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Subtalar fusion and Talonavicular arthrodesis (open technique) using Stryker anchorage 2 plating system

    Overview

    Learn the Subtalar fusion and Talonavicular arthrodesis (open technique) using Stryker anchorage 2 plating system surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Subtalar fusion and Talonavicular arthrodesis (open technique) using Stryker anchorage 2 plating system surgical procedure.
    Double arthrodesis of the subtalar joint(STJ) and talonavicular joint(TNJ) is a highly effective method of correcting deformity in the adult flat foot with or without arthritis. It is most commonly, though not exclusively, used for this indication. A double fusion will not only correct deformity but will also fuse the arthritic joints so achieving a dual objective of pain relief as well as deformity correction. The traditional approach to these situations would have been a triple fusion with the aim of abolishing movement in all three joints of the hind foot (Choparts joint). It is now recognised however that the calcaneocuboid (CCJ) joint is largely inactive with very little movement in these situations and that its inclusion into the fusion offers very little additional in terms of abolishing movement or pain as it is usually not primarily responsible for painful symptoms. Rather than arthritis of the CCJ, it is often sub-fibular impingement that causes the lateral pain in the approximate location of the joint, along with inflammatory changes in the sinus tarsi. It is also the case that the CCJ does not suffer OA changes after the double fusion and therefore the risk of recurrent symptoms is low. It is therefore now increasingly common to use a fusion of the STJ and TNJ joints and ignore the CCJ to achieve the same or similar results as a conventional triple fusion offers.
    The ability to correct deformity by the use of a double fusion can be augmented by performing adjuvant procedures such as the Evans calcaneal osteotomy (to lengthen the lateral column), calcaneal body osteotomy (medialising or lateralising) or a plantar flexion shortening osteotomy of the medial cuneiform(Cotton osteotomy). These are reserved for severe deformity where correction cannot be achieved by subtalar and corrective talonavicular fusion.
    The Stryker Anchorage 2 CP midfoot fusion plating system has many unique features. It is made of anodised titanium and is a low profile compression plate with 2 proximal locking, two distal locking and one compression screw from distal navicular to proximal talus. It uses a template to position the plate with a laser mark on the template that allows one to position the plate accurately. The laser line can be positioned over the joint line which will automatically position the screws holes over the talus and navicular in an optimal fashion. It has a compression hole which sits in a concavity on the plate with a corresponding convexity on its under surface. This requires the bone to be reamed so that this convex prominence sits into the bone to make the plate flush with the underlying bone throughout its length. It is normally used medially but can be used dorsally particularly if there is a dorsiflexion deformity of the first ray that requires to be corrected at the talonavicular level. The compression screw uses the principle of dynamic compression plating to effect a strong compression of the fusion site.

