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Unicompartmental Knee replacement- Persona Partial Knee Replacement (Zimmer-Biomet)

    Overview

    Learn the Unicompartmental Knee replacement: Persona Partial Knee Replacement (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 Unicompartmental Knee replacement: Persona Partial Knee Replacement (Zimmer-Biomet) surgical procedure.

    This is the case of a 77 year old man who had exceeded the benefits of non-operative treatment including analgesia and physiotherapy. He did not wish to use an offloader brace.
    My practice is to use a fixed bearing partial knee replacement for all lateral unicompartmentals and medial unis where the patient is over the age of 65 or there is concern over the ACL integrity.
    The Persona Partial Knee (PPK) is a minimally invasive replacement of one compartment of the knee joint with fixed bearing modular cemented components. It is produced (and in the UK marketed) by Zimmer Biomet. The PPK is a new design which is currently available to use through Beyond Compliance whilst it enters the marketplace. The PPK combines many positive features of previous fixed bearing UKR’s including those that achieved good 10 and 20 year survival. In addition there have been developments with better polyethylene wear properties by using Vivacit-E Polyethylene which is actively stabilized with Vitamin-E. By using large databases of patient morphotypes the shape of the PPK has been modified to represent the very best fit possible.
    As a surgeon with a background and current practice still using mobile uncemented Oxford implants as well, this system provides a very simple yet appropriate transition to the fixed UKR design using a resection rather than a milling technique.
    This case was performed as an overnight stay.

    Indications

    INDICATIONS
    Anteromedial arthritis of the knee, usually in the presence of a functioning anterior cruciate ligament.
    SYMPTOMS & EXAMINATION
    Symptoms:
    Localised pain in the anteromedial knee – often the patient is able to locate the site of pain with one finger on the medial side of the knee
    Stiffness
    Varus change in leg alignment
    Examination:
    Tendereness in the anteromedial knee around the tibiofemoral joint line
    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 – 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
    In the absence of full thickness disease on plain AP a varus stress view can be performed to try and elucidate a full thickness arthritis.
    Valgus stress XRays should be performed to ensure that the lateral joint is in good condition, where there is any clinical doubt such as if the Rosenburg shows some lateral joint reduction or osteophytes
    MRI
    Only selected patients are sent for an MRI; I would use MRI for those patients whose radiography suggests no full thickness disease, but clinically the patient is behaving as a failed joint with arthritis. There is good evidence not to proceed to arthroplasty until there is full thickness disease even if this is on 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 TKR. MRI does allow assessment of intra-osseous bone marrow lesions which are markers of increased bone turnover.

    ALTERNATIVE OPERATIVE TREATMENT
    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.
    Total Knee Replacement – if surgeons do not offer partial knee replacement then a TKR is still a valid treatment for anteromedial arthritis of the knee.

    NON-OPERATIVE MANAGEMENT
    Lifestyle modifications
    Analgesia
    Bracing – medial offloader braces which push the knee into valgus.
    Injection therapy – steroid for inflammation, or viscosupplementation.

    CONTRAINDICATIONS
    Absolute
    Active infection
    Active inflammatory arthritis in the same joint
    Untreated ligament laxity
    Significant loss of range of movement particularly extension
    Relative
    Inflammatory arthritis in other joints
    ACL damage

    Setup

    Two main operative setups are used for partial knee replacement;
    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.

    Drugs
    Intravenous prophylactic antibiotics should be administered early (30-45 minutes) to achieve adequate tissue concentrations at the time of ‘knife to skin’.
    Intravenous tranexamic acid on induction – 1000mg.
    If the wound is oozing then this induction dose can be repeated on closure.

    Operation – 1

    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.

    Palpate the medial border of the patella and the lateral border of the tibial tubercle.

    The anteromedial oblique incision and joint line (double line) is marked for teaching purposes.
    The oblique incision creates optimal access to the front of the medial compartment as close to the ACL as possible. Straight incisions can interfere with cutting block placement and cutting later on in the procedure. 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.

    Thick skin flaps are developed. Cut down to capsule straight away and then lift the skin off the capsule a little way to the medial and lateral; notice how I am confirming this full thickness dissection by my fellow (holding the scalpel) by holding the skin between my finger and thumb.

    Caution needs to be excercised 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.
    This achieves excellent visualisation of the medial condyle and reduces the chance of the lateral skin flap and patella tendon affecting the rotation of the tibial cutting block and the reciprocating saw used for the sagittal cut.

