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Osteochondral grafting of the talus (OATS procedure)

    Overview

    Learn the Osteochondral grafting of the talus (OATS procedure) surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Osteochondral grafting of the talus (OATS procedure) surgical procedure.
    Autologous osteochondral grafting of the Talus is normally reserved as a secondary procedure after a failed microfracture.
    Though there is some evidence that the high grade lesions do less well with an arthroscopic debridement and microfracture this is a much smaller operation than open grafting and a number will settle with no more intervention required.
    It is key that the Osteochondral grafts are placed as precisely (and flush) with the existing articular surface as possible which in most cases means a malleolar osteotomy will be required.
    Secondary interventions are also on occasion required post grafting and a return to normal and full function is not likely for at least 6 months.

    Indications

    INDICATIONS.
    -For “salvage” after failed primary debridement of an steochondral defect
    -For recurrence of a defect after initial resolution.
    -Some advocate this as a primary operation for more extensive defects (though their is no strong evidence on which to base this).
    SYMPTOMS & EXAMINATION.
    The predominant complaint is ankle level pain , felt deeply within the joint. In the majority of cases this will have started with a recalled single ,significant trauma, most often a severe “sprain”. On occasion the ankle will have been fractured and symptoms have failed to settle after union . It is also well recognised that in a minority of patients there has been no trauma prior to onset of the condition. The localising of pain with respect to the exact location of the defect poorly correlates with its anatomical location within the ankle joint. Pain is usually on weight-bearing activity and often felt most during impact and sporting activity rather than normal day to day activity.
    A number of these cases will present with a history of recurrent instability as well as pain and the question is whether this is mechanical due to an inter-current ligament laxity or whether it is more of a functional issue and due to the osteochondral joint pathology. Whatever the MRI findings these only indicate whether the lateral ankle ligaments (in particular) have been injured and is not an indicator of their likely stability .This is determined by an examination (which may only be definitive under anesthetic at the time of operative treatment).
    If post-traumatic in onset the other conditions which can be produced by the same injury should also be considered and questioned and examined for. The roll call of the commoner other pathologies includes peroneal tendon tears or subluxation, tibialis posterior injury ,posterior ankle impingement, lateral talar process fracture, 5th metatarsal base injuries , occult malleolar fractures, pure syndesmotic ankle injuries.
    Early arthritis should be considered in the differential diagnosis (see MRI section below)
    In the specific scenario of a micro-fractured ankle that has failed to settle in the expected time Osteochondral grafting is not immediately required. Activity should continue to be limited and the joint off-loaded. An intra-articular injection of steroid and local anaesthetic is appropriate anywhere after 12 weeks post-operatively and the use of serial , monthly MRI scans to monitor progressive reduction in bone oedema and defect healing. A secondary arthroscopy may be indicated in those defects in whom the MRI has significantly improved but in whom symptoms persist. The inference would be a diagnosis of recurrent synovitis, arthrofibrosis or possibly some delamination of the new chondral layer.
    Examination of an ankle with an isolated defect is often unrewarding with even minimal ankle joint tenderness. The additional pathologies listed above should also be examined for.
    INVESTIGATION.
    MRI: MRI is the standard investigation for both post-traumatic as well as most un-diagnosed ankle pain. It can be difficult on occasion to be sure of the state of the underlying bone if very significant oedema is present and in particular whether cystic change exists. Nevertheless it gives enough detail to plan operative treatment and to inform the Surgeon about the depth and extent of debridement required.
    The investigation is not 100% sensitive either for pure chondral injuries which may escape it entirely or show as very subtle and limited subchondral oedema. How to treat a purely chondral defect with no underling structural bone defect is not well evidenced. It is legitimate to simply debride the loose chondral tissue back to stable chondral surface without necessarily micro-fracturing. Treating as per an Osteochondral defect is also legitimate though in my experience many Chondral injuries settle with just careful debridement.
    An Osteochondral defect with contained (or uncontained) bony debris and areas of subchondral cavitation and sclerosis will need micro-fracturing or grafting.
    Limited cystic peri-articular change also can be seen in early ankle arthritis. In this case it will usually effect adjacent tibial and talar articular surfaces unlike a true Osteochondral defect which will effect just one side. This is almost invariably the talar side though the lesion can also occur on the tibial articular surface. Sometimes it is only at Arthroscopy that the distinction between early arthritis and a defect can be made. The latter will not benefit from a micro-fracture or grafting but may be appropriately treated with a debridement.
    As listed above there are a number of other conditions which will produce ongoing pain after an ankle injury. An MRI will be the investigation of choice to diagnose many of these also.
    CT SCAN: This is better for identifying definitively the amount of cystic bone loss associated with the injury than can be determined by MRI. It is not required though for this but can be used as an alternative to MRI and is of use when metallic artefact will degrade the MRI signal.
    X-Ray: On occasion an Osteochondral defect will be revealed on plain X-ray but this will only detect substantial defects and provides inadequate visualisation of the pathology to be used as a screening tool for the injury.
    ALTERNATIVE OPERATIVE MANAGEMENT.
    Arthroscopic debridement and micro-fracture of the defect.
    Retrograde drilling/micro-fracture of the defect under CT guidance.
    Allograft transplantation.
    Carticel transplantation. Patients own cells harvested , grown in culture then re-implanted.
    CONTRAINDICATIONS.
    The usual ones of inadequate vascularity , infection and poor patient compliance. Smoking should also be included as should the presence of arthritis.