    Indications

    INDICATIONS
    This procedure can be used for arthritis of the hindfoot without deformity, post traumatic situations, tarsal coalition , neuromuscular feet with deformity and in some cases of diabetes induced deformity. It is classically used in the Adult Acquired flat foot with associated arthritis or failed reconstructive surgery for tibialis posterior deficiency. It is also used in Myerson stage 4 (of the Johnson and Strom classification) Tibialis posterior deficiency when the ankle joint is arthritic, to effect a stable well aligned hindfoot and forefoot before ankle surgery such as a replacement or fusion is performed.
    It should not be performed in the presence of sepsis or ulceration, peripheral ischemia, and in the paediatric flat foot.
    SYMPTOMS & EXAMINATION
    The patient usually presents with features of subfibular impingement as a result of the severe valgus of the hindfoot. In addition patients complain of pain over the talar head as weightbearing and transfer of weight from hindfoot to forefoot primarily occurs on the talar head as the patient weight bears on the medial column. Patients may also complain of peroneal tendon pain, as they are impinged by the os calcis and the lateral malleolus. Some patients complain of instability and a feeling of giving way in eversion and in these situations the integrity of the medial deltoid ligament must be assessed carefully. This is not only due to the loss of push off generated by premature weightbearing on the talar head and a midfoot break but often also due to the hypodynamic condition of the Achilles tendon. This is most often seen in patients with diabetic Charcot feet and associated deformity. Most patients will suffer a gait abnormality due to the poor biomechanics of the foot. They also suffer complaints of pain on movement of the arthritic joints. Perhaps the most common complaint is of the inability to fit into their existing foot it into their existing footwear and the inability to get ones that fitted comfortably. Occasionally with a severe valgus hindfoot patients present with a stress fracture of the fibula due to the lateral load transfer generated by the severe deformity.
    A thorough standing examination of the whole lower limb in question is performed to confirm that there are no issues regarding alignment further up from the ankle. In particular care must be taken to ensure that there is no valgus or valgus instability of the knee. Rotational instability of the ankle due to medial deltoid deficiency must also be looked for, as the presence of such instability in external rotation will cause the deformity to recur in the ankle. The integrity of the tibialis posterior should also be assessed with tests including single heel raise. In severe deformity and arthritis this is often not possible due to pain. The hindfoot alignment should be carefully assessed to ascertain which joints contribute to the deformity and whether the deformity is “forefoot driven’ as is sometimes the case.
    IMAGING
    Routine radiographs including an AP/Lat Broden (subtalar) view and oblique view of the foot of the ankle and foot is essential. The AP and lateral views must be done in a weightbearing limb. In addition a Salzman view is very useful in assessing the alignment of the heel relative to the tibial axis.
    I do not routinely do a CT scan unless I am still uncertain about the location of the deformity. An MRI scan is very useful to assess structures such as the tibialis posterior tendon, peroneal tendons, articular cartilage and the spring ligament. It is especially important to assess the midfoot joints to identify those with severe pathology that may need also to be addressed surgically.
    With severe deformity I always perform vascular studies which may include angiography in addition to Duplex scans. Acute surgical correction of longstanding severe deformity can precipitate vascular compromise and if vascularity is demonstrated to to be tenuous (with little collateral circulation) a premptive review by a vascular surgeon may be appropriate.
    ALTERNATIVE OPERATIVE TREATMENT
    A medial approach to address both STJ and TNJ can be used as this is a very effective method of deformity correction without risk of stretching the lateral wound and suffering closure difficulties after correction of a severe valgus deformity. This is my preferred approach for a severe valgus deformity.
    The approach uses the bed of tibialis posterior and is positioned above the sustentaculum from medial malleolus to navicular but can be extended if needed to include the whole of the medial ray if necessary. It also has a significant advantage in being away from the neurovascular bundle throughout the procedure and also avoiding lateral wound problems. The ability to judge and effect correction of a severe valgus deformity is also better from a medial approach particularly if bony wedge resections have to be made on the medially.
    NON-OPERATIVE MANAGEMENT
    Non operative methods of treatment should be tried first including injection, orthotic correction of deformity, shoe modification and physiotherapy optimisation of function before the surgical route is adopted.
    CONTRAINDICATIONS
    Fusion operations cause stiffness and therefore should be avoided in patients who don’t have significant arthritis. Instead reconstructive procedures including osteotomy and tendon transfers are preferred.
    The operation should not be done in the presence of active sepsis or ulceration as well as significant peripheral ischaemia
    Fusion operations should be avoided if possible in the presence of active growth plates and in young adults and alternative surgical routes should be pursued wherever possible to avoid severe biomechanical sequelae of fusion procedures.

