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Total knee replacement- Vanguard XP cruciate retaining (Zimmer-Biomet)

    Overview

    Professional Guidelines Included
    Learn the Total knee replacement: Vanguard XP cruciate retaining (Zimmer-Biomet) surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Total knee replacement: Vanguard XP cruciate retaining (Zimmer-Biomet) surgical procedure.
    Bicruciate retained total knee arthroplasty (TKA) involves the preservation of both the Anterior and Posterior Cruciate Ligaments whilst replacing all three compartments of the knee, patellofemoral and both medial and lateral tibiofemoral.
    Early designs of knee replacement(TKR) tried to mimic the native knee and included Bicruciate retaining mono block designs (i.e. one piece tibial baseplate) and separate medial and lateral prostheses in the tibiofemoral joints such as the early Oxford Knee Designs.
    In the 1970’s Cloutier designed a bicruciate TKA (the Hermes 2C) which was implanted as an originator series in 163 knees in 130 patients. The results were published at 10 years and 22 years, with 82% implant survival at 22 years and objectively stable knees. There were 12 revisions due to polyethylene failure, but if aseptic loosening was used as the indicator for revision the survival rate was 96% at 22 years. This is better than the current gold-standard for longevity of the fixed bearing cemented PCL retained total knee replacement from a number of designs with 10 year survival around this 95-96% mark.
    With the advent of contemporary TKA and partial knee replacement designs bicruciate TKA never reached popularity.
    More recently there has been a global recognition that up to 20% of patients following TKA have a problematic pain in their knees. Consequently many avenues are being explored to try and improve outcome. Examples include the development of robotic and navigated knee arthroplasty surgery to multi-disciplinary schemes to manage patients experiencing pain after knee arthroplasty such as the STAR (Support and Treatment After Replacement) research programme in Bristol, UK.
    Fo more information on the STAR programme please visit:
    http://www.bristol.ac.uk/translational-health-sciences/research/musculoskeletal/orthopaedic/research/star/
    The Vanguard XP is a modified Vanguard PCL retaining TKR which mimics the shape of the Cloutier knee, to avoid resection of the tibial eminence and thus allow retention of the ACL and PCL. The femoral and patella designs are identical to ‘standard’ Vanguard cruciate retained TKA constructs. The tibial component is therefore very different compared to a standard implant because of the ‘cut out’ for the ACL and this also avoids the central keel / stem which is common on most TKA designs. To improve tibial fixation given the lack of stem and keel, the Vanguard XP relies on two small pegs and two small keels on either side of the retained bone island.
    One of the risks of bicruciate designed TKAs is fracture of the bone island which then may compromise the ACL. Extreme care must be taken not to under-resect thus over tightening in extension which will fracture the ACL island.
    Given the novel design and limited outcome studies about bicruciate knee replacement, all of the cases I have performed are included on the Beyond Compliance web site (https://www.beyondcompliance.org.uk/). This platform, which pools surgeons cases, allows careful monitoring of any cohort and optimises the chance of early warning signs being detected if issues become evident with an implant. In addition many of these cases were part of the ALLIKAT trial which is an RCT of Bicruciate retained versus PCL retained TKA, comparing the Vanguard XP with the CR implant; the details of this are available through clinicaltrials.gov and the Health Research Authority (SRCTN12584521). In summary there is a 1:1 RCT and a separate cohort of Vanguard XP patients.
    For more information on Beyond Compliance visit:
    https://www.beyondcompliance.org.uk/product.aspx?pid=7357
    For more information on the ALLIKAT trial visit:
    https://clinicaltrials.gov/ct2/show/NCT03302013

