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Orthosolutions 4WEB articulated total talar replacement for avascular necrosis of the whole talus

    Overview

    Learn the Orthosolutions 4WEB articulated total talar replacement for avascular necrosis of the whole talus surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Orthosolutions 4WEB articulated total talar replacement for avascular necrosis of the whole talus surgical procedure.
    Avascular necrosis (AVN) of the talus presents a challenge to the surgeon to offer pain relief with minimal loss of function to the foot and ankle. In the event of failure of non-operative treatment methods, surgical treatment is limited by the extent of necrosis within the talus and any secondary degenerative changes to the neighbouring joints.
    Avascular necrosis, also know as aseptic necrosis or osteonecrosis, of the talus is an uncommon condition. The most frequently seen aetiology is secondary to trauma with fracture either to the body or the neck of the talus accounting for 75% of cases. With these high energy injuries, there is often traumatic disruption of the tenuous blood supply either as a result of the fracture and/or by poorly planned surgical approaches to treat the injury. The remaining 25% of aetiologies are as a result of long-term corticosteroid therapy, alcoholism, hyperlipidaemia, irradiation/chemotherapy, anti-HIV therapy, thrombophilia and idiopathic causes.
    The talus is particularly prone to AVN because of its precarious blood supply. It has no muscular origins or insertions and 60% of its surface area is covered in articular cartilage. It receives its blood supply from branches of the posterior tibial artery, the peroneal artery and the dorsalis pedis artery through multiple intra-osseous and extra-osseous anastomoses.
    The disease process can be staged in a similar manner to avascular necrosis (AVN) of the femoral head using a modified Ficat & Arlet classification to assess radiographic findings:
    I Normal
    II Cystic and/or sclerotic lesions, normal talar contours, no subchondral fractures
    III Crescent sign, subchondral collapse
    IV Joint space narrowing, tibial cysts, osteophytes, arthrosis
    In its early stages, patients may present with pain and swelling with no evidence of collapse on any forms of imaging. In these instances, most surgeons would advocate a period of cast or boot immobilisation with restrictions placed on the amount weight borne through the affected limb. A patellar tendon bearing cast may have a role in sparing weight through the diseased talus. Some papers even advocate the use of extra-corporeal shock wave therapy. As in early staging of AVN of the femoral head (stage I disease), bone and joint sparing surgeries, in terms of core decompression and either vascularised or non-vascularised bone grafting, have been described and advocated.
    In stage II to III disease, in the absence of progressive arthritis or collapse of the body of the talus with minimal deformity, surgical treatment options are usually limited by the extent of osteonecrosis. For example, if the area of osteonecrosis is limited to the dome of the talus, an isolated ankle arthrodesis may be considered. This is clearly dependent upon good imaging to identify disease extent.
    Total ankle replacement is relatively contra-indicated in this condition simply because any talar re-surfacing component needs a firm bony foundation on which to be seated. In my opinion, planning the surgery for this condition is entirely dependent upon being certain of the viability of the talus by using MRI and CT to assess the extent of avascularity within the bone. It is usual for the head and neck of the talus to be relatively spared of AVN. In these earlier stages of AVN the ankle, subtalar and talo-navicular joints are relatively spared.
    Treatment options for stage IV disease depend upon the extent of the osteonecrosis. In the presence of collapse of the body of the talus combined with ankle and subtalar arthrosis, resection of the dead bone leaves a void that either requires grafting with bulk allograft or a custom truss as detailed on OrthOracle at https://www.orthoracle.com/library/ttc-double-fusion-using-4web-custom-talar-replacement-and-oxbridge-nail-orthosolutions/with tibio-talo-calcaneal fusion or ignoring the void and fusing the distal tibia to the calcaneus. In the presence of significant arthrosis, it may be that a total talar replacement would be less effective at achieving pain relief if it articulated against bare bone at the joint surfaces much in the way that a hip hemiarthroplasty for fracture is sore in the presence of acetabular arthrosis. This remains an unanswered question.
    In this particular case, a lady in her sixth decade presented with an 18-month history of severe pain and swelling in her ankle that was exacerbated by bearing weight but was unremitting at night. With no history of injury and no other risk factors, the cause of her symptoms was diagnosed as being from idiopathic AVN of the whole of her talus. Imaging suggested whole bone involvement with cyst formation, subchondral fracturing but in the absence of degenerative changes to the neighbouring joints and with minimal deformity. With whole talar disease, the options of arthrodesis are limited to pan-talar fusion with or without filling the void left by any resected talus.
    The literature offers some experience of dealing with this scenario in AVN, extensive osteochondral lesions and benign tumours of the talus using partial or total talar resection and replacement (see results section). One advantage that the talus has over most other bones is that it has no tendon origins or insertions. It is a stable intercalated segment due to its complex bony geometry and the fact that it is contained by strong capsular ligaments. Therefore, it does allow itself to be replaced by a prosthesis with a degree of confidence from the surgeon that this should be stable.
    After careful discussion, my patient decided she was keen to preserve joint motion and to consider a custom-made articulated total talar replacement. The consent for this novel technique is complex insofar as the only outcome data is limited to the literature detailed later in the results section. Ultimately, failure of the talar replacement would lead to pantalar/tibio-calcaneal fusion in some format which is the other initial treatment option. In terms of following up a case such as this, I would treat this part of managing the patient in exactly the same way as a total ankle replacement with regular long term follow-up.
    At present, the technology to develop total talar replacements using additive manufacturing techniques is in its relative infancy. Undoubtedly, many companies across the globe will offer this service but my rationale for choosing 4WEB was their overwhelming experience in leading the field in manufacturing prostheses that have had some follow-up in the scientific literature. In the UK 4WEB implants are supplied by Orthosolutions.

