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Medial Femoral Condyle Focal Resurfacing with HemiCAP(Arthrosurface)

    Overview

    Learn the Medial Femoral Condyle Focal Resurfacing with HemiCAP(Arthrosurface) surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Medial Femoral Condyle Focal Resurfacing with HemiCAP(Arthrosurface) surgical procedure.
    Focal Resurfacing is gaining popularity for the treatment of focal articular defects up to 20x20mm in the knee (when using HemiCAP), providing a rapid recovery and no post-operative restrictions, differentiating this from biological reconstructive techniques such as cartilage grafting or the use of scaffolds such as Chondrogide . Biological reconstruction techniques usually require a period of reduced weightbearing up to 2 months and often a restricted range of movement range using a brace. Similarly the lack of post-operative restriction to activity differentiates focal resurfacing from traditional arthroplasty or even partial knee arthroplasty for the usually middle-aged patient with focal chondral damage.
    The classic patient for focal resurfacing is in the 40-60 age range with a focal chondral lesion which is symptomatic and has failed traditional non-operative treatments such as offloader bracing and injection therapies such as visco-supplementation or steroid. Please remember to check alignment as osteotomy is an excellent proven treatment for the mal-aligned overloaded joint; focal resurfacing can be considered with or after osteotomy.
    The HemiCAP was released in 2003, but it has taken some time to ‘catch on’ probably due to its innovative approach using a metal articular ‘cap’ inset within the articular surface. This is fundamentally different from partial knee replacement where there is a partial replacement on both sides of a joint.
    There are now a number of implants available such as the HemiCAP, however it has the longest clinical experience and evidence base. Alternatives are the Bio-Poly, a cemented focal resurfacing which uses a novel combination of hyaluronic acid and polyethylene or the Epi-Sealer, a custom-made focal resurfacing relying on uncemented fixation with an option to cover defects up to 25mm in diameter.
    All the focal resurfacings are designed to encourage the native chondral surrounding tissue to overgrow the margins of the inset implant.
    The ArthroSurface HemiCAP condylar implant provides a surgical treatment for the painful chondral or osteochondral defect in the femoral condyles and has been in production since 2003. However the literature is sparse and as yet there is no independent guidance on its indications from the UK National Institute for Clinical Excellence (NICE) although this is planned a the time of writing (May 2021).
    Since the initial design and release in 2003, there have been many evolutions of the design to allow for treatment of the patello-femoral joint (the ‘Wave’ or ‘Kahuna’ implant), the shoulder and the great toe.
    The HemiCAP is an uncemented design and relies on cancellous fixation of the screw in the femoral condyle (the ‘fixation device’) and then the impaction of an Articular Component which matches the native anatomy via two sizes (15 and 20mm diameter) over 16 different curvatures. The two components combine with a morse taper.The Articular Component is made of Cobalt Chromium Alloy (Co-Cr-Mo) whilst the undersurface is Titanium plasma spray-coated and the morse taper is Titanium alloy (Ti-6Al-4V).
    The largest metanalysis gives a revision rate of 9% at 4 years, but this includes all focal resurfacings and there have been longer terms studies at 7 years mean showing better outcome with condylar focal resurfacing. There is no doubt that at present the literature is still sparse, but all of the papers have been positive suggesting functional improvement in the vast majority of cases with a small reoperation and even lower revision rate.
    At present focal resurfacings are not included in the National Joint Registry in the UK, but this is currently being debated and the relevant national bodies have been asked to comment on their future inclusion in the NJR. Please see the results section for the list of papers and summary results.