    Indications

    INDICATIONS
    This implant is ideal for any patient with retained cruciate ligaments (both ACL and PCL) who is not suitable for a partial knee replacement such as a medial Unicompartmental Knee Arthroplasty such as the Persona Partial Knee or a Patellofemoral Knee Arthroplasty such as the Journey PFJ.
    Readers may wish to refer to the Orthoracle operation techniques for both the Persona Partial Knee https://www.orthoracle.com/library/zimmer-biomet-persona-partial-knee-replacement-medial/and the Journey Patellofemoral Knee Arthroplasties https://www.orthoracle.com/library/smith-and-nephew-journey-patello-femoral-replacement/
    Thus the ideal candidate will have two or three compartment involvement but with bi-cruciate preservation. As there is no tibial stem this implant also preserves bone stock and so may be an excellent choice in the younger patient with multi-compartment knee disease contemplating knee arthroplasty. An alternative strategy would be bicompartmental partial knee replacement or a more ‘standard’ total knee arthroplasty with either preservation or substitution of the Posterior Cruciate Ligament.
    Given the novel design it should be implanted under Beyond Compliance monitoring in the UK https://www.beyondcompliance.org.uk.

    SYMPTOMS & EXAMINATION
    History
    Patients complain of generalised pain in the knee, effecting more than one compartment, either medial, lateral or patellofemoral. This is made worse by periods of inability and patients often complain of stiffness on starting activities (‘startup pain’) or early in the morning. Activities which load the affected compartment of the knee joint will be more painful with post-activity swelling and stiffness. Classic aggravating activities include stairs (both ascent and descent but often with descent as the most problematic), squatting and kneeling, getting out of chairs, getting into a car. In general pain is associated with load-bearing, but often improves once an activity starts, until the maximal tolerance is reached. Usually extra load-bearing is associated with delayed swelling and stiffness. There is often a reduced range of movement which patients notice as restricting certain activities for example cycling or getting out of a chair
    In this particular case the patient was a 50 year old lady who had previously had an opening wedge tibial osteotomy 5 years previously for medial grade IV disease. The osteotomy had helped for the medial pain but the anterior symptoms had deteriorated and stairs and squatting were a significant problem. Her sleep was disturbed most nights despite regular analgesic use.
    Examination
    The examination should start with an assessment of walking follwed by a Trendelenberg and an attempt at squatting. There is classically an antalgic gate if there is a unilateral disease or a stiff knee gate with bilateral disease. Frequently there is proximal muscle weakness/poor gluteal recruitment which may be assessed during gait pattern or on a Trendelenberg test. Personally I prefer to perform a Trendelenberg test (in this patient group) asking them to place their hands on the hips over the Iliac crests then standing on one leg at a time, observing pelvic tilt by inequality of hand position; if the abductors are weak in the standing leg then the opposite hand will drop down, and the patient will lean to the weak side to restore balance. During squat testing there is usually audible crepitus and the patient will be unable to proceed due to pain. Frequently patients will lean to their favourite side indicating which joint is most symptomatic.
    Sitting examination is very useful to demonstrate patellofemoral height and tracking. In this position it is also prudent to rotate the hip to exclude any referred pain from the hip joint. Palpate for crepitus (during knee flexion) in the patellofemoral joint (PFJ).
    Supine examination should then be performed to detect effusion, Range of motion, localised areas of tenderness usually in the affected compartments (for example in the medial and PFJ) and irritability of the PFJ on compression testing – Clarks test. Caution is required here as this is often painful; I would suggest gently positioning the patella into the trochlear groove passively and should this be painful stopping the test at that stage, quadriceps activation only being required if the initial test is negative. A standard knee examination should be completed to exclude intra-articular pathology, in particular the integrity of the anterior cruciate ligament which is required for a Bi-cruciate Knee replacement.
    In this particular case there was tenderness in the medial tibiofemoral and lateral patellofemoral joint and an intact ACL. The range of movement was from 0-120 degrees. The Patella was very irritable on Clark’s testing.
    IMAGING
    Plain x-rays including alignment views particularly looking for excessive mal-alignment due to bone loss, skyline x-rays, weight-bearing laterals and Rosenberg views should be performed both to demonstrate arthritis with complete loss of joint space in at least one compartment, but also to exclude any significant bone loss or excessive posterior osteophytes which would make a bicruciate knee extremely challenging.
    MRI scan may be required to demonstrate areas of full thickness loss if this is not visible on plain radiographs. Whilst MRI is not imperative it does have the advantage of clearly visualizing the ACL which makes the consenting process easier by reducing the chance of conversion to a standard TKR should the ACL be found damaged at the time of surgery. In this case there is a historic MRI scan from 5 years before the arthroplasty immediately predating the osteotomy procedure.
    ALTERNATIVE OPERATIVE TREATMENT
    Osteotomy had already been performed in this case 5 years previously and the joint had progressed particularly in the patellofemoral compartment. Given the bi-compartmental full thickness change this was beyond partial knee replacement although in occasional cases, bi-compartmental replacement of both PFJ and a tibiofemoral compartment may be considered.
    Total knee replacement is the standard treatment of end-stage knee arthritis. Bicruciate TKR is an alternative to bicompartmental replacement (for example medial unicompartmental and patellofemoral replacement) in the patient where there is desire to maximise function and minimise bone loss. Whilst there are results from earlier designs of bicruciate TKRs, as yet there is only limited data on the current generation of bicruciate TKR designs including the Vanguard XP.
    Standard PCL retaining or PCL substituting TKR of course has much data in its support.
    NON-OPERATIVE MANAGEMENT
    Like all arthroplasty, non-operative treatment must be exhausted before proceeding to replacement. Careful physiotherapy assessment, gait re-education where appropriate and strengthening should be performed. Consideration of shock absorbing insoles and walking aids as well as standard analgesic treatments. Consideration of hyaluronic acid injections and/or steroid injections should also be considered. Newer injection therapies such as fat-derived or platelet-derived therapeutic injections should still be considered in their early stages of assessment.
    CONTRAINDICATIONS
    General absolute contraindications include active infection and medical comorbidities precluding arthroplasty and the absence of full thickness disease.
    Specific absolute contraindications include cruciate injury (ACL or PCL).
    Relative contraindications include patient age (>75 in view of risk for ACL injury) and likely bone quality risking an island fracture intra-operatively thus defunctioning the ACL.

