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Posteromedial release for clubfoot in Spina Bifida

    Overview

    Learn the Posteromedial release for clubfoot in Spina Bifida surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Posteromedial release for clubfoot in Spina Bifida surgical procedure.
    Myelomeningocele (Spina Bifida) is a neural tube defect that occurs approximately one in every 2500 births. Antenatal screening and recommendations regarding the importance of folic acid during pregnancy have reduced the incidence.
    The clinicians most frequently involved in the management of patients with myelomeningocele are the neurosurgeon, urologist and orthopaedic surgeon. The severity of orthopaedic involvement depends of the neurological level, generally defined as the lowest level below which there is no function.
    The L3 level is an important delineator since these patients will have some quadriceps activity, which allows them to mobilise independently. Higher level lesions will require assistive devices to ambulate.
    Foot deformity is very common in myelomeningocele occurring in 30-50% of cases. The higher the level of neurological injury, the greater its incidence and Clubfoot (Talipes) is the commonest foot deformity seen.
    It is important to achieve a plantigrade foot whether a child is ambulant or not because even in “high level” patients (those with thoracic or thoracolumbar neurological levels) the objective is to stand them in into standing frames to improve bone strength, renal function and to boost patient psychological state.
    Whilst Ponseti manipulations, casting and tenotomy are successful in some cases failure rates are significant in teratological feet and posteromedial release remains an important alternative in such cases. The surgical principles to follow are similar to correcting idiopathic CTEV. However, it is important to realise that patients with Spina Bifida will usually be insensate which increases the risk of pressure sores and wound infections. In most cases in these patients the aim will be to provide a flail foot that can then be controlled in ankle foot orthosis (AFO).
    Ponseti IV, Smoley EN. The Classic: Congenital clubfoot: the results of treatment. Clinical Orthopaedics Related Res. 2009 May; 467(5):1133-1145.

    Indications

    INDICATIONS
    The introduction of the Ponseti regime of casting for the management of congenital talipes equinovarus (CTEV – clubfoot) has been one of the greatest advances in the whole of orthopaedic practice. However, syndromic talipes is less likely to be corrected by casting and a significant number of patients will require more invasive surgery.
    A plantigrade foot is particularly important in myelomeningocele if the patient is to weight bear. Since these patients will generally have absent/altered sensation in their feet they are particularly prone to pressure sores which can easily become infected. Weight needs to be distributed evenly across the plantar surface of the foot.
    In non ambulant patients (Thoracic/thoracolumbar level) it is still important that the foot is able to go into a shoe so that individuals can go out into the community. In addition, many of these patients will still want to go into standing frames in childhood.
    Posteromedial release was the gold standard of treatment prior to the advent of Ponseti technique. It remains an important option for those feet that fail Ponseti. Historically babies had surgery around 10 months age so that they have completed casting at around the time they would normally walk (1 year). In the management of spina bifida these time frames are less important since walking will be delayed or will never happen. The ideal time for surgery is between 1 and 2 years age but this can be extended up to age 5 or 6 years. Thereafter Ilizarov treatment is more likely to be effective for severe cases or recurrent cases.