    Indications

    INDICATIONS
    Unstable, painful chondral or osteochondral defects up to 20mm in diameter in the femoral condyles – medial or lateral. There is a patella-femoral variant of this implant made by ArthroSurface called the Wave for PFJ defects.
    The defect should be unifocal – in other words it should only be on one side of the joint. Focal resurfacing is therefore not for ‘arthritis’ where there is joint failure on both sides of the joint. It is possible that patients have have progressed to arthritis from an initial chondral lesion and I therefore consent for proceeding to partial knee replacement of the affected side of the joint (Medial or Lateral) should there be bipolar defects on both femur and tibial sides.
    In the young patient I would always try a biological reconstruction first – chondral grafting or scaffold (eg Chondrogide implantation). Historically microfracture or drilling has been performed although this is questioned now due to the risk of intra-lesional osteophytes and a poorer outcome with subsequent chondral regenerative techniques following microfracture.
    Consequently there has been a resurgence of drilling and abrasion techniques (using a burr) and a less invasive microfracture technique called nano-fracture which requires a very simple aiming device with a central cannula for a small bore wire which penetrates the subchondral bone; hopefully this will have less side effects than microfracture.
    The problem though with any regenerative technique is the lengthy rehab process and for that reason I am using more focal resurfacings in the middle-aged population to allow a clearer and simpler recovery pathway.
    Focal resurfacings can always be used as the salvage for biological reconstruction and similarly partial knee replacement is the salvage for a potential failed focal resurfacing.
    SYMPTOMS & EXAMINATION
    Symptoms:
    Localised pain over the affected compartment, most commonly the anteromedial knee – often the patient is able to locate the site of pain with one finger on the medial side of the knee. However if the patient is experiencing lateral femoral condylar damage then this pain and tenderness will be on the lateral side. Remember that for patellofemoral cases the pain is located anteriorly.
    In this case however the classic symptoms of anteromedial pain and finger-pointing were found
    Stiffness
    Examination:
    Tendereness in the anteromedial knee around the tibiofemoral joint line. Remember that for lateral or PFJ disease this will be in the relevant compartment and not the anteromedial knee; the rest of this examination is relevant to the anteromedial focal chondral lesion present in this case ( and the majority of focal chondral lesions)
    Pain on loading in varus at 20-30 degrees of flexion.
    No pain in the lateral joint on valgus loading – sometimes there may be exacerbation of the medial pain on valgus loading.
    Intact ACL – or reconstructed ACL. The ACL should be functional – without this the knee will not work normally and degenerative progress is likely. However as we are seeing in the partial knee replacement space, extended indication proponents would debate this. For example if a patient was not functionally unstable even in the presence of ACL damage, use of a fixed bearing medial partial knee replacement (PKR) may still be appropriate. However the classical indication is an intact ACL
    IMAGING
    Radiographs– 4 views for all patients.
    AP weight bearing– ideally long leg alignment views
    Weight-bearing lateral
    Skyline patella view
    Rosenburg (PA flexion at 45)– this really stresses the lateral tibio-femoral compartment. If there is any suggestion of lateral wear then a stress XR should be performed with values to check the state of the Lateral TF joint under increased load.
    Stress radiographs – only in selected cases – if the joint is failing then focal resurfacing is not the correct option and a partial knee replacement would be far more sensible. Please see :
    Unicompartmental Knee replacement: Persona Partial Knee Replacement (Zimmer-Biomet)
    In order to ensure that there is no full thickness disease on plain AP a varus stress view may be performed if there is clinical concern, but this is not my usual practice and in this case I just used radiograph and MRI.
    MRI
    All patients will have an MRI. Whilst MRI is the most objective modality of imaging the chondral surfaces (& excluding degenerative change of note), the sensitivity of this for chondral defects depends on the strength of the magnet and sequencing protocol; 1.5T is the current standard, but this is by no means perfect and all my cases are warned of the small chance of intra-operative conversion to a partial knee replacement if I find bifocal defects – damage on both sides of the medial tibio-femoral joint. MRI does allow assessment of intra-osseous bone marrow lesions which are markers of increased bone turnover.
    ALTERNATIVE OPERATIVE TREATMENT
    Arthroscopic Chondroplasty to remove unstable margins from the cartilage lesion. In full thickness disease, drilling and nano- or micro-fracture are still performed although there is debate regarding microfracture in particular. The vast majority of patients for focal resurfacing would have already undergone chondroplasty at least.
    Chondral regenerative procedures – scaffolds or autologous chondrocyte implantation may well have been performed and failed. Whilst these treatments can certainly work, when they do not, focal resurfacing is a logical next step.
    Osteotomy – if the long-leg alignment deviation is due to an extra-articular deformity then a realignment procedure can be performed in any age, although classically this is preferred for younger patients with optimal bone stock. Osteotomy surgery should be encouraged if alignment is abnormal.
    Joint Arthroplasty – Partial or Total Knee Replacement – although in this case the defect is not full thickness loss and thus arthroplasty (partial or total) is not indicated.
    NON-OPERATIVE MANAGEMENT
    Lifestyle modifications
    Analgesia
    Bracing – medial offloader braces which push the knee into valgus.
    Injection therapy – steroid for inflammation, or viscosupplementation for stiffness and pain. Platelet Rich Plasma Injections such as N-Stride from Zimmer Biomet.
    CONTRAINDICATIONS
    Absolute
    Active infection
    Active inflammatory arthritis in the same joint
    Untreated and symptomatic ligament laxity
    Relative
    Inflammatory arthritis in other joints
    ACL damage
    Significant loss of range of movement – focal resurfacing will not improve range.