    Setup

    The operative table should be placed with the head of the patient on the outline of the laminar flow. This ensures sufficient space within the laminar flow for all the operative sets.
    The set-up position is identical to any total knee replacement with a side support and foot roll. Patient warming may be achieved by warmed under blanket or hot air surrounding blanket, however caution must be observed during application of a forced air warming device to ensure that there is no leak of air over the operative site. Instead the leak of hot air should be from the head end and outside of the laminar flow zone.

    Operation – 1

    Preoperative long leg AP Radiograph
    My routine is to obtain long leg weight bearing AP radiographs for planning. This as slows measurement of distal femoral valgus angles and checking for any deformity.
    In this case, weight bearing axis passes through the centre of the knee and there is evidence of a healed medial opening proximal tibial osteotomy with removal of plate and healed screw-holes.

    Weight bearing lateral radiograph with moderate PFJ OA and full thickness medial tibiofemoral OA – bone on bone contact.

    Coronal MRI from 5 years prior to TKR. These were taken immediately before the medial opening wedge osteotomy.
    This image demonstrates a normal ACL and full thickness chondral loss in the medial joint.

    My personal preference is for a foot pump on the contralateral leg, a pre-wash with chlorhexidine and then 2% alcoholic preparation of chlorhexidine to include the whole lower limb and then draping with U-drape then an exclusion limb drape.

    The leg is wrapped in a sterile Ioban and the foot roll is set with a knee flexion of approximately 90°.
    The old osteotomy scar and the planned TKA scar are marked.

    Free draping of the limb to allow flexion extension with a resting position of approximately 90°

    Perform a slightly oblique skin incision proximal medial to distal lateral centred on the medial side of the patella.I prefer a subvastus medial approach, but I would advise surgeons to use their standard set-up and approach for TKR.

    The skin is raised medially to expose the vastus medialis muscle(1) and laterally to expose the patella. It is imperative to maintain full thickness skin flaps to avoid problems with superficial necrosis.
    Haemostasis is obtained. There are two very reproducible vessels which require electrocautery during the medial sub-vastus approach; The first of these is in the centre of the vastus medialis seen here held by the forceps and the second is adjacent to the MPFL (medial patellofemoral ligament) which runs on the deep surface of the vastus medialis between the femur and the patella.