    SYMPTOMS & EXAMINATION
    The majority of cases of talipes in association with myelomeningocele will be high level (thoracolumbar) and therefore insensate. Most (but not all) will be not be community ambulators. However, many will have limited mobility with crutches or frames (Hip guidance orthosis – HGO, reciprocating gait orthosis – RGO). Even non ambulant children will go into standing frames.
    The foot in talipes (whether syndromic or idiopathic) is in a position of equinus and various in the hind foot with cavus (plantaris of first ray) and adduction of the mid foot. The forefoot is pronated relative to the hind foot. The relative contribution of each component may vary but typically all are severe in syndromic Talipes.
    In idiopathic CTEV feet are often scored according to Pirani. This has 6 components. Three hind foot (posterior crease, empty heel, rigid equinus) and 3 mid foot (medial crease, curvature of lateral border, position of head of talus. Each component is given score of 0/0.5/1. The most severe score is 6.0. In syndromic feet Pirani score is typically 5-6.
    Patients will weight bear through the 5th metatarsal if mild deformity and dorsum of the foot (talipes – walk on talus) in severe cases.
    It is crucially important that children can achieve a plantigrade foot that can be controlled in an ankle foot orthosis (AFO).
    It is often preferable to have a completely flail foot rather than an imbalanced foot. Typically in talipes the invertors will have more activity than the evertors. Activity in all muscle groups should be identified as should the sensory level. Check for peripheral pulses since many patients with myelomeningocele have poor perfusion of the extremities due to lack of autonomic innervation.
    IMAGING
    Plain radiographs are useful in older patients but rarely alter management in infants.
    ALTERNATIVE OPERATIVE TREATMENT
    Ponseti treatment should remain the first line form of management. However, care must be taken with casting because of the risks of pressure sores. Failure rates are much higher than in idiopathic CTEV, ranging from 15-30% (Gerlach 2009, Janice 2009).
    The standard sequence of correction by Ponseti is
    1. Correct cavus by supplanting 1st ray
    2. Correction of adduction using talar head as fulcrum
    3. Hindfoot various should correct as forefoot abducts and everts.
    4. Correction of equinus
    5. The majority of patients (>90%) will require achilles tenotomy after 5-6 weekly cast changes.
    In older children (>5yrs) correction of foot deformity with an ilizarov type frame is attractive because this removes the problem of pressure sores under a cast. In addition, since most feet will be insensate the frame is well tolerated and the rate of correction can be accelerated. The limiting factor in Ilizarov treatment is the size of the foot. It is rarely big enough to apply a frame before age 5 years.
    In the most severe cases talectomy remains an option to provide a plantigrade foot although this option is not recommended for an ambulant child.
    NON-OPERATIVE MANAGEMENT
    Ponseti casting should be attempted in younger infants
    CONTRAINDICATIONS
    The only contra indication is active infection or open pressure sores.

    Setup

    Posteromedial release (PMR) can be performed with the patient supine or prone. The prone position is often favoured if a Cincinnati incision/approach is used. In cases where there is fixed flexion deformity of the hip supine position is preferable.
    Surgery is performed under general anaesthetic. Tourniquet is required.
    Since most patients are either insensate or have impaired sensation regional nerve blocks are generally not necessary. The presence of spinal deformity precludes spinal/epidural anaesthetic.
    Loops are advantageous in younger children.
    Historically many patients with Spina Bifida had latex allergy. This was the result of repeated urinary catheterisation with latex catheters. Since such catheters are rarely now used the incidence of latex allergy has significantly reduced. Check whether the patient is latex sensitive. If so, use latex free gloves. For severe allergy the anaesthetic team need to be made aware so that circuitry may need changing.

    Operation – 1

    This 4 year old patient has high level (thoracolumbar) lesion. Non ambulant. Bilateral severe talipes. Pirani score 5.

    Patient placed supine position with thigh tourniquet.Patient is placed supine in this case. Prone positioning allows good access to the hind foot (especially posterolateral structures) for PMR but this patient had fixed flexion deformities of both hips. Note the equinovarus foot position (A). Pressure sores (B) are a major concern in patients with insensate skin. 4o degree fixed flexion deformities of both hips (C).

    In tis case there is fixed extension of knee with maximum of 20 degrees knee flexion. The ankle has fixed equinus at 60 degrees. Note prominent talar head (A).
    Surgical anterior release of knee was performed during the same operation. Surgery planned to release hip at later stage.

    Place sandbag under the control lateral hip to ease surgical accessBy placing a sandbag behind the contralateral hip access to the medial side of the foot and posterior aspect of the ankle is made easier.

