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Correction of the Cavo-varus foot using Orthosolutions Titanium screws and Ultos plate

    Overview

    Learn the Correction of the Cavo-varus foot using Orthosolutions Titanium screws and Ultos plate surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Correction of the Cavo-varus foot using Orthosolutions Titanium screws and Ultos plate surgical procedure.
    Pes Cavovarus describes a deformity of the foot characterised by a high arch, and a plantar-flexed 1st ray. Whilst some subtle deformities may represent a physiological normal variant, pes cavovarus is often associated with neurological disorders; the commonest being Charcot-Marie-Tooth disease (Hereditary sensori-motor neuropathy).
    The deformity progresses as a result of asymmetrical denervation of the flexor and extensor musculature. The power of the Gastocnemius-Soleus, Tibialis posterior and Peroneus Longus muscles are usually preserved relative to the Peroneus brevis, tibialis anterior and intrinsic foot muscles, which are demonstrably weak.
    The driver for the deformity is usually a plantar flexion of the 1st metatarsal. In order to engage the ground, the rest of the forefoot compensates by an obligatory supination. The effect of the forefoot supination is (via the forefoot-hindfoot couple) an inversion of the hindfoot, producing the characteristic varus heel. The concept of contracture or tightness of the plantar fascia remains controversial.
    In those patients with flexible deformity, joint preserving surgery can be considered and such a case is detailed here treated with osteotomies and tendon transfers.