    Indications

    INDICATIONS
    In Stage II to III of the modified Ficat & Arlet staging for AVN of the talus: In the presence of AVN affecting the whole bone but without significant collapse or arthrosis, then, to my mind, an articulated total talar replacement can be considered.
    SYMPTOMS & EXAMINATION
    For reasons that are unclear to me, AVN in any site is always unremittingly painful. Nocturnal pain is a red flag symptom for this condition although bearing weight often exacerbates the pain. Swelling is another significant feature, often more abundant than in degenerative conditions. In earlier stages of AVN, deformity and instability of the hindfoot are not expected features. Immobilisation in a walking boot or cast often provides security and some pain relief.
    Inspection of the standing patient should look for associated deformity. The presence and site of old surgical scars are important as their positioning may influence your surgical approach for treatment. Palpation reveals areas of tenderness but motion of the ankle, subtalar and talo-navicular joints should not exhibit crepitus or stiffness.
    IMAGING
    For AVN, I find both CT and MRI useful to assess the bone stock, extent of bony necrosis, the involvement of both the ankle and subtalar joints and, in this case, for pre-operative planning using a custom prosthesis. To this extent, standing CT views would be the ideal gold standard.
    MRI and CT assessment of the whole talus demonstrates the extent of the disease process, in particular bony collapse, deformity or arthrosis in neighbouring joints.
    CT imaging of the contralateral ankle is the most reliable assesement of the normal anatomy of the talus, which is required in the planning process for the custom talar implant. It is particularly helpful in assessing the complex radii of curvature of the head of the talus.
    ALTERNATIVE OPERATIVE TREATMENT
    In my opinion, there are no proven alternative operative techniques for stage II to III AVN. Core decompression is unlikely to work where cyst formation and subchondral fracturing exist. The only key steps in decision making are whether there is any evidence of neighbouring joint arthritis. If there is, then some form of arthrodesis would have to be considered together with replacing the diseased area of bone.
    NON-OPERATIVE MANAGEMENT
    By and large, because of the degree of pain, there is little role for non-operative measures other than to afford pain relief by immobilisation in a walking boot together with good analgesia. By the time patients present, these simple measures will often have been tried. Unfortunately any swelling means that a custom-made rigid ankle-foot orthosis is unlikely to be well tolerated.
    CONTRAINDICATIONS
    Logically, in any patient with AVN of the whole talus, a relative contra-indication to total talar replacement surgery would be any suspicion of ankle or subtalar instability particularly in hypermobility or ligamentous laxity. Be very aware of the red, swollen and unstable foot with little pain. This presentation should raise the suspicion of a neuropathic foot undergoing a Charcot process. The management of this condition is very different and joint replacement is contraindicated. For a comprehensive review of the condition see also https://www.orthoracle.com/library/medial-column-arthrodesis-for-a-midfoot-charcot-rocker-bottom-deformity-wright-salvation-system/
    Open incisions to the ankle in the presence of diabetes, vascular disease or metabolic compromise from steroid treatment are relative contra-indications for surgical intervention due to the high incidence of surgical wound breakdown.
    Active infection or recent active infection and potential patient non-compliance are also to be considered contraindications to this type of surgery.