    Setup

    GA or regional anaesthesia
    Femoral & sciatic blocks for post-operative pain relief
    Laminar flow , peri-operative antibiotics , 2-4 weeks of post operative LMW Heparin
    Thigh tourniquet and Flowtron on contra-lateral calf
    Ankle positioned into neutral using sandbags & side supports
    Large , rolled up sterile towels behind the ankle to improve access for cuts.

    Operation – 1

    The approach for a medial defect is through a trans-malleolar incision. The skin incision should be centered along the mid-line of the medial malleolus.
    For a lateral defect a Fibula osteotomy is likely to be required. This should be fixed with a contoured plate such as a small fragment DCP. The anterior Talo-fibula ligament may also require division for access.

    Once the fat is blunt dissected through the deep fascia is exposed.

    The extent of the dissection is from the Tibialis posterior tendon (2) to the antero-medial aspect of the ankle. Here the long saphenous vein is seen antero-medially (1).

    Further exposure for osteo-chondral grafting is required. The deep fascia and medial ankle capsule are further exposed (2) by “swab-dissecting” the fat layer off .The medial joint line is identified by plantar and dorsi flexing the ankle. The Tibialis Posterior sheath is also opened to reveal the tendon so it can be later avoided.

    The ankle joint is now fully opened (3) with by sharp sub-periosteal dissection of the capsule off the bone . The objective is to reveal the junction of medial malleolus and tibial plafond(2).

    The medial malleolar osteotomy will run transversely across the malleolus ( from medial to lateral) , perpendicular to the long axis of the Tibia. Its level is approximately 1 cm above the joint line and ceases at the point of intersection of the Tibial plafond to the medial malleolus.
    The periosteum is initially marked with a blade to define the level of the malleolar osteotomy (2). This should be about 1cm above the level of the joint line medially and taken across the anterior tibia to where the medial malleolus joins the plafond.

    The periosteal marking cut has been made(1). The Tibialis Posterior (2) should be fully exposed to allow its protection during the osteotomy.

    The medial malleolus is predrilled (2) with two drill holes prior to the osteotomy. This assists in ensuring anatomical repositioning of the malleolus when the osteotomy is fixed.
    This is normally done with a cannulated screw system.
    The entry point on the tip of the Malleolus should avoid the Tibialis posterior tendon and be placed such that there is room for 2 neighbouring screws.
    The guide/drilling should avoid going intra-articular and a finger placed at the joint line(1) helps orientate. This step is normally done with image intensification.

    The orientation of the guide wires can be checked with image intensification. Given that the medial joint is exposed and most of the malleolus is visible this is not necessairily required.

    A fine high speed saw with a narrow arc is required to cut the osteotomy.
    The initial periosteal mark is not in the correct plane so the line 1-2 will be followed. It can be seen that the Tibialis posterior tendon is being retracted posteriorly to protect it.

    Probing cuts are made along the length of the osteotomy with the saw to avoid overshooting to any degree. The depth of the cut can be referenced from the anterior aspect of the joint.

    The osteotomy is completed from anterior to posterior 1 cm above the junction of the malleolus with the Tibial plafond with the a sharp Lambotts osteotome.
    It is aimed not to enter the joint but to cut the subchondral bone at the point where the medial malleolus meets the tibial plafond( and where the saw cut has reached above the joint).