    Indications

    Pes Cavovarus describes a deformity of the foot characterised by a high arch, and a plantar-flexed 1st ray. Whilst some subtle deformities may represent a physiological normal variant, pes cavovarus is often associated with neurological disorders; the commonest being Charcot-Marie-Tooth disease (Hereditary sensori-motor neuropathy) with a predisposition to progressive weakness and deformity. Progressive unilateral Pes Cavus is unusual, it is associated with spinal compression and spinal tumour and must be investigated.
    The deformity progresses as a result of asymmetrical denervation of the flexor and extensor musculature. The power of the Gastocnemius-Soleus, Tibialis posterior and Peroneus Longus muscles are usually preserved relative to the Peroneus brevis, tibialis anterior and intrinsic foot muscles, which are demonstrably weak.
    The driver for the deformity is usually a plantar flexion of the 1st metatarsal. In order to engage the ground, the rest of the forefoot compensates by an obligatory supination. The effect of the forefoot supination is (via the forefoot-hindfoot couple) an inversion of the hindfoot, producing the characteristic varus heel. The concept of contracture or tightness of the plantar fascia remains controversial.
    Pes Cavovarus deformity may be flexible or stiff, which inevitably has a bearing on management.
    Flexibility is assessed clinically, by testing movements and correctability of the ankle, subtalar and Chopart joints, and using the Coleman Block test.
    Initial treatment should involve non-operative measures, such as physiotherapy and orthotic management. Corrective Orthotics may be used in flexible deformity, they are designed to compensate for the plantar-flexed 1st metatarsal and correct the obligatory forefoot supination, by incorporating a lateral forefoot build up (posting). In those with uncorrectable deformity, orthotics are less useful as they can only accommodate the deformity.
    In those patients with flexible deformity, joint preserving surgery can be considered.
    In patients who have non-correctable, stiff deformity, fusion as opposed to joint preserving surgery would be more appropriate.
    INDICATIONS:
    Joint preserving surgery should be considered in those whose symptoms have not been controlled with non-operative treatment, and in those with severe or rapidly progressive deformity, in order to preserve or improve mobility.
    SYMPTOMS & ASSESSMENT:
    Patients with Pes Cavovarus have varying degrees of weakness and deformity. Ensure that there is adequate exposure so that feet, ankles, knees, hips, pelvis and trunk alignment can be assessed. Initially examining the patient standing, and walking will provide valuable information regarding the severity of deformity, and degree of functional restriction. When viewed from the front, the arch of the foot will appear high, and the medial aspect of the heel looks prominent (peekaboo sign), there is frequently some degree of clawing of the lesser toes. When viewed from behind, the heel will be varus. The plantar aspect of the foot may reveal callosity or ulceration, frequently under the 1st and 5th metatarsal heads, the base of the 5th metatarsal and the heel.
    If the Tibialis Anterior is sufficiently affected, a high stepping foot drop gait may result, and proximal weakness may lead to a trendelenburg gait. The Hindfoot flexibility can be assessed at this stage using a ‘Coleman Block Test’, when the first ray is left unsupported, the block corrects the obligatory forefoot supination, which, in the case of a flexible hindfoot will lead to correction of the heel varus, if the hindfoot is stiff, it will not correct. Flexibility is also assessed clinically, by testing movements and correctability of the calf, the ankle, subtalar and Chopart joints. Each individual muscle group, including quadriceps should be tested and assigned an MRC muscle power grade.
    INVESTIGATION:
    Antero-posterior and lateral radiographs of the ankle and foot are useful in assessing alignment, deformity and degenerative change, these should be performed weight-bearing.
    MRI or CT scans can provide more information on joint and ligament intergrity. MRI spine should be performed in cases of unilateral pes cavus to exclude spinal tumour or compression, and is often used in the investigation of underlying neuropathy.
    Nerve conduction studies and electromyography are useful in diagnosing underlying neuropathies and for further assessment of muscle function.
    Specialist neurology work-up.
    OPERATIVE ALTERNATIVES:
    Joint preserving surgery should be considered in flexible deformity, stiff deformity will usually require arthrodesis.
    The goal of joint preserving surgery is firstly, to correct the structural deformity in order to re-align the mechanical axis, which is usually achieved with osteotomies and soft tissue release. Secondly to balance the deforming forces using tendon transfers to achieve equipoise.
    A dorsal closing wedge osteotomy of the base of the first metatarsal corrects the plantar flexed 1st ray, whilst a Robert Jones procedure (Extensor hallucis longus tendon transfer plus interphalangeal joint fusion of the hallux) is a useful adjunct if there is clawing of the hallucial interphalangeal joint, this is generally insufficient to correct the deformity in the adult. Heel varus is corrected with a lateralising calcaneal osteotomy. An achilles tendon or Strayer procedure is performed if there is a contracture of the achilles or gastrocnemius.
    In order to balance the foot, The strong tibialis posterior tendon can be transferred through the interosseous membrane to the outer foot in order to act as an evertor and dorsiflexor of the foot. The strong peroneus longus may be tenodesed to the relatively weak peroneus brevis.

    Setup

    Pes Cavus correction is usually performed under a general or spinal anaesthetic.
    A popliteal regional block is performed pre-operatively.
    Prophylactic antibiotics are administered intra-venously.
    A thigh tourniquet is inflated immediately prior to skin preparation and after a WHO check.

    The patient is positioned supine on the table, a sandbag is placed under the ipsilateral buttock which rotates the leg inwards, allowing good access to the lateral heel. The extended lateral approach exploits the watershed between the posterior peroneal, the posterior tibial and the lateral plantar angiosomes, preserving the vascularity and reducing ischaemia to the lateral skin flap. The incision is posterior to the sural nerve reducing injury and neuroma formation.

    Operation – 1

    The extended lateral approach to the calcaneum, extends from the midline superiorly, and the junction of plantar and dorsal skin on the plantar limb.
    The extended lateral approach exploits the watershed between the posterior peroneal, the posterior tibial and the lateral plantar angiosomes, preserving the vascularity and reducing ischaemia to the lateral skin flap.The incision is posterior to the sural nerve reducing injury and neuroma formation.

    Extended lateral approach to the calcaneum. Full thickness flaps should be developed down to bone.

    The full thickness flap is developed sub-periosteally, using a priosteal elevator with gentle retraction using a cats paw retractor.