    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

    Osteophytes are cleared from the mesial wall of the MFC to prevent impingement on the PCL
    The Jensen-Middleton rongeur (an otolaryngology instrument often used in foot and ankle surgery too) is an excellent tool for the surgeon in a minimally invasive approach due to the double action and bend. This can be used to clear around the patella, the femoral notch and the anterior tibial spine – the common sites of osteophytes.

    A straight osteotome is used to clear the medial femoral condyle (MFC) osteophytes. Align the osteotome on the border of the MFC and osteophyte and ‘shape’ around the medial condyle with 3-5 osteotome blade widths depending on the size of the condyle. Then remove altogether by rongeurs as below….

    The corresponding extension block is inserted with the leg in full extension.
    If the leg holder technique is being used then the thigh needs to be lifted out of the holder and the leg replaced on the operating table in full extension.

    Removal of loose osteophytes from the medial femoral condyle.
    The Jensen Middleton Rongeur is extremely useful here

    The centre of the medial tibial plateau (MTP) is ‘drawn’ with diathermy along the flexion axis of the knee – in other words a straight line representing the vector through which the knee rotates in flexion, centred on the MTP.
    The centre of the MFC is marked in flexion corresponding to the tibial line

    The knee is moved into extension and the corresponding position of the tibial line on the MFC in extension is then marked, producing two points on the MFC anteriorly and posteriorly.

    The two points on the MFC are then joined to represent the optimal contact point of the MFC on the tibial plateau during flexion

    The tibial PPK jig is held in place using the stylus to guide positioning relative to the defect on the anteromedial tibia

    The jig is then temporarily secured in position using the sliding drill pin hole, allowing for fine tuning of the position both varo-valgus by moving the distal end of the jig medially or laterally as well as independent proximal-distal movement of the cutting jig within the tibial extra medullary alignment guide.

    Once happy on the cutting jig position a 2nd drill pin is inserted.

    3rd fixation drill pin and a blocking drill at the apex of the Saggital and axial transverse tibial cuts is positioned. The blocking drill prevents unnecessary deepening of the sagittal cut or undermining of the tibial eminence with the axial cut.

    The sagittal cut is made with a reciprocating saw:
    Feel the track of the cutting guide
    Turn on the saw
    Keep parallel to the guide pin which will stop over-deep cutting.
    Gently allow the saw to move to the posterior cortex and then through the posterior cortex carefully.
    Do not lift the hand, despite the protection drill-pin.

    The axial transverse medial tibial plateau cut made with an oscillating saw.
    Not the medial retractor protecting the MCL and the drill-pin at the apex of the cutting jig slot.

    The medial tibial plateau resection piece is lifted UP (proximally) with an osteotome.
    Caution should be taken NOT to lever distally onto the residual medial tibia

    The MTP resection piece can be levered forward by an osteotome gently tapped into the resected plateau whilst levering forward on the MFC.

    Operation – 2

    Measurement of the flexion space with a feeler gauge

    An alignment rod is attached to the extension distal femoral cutting guide to check alignment – both varo-valgus and flexion – extension.
    The alignment rod should run for the ipsilateral hip to the ankle, being parallel to the leg in full extension.

    The distal femoral cut is made with protection of both cruciates (mesially) and MCL (medially).
    Extreme caution when cutting the posterior cortex due to the potential neurovascular risk.

    The distal femoral block is removed and the posterior cut is completed by hand using an osteotome and controlled mallet use.

    The extension gap is checked with the corresponding size of ‘gap stick’ but with the opposite end inserted. This allows for the total construct thickness in full extension of the femoral component, polyetheylene size as per thickness of the gap stick and the tibial tray thickness.
    Full extension must be possible.
    In general it is better to be slacker in flexion than extension.

    The most appropriate sized femoral chamfer block is inserted flush to the distal femoral cut.
    There should be no medial overhang nor should the block overlap the anterior extent of the distal femoral resection.
    Once happy with the position this should be secured in position with 3 hex-head drill pins.

    Checking for no anterior or medial overhang of the cutting block. The block corresponds to the implant size of the same number.

    The femoral cutting block is then secured with hex-head drill pins. One of the three hex-head drill pins being inserted here.

