the chance of them catching upon each other.

    Countersinking the distal screw is easier done with a fine pair of nibblers to clear a space for the undersurface of the screw head to sit into within the cortical bone.
    Care should be exercised when screwing this final screw home that a fracture does not occur and propagate into the joint from the proximal aspect of the screw hole.
    If it does, assess the stability of the construct. If not effected one might consider simply non-weight bearing in the post-operative period or strict heel weight bearing.
    If effected then a dorsal plate may need to be applied instead of this distal screw.

    Operation – 2

    The distal to proximal screw is inserted, following which image intensifier images are taken on table to confirm appropriate implant length and position.The final position of the crossing 4.0mm titanium screws. Lengths can now be checked with image intensifier. The threads should not span the arthrodesis site and avoid leaving the screws ends over-long plantar or laterally.
    In particular pay attention to the sesamoids and make sure screw threads are well away from them.
    It is important to check the stability of fixation at this stage. The screw length or diameter may need to be upgraded if fixation is inadequate.
    There are many MTP joint plating systems available and these most definitely have a significant role (usually combined with a single longitudinal screw) in this operation .

    Pre (left) and post operative(right) X-rays of a first MTP fusion using the crossed screws technique.

    Pre (left) and immediate post operative(right) X-rays of a first MTP fusion showing the effectiveness of combining it with a lateral release in achieving acute reduction of the inter-metatarsal angle in a case of severe Hallux Valgus.
    Usually a dorsal plate is advisable in this situation to maintain the reduction whilst bony union occurs.

    On table image intensifier pictures showing the immediate coverage of medial sesamoid (1) and correction of Inter-Metatarsal angle which is possible using a simple fusion and lateral release.
    The top left image shows the increased inter-metatarsal angle and Hallux Valgus deformity still present after joint preparation and a lateral release performed through the joint.
    In the top-right image an assistant has applied laterally directed pressure to the medial aspect of the metatarsal head thus closing the inter-metatarsal angle. The hallux has then been reduced onto the metatarsal head and the K wire is then driven across the joint in the corrected position. Note the new position of the medial sesamoid (1) relative to the metatarsal head.
    The bottom image shows the position maintained with the definitive fixation performed (on the occasion using the more advisable combination of a single axial screw and a dorsal plate.

    Post Operative

    Day-case or overnight stay
    An on-table or immediate post-operative X-Ray is always required.
    Prophylactic LMW Heparin for 2 weeks.
    Weight bear using post operative shoe for 5-6 weeks.
    Crutches likely required 1-2 weeks.
    Change dressings at 1 and 2 weeks and use a heavy , padded forefoot dressing /Kellers bandage for this duration. From 2 weeks just local dressings to the wound which should be continued 24/7 until wound completely dry and healed. After this continue dressings whenever in shoe wear for a further month.
    If the wound is slow to heal (or breaks down) swab for microbiology , ensure patient is non-smoking and also complying with post-operative advice, and continue with regular (daily or more frequently as required) dressing changes.
    From 3 weeks the patients should cleanse the foot twice a day, once in a salt water bath and once by bathing/showering.
    Check X-Ray is required at 5 -6 weeks to confirm bony union and also a clinical review is required.
    If at all equivocal (due to ongoing pain or inconclusive X-ray) then re X-ray in a further 3-4 weeks (or consider CT scan for a more objective view) and limit activity according to symptoms until then. If in pain from the 1st MTP also consider using a post-operative boot instead of the standard post operative shoe. The patient should aim for pain-free function and strictly limit activity and weight-bearing to achieve this.
    Appropriate shoe-wear fit is vital in the first month or so after the post-op shoe.
    I advise fit-flops ,Ugg boots, wider fits or open stiff soled sandals. Stiff low heels ( platform or wedge shoes ) are encouraged in women , from when comfortable. A similar rocker-profile and stiff soled shoe will help in men also for this period.
    Patients may use a static bike & swim from 5-6 weeks , Cross-train from 6-7 weeks and re-start light jogging on treadmill from 10 weeks at soonest under normal circumstances.

    Recommended Reading

    Manipulation and injection for hallux rigidus.
    J Bone Joint Surg.2001.83-B:706-708
    M.C.Solan , J.D.F.Calder ,S.P.Bendall
    Injection & MUA demonstrated to be of use for grade 1 & 2 Osteoarthritis.
    Mean follow up of 41 months
    In patients with Grade 1 X-Ray changes relief for 6 months median was achieved with the intervention.
    Arthrodesis of the first MTP joint using a dorsal titanium contoured plate.
    Foot & Ankle International.2004.25(11):783-787.
    R.Flavin, M.M.Stephens.
    12 patients , all united radiographically by 6 weeks using a purpose designed dorsal plate.
    Non-union after arthrodesis of the first Metatarsal-phalangeal joint:A systematic review
    J Foot Ankle Surg. 2011; 50(6): 710-13.
    T S Roukis
    37 papers reviewed , which included as a minimum 12 months follow up , at least 30 patients and modern internal fixation techniques. This resulted in 2,818 cases being considered. Almost 50% of cases were for Hallux Valgus , just over 30% for Hallux rigidus and approximately 10% both for Rheumatoid Forefoot and as a revision procedure. Non-union overall was at 5.4% with one third only of those being symptomatic.
    Hallux Metatarsophalangeal joint arthrodesis with a hybrid locking plate and a plantar neutralisation screw:A prospective study.
    Foot Ankle Int 2013 34(11): 1535-40
    J Doty, M Coughlin , C Hirose, T Kemp.
    49 feet post-operatively were followed up for a minimum of 12 months.
    Visual analogue score for pain reduced from a mean of almost 7 to less than 2. Over 50% had an improvement in gait , over 40% no change and fewer than 5% were worse. Non and delayed union or 4%.
    Almost 90% of patients rated the outcome as excellent or good.
    Hallux rigidus. Grading and long term results of operative treatment
    J Bone Joint Surg 2003.85-A(11): 2072-88
    Coughlin MJ, Shurnas PS
    Outcome of fusion and debridement surgery reported as well as a classification system which has been fairly widely adopted since. The grading runs from 0 to 4 and is based on clinical and radiographic features as well as range of dorsiflexion at the MTP joint (versus the normal side or in absolute terms).

    Reference

    • orthoracle.com

    Tags:

    You might be interested in

    Dark mode powered by Night Eye