    Setup

    The patient is positioned supine on the operating table and may require a sandbag under the ipsilateral buttock so that the foot points vertically towards the ceiling. Fluoroscopy should be available with an image intensifier and a trained radiographer.
    Appropriate antibiotics are administered and a thigh tourniquet and exclusion drape are applied. The limb is prepared with Chlorhexidine from toes to tourniquet.

    Operation – 1

    A 60 year old lady presented with pain and swelling in her left ankle and was diagnosed with idiopathic avascular necrosis of the talus from the plain radiographs. Note the appearance of increased density within the talar dome and the significant soft tissue swelling.

    From both the A-P and lateral radiographs, there is a lack of significant deformity within the foot other than a little planus through the midfoot. Further imaging with CT and MRI was arranged.

    CT is useful in demonstrating the state of the neighbouring joints. From this image, it can be appreciated that the ankle is not degenerate. Note the fractured lateral talar process.

    MRI is also useful in demonstrating the extent of the avascular changes within the talus. It is clear from this T1 weighted image that the whole of the talus is involved. The classic “serpiginous” lines (lines with a wavy margin) are visible propagating from the body of the talus into the talo-navicular joint [A].

    This T2 weighted image clearly shows cystic change in the body of the talus.
    It was clear from extensive discussions with the patient that further non-operative treatment was not possible. Surgical options involving arthrodesis were not attractive given the loss of joint motion. Therefore, plans were made for a custom 3D printed total articulating talar replacement.

    The design process requires a web-based meeting with the current 4WEB design and manufacturing team based in the US. In order to plan for any 4WEB custom implant, CT images with 1mm slices are obtained of both feet. the unaffected foot clearly acts as a template in planning. The design team re-format the 1mm CT images into 3D reconstructions for the start of the meeting. The diseased talus is outlined in red.
    The first step in the planning is dependent upon the desired surgical approach. A planned anterior approach was selected based upon cases described in the literature and consulting the experience of the 4WEB design team based upon other surgeon’s experiences.

    The inverted CT images from the contralateral talus are then used to aid in assessing for any collapse or deformity (which was not significant in this case). Here, the image shows the inverted right sided talus sitting in the defect following computer resection of the diseased talus.
    It is noteworthy that the tali are not mirror images of each other. This was most notable in addressing the complex radii of curvature of the head of the talus in both the sagittal and coronal planes a question of estimation for designing the replacement.

    As well as prosthesis design, specific instrumentation such as trial implants are part of the design process. Here, the image in green is the proposed trial with its handle projecting from the the neck of the talus.

    Positioning the patient on the table to rotate the foot into a vertical positionThe patient is positioned supine on the operating table with a sandbag under the ipsilateral buttock to rotate the foot into a vertical position.

    The planned surgical route is via an anterior approach. The tendon of tibialis anterior [A] is marked on the skin as are the joint lines of the ankle [B] and talo-navicular [C] joints.The skin incision is marked by the interrupted line from D to E, lying immediately lateral to the tibialis anterior tendon and coursing across the middle of the ankle and talo-navicular joints.

    Division and preservation of the tibialis anterior tendon sheath The skin is incised to reveal the subcutaneous fat, the superior extensor retinaculum [A] and the sheath investing the tendon of tibialis anterior [B].

    Careful incision in the lateral border of the sheath of tibialis anterior is required because meticulous repair of this structure is mandatory to prevent bow-stringing of the tibialis anterior tendon. Should bow-stringing occur, it can compromise wound healing.
    With careful retraction of this sheath, the tendons of tibialis anterior [A] and extensor hallucis longus [B] are revealed.