    Once the block is securely fixed, the posterior chamfer cut is made

    ….and then the posterior cut is made.
    Again – caution in flexion cutting posteriorly in view of posterior neurovascular structures

    Two femoral lugs are drilled.
    These are jigged but are oblique so it is important to ‘drop the hand’ to find the correct orientation in the cutting jig.

    The posterior chamfer and posterior cut are removed – sometimes this needs completion with an osteotome.

    The tibial tray is sized by inserting trials and assessing the AP size of the plateau through a measurement window on the trial. The most appropriately sized tibial tray trial is then inserted and impacted down, cutting the keel in the process .
    Caution to support the foot during this step if a thigh holder set-up is being used.
    The tibial trial introducer is removed….

    The femoral trial is inserted and impacted – here a size 4 to match the size 4 femoral block used to cut the chamfers and drill the 2 lug holes.

    Full range of movement should be achieved at this stage with trial tibial and femoral components impacted and the most appropriate polyethylene trial inserted.
    It is better to be slightly loose in flexion, as an over tight knee will flex poorly and unlike in mobile bearing partial knee replacement there is no risk of bearing dislocation.

    Local Infiltration Anaesthesia 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.
    We use a cocktail (known locally as ‘Murray Mix’) 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.

    Pulsed lavage with Normal Saline (as opposed to my usual chlorhexidine for total knee arthroplasty) in view of partial joint replacement and concern over the remaining cartilage with chlorhexidine.

    Cementation onto bone surface of the tibia.
    Cement is also added to both tibial and femoral components.
    A wet osteotome is a useful tool to compress the cement into the tibia.

    The tibial component is inserted prior to impaction.

    Tibial component impaction

    Femoral condyle lavaged, dried and cemented. This is Palacos Regular cement with Gentamycin (Heraeus)

    Cement on both surfaces prior to femoral implantation

    Femoral impaction

    Extruded cement prior to removal of the excess cement medially.
    Take care to remove all remnants particularly posteriorly on the tibial component where it is easy to leave excess cement.

    The trial bearing is inserted and the knee is held in full extension and various to compress the implants.

    Operation – 3

    Checking for extruded cement. There are some very useful cement removal instruments on the PPK set.

    Removing the trial bearing allowing access to the posterior tibial component

    Removing excess cement with another PPK set cement removal tool.

    Tibial bearing inserted and clicked into position with a positive ‘click’ with the compression device supplied by the manufacturer.

    Definitive Polyethylene inserted – note how the femoral component sits exactly over the tibial component.

    Closure in layers:
    Capsule – I use a barbed number 1 monofilament absorbable suture.


    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.

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

    Clear occlusive, showerproof dressing.
    Wool and Crepe for 24 hours, which is then reduced and a tubigrip applied

    Postero-Anterior radiograph (Rosenburg view) showing anteromedial arthritis of the knee, with good lateral tibiofemoral preservation.

    Preoperative lateral radiograph

    Anteroposterior postoperative radiograph

    Lateral postoperative radiograph

    Post Operative

    Standard care postoperatively
    Antibiotics: 24 hours prophylaxis – we use Flucloxacillin 1000mg x 3 postoperatively, in addition to the induction Flucloxacillin and Gentamycin on induction
    Hospital Stay: increasingly this is being performed as overnight stay or 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: Bulky wool compression bandage reduced at 24 hours and occlusive 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