    Setup

    Informed consent is obtained from the patient. In particular the patient should be informed that all movement in inversion and eversion along with most of abduction, adduction, and movement across the Chopart joint complex will be lost irreversibly.
    The patient is placed supine with with access to the medial posterior and lateral aspects of the ankle and midfoot. In addition if a Gastrocnemius release is contemplated this is performed as the first stage of the operation so as to negate the confounding effects of a tight gastrocnemius. This will initially require a sandbag under the contralateral buttock to allow access to the proximal medial gastrocnemius. The operation follows a dual approach medial and lateral as well as needing access in the posterior heel for the placement of the subtalar fusion screws.
    The patient was anaesthetised using a spinal anaesthetic with Morphine. An above knee tourniquet was used after antibiotics were administered intravenously .
    The leg is supported using a a semi-rigid radiolucent block. This is especially necessary when performing the STJ fusion to allow the leg to be elevated off the table to allow access to the operating hand and create a space between it and the table. Sand bags are used underneath the ipsilateral buttock when performing the STJ fusion and removed when performing the TNJ fusion. The systems used in this operation are the Stryker Midfoot fusion (Anchorage) system for the TNJ joint fusion and the ACE (Zimmer Biomet) 6.5 cannulated cancellous screw system for the STJ.
    The Stryker Anchorage 2 CP midfoot fusion plating system has many unique features. It is made of anodised titanium and is a low profile compression plate with 2 proximal locking, two distal locking and one compression screw from distal navicular to proximal talus. It uses a template to position the plate with a laser mark on the template that allows one to position the plate accurately. The laser line can be positioned over the joint line which will automatically position the screws holes over the talus and navicular in an optimal fashion. It has a compression hole which sits in a concavity on the plate with a corresponding convexity on its under surface. This requires the bone to be reamed so that this convex prominence sits into the bone to make the plate flush with the underlying bone throughout its length. It is normally used medially but can be used dorsally particularly if there is a dorsiflexion deformity of the first ray that requires to be corrected at the talonavicular level. The compression screw uses the principle of dynamic compression plating to effect a strong compression of the fusion site.
    Other essential apparatus includes intra-operative fluoroscopy, Hintermann distractor, laminar spreader, Bone Graft Harvest Kit (Acumed Bone Graft Harvest Kit), fine osteotomes, drills and gouges.

    Operation – 1


    The patient in this operation is a 76 year old female with severe tibialis posterior deficiency, arthritis of the subtalar(STJ) and talonavicular(TNJ) joints, early arthritis of the ankle joint but with no medial instability. She also has severe forefoot abnormalities, which preceded the hindfoot problems, for which a previous Kellers arthroplasty and soft tissue release was done 30 years ago.
    She was asymptomatic in the ankle but was painful on movement of the STJ and TNJ. She had some symptoms of lateral sub-fibular impingement. Plain radiographs and MRI confirmed the findings of severe tibialis posterior deficiency, arthritis of the STJ and TNJ with mild arthritic changes in the ankle.
    She did not require a gastrocnemius release, which on occasion is required in the context of correction of a severe flatfoot deformity. She however did undergo corrective forefoot surgery at the same sitting.
    The lateral radiograph highlights the problems in the sagittal plane. Note the severe plantarflexion of the talus subluxing plantarwards. Also note the inability to see the sinus tarsi or the subtalar joint due to the rotational deformity of the talus. The talonavicular joint is noted to be severely arthritic and is the main pain generator in this patient.

    The AP radiograph shows the severe valgus position of the os calcis with part of it articulating with the lateral malleolus.

    The Gastrocnemius is tested again on table to ensure that it does not require lengthening. This is confirmed by the Silvferskiold test which tests the length of the gastrocnemius in straight leg and knee flexed positions. This is performed by first neutralising the position of the heel and then assessing dorsiflexion with the knee straight and then flexed. if the equinus is corrected with the knee bent but not when the knee is straight confirms a tight gastrocnemius. I would look to get the ankle joint to plantigrade with the knee straight . if I am unable to achieve this then i would lengthen the gastrocnemius by performing a proximal medial gastrocnemius release.
    The limb is prepped with Alcoholic Iodine solution and must include the knee so as to get an appreciation of the alignment of the limb relative to the tibia, patella and the knee joint line. The direct lateral approach is used for the subtalar joint and a dorsal approach for the talonavicular joint fusion