    Retract the tibialis anterior retracted medially and the EHL laterally to reveal the neurovascular bundle .There is a venous plexus lying immediately superficial to the deep peroneal nerve [A].

    The deep peroneal nerve and vessels are mobilised and retracted to reveal the fat lying immediately anterior to the ankle joint.Notice that for retraction, gentle use of Langenbeck retractors reduces the pressures on the soft tissue structures.

    Incise the anterior fat of the ankle joint pad longitudinally and reflected both edges to preserve rather than resect it. This is because it is useful to have as much soft tissue coverage of any prosthetic ankle joint.

    Identify the talo-navicular jointWith the edges of the fat pad retracted, a dorsal incision is made in the capsule of the talo-navicular joint to reveal each side of the joint [A].

    Using a fine oscillating saw, the neck of the talus is osteotomised to start the process of resection of the avascular talus.Using the saw for the osteotomy requires care to prevent lunging through the plantar cortices and compromise of any joint surfaces on the calcaneus. Apart from the feedback gained from the saw, most saw blades have etched measurement marks on them that can help you stay within the bone.

    Complete the osteotomy of the neck of the talus with osteotomesThe saw is best used to do the majority of the osteotomy but completion should be with an osteotome in order to reduce the possibility of damaging the middle and anterior facets of the subtalar joint. After all, the intention of this procedure is to preserve the articular surfaces.

    Resect the head of the talus.The head of the talus can then be mobilised and, using rongeurs, lifted out. I remember removing pieces of cut bone from the proximal tibia in knee replacement surgery and making sure that your wrongers have a firm grip on the bony fragment and then I twist the bony fragment to avulse it.

    Commence piecemeal resection of the talusThereafter, the rest of the talus is resected piecemeal using the saw and osteotomes in the same manner. There are parts of the talus that are less easy to resect. This tends to be medially where the talus articulates with the sustentaculum tali (anterior and posterior tibio-talar parts of the deltoid ligament) and posteriorly with the capsular condensations around the ankle and subtalar joints (posterior talo-fibular and posterior talo-calcaneal ligaments).
    Take care not to injure any of the neighbouring articular surfaces.

    Here is the whole of the talus which contained several viscous cysts within it.

    All bone should be removed from ligamentous attachments taking care to preserve their integrity as it will be these ligaments that will confer stability to the total talar replacement.
    Here, the posterior facet of the calcaneus [A] is visible and in good health. Unfortunately, I could not photograph the tendon of flexor hallucis longus which was clearly visible passing inferior to the sustentaculum tali – not a view I am used to seeing!

    The articular surface of the medial malleolus is clearly visible [A].

    Following removal of the talus all articular surfaces are inspected.The articular surfaces of the tibial plafond [A] and the lateral malleolus [B] are specifically reviewed. Unfortunately there is some clotted blood on the surface of the tibial plafond. This was washed away with saline as the whole void left by the resected talus is cleared of debris with lavage and suction removal of the effluent. The purpose of inspecting the joint surfaces is to allow removal of any minor chondral flaps.

    Two plastic trial implants are available to use. One trial is made to the exact size based upon CT measurements and the other 1mm smaller in the medial-lateral distance across the dome of the talus with a 1mm reduction in the A-P height of the body of the talus to allow for error in the CT data.

    Operation – 2

    Ascertain prosthesis size with the trials suppliedUsing the T-handle, the smaller trial was placed into the void.

    With trial in situ, assess range of motion and prosthesis stabilityThe fit is best assessed by toggling the T-handle and also feeling the quality of range of motion at all three joints – ankle, subtalar and talo-navicular. Although I had not performed this procedure before, this assessment is remarkably easy because any looseness in the trial was easily appreciable. In this instance, the larger of the two trials conferred the better stability to the hindfoot.

    This is the total talar replacement showing the talar head [A], the lateral process [B] and superior surface [C].
    The prosthesis is made from powdered titanium heated with an electron beam so that the implant is effectively made in layers as in any additive manufactured methodology. Once complete, the prosthesis is then coated in cobalt-chrome and polished.

    This view of the implant shows the inferior surfaces to articulate with the calcaneus.