    The subvastus arthrotomy is marked out (between points 1 and 2) and performed.

    A sub-muscular (deep to Vastus Medialis) pocket is developed by blunt dissection with the operator’s finger and then the capsulotomy is made in an L-shaped manner for a subvastus approach.
    The distal half of the capsulotomy is identical to a medial parapatellar approach. More proximally the fascia just distal to the Vastus Medialis (VM) should be incised and then the MPFL divided close to its origin.Once this is released the VM will mobilise allowing for subluxation of the patella laterally.

    Hohman retractors are inserted under the vastus medialis and the patella subluxed laterally as the knee is flexed, exposing the trochlea.There is often trochlea dysplasia in these patients and hence the early PFJ arthritis.
    In severe cases this may require debulking with a freehand anterior femoral cut in the anterior-most part of the trochlea, prior to a measured resection using a jig and stylus.

    Osteophytes are removed with a combination of Rongeurs and osteotomes from the femoral condyles.Remember to be careful with the cruciate ligaments.

    The peri-patella osteophytes are removed using a saw.Attention is then turned to the patella.
    In this slide the patella is exposed by two Hohman’s retractor lifting the vastus medialis away proximally and lifting the lateral edge of the patella up vertically into the wound.
    I find that preparing the patella first and then subluxing the flat cut surface of the patella into the lateral gutter creates some space and makes this operation easier.

    The patella is measured in both width and thickness.
    I resurface the patella to maintain as close as possible the natural ratio observed in the native knee as published by Sullivan et al and described as BIPWiT (Bristol Index of Patella Width to Thickness)
    A ratio of 1.8 to 1.0 (width to thickness) is the native ratio and I aim for this in all my knee arthroplasty cases.
    Sullivan et al. Knee. 2014 Dec;21(6):1058-62.

    The patella is resected to leave sufficient bone such that in addition to the patella implant the thickness will be in the native ratio of 1.8.The image shows the post-resection cut surface of the patella ready for an only patella button.

    The patella bone thickness is re-measured after cutting, which ensures that the cut is even across the patella from superior to inferior and medial to lateral.
    Once the remaining bone thickness is known (13mm in this case) then the construct thickness with the patella button can be calculated simply by addition of the patella button thickness.

    An appropriate size patella cutting clamp is applied. Aim to gain good coverage, but without overhang.
    Three (positively stopped) drill holes are then performed for the patella lugs through this guide clamp. The clamp applies from the medial side through the arthrotomy so will only fit in one orientation.

    Once the patella trial is in place the construct thickness is remeasured (26mm).In the Vanguard system there are standard and thin patellae whose thickness varies according to the size of the implant.

    The knee is moved through a flexion arc to ensure full flexion is possible with the patella trial in place.
    If too thick this is likely to reduce knee flexion.

    Notice the predominantly medial degenerative change, but that there is also some lateral change, precluding partial knee replacement.
    I prefer to operate from the foot end of the bed rather than from the side. This allows the advantage of an excellent ‘end on’ view particularly useful for the assessment of component rotation. In addition this also protects the surgeon’s back from twisting during the procedure.

    The femoral canal is opened up using the intramedullary drill from the Vanguard set.
    Remember that the entry point is in line with the anatomical axis of the femur and should be marked on your Radiographs using a digital angle measurement system or preoperative templating platform.
    This should be assessed on each case to avoid excessive valgising of the femoral component.

    Distal Femoral Vanguard Cutting Guide
    The Vanguard cutting guide on an intramedullary rod, sitting on the Mayo table.
    Notice the two adjustable dials:
    ‘1’ for resection depth
    ‘2’ for valgus angle.
    The minimum distal femoral resection is 9mm.