    Setup

    My setup for this operation is usually as shown in:
    Unicompartmental Knee replacement: Persona Partial Knee Replacement (Zimmer-Biomet)
    However in this case I was also performing a tibial tubercle osteotomy and therefore I chose my ‘TKR setup’ as in
    Total knee replacement: Vanguard XP cruciate retaining (Zimmer-Biomet)
    Two main operative setups are used for focal resurfacing;
    Leg holder – the operative thigh is held on or in a leg holder such that the knee can flex freely and hang dependently under gravity. The surgeon may sit or stand. If a sitting style is chosen consider a surgical stool whose height may be altered with a foot pedal intra-operatively by the surgeon
    As a standard TKR position with side support and foot roll. Surgeon standing
    Tourniquet
    Where a surgeon chooses to use a tourniquet this should be applied at the start of the operation high on the thigh before skin preparation.
    My personal choice is to avoid the tourniquet and so attention must be paid to haemostasis during the procedure. Simple techniques such as raising the feet of the operating table and instillation of local anaesthetic with adrenaline at the start of procedure are sensible.

    Drugs
    Intravenous prophylactic antibiotics should be administered early (30-45 minutes) to achieve adequate tissue concentrations at the time of ‘knife to skin’. We use Cetriaxone as a one-off dose.
    Intravenous tranexamic acid on induction – 1000mg.
    If the wound is oozing then this induction dose can be repeated on closure.
    The leg, and knee in particular, is freely accessible by using a thigh holder.
    The thigh holder I favour is that designed by David Murray of the Nuffield Orthopaedic centre, Oxford, which allows deep knee flexion. It is available through Zimmer Biomet Product number 32-420950.
    My standard layout of the sterile field. The surgeon is seated with patient’s leg surrounded by sterile drapes and the assistant is standing proximally towards the patient’s head. The Scrub Nurse stands on the opposite side with easy access to the Mayo table for instruments.

    Operation – 1

    Pre-operative Rosenburg radiograph shows a well-preserved medial joint space. It is critical to differentiate from arthritis where there is joint failure of the medial compartment from an osteo-chondral lesion of the medial condyle as in this case.

    Long-leg alignment radiographs show that the weight-bearing axis passes through the lateral tibial spine. This is useful to know in this particular case as it rules out osteotomy as a potential therapeutic option. Similarly it protects the medial compartment that has the osteochondral lesion.