    The incision is marked on a line between the tip of the lateral malleolus and the base of the 4th metatarsal. It is important to recognise that the sural nerve and the peroneal tendons lie plantar to the incision and the nerve may have aberrant branches that may travel in the line of the incision.
    The Superficial peroneal nerve (SPN) lies anterior to the incision and is usually protected by the dorsal flap. The incision can be extended more distally taking care not to damage the SPN. This allows access to the CCJ if required. The extensor digitorum brevis takes origin from the lateral aspect of the anterior calcaneal process and can be elevated off the Os calcis to provide additional exposure. This is not usually required for the STJ. The main areas of fusion are the posterior and middle facets along with the area around the sinus tarsi which is usually very sclerotic especially in an arthritic joint.
    The order of operation is always proximal to distal to ensure that deformity correction is performed based on a well aligned proximal limb. Thus the gastrocnemius lengthening is done first followed by the STJ and TNJ fusions. The CCJ is performed last. It is also important to not definitively fix the STJ fusion prior to satisfactory reduction of the TNJ as adjustments may have to be made to allow satisfactory positioning of the TNJ.

    The skin incision is made taking care not to laminate the deeper fat layer but also ensuring that no aberrant nerves lie in the way. The incision is deepened to reach the sinus tarsi.

    The peroneal tendons are found plantar to the wound and inferior to the posterior facet of STJ. It is a common error to underestimate the height of the posterior facet: it is usually more superior than is usually thought. The tendency is therefore to reach the lateral wall of the Os Calcis and eventually violating the peroneal sheath with the potential for sural nerve injury.
    The easiest way to identify the posterior facet is to reach the Sinus Tarsi which is easily recognised as it is cavernous and contains the interosseous talocalcaneal ligaments which are easily identifiable., Then the crucial angle of Gissane is identified on the Os Calcis which when followed along its proximal limb will lead on e to the posterior facet. This is the easiest way to identify the posterior STJ even in the presence of severe deformity. The joint may be hidden under large osteophytes or may be difficult to access due to the deformity compression the lateral gutter or even causing a pseudo-arthrosis between the os calcis and the fibula. However following the superior border of the os calcis will almost always allow one to correctly identify the posterior facet. the anterior edge of the posterior facet on its medial side will lead one to the middle facet of STJ. The os calcis is moved relative to the talus in valgus and varus so that the subtalar joint movement can be used as a guide to recognise the line of the joint.

    The joint capsule is carefully cut along the joint to expose the posterior facet completely . It must be noted that the posterior 1/3rd of the posterior facet is actually medial to the fibula and can only be accessed from the joint anteriorly: one cannot access it laterally as the lateral malleolus will be in the way! The dimension of the STJ are identified from anterior to posterior and one must ensure good access is available to assess the whole joint.

    The body of the Os calcis is then identified just below the joint midway along the joint line of the posterior facet and a 2mm wire is inserted lateral to medial to just enter to distal cortex. care should be taken to ensure that the wire does not go too far medial for fear of damaging the medial neurovascular structures and not superiorly so as to enter or be too close to the joint itself. The positioning of the wire can be checked on image intensification.

    The Hintermann distractor ( Innomed http://www.innomed.net/smallbone_footankle_exposure.htmis) used to template the position of the second wire on the body of the talus. The wire is introduced from lateral to medial taking care not to protrude too much on to the medial aspect of the talus risking injury to the medial structures including the tibialis posterior if directed inferiorly as also the terminal saphenous vein and nerve if directed superiorly.

    The Hintermann distractor is carefully positioned to be centred perpendicular to the inclination of the posterior facet so that distraction can be even across the posterior facet. This is a very useful tool to gain good visualisation of the joint.