    Exsanguinate the leg with Esmarch bandageThis surgery requires a bloodless operating field. Exsanguinate the limb with Esmarch bandage.

    Incision should extend from medial to the achilles tendon well above the ankle to the base of the first ray, running along the junction of plantar and dorsal skin.There are two incisions classically described for a posteromedial release.
    The Cincinnati incision is horizontal cut running from the base of the 1st metatarsal, below the medial maleollus and around the back of the hind foot below the lateral maleollus and as far as the calcaneocuboid joint.
    It provides excellent exposure of the posterolateral structures.
    The incision used in this case is a ‘Turco’ incision.
    It commences parallel and medial to the achilles tendon and then progresses below the medial malleolus (marked MM in the image).
    The incision then extends along the junction between the plantar skin on the sole of the foot and the smoother skin on the medial side of the foot. This is approximately parallel to the tendon of tibialis posterior. The incision should extend to the 1st metatarsal.
    Whilst this provides less exposure to the posterolateral structures it is easier to close when extreme equinus is to be corrected. This is particularly important in patients prone to pressure sores and skin breakdown such as patients with myelomeningocele.

    Sharp dissection through skin and fat.Skin and fat are divided, meticulously diathermying any superficial vessels.

    Identify the neuromuscular bundle, which sits beneath an obvious fascial layer deep to the fat.The neurovascular bundle must first be identified and protected throughout the procedure. After making skin incision the fat layer is next divided. By blunt dissection fat is lifted off the fascial compartment in which the neuromuscular bundle runs.
    In cases of myelomeningocele the nerve is likely to be non functional and may be quite atrophic. The posterior tibial vessels must be very carefully preserved.
    The bundle lies approximately 1/3 of the distance from the medial malleolus to the tip of the heel.

    Open up the fascial tunnel in which the neuromuscular bundle runs and and pass a sloop around neurovascular bundleThe neuromuscular bundle runs in a fascial tunnel. This should be carefully opened and split longitudinally.
    Start at the level of the medial malleolus and run proximally and distally. Tenotomy scissors are ideal. It will not be possible to completely free up the neurovascular bundle in the 1st instance and further release may be necessary as the operation proceeds. The bundle splits into medial and lateral plantar nerves as it enters the foot. Both can be followed if necessary.

    A right angle forceps such as a Lahey is passed around the neuromuscular bundle so that a sloop can be threaded. The nerve is not dissected away from the vessels (it is generally non functional) but rather the whole bundle is isolated with sloop

    The achilles tendon is easily identified posterior to the neurovascular bundle once released and needs to be dissected free of surrounding tissues as far proximally and distally as possible. If a previous achilles tenotomy has been performed there may be considerable scar tissue and adherence to local tissues
    This is quite easy when the tendon sheath is opened. The tendon should be split longitudinally. Make a stab incision using a size 15 blade. Make the stab in the middle of the exposed tendon.

    Split the achilles tendon longitudinally by introducing a mosquito forcep into the stab incision created and then opening the limbs of the forcep.The tendon achilles will split in line with the fibres. Remember that the fibres descend in a spiral fashion (clockwise). As the limbs of the mosquito are opened they should automatically follow this spiral.

    The tendon is divided on the medial side distally and the lateral side proximally, then dorsiflex the foot once the tendoachilles has been dividedThe aim is to perform a Z lengthening. The foot is invariably in varus. The tendon is split in the longitudinal plane. If the medial side of the tendon is detached distally (and proximal laterally) this will in effect direct the pull of the tendon achilles into slight valgus.

    Once the achilles tendon has been divided there will be some improvement in dorsiflexion of the ankle. However this is unlikely to be complete.
    There is an argument to excise a segment of tendon achilles (1-2cm) and not repair it. This reduces the risk of recurrent equinus in the most severe feet.
    In idiopathic CTEV the sural nerve should be identified lateral to the tendon achilles. There is often a ‘sentinel’ vessel with the nerve. It is protected with a sloop. In myelomeningocele the nerve is unlikely to be functional in which case protection is not necessary.