    Separate image of the assembled intramedullary femoral cutting guide

    The distal femoral resection block is inserted on the intramedullary alignment rod and pinnedI plan for a 10mm distal femoral resection which is 1mm more than the minimum for this implant.
    Distal femoral valgus is measured from the long leg XR. In this case I used 5 degrees.
    This step is identical to many standard total knee arthroplasty techniques with a distal first cut off the femur. The block should be aligned slightly externally rotated to the transepicondylar axis and posterior condylar axis. Perpendicular to the tibial long axis is also a helpful landmark.

    Pinning the distal femoral block
    Notice the angel wing through the distal femoral cutting slot – I like to see some resection from the central trochlea.
    There are two distal cutting slots and 3 parallel pin holes to allow for fine tuning should there be insufficient cut made.

    Operation – 2

    The distal femoral cut is made with careful protection of the MCL and lateral collateral and popliteus using a pair of Hohman’s retractors.

    Distal femoral cuts are removed, block still in place.

    Removing the dysplastic trochlea freehand.
    The reason to remove the anterior trochlea is the significant dysplasia in this patient which can prevent appropriate anterior sizing with later cutting jigs in the workflow.
    Unfortunately in severe dysplasia the trochlea boss can often catch the femoral anterior stylus preventing appropriate contact on the anterior femur. The result would be excessive oversizing or anteriorisation of the femoral component.

    The femoral sizing jig allows for changing the degrees of external rotation relative to the posterior condylar axis.
    The jig is placed on the femoral distal cut surface with the feet of the jig under the posterior condyles.
    The correct size is read on the stylus once the stylus has been closed down onto the anterior femur.
    Two drill holes are then made as in most TKAs to accept the lugs from the femoral chamfer block.

    The Femoral chamfer block with cruciate protector is applied to the cut femoral surface and impacted, following sizing.Here a 70mm femoral cutting block is shown demonstrating the ‘backside’ of the jig (with the attachment lugs showing) to demonstrate how the cruciates are protected.
    Notice the cruciate protection (where the forceps are pointing) – this is a cruciform shape of metal which slots into the distal femoral chamfer block from the bone side to block off access for the surgeon’s saw to the ACL / PCL.
    The forceps point to the cruciform insert.
    Whilst this appears a good mechanism, the risk of damaging the cruciate is high so surgical vigilance is required.

    The femoral chamfer block is impacted.
    The 70mm block has been rotated from the last slide to engage the lug holes.
    Ensure that the block is in close contact to the distal femur.

    Ensure that there will be no notching on the anterior femur by using an “angel wing” anteriorly (A), seen here sitting in the anterior slot of the jig, then pin the block in situ medially and laterally.

    The distal femoral chamfer cuts are made.Caution needs to be excercised to avoid injuring the ACL / PCL centrally in addition to the standard structures at risk during this stage of a total knee replacement:
    Medially: the MCL
    Laterally: the LCL and popliteus
    Posteriorly: the tibial artery and vein
    A narrow blade should be used for this step and despite this it is necessary to complete these cuts with removal of the block as in future pictures.
    I am very particular to hold the saw with both hands to minimise ‘jumping’ of the saw which can jeopardise the named structures.

    When completing the femoral chamfer cuts the anterior chamfer is performed last as this is the most destabilising for most distal femoral blocks.

    After removal of the block check the ‘corners’ behind the femoral chamfer block. Completion cuts are made under direct vision, again with care for the cruciates and collaterals. It is particularly the ACL (annotated as ‘1’) which is at risk.

    The femoral trial component is impacted.It is sensible to trial the femur with the patella trial and the native tibia. This ensures there has been sufficient resection from the femur – in other words we wan to ensure this construct is not tight.
    This is a standard Vanguard CR component with lugs on the posterior surface that correspond to those for the cutting block.
    If the knee is tight (inability to fully extend with slight laxity as in a native knee) there is a risk of island fracture intraoperatively or postoperative stiffness.
    Should this be the case then the distal femoral cut needs to be related proximalising by 2mm. Then the chamfer block must be replaced and the anterior and posterior cuts repeated.

    The femoral component is introduced and then impacted flush to the cuts.

    A range of motion examination is performed, but with caution moving into extension, after the femoral trial is seated. Full extension should be possible.
    If it feels tight and full extension is not possible then stop and cut more distal femur. Do not force this as you will cause an island fracture.