    A ring handled retractor is placed adjacent to the plantar and dorsal calcaneum to protect the soft tissues. The saw blade in this image is directed too distally .

    The saw blade should be orientated perpendicular to the lateral border of the calcaneum even slightly proximally, to reduce tension on the soft tissues and plantar fascia, which aids lateral displacement of the tuberosity.

    Incorporating a laterally based wedge allows rotational correction to the displacement osteotomy.
    Care should be taken not to penetrate the medial soft tissues with the saw.

    The medial wall of the calcaneum is gently penetrated using a broad osteotome.

    A laminar spreader is used to distract the osteotomy and a periosteal elevator to free up adherent medial soft tissue.

    The proximal tuberosity is displaced laterally and the laterally based wedge closed

    Dorsiflexion of the ankle ‘locks’ the correction.

    A guidewire is passed from the posterior calcaneum, above the weight bearing surface through a longitudinal incision, and passed into the body of the calcaneum, taking care to avoid penetrating the subtalar joint. Aligning this on the lateral side of the osteotomy, helps compress the lateral wedge.

    The postion of the guidewire should be checked flouroscopically before drilling and screw fixation.

    Screw length is determined using a depth gauge.

    A cannulated drill is passed over the guidewire, again taking care not to penetrate the subtalar joint. Saline is used to cool the drill and prevent heat necrosis.

    The osteotomy is fixed here with an orthosolutions 8mm cannulated screw. It is adviseable to countersink the screw head.

    Stability of the osteotomy once fixed is assessed using a chisel test, whereby the blade of the osteotome is toggled in the osteotomy, which should be stable, if not a second screw may be required.

    the wound is closed in layers with absorbable sutures to subcutaneous tissue.

    Interrupted mattress sutures to the skin.

    Plantar flexion of the first ray is revealed when the hindfoot is reduced to ‘Talar-neutral’ a position.

    Forceps placed along the lesser metatarsal heads demonstrate the plantar-flexed 1st metatarsal.

    A dorsomedial incision located over the base of the 1st metatarsal.

    Care is taken to protect the medial cutaneous nerve situated deep to the vein here.

    The 1st tarsometatarsal joint is located, here, demonstrated by a green needle.

    A dorsally based wedge oteotomy is created using a fine power saw, careful retraction of the soft tissues. Care to avoid breaching the plantar cortex.

    The dorsal wedge is removed.

    Operation – 2

    If not mobile, the osteotomy site is gently levered using a small osteotome, again taking care not to break the plantar cortex.

    The osteotomy is closed by applying upward pressure under the first metatarsal head.

    The osteotomy may be fixed with a plate, screws or compression staple.

    Here the osteotmy is fixed with an Orthosolutions 2.7mm ‘T’ shaped Ultos locking plate.

    The Orthosolutions Ultos plate producing low profile stable fixation.

    Correction is assessed clinically. Here, with the hindfoot reduced, the first ray now looks well corrected, flush with the lesser metatarsal heads.

    The tibialis posterior tendon is harvested from its navicular insertion. It is approached via an incision between the posterior medial malleolus and the navicular tuberosity.

    The tendon sheath is opened using Mcindoes dissection scissors.

    The tendon is exposed down to its navicular insertion where it is elevated with a layer of periosteum. The plantar extensions of the tibialis posterior tendon will also need to be divided.

    The distal tibialis posterior tendon is whipstitched using a strong non-absorbable suture.

    The tendon with whip stitch in-situ, the stitch should emerge from the distal end and care should not be too bulbous.

    An incision is made over the tip of the tendon passing forceps which has been passed up the tib post sheath. The proximal tibialis posterior tendon is identified lying posterior to the tibia.

    The tendon is brought into the wound with the help a tendon hook.

    The tibialis posterior tendon delivered into the proximal incision.

    A Tunnel is developed through the proximal incision, hugging the posterior tibia through the interosseous membrane using a Mcindoes scissors. An incision is made over the tip of the forceps, taking care to protect the superficial peroneal nerve, which is at risk here.