    The flexor hallucis longus (FHL) sits anterior to the neurovascular bundle and is closely applied to the back of the ankle. It should be Identified and divided.Once identified it can be followed distally under the sustentaculum tali. It serves as a useful guide to the subtalar joint.
    In the sole of the foot it crosses over the flexor digitorum longus (FDL) at the ‘knot of Henry’.
    In idiopathic CTEV there will be muscle fibres inserting low down into the tendon (“beef to the heel”). In myelomeningocele the muscle and tendon will be very small and atrophic. The muscle is likely to be non functional and a 0.5-1cm segment should be excised. This will reduce chance of unintended healing and recurrent deformity.

    Following excision of the FHL, a careful subperiosteal release of the posterior ankle and an initial release of the posterior aspect of the subtalar joint is undertaken.Once the FHL tendon has been excised there should not be any further important structures hindering access to the back of the ankle. There will be a layer of fat which should be excised.
    Posteriorly the ankle and subtalar joints are in close proximity. Careful palpation with a blunt instrument such as a McDonald or Watson Cheyne should allow identification.
    Confirmation of location can be obtained once the joint is open by passing the curved side of the McDonald over the dome of the talus and also by looking at the movement that is occurring at the joint, which is in different planes for the ankle and subtalar joints.
    Both joints will need to be opened in the majority of cases so inadvertent entry into the subtler joint 1st is of little consequence.
    The posterior ankle joint should then be opened to the medial malleolus and lateral malleolus, using subperiosteal dissection . The deep part of the deltoid ligament should be preserved to stop over correction into valgus.

    Identify the tibialis posterior and flexor digitorum longus tendons, open their tunnels and divide them.The tibialis posterior and FDL tendons are anterior to the neurovascular bundle, and both run in tunnels over the posterior aspect of the medial maleollus, on occasion sharing a tunnel. Initially they can be difficult to identify. Unlike in the idiopathic clubfoot, in Spina Bifida they will be small and atrophic.
    FDL tendon (A) can just be seen on posterior aspect of maleollus (B). Fat will need to be cleared off the tendon sheaths.

    The FDL (A) tendon lies just behind tibialis posterior (B) and it is much smaller. In idiopathic CTEV it is important to retain at least part of the tunnel that FDL and tibialis posterior run through. In spina bifida this is not necessary since in the majority of cases the tendons will be excised rather than lengthened. Open the tendon sheath by making a small nick with a 15 blade longitudinally over the maleollus. Open the sheaths with tenotomy scissors.
    Follow both tendons distally into the foot. The FDL passes towards the knot of Henry whilst tibialis posterior runs towards the navicular. At the knot of Henry the FDL crosses FHL. In spina bifida it is not generally necessary to dissect the FHL and FDL at the knot of Henry since both will be excised rather than lengthened.

    Excise a 1-2cm segment of both tendons but mark the distal stump of tibialis posterior since it is useful to follow to identify the talonavicular joint.

    Release the subtalar jointA subtalar release will be required in nearly all cases. In talipes associated with spina bifida a complete release of the posterior, medial and lateral aspects of the joint will generally be necessary. This will also include the interosseous ligament between talus (A) and calcaneum.
    Deep deltoid ligament (B) protected by MacDonald.
    Identification of the FHL tendon stump will help since this runs immediately below the sustentaculum tali. The medial side of the subtalar joint is released with sharp tenotomy scissors (C). Freer elevator is seen inserted into posterior aspect of subtalar joint (D).
    The neurovascular bundle runs inferior to this so care must be taken.