    Coronal MRI scan.
    The MRI scan shows chondral damage in the MFC (1), but no damage to the Medial Meniscus (2) – this is important as the meniscus is the load transfer device that protects the tibiofemoral chondral surface from excessive loads.
    As the medial meniscal roots are intact and the meniscus is not extruded, this fits with the diagnosis of an osteochondral injury rather than a failing medial compartment on the pathway to arthritis.

    Sagittal MRI scan through the medial condyle, close to the notch showing a normal posterior meniscus (2). The area of chondral damage is just starting on this slice (1).

    Axial MRI scan.
    Notice the integrity of the medial meniscus (1) and the position relative to the tibia. The meniscus is not extruded at all. If this had been the case then I am concerned that the joint is already failing and on the road to arthritis. Consequently focal resurfacing would not be sensible. However in this case it is perfect.

    This is from a different case where I used a HemiCAP, with a medial femoral condyle lesion, previously treated with chondral regeneration techniques. There was persistent pain after 2 years following the attempt at cartilage repair and the decision was made to focally resurface – this image was taken with an arthrosocopic camera (Sterile cover in place) so that I could hold this myself to get these images and so the resolution is poorer than our standard photographic imaging, but the point is well made that the surrounding cartilage is healthy.
    This is a standard sized incision for focal resurfacing, whereas the case used in this technique was with an additional patellofemoral realignment technique and so the exposure is much better making standard photographic imaging possible.
    The damaged cartilage is adjacent ‘1’ and normal Medial condyle is marked with a ‘2’.

    I have used the uncemented Arthrosurface HemiCAP for focal resurfacing for 5 years – there are alternatives but the instrumentation is simple and there is some data to support its use – see results.
    The HemiCAP allows defects of 15mm or 20mm diameter to be covered.
    I have highlighted the initial sizing defect and centralising device:
    1 = 15mm guide
    2 = 20mm guide

    There are very few instruments arranged over 3 trays.
    The trial implants are labelled as ‘1’ – the trials have a handle on the articular side of the implant to allow removal of the trial form the morse taper / prepared articular bed.

    The anteromedial incision ‘1’ and the standard incision for a Tibial tubercle osteotomy ‘2’ are marked on the image for teaching purposes.
    In this case due to the combination of surgery, a single incision was used combining lines ‘1’ and ‘2’ into a single oblique incision.
    The setup is as a TKR, but I have used an arthroscopic drape.
    I have documented my set up and preparation on multiple Orthoracle techniques such as:
    Total knee replacement Genesis 2 (PS) with bi-convex patella (Smith and Nephew)

    The wound is pre-infiltrated with local anaesthetic using a long needle; a grey (16G) venflon needle with both screw cap and adaptor removed makes a good, cheap and long needle for this purpose. REMEMBER TO ASPIRATE AND TELL THE ANAESTHETIST BEFORE INFILTRATING.
    I use a cocktail of 150ml of 0.1% Marcain with 0.6mg Adrenaline, 30mg Ketorolac and 10mg Morphine.
    The Ketorolac and Morphine are placed in one of the three 50ml syringes.
    Syringe 1. Skin – infiltrated at the start of the procedure.
    Syringe 2. Periosteal and capsule – instilled after preparation
    Syringe 3 (Morphine and Ketorolac) – instilled deep into the posterior capsule – it is vital to aspirate and I suggest moving the needle 4 times to guard against intravascular infiltration.

    The skin incision should allow sufficient access for full visualisation. For an isolated MFC focal resurfacing I would normally incise from the superomedial border of the patella to the tibial tuberosity; the length will depend on the patient.The oblique incision creates optimal access to the front of the medial compartment. There is also a theoretical lower risk of damage to the infra patella branches of the saphenous nerve.
    The Saphenous nerve crosses from medial to lateral and bifurcates into its terminal branches approximately 1cm distal to the tibiofemoral joint line. These branches are responsible for the lateral anaesthesia or worse paresthesia or dysethesia following midline anterior incisions around the knee most commonly in TKR.
    The incision is made, with caution in the distal end not to damage the patella tendon. By making an oblique incision an excellent view of the joint is established with a limited skin incision.
    In this case the incision is much longer than normal for a focal resurfacing as a TTO is also being performed.
    Please see the patella stabilisation technique on Orthoracle for MPFL and Tibial Tubercle Osteotomy.