    Using fine sharp osteotomes, the articular cartilage is removed piecemeal from the talar and calcaneal surfaces right to the posterior border of the posterior facet. Difficulty is usually encountered when attempting to remove postero-lateral cartilage as this is well hidden deep to the lateral malleolus in the posterior recess of the subtalar joint. It is essential that this is removed as otherwise it is difficult to oppose the surfaces after preparation if a rim of cartilage is left behind. This may be removed using a sharp small curette . It is extremely important not to remove wedges of bone as it again becomes extremely difficult to fill the void. Correction of deformity in the subtalar joint is easily gained by rotation of the Os Calcis either internally for a valgus or externally for a varus deformity. Removal of wedges of bone or addition of bone wedges are rarely required . If there is considerable difficulty in correcting deformity then it is preferable to access the STJ medial through a medial approach using the bed of the tibialis posterior in the vicinity of the sustentaculum where more predictable resections can be made to correct deformity in valgus. If further deformity correction is needed, adding a calcaneal osteotomy in addition to the fusion is a much more predictable way of correcting deformity.

    Similarly the area of the joint anteriorly and the middle facet alonmg with the sinus tarsi is carefully denuded of cartilage and surfaces prepared

    All loose fragments of cartilage and bone are carefully removed using artery forceps especially in the posterior part of the joint

    Using a threaded 3.2 MM guide wire and with the driver in ream mode multiple holes are next made in the joint surfaces of the talus and Os Calcis to expose the subchondral bone and induce bleeding. I use this method rather than a drill for 2 reasons: 1. it is high torque and low speed and will not generate heat causing thermal necrosis to bone 2. the threaded facility allows a good grip on the bone preventing it from sliding away from the sloping surfaces. In addition there is little danger of the guide wire breaking unlike the drill. It can also be used without a guide which is useful when space is at a premium with a narrow joint such as the STJ.

    The joint is now fully prepared and ready to be stabilised. The process of correction of deformity is by internal rotation of the os calcis. This is carefully checked by aligning the patella the tibial crest and the os calcis . It will be obvious to see that the forefoot will supinated as a result of this correction. This would need to be rectified whilst performing the TNJ fusion when the medial ray can be plantar-flexed and pronated. It may occasionally be necessary to do an additional procedure such as a plantarflexion osteotomy of the 1st metatarsal to achieve good correction if this cannot be done at the level of the TNJ.

    The subtalar deformity must be fully correctable at this stage. If difficulties are encountered in getting the Os Calcis aligned underneath the talus further steps can be taken at this stage to achieve this objective. The gastrocnemius can be release to decrease the plantarflexion force on the Os Calcis. Careful concentric excision of the calcaneal part of the joint can be undertaken until the Os calcis can be positioned underneath the talus (Reversed Lambrinudi procedure). It is preferable to excise more from the calcaneal side of the fusion rather than the talar side of the joint for fear of causing damage to the tentative circulation of the talus from the sinus tarsi region and risk the devastating complication of avascular necrosis. One would have to take the precaution of avoiding damage to the medial neurovascular structures however on the medial side of the Os calcis and if there are any concerns then a medial approach should be utilised to access the medial calcaneal region for careful excision to avoid damage to the medial neurovascular structures.
    It may also be necessary to excise the under surface of the talar head and the superior surface of the anterior process of the os calcis. These can then be planed off to create congruous structures and avoid the risk of these apposing surfaces preventing concentric compression of the STJ.
    The Ankle should be able to dorsiflex until plantigrade with the knee straight and if there are any difficulties with achieving this there should be no hesitation in lengthening the gastrocnemius even at this stage.

    The foot is then screened to confirm correct alignment and dorsiflexion of the talus from its plantarflexed position as noted on the preoperative radiograph. The overlap noted of the talus and the os calcis must now show a clear subtalar joint interface and the talus should be aligned to the first metatarsal correcting Meary’s angle.

    A 3.2 mm guide wire is then inserted almost perpendicular to the angle of the posterior facet of STJ. The tip of the guide wire must extend to the subchondral bone of the talus just below the articular surface of the ankle joint.

    A second guide wire is inserted adjacent to the first . If it is an isolated STJ fusion, then I would pass this guide wire in a divergent fashion into the neck or even the head of the talus. However if a TNJ fusion is also being performed then this wire can be passed parallel to the first to enter the anterior part of the body of the talus or the proximal part of the neck of talus. This would ensure that the screw will not interfere with the fixation of the TNJ fusion.