    Once the osteotomy is complete the malleolus is levered gently(1) to open the medial aspect of the joint. The Tibialis posterior will be attached to the malleolar fragment (2).

    The appearance of the defect may be fairly subtle as here (1). It is always reassuring to have a current MRI which will confirm the true extent of the subchondral change. Note the minimal trauma to the Tibial articular surface at the point of the osteotomy cleavage.

    Another medial osteochondral defect which had undergone primary debridement and microfracture. Despite its immediate appearances the MRI indicated significant ongoing bone oedema and the patient remained symptomatic despite various periods of immobilisation and intervention.

    The appearance at revision surgery was of a stable and well healed fibrocartilage surface layer but with very sclerotic (though healed) subchondral bone.

    As the medial malleolus is reflected the deltoid ligament is visible (1) as is the Tibialis posterior tendon(2).

    The defect has been cored out using the recipient tube harvester which removes the plug to a depth of 13mm. The depth needs to be into healthy bone and the margins of the cut cartilage need also to be into a rim of healthy tissue. Also key when removing this plug of defective tissue is that it is removed at precisely perpendicular to the joint line (allowing the grafted plug exactly the same & appropriate joint-line fit).
    The surface area of the defect needs first of all to be judged and using an OATS sizer on the Arthrex kit. These run from 5-10mm in 1mm increments. It is possible that more than one graft may be required to fill a defect.
    The depth is estimated on the MRI and measured on the tube harvester directly. Usually a size of 15mm graft depth is chosen to allow some impaction of the graft.

    A sound of appropriate diameter is used to confirm directly the depth required. Also this allows a “dummy run” to confirm that the approach and set up allow a graft to be inserted a right angles to the articular surface.

    The ostechondral plug has already been harvested from a superior , peripheral and almost “non-articular” zone of the lateral femoral condyle of the knee using a mini arthrotomy and the harvesting tube seen here. Again it is key that the graft has been taken exactly at right-angles to the surface of the joint so that it conforms to be prepared defect into which it will fit.
    Once being implanted the total depth of the graft can be directly seen on the harvesting tube which has a graduated window.
    The graft is removed from the tube when being implanted by using alternate firm clockwise followed by anti-clockwise rotations as it is being tapped in.
    It is important that during implantation the graft is inserted as close as possible to perpendicular to the articular surface of the Talus. Getting a Talar exposure to allow this usually requires an assistant to firmly plantar flex the ankle ,thus bringing the Talus forward , whilst also distracting the Malleolus.

    On the “shoulder” of the Talus (junction of the main weight-bearing surface and the gutter) it is not possible to get an exact match from the knee for the dimensions/profile of the cartilage surface. The graft will need to be carefully impacted with reference to both these surfaces. Impaction can be with a plastic “tamp” which is on the set but extreme care should be excercised to avoid splitting the chondral surface. If the graft is proud to any degree it should be removed and repositioned. In reality it is not often possible to salvage the graft and another should be harvested if required.

    The osteotomy is reduced and held reduced with AO reduction clamps during malleolar fixation. It is key to ensure that this reduction is as anatomical as possible before screws are inserted. A drill is placed into the second hole (2) to help maintain the reduction during screw insertion (1). Some malrotation can still occur and attention should be paid to the visible margins of the osteotomy. There will inevitably be some bone loss at the osteotomy site no matter how well performed it is.

    The second screw will be driven home over its guide wire (2) after seating the first screw(1). Care should be taken to avoid impinging upon the Tibialis posterior by the screw head. Two screws provide more rotational stability than a single screw. Fixation should be checked and copy taken with an Image Intensifier.

    The approach for a medial defect is using the medial malleolar osteotomy. Here the medial malleolar osteotomy is well healed in anatomical position (2) and the Osteochondral defect has been reconstructed (1).

    The approach for a lateral defect requires a fibular osteotomy. Consideration should also be given to sectioning (and later repair) of the syndesmotic or ATF ligament if required for adequate exposure.

    Operation – 2

    An MRI of a cystic medial Talar Osteochondral defect before treatment with micro-fracture technique (the normal first line of management)

    An MRI of the same medial Talar osteochondral 18 months after micro fracture technique.
    The defect has filled fully with bone ,the Chondral signal appears normal and the bone oedema in the Talus has resolved.
    Often the MRI results are more equivocal and require interpretation of both T1 & T2 images to get the clearest picture of structural improvement.