    Thick skin flaps are developed. This minimise the risk of wound necrosis. I perform a mini-medial subvastus approach as documented in my PPK technique on Orthoracle.
    Caution needs to be exercised at the distal end in looking for infra-patella branches of the saphenous nerve. These are often not seen but being aware of them will reduce the risk of inadvertent dissection or suturing into the wound upon closure risking neuroma formation.
    Identify the vastus medalis obliquus (VMO) and perform an arthrotomy paramedially from the tibial tubercle to the superomedial corner of the patella and then continue in the manner of a mini-subvastus, incising approximately 2cm along the VMO / capsule junction.

    Identify the vastus medalis obliquus (VMO) (deep to my fingers!) and perform an arthrotomy paramedially from the tibial tubercle to the superomedial corner of the patella and then continue in the manner of a mini-subvastus, incising approximately 2cm along the VMO / capsule junction.

    Depending on the areas of the knee to be reached, Hohman retractors are placed. For an isolated MFC defect I would normally place these along the MFC condyle medially and on the lateral side of the MFC, in the femoral notch. In this particular case as multiple areas of the knee were needed to be operated upon, I have placed the retractors on the medial side of the MFC and the lateral side of the lateral femoral condyle.
    The assistant stands at the head end proximally and retracts with Hohman’s or specific curved retractors to protect the cruciate laterally (or ‘mesially’ towards the centre of the knee) and the Medial Collateral Ligament medially

    Decide on the size of HemiCAP required to cover the chondral damage. This should be planned by the imaging, but is checked at this stage by using the drill guides ‘1’ and ‘2’.
    In this case I need a 15mm HemiCAP and so I have used guide ‘1’ which is a 15mm diameter.

    Place this drill guide (1) from the previous slide of the correct size (15 or 20mm) to cover the chondral defect(2) completely. Here I am holding a 15mm guide on the MFC of the left knee (1).

    Ideally this guide (20mm in this case) should be held perpendicular to the radii of curvature of the medial femoral condyle (MFC) over the damaged surface.
    Position this guide so that all four quadrants of the guide are making contact with the chondral surface surrounding the lesion.
    There are only two guides 15mm and 20mm diameter. The object of using these guides is to cover the defect so that the wire down the centre of the guide is at the centre of the defect allowing for future reaming.
    It is always easiest if the guide is perpendicular to the articular surface – this minimises the differences in curvature of the articular surface.

    Once the alignment guide is in position, ensure that the guide-wire hole (1) is clear to allow insertion of the wire in the next slide.


    Insert a guide pin ‘1’ with a powered driver down the drill guide ‘2’, ensuring that the wire enters the centre of the defect. With the guide covering the defect, this will be achieved by the central hole marked ‘1’ in the previous slide.

    BY holding the wire at the laser line ‘1’ (highlighted with forceps) with the drill, sufficient wire length will be introduced into the MFC so that it does not dislodge during reaming later

    Using the cannulated drill for the HemiCAP set, drill over the guide wire….

    …and ensure that the thickened base of the drill bit (1) goes deep enough into the MFC to dissapear from view inside the chondral surface


    Then use the HemiCAP cannulated tap (1), tap over the guidewire – again make sure this is beneath the chondral surface.

    There is a laser line (highlighted with forceps and ‘1’) to reference the joint line – if the line is still visible another turn is required.

    The laser line is now just beneath the chondral surface.

    Operation – 2

    Insertion of the the Hemicap screw – this provides the fixation and a morse taper to accept the Hemicap articular surface.The HemiCAP screw ‘1’ is opened and inserted onto the HemiCAP screwdriver ‘2’.
    The screw provides the fixation in the cancellous bone of the relevant condyle.
    There is one size – no differences in diameter or length.