    The prosthesis is simply reduced into the void with combined longitudinal traction together with plantar-flexion applied to the foot .

    The joint is comprehensively lavaged with with saline.

    Image the reduced prosthesis on the table.Fluoroscopy confirms the satisfactory positioning of the implant in the A-P view.

    The lateral view also confirms a satisfactory position of the talo-navicular joint.

    Repair the sheath of tibialis anteriorUsing 1/0 vicryl, the fat layer is closed over the prosthesis. More crucially, the sheath overlying the tendon of tibialis anterior is repaired with the same suture material.

    Close the skin then apply dressings and casting.The skin is closed with everted edges using 3/0 monocryl. Jelonet gauze is applied directly to the wound followed by dressing gauze and orthopaedic wool. With the foot in a plantigrade position, back and stirrup plaster of Paris slabs are applied and secured with a crepe bandage.

    At 8 weeks post surgery, the patient is feeling much more comfortable than prior to surgery. These weight bearing views were taken. Here is the A-P view showing the concentric appearance of the implant in the ankle mortise.

    The lateral view suggests and improvement in the midfoot planus since the pre-operative views.

    The D-P foot view shows the concentric appearances of the talonavicular joint.

    Post Operative

    The patient is placed in a below the knee back slab for the first two weeks after surgery and not permitted to bear weight. The purpose of this is to rest the surgical wound. At two weeks, after wound inspection, bearing weight in a walking boot is permitted with physiotherapy to encourage active range of motion of the ankle, subtalar and talo-navicular joints.

    Rivaroxaban is prescribed for the two weeks when weight-bearing is restricted to lessen the chances of thrombo-embolic events.
    At six weeks, the patient can commence bearing weight in normal footwear. At twelve weeks, the foot is assessed radiographically with standing views of the foot and ankle in three planes.

    Recommended Reading

    Harnroongroj T & Vanadurongwan V. The talar body prosthesis. J Bone Joint Surg 79A; 1997; 9: 1313-1322.
    In this article originating from work pioneered in the 1970s, a polished stainless steel talar body replacement was fashioned based upon measurements from scanograms and implanted in patients mainly suffering from AVN talus. The design differed from a total articulating talar replacement because the design included a peg intended to be cemented into a viable talar head.
    Harnroongroj T & Harnroongroj T. The talar body prosthesis: Results at ten to thirty-six years of follow-up. J Bone Joint Surg 96A; 2014; 14: 1211-1218.
    The same author from the preceding paper reviews the long term results which showed an almost 85% implant survival rate at a minimum of 10 years. Early failures were thought to be as a result of an inability to measure the correct dimensions of the talus and later failures from the interface between the implant peg and the head of the talus. The paper does not cover total articulating talus replacements.
    Taniguchi A, Takakura Y, Sugimoto K et al. The use of a ceramic talar body prosthesis in patients with aseptic necrosis of the talus. J Bone Joint Surg 94B; 2012; 11: 1529-1533.
    This is a retrospective series of two generations of ceramic talar body replacements mainly for idiopathic AVN of the talus. In the main, these were talar body replacements with a peg designed to integrate with a viable talar head. In the small number of total articulated talus replacements, the outcomes appear superior to those prostheses designed to integrate with remaining talus. The authors conclude that replacing the whole talus leads to better outcomes than partial body replacements.
    Angthong C. Anatomic total talar prosthesis replacement surgery and ankle arthroplasty: an early case series in Thailand. Orthop Rev 2014; 6: 5486; 123-7.
    This case series of four only covers the outcome of one total articulated stainless steel talus replacement in a patient treated for a traumatic extruded talus. At the time of reporting the patients had good functional outcomes.
    Tracey J, Arora D, Gross CE, Parekh SG. Custom 3-D printed total talar prostheses restore normal joint anatomy throughout the hindfoot. Foot & Ankle Spec; 2018; 12(1): 39-48.
    This is the largest series of custom implants have since established a role for improving hindfoot anatomy in patients with AVN. All patients had a total articulated talus replacement 3D printed in nickel-plated cobalt. It s not clear whether this series included patients with Ficat stage IV disease as there are no clinical outcomes documented in the paper.




    Reference

    • orthoracle.com

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