    The position of the subtalar guide wires shown. It is critical that the anterior aspect of the ankle joint is not breached and the wires and centrally placed.
    This II picture is from a later stage following fixation of the talonavicular joint.

    It is very important to get an on-table axial view of the Os calcis to ensure that the 2 guide wires are within the body of the os calcis. The subsequent screw should not abut the medial cortex or breach it with attendant problems with the neurovascular bundle of the flexor tendons lying immediately beneath the sustentaculum tali. It also ensures maximal compression of the fusion surfaces. An anterior posterior view of the ankle joint to show the talus will also ensure that the guide wires lie within the talus.

    Now the approach to the TNJ is planned. The tendons of the tibialis anterior and extensor hallucis longus are marked out. This marks the boundaries of the incision as it is in this inter-tendinous gap that the dorsal approach to the TNJ lies.
    If it is an isolated TNJ fusion a dorso-medial approach can be used but if a double or triple fusion is done, especially to correct deformity, then a more central approach is preferred. This is useful not only to access the whole of the medial and lateral aspects of the TNJ but is especially useful to release the ligamentous connections between the navicular and the anterior process of os calcis or in the case of a calcaneo-navicular coalition it serves to expose the bar and excise it.

    The TNJ is identified by the medial navicular prominence which when palpating along the medial border of the foot from the medial malleolus is the next bony prominence to arrive at. The joint can be marked either by palpation or by screening to ensure correct positioning of the incision. It is important not to open the ankle joint if possible. The skin and subcutaneous tissue is incised as one layer to avoid laminating the deeper layers from skin.

    The TNJ is identified and exposed and confirmed by fluoroscopy if in doubt(before any destructive joint preparation is commenced). Sometimes this is hidden by osteophytes which will need to be excised in order to expose the joint. It is important to expose the joint carefully and I often use Homan retractors to expose the medial plantar and lateral edges of the joint after careful dissection of the flaps. It is especially important to avoid damage to the tibialis anterior and EHL tendons by power tools. It is important to remove the self retaining retractors before Homans retractors are used for causing soft tissue injury due to too much tension. The use of a Hintermann retractor will often obviate the need for the Homans retractors

    The joint should be fully exposed from medial to lateral and if need be the lateral aspect of the anterior process of the Os Calcis should also be exposed if soft tissue release or coalition excision is required.

    Operation – 2

    As in the STJ wires are placed in the talar head and the navicular body to use through the Hintermann distractor. This will offer an excellent view of the joint.

    A sharp curette is particularly useful in this joint as it very efficient in excising cartilage from the curved joint surfaces. It is to be noted that the navicular bone of its articular surface is very hard more so in an arthritic situation and may require osteotomes or even burrs to break into it

    The 3.2 guide wire is again used to perforate the hard cortical bone of the articular surface with irrigation in the case of the navicular due to its sclerotic nature.

    The procedure is repeated on the talar side of the fusion. It is important to ensure that the plantar lateral side is carefully prepared: any cartilage left here will hinder the apposition of the joint surfaces and prevent compression.

    The foot is now carefully positioned so as to correct the abduction supination and dorsiflexion seen in the first ray in cases of sever valgus deformity of the hind foot such this patient.The talus is elevated from its plantarflexed position so as to line up with the first metatarsal. The navicular is medialised on the talar head to provide optimal coverage to correct the abduction deformity. The navicular is plantarised on the talar head to correct the dorsiflexion deformity. This is carefully assessed in conjunction with the position of the Os Calcis and its alignment to the tibial axis so as to achieve complete correction. If there is residual valgus of the hindfoot noted at this stage the guide wires must be removed and the Os Calcis realigned to get perfect position. Failure to do so will invariable result in incomplete correction of the deformity.
    The final position of the fusion site is temporarily stabilised with a K-wire.

    The Stryker Anchorage 2 CP system midfoot fusion plate template is then positioned over the fusion. A Laser mark on the plate marks the joint line and the plate is aligned so that the tow proximal locking screw holes are positioned on the talar head and neck. The template carries a guide attached to it that marks the position of the convexity on the plantar aspect of the plate.