    Post Operative

    2 weeks in back-slab
    dressing changes at 1 & 2 weeks
    Complete cast between weeks 2 to 6 & non-weight bear
    Check X-ray at 6 week stage .
    Into long post-operative boot and gradual increase in weight-bearing at this stage.
    Start ankle & subtalar range and non-weight bearing strengthening program.
    Once patient comfortable full weight-bearing in boot commence balance and proprioception program out of boot with physio.
    May be comfortable enough to make transition into stiff soled walking boot by 9-10 weeks.
    Bike & pool work weeks 12-18
    Cross-training weeks 18-24
    Light treadmill jog by week 24 earliest.
    If equivocal improvement patient will require sequential MRI scans and may need further activity modification. On occasion local/steroid injection is required post surgery if synovitis occurs . A failure to respond to injection (with improving/fully settled MRI scan) may indicate some delamination of the chondral surface or the presence of arthro-fibrosis both of which are likely to require a theraputic arthroscopy if they fail to settle.

    Recommended Reading

    Outcome of osteochondral autograft transplantation for type-V cystic osteochondral lesions of the talus.
    J Bone Joint surg.2006.88-B:614-619.
    P.E.Scranton jr , C.C.Frey , K.S.Feder.
    50 patients retrospectively reviewed at a mean of 36 months 90% with good or excellent outcome.
    20% did however require a subsequent arthroscopy for ongoing symptoms and 4% needed fusion(both with degenerate ankles at the time of grafting).
    A malleolar osteotomy only required in 26 of the 50 patients (10 lateral and 14 medial did not need one). 64% had undergone one previous operation and 22% had at least two operations.
    Early results of autologous chondrocyte implantation in the talus.
    J Bone Joint surg.2005.87-B:179-183.
    J.Whittaker , G.Smith , N.Makwana, S.Roberts , P.E.Harrison , P.Laing ,J.B.Richardson.
    10 patients with a mean 23 month follow up. 6 of these had already had surgical treatment, one with bone grafting.
    9 pleased /extremely pleased & 1 unchanged.
    9 patients re-scoped at average of 12 months and biopsied (defects healed in all and histology revealing mainly fibrocartilage with some hyaline cartilage. At 12 months ongoing minor knee symptoms in 7.
    Arthroscopic treatment of osteochondral lesions of the talus.
    J Bone Joint Surg.2003.85-B:989-993.
    D.E.Robinson , I.G.Winson , W.J.Harries ,A.J.Kelly.
    65 patients retrospectively reviewed who had undergone debridement and micro-fracture operation arthroscopically. Post op protocol allowed partial weight bearing for the initial 6 weeks.
    51 were graded good or fair at a mean follow up of 3.5 years. Worse outcome noted in medial and also cystic lesions.
    Osteochondral lesions of the Talus:A revised classification
    Foot & Ankle Intl 1999. 20(2):789
    Hepple S, Winson I , Glew D.
    A useful MRI modification of the original Berndt & Harty plain X-Ray classification , now much adopted. Stage 1:articular cartilage damage 2a:cartilage damage with bone fracture & oedema 2b: cartilage damage with bone fracture & no oedema3:detached and undisplaced fragment 4: detached and displaced fragment 5:Subchondral cystic change.
    Osteochondral defects of the Talus treated with autologous bone grafting.
    J Bone Joint Surg (Br)2004;86-B:521-526
    Kolker D, Murray M, Wilson M.
    13 patients underwent curetting and grafting with autogenous cortico-cancellous graft .4 patients had already undergone previous micro-fracture surgery. Non-weight borne for 12 weeks post operatively.
    4 patients required subsequent ankle fusion due to ongoing pain and the development of ankle arthritis (one after osteochondral grafting), 3 required osteochondral grafting due to ongoing pain .
    7 patients were improved and required no further surgery , 5 with mild to moderate pain .
    Engineering custom-designed Osteochondral tissue grafts
    Trends Biotechnol 2008. 26(4):181-189.
    Grayson WL et al
    An excellent full text review of the tissue engineering side of manufacturing products for these defects
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2771165/

    Reference

    • orthoracle.com

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