    Trace the posterior aspect of the ankle joint laterally to the fibula and divide the peroneal tendons and lateral ligaments.The advantage of a Cincinnati incision is that access to the lateral structures is easier. However it is still possible to perform a thorough lateral release from the medial Turco incision.
    Trace the posterior aspect of the ankle joint laterally to the fibula. The peroneal tendons will lie behind the fibula but in neuromuscular patients may be small, atrophic and usually non functional. In idiopathic CTEV the peroneal tendon sheath is divided but the tendons are preserved.
    The calcaneofibular ligament (A) is generally tight and is divided (same as idiopathic CTEV). The peroneal tendons lie behind the fibula B) and serve as a guide to the lateral part of the subtalar joint which is opened using tenotomy scissors.
    In Spina Bifida the peroneal tendons plus sheath are all excised.

    Once the hind foot has been released posteromedially and posterolaterally it should be possible to dorsiflex the ankle past neutral and evert the heel into slight valgus

    Once the hind foot has been released posteromedially and posterolaterally move attention to the talonavicular joint.One of the main aspects of deformity in talipes is the fact that the navicular sits very medial on the talar head.
    The navicular is in close proximity to the medial maleollus. The talar head (marked with ‘T’) is prominent on the lateral side of the foot and accessing the talonavicular joint can be very difficult.
    It is key to reduce the navicular back onto the talar head.

    In addressing the talonavicular joint firstly trace the distal stump of the tibialis posterior tendon to the navicularRemember that the navicular will be lying on the medial side of the taller head. Sometimes, as in this case, the tibialis posterior tendon is very atrophic.
    Place a mosquito forcep on the stump of tib post(A) and move distally towards the navicular with tenotomy scissors.

    To further assist identification of the talonavicular joint follow the subtalar joint forwards to identify the talonavicular joint
    The midfoot bones will be mostly cartilage in the first few years of life. Attempts to identify the talonavicular joint using sharp dissection can easily result in excising parts of the taus or navicular.
    The anatomy will be distorted and passage of a McDonald or Watson Cheyne (A) along the medial side of the subtalar joint may help lead to the talonavicular joint.

    Operation – 2

    To release the talonavicular joint it should be carefully levered open with a McDonalds and tenotomy scissors used to free its soft tissue attachments.Carefully open the talonavicular joint with tenotomy scissors. A McDonald probe can then be placed over the head of the talus (A). The spring ligament inferiorly should also be released.
    In severe cases the calcaneocuboid joint may also need to be released. This can either be done from the lateral side using a Cincinnati incision or from the medial side with a Turco approach. However, the plantar structures will need to be carefully elevated to access from the medial side which does add significantly to the surgical exposure. This was necessary in this case, but is not shown.

    Once a satisfactory release of the talonavicular joint has been achieved it is generally necessary to maintain this with one or more K wires.
    In the case of myelomeningocele this is very important since it means less pressure has to be applied through the cast, and therefore less risk of pressure sores. On the other hand, the surgeon needs to appreciate that unrecognised wire infection can occur under the cast.
    A wire across the talonavicular joint is nearly always required. A second wire passed through the heel and across the subtalar and ankle joint joint is sometimes also necessary.
    The talus is invariably misshapen. Insert a K wire (1.4 – 1.8mm) from posterior. The neurovascular bundle will need to be protected with a Langenbeck retractor. Aim along the body of the talus toward the talar head.

    Reduce navicular onto head of talus and K-wire it into position, wiring from the posteromedial talus. The talus is usually externally rotated within the ankle mortice. Once the K wire is engaged in the body of the talus it can be used as a joystick to rotate the talus. At the same time a McDonald is inserted into the talonavicular joint. The navicular is then levered into position.
    Advance the K wire until it hits the Mc Donald. Verify that it is exiting the taller head in its middle. The surgeon should then position the foot in the desired position while the assistant advances the K wire across the joint.

    Advance the talonavicular K wire until it exits through skin in the forefoot, then cut and bend it in the forefoot, having advanced in entirely into the talus posteriorlyThe K wire is then advanced until it exits the skin in the forefoot. If the foot has been corrected satisfactorily this will generally mean the wire exits on the dorsum of the foot between great toe and second toe.
    Apply wire driver to the proximal end of the wire anteriorly and pull the wire forwards until the wire has just disappeared into the talus at the ankle.