    The femoral component is removed and the anterior tibia is then exposed.
    It is important to clear the fat pad (1 shows where the fat pad has been removed) to allow exposure of the lateral plateau. Unlike standard TKA there is no subluxation possible as this would rupture the ACL.
    I like to operate from the foot end of the table to gain an ‘end on’ view of the knee.
    There are tibial sizing templates available to gain an idea of which tibial size will be used. These are often referred to as the ‘pitch fork’ due to their shape. The tibial and femoral sizes are all independent so there is no need to ‘match’ the femoral size.
    The pitch fork is introduced into the knee straddling the cruciates and the size which fits best – achieving most coverage without overhang is then chosen.
    In this case the 71mm tibia was ideal.

    The proximal tibial cutting block (not size specific) is open and extra-medullary aligned. The block should be applied to the tibia aligned to the tibial anterior crest for rotation and pinned.

    The block should be applied to the tibia aligned to the tibial anterior crest for rotation and pinned in one of the fixed holes (the spare hole is annotated ‘1’) which allows movement of the block proximal and distal independent of the extra-medullary alignment rod.
    Notice how the tibial proximal cutting block fits flush to the tibia with the patella tendon subluxed laterally and the fat pad removed.

    This image shows the ‘slope’ checker’ (annotated ‘1’) slotted into the cutting slot of the proximal tibial jig. This highlights the proposed cutting angle. This should be compared to the proximal tibia and the position of the distal trial alignment rod moved to increase or decrease tibial slope to match the native tibia.

    A close up of the tibial proximal cutting jig, this time without the slope checker in position.

    The extension gap checker (1) slots onto the same cutting section in the tibial jig and allows checking that sufficient bone resection has occurred before the cuts are made.Consequently of the mobile areas of this gap measurer do not close comfortably in full extension. The tibial block can be adjusted by rotating the central wheel on the jig(2) and the block will move distally.
    The gap checker should be used again to ensure the new position is satisfactory.

    The mobile arm of the extension gap checker (annotated ‘1’) closes easily between my fingers indicating that sufficient bone will be resected with this jig position when the cuts are made.

    The depth of resection can also be measured with a more traditional stylus.

    The next assembly onto the proximal tibial jig is the bone island jig which is tibial size dependent.This has been introduced in this image but not locked into position as the central lever (annotated ‘1’) is parallel to the floor rather than the tibia.
    To lock the position this central lever is lifted vertically towards the patients head to the position annotated ‘2’.

    I am fine tuning the position of the island protector by use of the ‘tuning fork’ (1).
    The idea is to align the tuning fork with the inter-condylar tibial eminences marking the medial and lateral margins of the ACL insertion. Once this is achieved then the central lever is lifted up to lock.

    The tuning fork is positioned and locked onto the tibial cutting block. Two drills are then inserted into this island protector in the holes directly distal to the tuning fork (1), which are followed by pins.

    The drill pins have been inserted and the island protector has been changed to the closed proximal tibial cutting jig. This slots over the same two pins and then engages in the tibial block and this is locked in position by lifting the lever up (1).

    Operation – 3

    A reciprocating saw is then used to cut down to the drill pins either side of the bone island for the cruciates. The saw is kept perpendicular to the tibial block and runs through to the posterior cortex.
    This is very similar to cutting in a unicompartmental Knee Arthroplasty.
    Caution must be exercised not to lift one’s hands which will increase the tibial slope and cut deeper posteriorly.
    Similarly it is vital not to ‘plunge’ into the knee as the posterior cortex is being cut to protect the posterior neurovascular structures.

    The medial plateau cut is then completed through the tibial jig and the medial tibial plateau bone resection removed.

    There are 9 and 10mm black blocks which are used to check the gap in full extension. Initially this is done after the medial tibial plateau resection. In this image there is a ’10mm’ black block (1) in the medial tibia and medial femoral extension space to show there is sufficient space in full extension on the medial side.

    The same procedure is then repeated with a reciprocating and then oscillating saw to resect lateral plateau bone as has been done on the medial side.