    The Hemicap screw is inserted into the tapped socket in the medial femoral condyle.
    As the screw is inserted over a guide-wire and down a drilled and tapped thread, it would be very unusual for this to deviate from the desired course, but care should be taken to maintain co-linearity between the screwdriver handle and the guide-wire

    The screw needs to be seated within the femoral condyle. IN order to achieve this there is a laser line on the screw driver from the Hemicap set – the line shows where the eventual articular surface of the Hemicap dome will be after impaction of the Hemicap into the Screw.
    This line ‘1’ should be just deep to the articular surface – it must not be proud otherwise the implant will be too prominent and is likely to cause damage to the tibial surface.
    Another turn is needed here!

    Surgeon’s eye view of a different case at the moment of inserting the HemiCAP screw .

    Now the screw is sufficiently inserted as the laser line previously visible has dissappeared.

    The guide wire ‘1’ is then removed

    Once the guide-wire is removed, it is replaced with the centering shaft ‘2’. As there is only ones screw size, there only needs to be one size of centring shaft – this fits the morse taper which ultimately will hold the articular component too.

    Over the centering shaft ‘2’, the contact measuring probe ‘3’ is placed to measure the depth from the central apex of the articular defect to the margin of the defect in the four quadrants.
    The measurement is read from the gauge on the measurement probe – ‘5’
    In this slide the contact probe is measuring down at 6 o’clock or ‘South’ (highlighted as ‘4’ on the image)

    In this slide the contact probe is measuring at 9 o’clock or ‘West’ (highlighted as ‘6’ on the image)

    The HemiCAP comes with a sizing card (from Arthrosurface) that can be completed at this stage.
    The surgeon measures the radius of curvature variation at North, East, South and West and these are then recorded on the card and matched to the most appropriate radius of curvature implant.
    This card has been used from the case in question and was supplied with permission from Joint Operations who distribute the HemiCAP in the UK, Germany and Ireland.

    The entering shaft is then replaced with the guide-wire ‘1’ again.

    The articular surface circle cutter is cannulated and passes over the guide pin. There are of course 2 sizes of circle cutter to match the diameter of the guide initially used – 15 or 20mm. Please remember to use the correct circle cutter at this stage!
    Here I am using the 15mm circle cutter.

    The 15mm circle cutter is rotated clockwise/anti-clockwise over the guide wire to make a circular cut in the articular surface. This prevents shear of adjacent cartilage when the reamer starts in the next slide.

    The core cutter is removed and the guide-wire left in place – notice the articular surface circumferential cut – ‘7’

    As the defect was symmetrical – apex to the 4 quadrants – a 15mm x 1mm reamer is taken. If there was a tighter radius of curvature (ie a larger size difference from the apex to the circumference of the resurfacing) then a deeper ream is required, but with the same 15mm diameter.

    The cannulated reamer is placed over the guide wire.

    The reamer is then ‘turned on’ – rotating clockwise using the driver – this is positively stopped, by the centre of the reamer bottoming out on the centring shaft, so it is impossible to over-ream.

    The reamer and debris are removed, leaving the guide-wire, which is then in turn removed.

    Surgeon’s eye view showing the:
    Fixation screw – ‘1’
    The prepared articular ‘socket’ – ‘2’

    The trial implant ‘1’ is inserted to ensure that the implant is not proud to the native joint articular surface.
    If the Articular Component trial is proud then simply go back to the Fixation device Screwdriver and turn a quarter turn more clockwise and then replace the trial implant.
    Remember that there are many variations of curvature to the 15 and the 20mm implants – that is a particular advantage of the HemiCAP. In this case we showed goo symmetry at the four reference points (North, East, South and West) so a 1mm x1mm radius, 15mm trial implant has been used.
    If the trial implant is proud on two quadrants then it would be possible to ream an extra 1mm (2mm reamer should be used) and a 15mm diameter 1mm x 2mm radius implant chosen.