    The jaws of a curved tendon passing forceps, are closed over the tips Mcindoes scissors and railroaded back through the tunnel to emerge in the medial incision.

    The forceps emerging through the medial incision, retrieving the tibialis posterior tendon whip-stitch.

    The tibialis posterior tendon is then pulled laterally through the tunnel. A thick suture tie (blue) is passed through the resulting tendon loop before it disappears into the incision, which makes retrieval straightforward if the tendon was to become stuck, or lost in the tunnel.

    The tendon is delivered into the lateral incision.

    Assess the length of the tendon, by dorsiflexing the foot in order to determine suitable implantation sites.

    The tendon can be implanted into bone or on to tendon. I tend to tenodese to peroneus brevis, which provides a strong repair and a strong everting moment.
    Here the elected implant site is the peroneus brevis tendon, an incision is made over the tendon, taking care to respect the plantar skin bridge and sural nerve.

    the peroneus brevis is exposed.

    a subcutaneous tunnel is developed between the two lateral incisions using a McIndoes scissors.

    A curved tendon passer is driven through the tunnel to emerge in the proximal incision.

    The tibialis posterior whip stitch is pulled through the tunnel. The tendon sometimes gets snagged in the incision and can be fed into the tunnel with forceps. Again a strong tie (blue) is threaded through the resultant tendon loop, to aid recovery if the tendon gets stuck or lost in the tunnel.

    Operation – 3

    The tibialis posterior tendon is delivered into the distal incision.

    The tibialis posterior tendon is passed underneath the peroneus brevis, and is tensioned with the foot dosiflexed and everted.

    Finally the tibialis posterior tendon is sutured to the peroneus brevis as a side-to-side repair using 4 interrupted stitches.

    The simulated weight-bearing position of the foot and ankle is finally checked prior to closure.
    It is well balanced now medio-laterally and the significant cavus is no longer evident.

    Post Operative

    A below knee Backslab is applied in the operating room.
    The leg is elevated.
    The leg is immobilised in a below knee plaster for 6 weeks, non-weight bearing, during which time daily low molecular weight heparin is administered.
    At 6 weeks radiographs are performed to ensure union across the osteotomy sites has occurred.
    From 6-12 weeks full weight bearing in a pneumatic boot is encouraged, during which time the boot can be removed to allow gentle exercise, and physiotherapy should commence, concentrating on maintaining flexibility and isolating and gentle strengthening of the tibialis posterior tendon. Excessive load, inversion and plantar flexion should be strictly avoided

    Recommended Reading

    Foot Ankle Surg. 2010 Sep, Flexible cavovarus feet in Charcot-Marie-Tooth disease treated with first ray proximal dorsiflexion osteotomy combined with soft tissue surgery: a short-term to mid-term outcome study.
    Leeuwesteijn, de Visser, Louweren.
    Retrospective study 33 patients with dorsiflexion osteotomy of 1st ray with associated tendon transfers and calcaneal osteotomies. Good results in 90% short to mid term.

    Foot Ankle Clin Sep 2001
    Combined calcaneal and metatarsal osteotomies for the treatment of cavus foot.
    Sammarco, describes combined metatarsal and calcaneal osteotomies to reduce arch height, increase ankle stability and reduce pain.


    Foot Ankle Int Oct 2018
    Comparison of hindfoot osteotomies in the correction for varus hindfoot correction.
    Closing wedge in combination with closing wedge osteotomy achieved greatest correction when compared to lateralising or Dwyer closing wedge osteotomy alone.
    Pfeffer. G
    Foot Ankle Clin 2013
    joint sparing correction of cavovarus feet in Charcot Marie Tooth disease: What are the limits?
    Emphasises the range of deformities and weakness in Charcot Marie Tooth disease, and the need for an individualised approach to surgery.
    Winson.I


    Reference

    • orthoracle.com

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