    The bones are prepared in the standard manner for cementation using pulsed lavage with 0.05% Chlorehexidine, followed by packing with dry gauze.

    The 9mm U-Block allows for the thickness of the femoral and tibial components and the polyethylene, which ensures there is sufficient extension space to allow the minimum 9mm polyethylene (or shimmed to make 10mm).
    The U block placed into the cut medial and lateral tibial plateaux and the leg taken into full extensionThe reason there is a U-block (1) rather than a standard Extension Gap spacer block is the retained bone island for the ACL insertion, The U-block straddles the bone island but allows testing of the extension gap. This should not be tight – in other words there should be no springiness moving into full extension and ideally there should be a small degree of hyperextension, be careful at this stage as it is very easy to hyperextend and damage the bone island.

    The anterior part, approximately 15mm of the tibial ACL bone island, then requires resection. The XP set has a sharp bone cutter for this job.In this image I am squeezing the bone cutter handles shut (1)
    I like to remove a little off the corners of the remaining bone island antero-medially and antero-laterally to allow the potential for slight rotational adjustment of the future tibial trial to achieve best rotation and coverage. There is not much movement though as the tolerance is fine and hence the importance of a decent rotational position intiially during this procedure.

    The tibial slope checker (1) is used to measure the difference in slope between the two plateaux. The operative technique allows for this small discrepancy, half a millimetre is shown in the image.However if there is any greater disparity in slope then the hand file on the set should be used to rasp the required plateau to fine tune this slope.

    I have filed down the anteromedial tibia slightly to align the cut plateau. This slope checker now shows no difference in slope between medial and lateral cuts.

    The correct sized tibial trial is implanted and an extra-medullary rod is position to check rotation and slope alignment.

    The tibial trial baseplate pinned in position and lug holes drilled in each plateau.

    A very small keel is cut in each plateau by an ‘electric toothbrush’ saw, similar to the Oxford Microplasty blade for keel resection, but even smaller.

    The tibial trial (with keels / lugs) is then inserted.There is a C-arm impactor available but at this stage it is rarely necessary.

    The femoral component is introduced and impacted home. Again caution with excessive impacting as this can also damage the cruciates and their insertion on the bone island.

    The medial and lateral tibial trial bearings are insertedThese are independent and can be different sizes, although I have found that with this technique they are virtually always the same. It is possible that this (Vanguard XP) technique would lend itself well to kinematic alignment and differing bearing thickness.
    The bearings start at 9mm and rise to 13mm

    The knee is then put through a range of motion and an EUA to test for stability.

    Once the happy with the component stability and sizing the femoral lug holes are drilled through the femoral trial.

    I use Palacos Regular Viscosity Cement with Gentacmin (Heraeus). I like to gun this into the tibial cut surfaces and place onto the tibial undersurface of the component.

    The tibial component is the first to be gently hit home with the tibial impactor (1) after cementation.Excess cement is removed in a standard manner with a MacDonald.
    Here the jig for implanting the

    A similar approach is made to cementation on the femur – gunned into the distal femur and applied to the undersurface of the implant – all over.

    The femoral component is inserted and impacted after cementation.

    Trial tibial bearings are inserted on the medial and lateral sides.In this image the lateral trial bearing is in place (1) but the medial bearing is not in position within the medial side of the tibial tray (2).
    The ACL is still present with no island fracture

    The patella is lavage, dried and cemented in place before clamping. Excess cement is removed.

    Ensure the definitive lateral and medial tibial bearings are located in position before passing the lock pin.Once cement has cured, all excess is removed and a further chlorhexidine lavage performed.
    Then the medial and lateral definitive bearings are opened and introduced, remembering which is medial and lateral respectively.
    This instrument (1) ensures that the individual polyethylenes are sitting in the correct position within the medial and lateral sides of the tibial tray. This is important because if the two bearings are not co-located to the tray and thus to each other then the locking pin will not pass smoothly though both bearings and the anterior central tibial component thus locking both bearings securely to the tibial tray.
    Here the lateral bearing is being checked.