    A 1.4 mm wire is passed through the guide to mark the position of the hole to be reamed in the navicular and to seat the plate flush with the bone so that the compression screw can be inserted from distal to proximal. The proximal part of the plate is positioned carefully on the talus and secured with a 1.4 mm wire through an oblong hole at its proximal end. This is a marker for assessing the extent of compression (by measuring the distance travelled by the plate proximally during the process of tightening the compression screw).

    The template is now removed leaving the two wires in situ in bone.

    The countersinking cannulated reamer is now introduced over the distal wire and reamed to the depth of the reamer. Care must be taken to ensure the reaming is adequate whilst not over reaming so as to weaken the bone and predispose to a stress fracture.

    The distal wire is then removed and the plate is positioned over the fusion site with the proximal wire passing through the oblong hole in the plate. The wire will automatically lie in the proximal end of the oblong hole as its position is predetermined by the template.

    The distal two holes are drilled and measured using a speed guide which is calibrated to read the screw lengths from it.. The speed guide is used for both fixed angle and polyaxial drills

    The drill holes are measured and locking screws are inserted. These are polyaxial screws with a cone of 15 degrees in all directions and can be angled suitably to make sure that they do not enter the fusion site or broach the adjacent naviculocuneiform joints.

    Now the guide for the CP screw (compression) is used to drill a hole across the fusion site. The position of this screw hole is of paramount importance and is positioned to capture the plantar cortex of the talus to gain maximum compression.

    The hole is measured and an appropriate length of screw chosen so that it captures the plantar talar cortex. Before it is tightened completely the temporising K-wire fixation is removed so that the screw can capture the talus and effect compression. The degree of compression can be assessed by the movement of the 1.4 mm wire in the oblong hole in the proximal part of the plate as well as the expression of fluid from the fusion site.

    The proximal screws are now inserted after drilling and measuring. These are locking screws to secure the plate. Any voids at the fusion site are filled with bone graft if necessary.

    The construct is now screened to ensure that the talus is well aligned in the fusion and the fusion site is well apposed with the metal work in situ. The position of the guide wires securing the STJ fusion can also be adjusted.
    It is critical that the guides wires ( and subsequent screws) do not breach the talar cortex superiorly so various oblique screening shots should be used to be certain.

    A counter sink is used over the STJ fusion guide wires to seat the headed screws flush with the bone after creating stab incisions and widening them with artery forceps. This is an important step not only to seat the screws but to accurately measure the screw lengths so that they are not too long and broach the articular surface of the talus in the ankle. If the counter sink is used on power it is extremely important to ensure that it is used only on ream speed and is done very slowly so as to ensure that the countersink does not sink into the medulla of the os calcis. This will result in the screw being tightened in the medulla which will almost certainly cause failure of compression. If in doubt as to the experience of using this tool on power then i would suggest that this be used by hand. It is important to sink the screws so that they lie flush with the cortical surface. Failure to do so will result in the patient complaining of pain from the protruding screw and may require a removal at a later stage. In the event of this occuring, it may be necessary to use a washer or even a 1/3rd tubular plate being cut and moulded to fit the contour of the posterior tuberosity so that compression can be achieved.

    Screws are now inserted and tightened to compress the fusion site. This is confirmed with fluoroscopy both to ensure that the fusion is compressed and also to ensure that the partially threaded screws are positioned so that all of the threads cross the fusion site. This is necessary to achieve maximal compression. Any voids at the fusion site are filled with bone graft

    Wounds are closed with 2-0 vicryl for the deep layer and undyed Vicryl for skin. Do not forget to close the stab wounds in the heel!
    30 mls of 0.5 % Chirocaine is infiltrated into all the wounds and the limb is encased in a plaster of paris back/U slab.
    This patient also required correction of claw to deformity which was dealt with by soft tissue release, PIPJ fusion and stabilisation with K-wires.