    Cut the K wire and bend it with needle tip pliers

    Assess plantar fascia, if tight it will require release.Asses the plantar fascia. If tight this can be addressed in different ways. In the classical PMR the abductor hallucis (gateway to the foot) is released through the Turco or Cincinnati incision. The plantar fascia is then approached and divided.
    Alternatively the plantar fascia can be divided in necessary via a small wound centred over the medial side of the fascia on the plantar-medial side of the foot.

    By dorsiflexing the great toe the plantar fascia will be put under tension which facilitates its division with the scissors.The plantar fascia is superficial. It is possible to palpate with an instrument such as tenotomy scissors without having direct visualisation.

    Check that full correction has been obtained prior to release of tourniquet, ensuring that ankle dorsiflexes to just past neutral and that hind foot is in slight valgus.Note how wound is wide open following extensive release.

    release tourniquet and ensure haemostasis, adequate circulation of foot and close in layersRelease the tourniquet and ensure that there is adequate perfusion of the foot and toes. Haemostasis of small vessels may be necessary.
    In myelomeningocele tendons are not usually repaired. The aim is to produce a flail foot that can be controlled in an AFO orthosis.
    If there is some activity in the dorsiflexors (tibialis anterior) then either this should be divided or the tendoachilles should be repaired to stop later calcaneus deformity. Use 1 vicryl Kessler type repair.

    The fat layer should be repaired with 2/0 vicryl interrupted sutures. This will reduce tension in the skin closure.

    Skin closure with interrupted suturesSkin closure will be tight. Use interrupted 3/0 suture such as monocryl.

    In patients with delicate skin and risk of pressure sores a well padded cast must be applied. In this case an anterior release of the knee has also been performed to allow knee flexion.

    Above knee cast is applied with knee flexed and foot in corrected position.The knee must be flexed in the cast. This stops plaster slippage. It also allows external rotation of approximately 30 degrees to be applied to the foot.
    A backstab is applied and then completed the next day with scotch-cast.

    Post Operative

    The foot is kept elevated for 24 hrs to avoid excessive swelling. The cast is completed the day after surgery.
    The cast should be changed at one to two weeks. Since most patients are insensate this can often be done in clinic. A further above knee cast is applied and well moulded. At 4 weeks the cast is changed again and at the same time a cast is made for an AFO. The K wire is removed at 4 weeks and the patient should be ready to go into AFO at 6 weeks.
    Whilst boots and bar are typically recommended for idiopathic CTEV post Ponseti, they can result in excessive eternal torsion on the tibia and foot in spina bifida. These patients will require long term orthotic support.

    Recommended Reading

    Whilst it is usually possible to obtain some correction of deformity a perfect correction is rare and many patients will require further interventions over time. Overall approximately 2/3 patients have a good result. Patients with high level lesions tend to have poorer results than low level spina bifida.
    References
    Gerlach DJ, Gurnett CA, Limpaphayom N et al. Early results of the Ponseti method for the treatment of clubfoot associated with myelomeningocele. J Bone Joint Surgeons Am (2009);91(6):1350-1359.
    Janicki JA, Narayanan UG, Harvey B et al. Treatment of neuromuscular and syndrome associated (non idiopathic) clubfeet using the Ponseti method. J Pediatr Orthopaedic (2009);29(4):393-397.
    Kelly SP, Bache CE, Kerr Graham H, Donnan LT. limb reconstruction using circular frames in children and adolescents with Spina Bifida. Journal Bone and Joint Surgery. 2010;92-B(7)
    de Carvalho Neto J, Dias LS, Gabrieli AP. Congenital Talipes equinovarus in Spina Bifida: treatment and results. J Pediatr Orthopaedics 1996;16(6):782-785.

    Reference

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