    Ensure the definitive medial tibial bearing is located in position before passing the lock pin.

    Operation – 4

    Finally a locking pin (1) is placed from the medial side to lock the bearings in place.

    A locking bar (1) then slides in for the medial side (2) into the tibial tray and ‘clicked’ in as the handles (3) close.

    Standard capsular closure should be employed.
    I use a barbed number 1 monofilament absorbable suture.

    A watertight capsular closure should reduce wound problems.

    Deep dermis is closed with interrupted absorbable size ‘0’ to oppose the wound then continuous 2-0 absorbable suture.

    Skin: subcuticular absorbable barbed 2-0 monofilament is my personal preference
    Skin glue: application of this with the skin wet makes the glue cure much quicker.

    Clear occlusive, showerproof dressing.
    Wool and Crepe for 24 hours, which is then reduced and a tubigrip applied
    When I perform day-case arthroplasty (as in this case) the post-op staff reduce the bandage later the same day (not disturbing the wound occlusive dressing) and apply tubigrip (as a lightweight compression) before discharge.

    Well sized components on the AP radiograph.
    Notice how they tibial implant sits centrally on the tibia and the bone island (1) is visible in the centre of the knee.
    There is a good mantle of cement around the tibial implant.

    The lateral radiograph again shows appropriate sizing with healthy interdigitation of cement.
    Notice how flush the femoral component sits relative to the anterior femoral cortical line.

    Post Operative

    POST OPERATIVELY
    Foot pumps when on bed.
    Weight bear ASAP – DAY CASE ARTHROPLASTY Protocol
    Full weight bear.
    Aspirin 150mg orally for 6 weeks OR Clexane 20mg today at 1800 and then 40mg from day 1 until day 10 at 40mg – self-administered (if intolerant of aspirin)
    Xray
    Reduce bulky dressing later today and apply single Tubigrip ankle to thigh, ICE band please.
    Home when safe – later today please
    Follow up in Outpatient’s at 2 weeks then 6 weeks

    Recommended Reading

    As at the time of writing there are no meaningful results published for the XP Vanguard system, as it’s a implant that is fairly new to market.
    The results of each implant should be carefully monitored prospectively, ideally as part implanted as part of a monitoring system. In the UK we use Beyond Compliance and all my cases are enrolled.
    There are potential advantages of the Bicruciate retaining system. For example the longterm data from the Hermes 2C by Cloutier suggest that this bicruciate retaining design can last well out to 22 years. Arnout et al in a cadaveric study demonstrated a more normal laxity envelope in bicruciate TKA design which mimics the native knee envelope compared to a more distracted and artificial picture form standard TKA.
    A kinematic and electromyographic study by Simon et al showed lower peak muscle activity in vastus medialis on downhill walking in bicruciate TKA patients compared to ACL sacrificed ‘standard’ TKAs. Similarly the bicruciate group had better peak knee flexion at heel strike.
    Thus there is a sound basis to believe that there exists the potential for excellent longevity and possibly for better functionality with bicruciate TKA designs.
    References:
    Total knee replacement with retention of both cruciate ligaments: a 22-year follow-up study.
    Sabouret P, Lavoie F, Cloutier JM.
    Bone Joint J. 2013 Jul;95-B(7):917-22. doi: 10.1302/0301-620X.95B7.30904.
    PMID: 23814243

    Knee Surg Sports Traumatol Arthrosc. 2019 Aug 3. doi: 10.1007/s00167-019-05639-4. [Epub ahead of print]
    Knee joint laxity is restored in a bi-cruciate retaining TKA-design.
    Arnout N, Victor J, Vermue H, Pringels L, Bellemans J, Verstraete MA

    J Arthroplasty. 2018 Sep;33(9):2884-2889. doi: 10.1016/j.arth.2018.05.010. Epub 2018 May 8.
    Level and Downhill Walking to Assess Implant Functionality in Bicruciate- and Posterior Cruciate-Retaining Total Knee Arthroplasty.
    Simon JC, Della Valle CJ, Wimmer MA.

    Reference

    • orthoracle.com

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