    Postoperative lateral view non weightbearing of the fixation confirms the significant correction of deformity including dorsiflexion of the plantarflexed talus, correction of the talar to first metatarsal angle (Meary), progression of fusion in the STJ and slow progress of the TNJ, and restoration of the calcaneal pitch.

    AP radiographs of the foot showing in particular good bone to bone contact at the talo-navicular joint and no encroachment on the navicular-cuneiform articulation.

    The oblique view of the foot show a satisfactory appearance of the TNJ fusion with good coverage of the talar head by the navicular.
    It is not possible to offer comment on the length of the implants across either subtalar or talo-navicular articulations, though they look broadly appropriate.

    Post Operative

    The limb is elevated overnight and the plaster is completed the following day providing the limb is not too swollen.
    Patient is provided with anticoagulant prophylaxis. I use 5000 IU Dalteparin once a day subcutaneously administered.
    The patient remains non weight bearing for 6 weeks. The wounds are checked at 1 week when the plaster is changed to a light wight cast. At 6 weeks radiographs are taken to confirm satisfactory appearance of fusion and a further 4 – 6 weeks of protection in a pneumatic boot is instituted. The patient is allowed to partial weight bear . at 10-12 weeks further radiographs are taken to confirm completion of the fusion and the patient is gradually allowed to wean off the boot with physiotherapy instruction to normalise ankle range of movement.

    Recommended Reading

    The postoperative results of a double fusion are similar to the triple and appear to mimic the triple in their ability to correct deformity and restore a plantigrade foot with similar complication rates. The talonavicular joint is usually at higher risk of non union than the subtalar joint. Wound complications are low and are governed by the quality of soft tissue handling and the presence of risk factors such as smoking and in some cases the use of certain drugs such as powerful anti-inflammatories. Patients with renal failure, diabetics, renal transplant patients on immunosuppressive and steroid therapy may be at higher risk of developing both non union and wound complications.
    Wound complications need to be treated aggressively with debridement removal of metal work if feasible and wound care with vacuum wound therapy and local antibiotics delivered in a carrier material such as Stimulan or Cerement.
    It is often the case that bone graft is used in the primary procedure to act as an osteoinductor and osteoconductor. In the revision setting for a non union this becomes mandatory.
    Functionally, patients are improved as the weight bearing stance improves dramatically after surgery. In particular heel strike can often be restored to normal although the normal valgus angulation of the heel on weight bearing is lost following fusion. Nonetheless the pain relief felt by the patient and the ability to mobilise in a much more comfortable fashion as well as the ability to fit into off the shelf shoes are more significant factors.
    On a biomechanical basis there is an increased risk of suffering adjacent joint arthritis as a result of fusion and this is also reflected in the literature. In clinical practice though I have not seen this to be intrusive or problematic if it occurs. However patients must be warned of this possibility especially if there is radiographic evidence of arthritis in the intertarsal or tarsometatarsal joints even if they are asymptomatic. The ability of the double arthrodesis to correct deformity has been studied and published . The results appear to suggest that at least radiographically the double arthrodoesis is able to correct significant valgus deformity as well as a triple fusion.
    J Foot Ankle Surg. 2015 May-Jun;54(3):424-7. Hindfoot Deformity Corrected With Double Versus Triple Arthrodesis: Radiographic Comparison. DeVries JG, Scharer B.
    Kinematic Changes in Patients with Double Arthrodesis of the Hindfoot for Realignment of Planovalgus Deformity. Reinhard Schuh, Florian Salzberger, Axel H. Wanivenhaus, Philipp T. Funovics, Reinhard Windhager, Hans-Joerg Trnka. Department of Orthopaedics, Vienna General Hospital, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria Foot and Ankle Center Vienna, Vienna, Austria.
    J Foot Ankle Surg. 2018 Mar – Apr;57(2):364-369. Medial Double Arthrodesis: Technique Guide and Tips.So E, Reb CW, Larson DR, Hyer CF.

    Reference

    • orthoracle.com

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