    The trial implant is removed and a final wash performed with normal saline.

    Implantation of the HemiCAP articular implantThe Articular HemiCAP Implant is then opened and the suction device ‘1’ (which implants the Articular component) is prepared.

    The standard into-operative suction tube ‘2’ is placed onto the HemiCAP femoral insertion device ‘1’.

    The HemiCAP articular component ‘3’ is sitting in its packaging – untouched.

    The suction device ‘1’ is placed over the Articular Component still sitting in its sterile packaging container.

    Operation – 3

    The suction is applied and the implant ‘3’ is ‘picked up’ by the suction device ‘1’

    Surgeon’s eye view:
    1 = Suction Device for holding the Articular component
    2 = Fixation Screw – previously inserted to the correct depth
    3 = Articular Component

    The Articular Component ‘3’ is docked into the morse taper of the Fixation Screw ‘2’.

    The suction device is removed simply by relieving the suction.

    The HemiCAP articular component is in place, but not yet impacted into its morse taper.

    The implant is impacted to engage the articular component into the morse taper of the fixation screw. There is a femoral impactor on the HemiCAP set – ‘4’

    Final position of the HemiCAP ‘3’ articular component docked in the fixation screw.

    I use a barbed number 1 monofilament absorbable suture to close the capsule. This suture has a double needle – I start centrally at the apex of the mini-subvastus approach – the superomedial part of the patella and travel distally with one needle and medially with the second needle. At the MPFL region I reverse the direction of travel and complete a 2nd layer capsular closure from proximal to distal.

    Deep dermis – interrupted then continuous 2-0 absorbable
    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.

    Wash the wound with 0.05% aqueous chlorhexidine.

    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.

    Skin glue – application of this with the skin wet makes the glue cure much quicker.

    Steristrips crossed so that they sit within the non-adherent part of the occlusive dressing

    Clear occlusive, showerproof dressing.
    Wool and Crepe for 6 hours, which is then reduced and a tubigrip applied

    Post Operative Images – AP and Lateral Radiographs should be taken to confirm implant positions.

    Lateral Knee radiograph showing the MFC HemiCAP in position.
    Notice the contour of the articular component relative to the native MFC contour on the lateral projection. Remember that the chondral surface sits on top of the native subchondral bone that is visible on the XR and this confirms that the implant is not ‘proud’ relative to the surrounding native chondral surface.

    Post Operative

    Standard care postoperatively
    Antibiotics: single dose of Ceftriaxone given on induction – no further doses required.
    Hospital Stay: increasingly this is day case surgery.
    Weight Bearing: full weight bear as soon as possible.
    Bloods: Full blood count, Urea, Electrolytes and Creatinine
    Radiograph: Anteroposterior and lateral XR
    Dressing: left in situ for 2 weeks, ideally undisturbed from theatre, but changed on the rare occasions that the wound leaks.
    Venous thromboembolism prophylaxis: Aspirin 150mg for 6 weeks orally for standard risk. Patients with previous VTE receive 10 days of low molecular weight heparin (LMWH) in addition to their Aspirin. Patients on prophylactic long term anticoagulants including NOACs should simply return to their normal medication on day 2, using LMWH at prophylactic dose on day 1.
    Follow-up – depending on the patient’s functional ability we usually ask them to remove their own dressing at 2 weeks, but where this is impractical we review in our outpatient department at 2 weeks. Subsequent review is scheduled as: 6-8 weeks, 12 months, 2 years, 7, 10,13 years continuing every 3 years as per UK National Guidance
    Variance – Any concerns with the wound should trigger a review by the treating surgical team and must not be managed in the community.

    Recommended Reading

    Bollars P, Bosquet M, Vandekerckhove B, Hardeman F, Bellemans J. Prosthetic inlay resurfacing for the treatment of focal, full thickness cartilage defects of the femoral condyle: a bridge between biologics and conventional arthroplasty. Knee Surg Sports Traumatol Arthrosc. 2012 Sep;20(9):1753-9. doi: 10.1007/s00167-011-1757-9. Epub 2011 Nov 11. PMID: 22076054.
    In one of the first papers of a series of HemiCAPs, Bollars reported on a series of 27 patients, reduced to 19 after exclusions, who were reviewed at a mean of 34 months. 83% showed normal or near-normal IKDC scores and the mean WOMAC was 90 showing very good functional results.

    Becher C, Kalbe C, Thermann H, Paessler HH, Laprell H, Kaiser T, Fechner A, Bartsch S, Windhagen H, Ostermeier S. Minimum 5-year results of focal articular prosthetic resurfacing for the treatment of full-thickness articular cartilage defects in the knee. Arch Orthop Trauma Surg. 2011 Aug;131(8):1135-43. doi: 10.1007/s00402-011-1323-4. Epub 2011 Jun 4. PMID: 21643800.
    Christoph Becher looked at a series of patients with focal resurfacings at a minimum of 5 years and found 16/21 were satisfied.
    This was then followed with a case series of two case from the same author with 12 year follow-up, showing good clinical outcome, retained implants as well as a review of the literature of 6 papers:
    Becher C, Cantiller EB. Focal articular prosthetic resurfacing for the treatment of full-thickness articular cartilage defects in the knee: 12-year follow-up of two cases and review of the literature. Arch Orthop Trauma Surg. 2017 Sep;137(9):1307-1317. doi: 10.1007/s00402-017-2717-8. Epub 2017 May 19. PMID: 28526923.

    Fuchs A, Eberbach H, Izadpanah K, Bode G, Südkamp NP, Feucht MJ. Focal metallic inlay resurfacing prosthesis for the treatment of localized cartilage defects of the femoral condyles: a systematic review of clinical studies. Knee Surg Sports Traumatol Arthrosc. 2018 Sep;26(9):2722-2732. doi: 10.1007/s00167-017-4714-4. Epub 2017 Sep 16. PMID: 28918523.
    The metanalysis by Fuchs of 187 patients with focal resurfacing at medium term found a 9% revision rate for HemiCAP at mean of 4 years.

    Laursen JO, Backer Mogensen C, Skjøt-Arkil H. HemiCAP Knee Implants: Mid- to Long-Term Results. Cartilage. 2019 Dec 21:1947603519894732. doi: 10.1177/1947603519894732. PMID: 31867991.
    Laursen et al found significant clinical improvement in patient reported outcome at a mean of 7 years (4-10 years range) in 64 Hemicaps (62 patients) with focal resurfacings; of these 64 implants 36 were HemiCAP condylar implants.

    Nahas S, Monem M, Li L, Patel A, Parmar H. Ten-Year Average Full Follow-up and Evaluation of a Contoured Focal Resurface Prosthesis (HemiCAP) in Patients in the United Kingdom. J Knee Surg. 2020 Oct;33(10):966-970. doi: 10.1055/s-0039-1688921. Epub 2019 May 24. PMID: 31127601.
    Nahas et al showed excellent patient reported outcomes at 10 years in a consecutive single surgeon series of 10 HemiCAPs.

    van Buul GM, Stanclik J, van der Stok J, Queally JM, O’Donnell T. Focal articular surface replacement of knee lesions after failed cartilage repair using focal metallic implants: A series of 132 cases with 4-year follow-up. Knee. 2021 Mar;29:134-141. doi: 10.1016/j.knee.2021.01.014. Epub 2021 Feb 19. PMID: 33610953.
    In a prospectively collected series of 107 Condylar HemiCAP implants within a series of 137 focal resurfacings, there was a 12% re-operation rate at 4 years and a 97% survival of implant rate. Significant PROM improvements were reported.

    Reference

    • orthoracle.com

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