    It is interesting to note that the according to the National Joint Registry’s 2017 report the recorded use of fixed bearing insert prostheses has grown since the registry’s inception in 2003 against the mobile-bearing prostheses (In 2003 fixed-bearing vs mobile bearing: 17.5% vs 81.25%; in 2017 fixed vs mobile: 44.6% vs 55.4%).
    Revision rates amongst UKRs remains relatively high compared to primary total knee replacements. Many reasons for this have been postulated. There is a perception that revising a UKR is a simpler procedure than revision of a total knee replacement, which may lower a surgeon’s threshold to proceed. It should be appreciated however that the patient reported outcomes (PROMs) for revised UKRs, including those revised to a primary total knee prosthesis, mirror the PROMs of full revision TKRs. While this fact should not prevent a surgeon from revising a failing UKR it should influence their original decision about using a UKR as a “stop gap” procedure in younger patients.
    Partial knee replacement is simply a treatment for selective arthritis irrespective of age and should not be used as a ‘stop-gap’ treatment trying to delay an inevitable primary TKR. In addition the risks of partial knee replacement are significantly lower than those of TKR with respect to rates of VTE, infection and medical complications. Two independent landmark papers published in the Lancet demonstrated a significantly lower mortality in patients treated with partial knee replacement compared to those receiving TKR.
    The “bottom line” figure for 10 year survivorship of a UKR for a 65-year old patient is 90% (or a 1% failure per year.) This compares to around 95-97% for a total knee replacement. The probability of revision for a 55 year old and younger male and female with a UKR is in the order of 18-19% at ten years which compares to 8-9% for total knee replacement. There is no significant variability across genders. A surgeon’s reluctance to perform arthroplasty in younger patients is understandable when taking into account these comparable data.
    However fixed bearing unicompartmental with the Miller-Galante produced 98% survivorship at 10 years and 90% at 20 years.
    Complication rates and mortality rates favour UKR over TKR. Furthermore the improved, or more physiological, function attained due to sparing of the cruciate ligaments leads to higher early PROMs results.
    Careful patient selection and good surgical execution with the surgeon’s preferred implant can lead to excellent results from unicompartmental knee replacement. Furthermore careful follow-up and auditing of results can improve vigilance especially for failing knees. A paper produced with reference to the New Zealand Joint Registry, which collects Oxford Knee Scores as part of the audit, demonstrated a strong correlation between low 6-month Oxford Score and early (<2 year) revision for UKR.

    National Joint Registry for England and Wales. 14th Annual Report. http://www.njrreports.org.uk
    14th Annual Report is available to download. The revision rates of fixed and mobile bearing UKRs is shown on page 121 (Fig 3.19 (c)).
    Survival and functional outcome after revision of a unicompartmental to a total knee replacement: the New Zealand National Joint Registry.Pearse AJ, Hooper GJ, Rothwell A, Frampton C.J Bone Joint Surg Br. 2010 Apr;92(4):508-12
    Analysis of the revision rates and PROM scores of patients who had undergone revision of UKR to total knee replacement should significantly poorer results that patients with primary TKR. This suggested that the practice of using a UKR as a “stop-gap” procedure in younger patients was ill-advised.
    Patient-reported outcomes after total and unicompartmental knee arthroplasty: a study of 14,076 matched patients from the National Joint Registry for England and Wales. Liddle AD, Pandit H, Judge A, Murray DW. Bone Joint J. 2015 Jun;97-B(6):793-801.
    Early (6-month) Oxford knee score was higher for unicompartmental knee replacement over total knee replacement. This paper also found that overall complications and re-admission rates were lower for UKR.
    Long-term Survivorship and Failure Modes of Unicompartmental Knee Arthroplasty. Foran, JR. et al. Clin Orthop Relat Res. 2013 Jan; 471(1): 102–108.
    Analysis of the revision rates and PROM scores of patients who had undergone revision of UKR to total knee replacement should significantly poorer results that patients with primary TKR. This suggested that the practice of using a UKR as a “stop-gap” procedure in younger patients was ill-advised.
    Patient-reported outcomes after total and unicompartmental knee arthroplasty: a study of 14,076 matched patients from the National Joint Registry for England and Wales. Liddle AD, Pandit H, Judge A, Murray DW. Bone Joint J. 2015 Jun;97-B(6):793-801.
    Early (6-month) Oxford knee score was higher for unicompartmental knee replacement over total knee replacement. This paper also found that overall complications and re-admission rates were lower for UKR.
    Long-term Survivorship and Failure Modes of Unicompartmental Knee Arthroplasty. Foran, JR. et al. Clin Orthop Relat Res. 2013 Jan; 471(1): 102–108.
    An analysis of the Oxford hip and knee scores and their relationship to early joint revision in the New Zealand Joint Registry A. G. Rothwell, G. J. Hooper, A. Hobbs, C. M. Frampton. J Bone Joint Surg [Br] 2010;92-B:413-18.
    Whilst demonstrating that low Oxford hip and knee scores at 6-months correlated well with early revision this paper’s strongest demonstration of a relationship was with a Oxford score of <27 (poor) being associated with a 27% risk of UKR revision within 6-months.
    Fixed- versus mobile-bearing UKA: a systematic review and meta-analysis. Peersman G, Stuyts B, Vandenlangenbergh T, Cartier P, Fennema P.Knee Surg Sports Traumatol Arthrosc. 2015 Nov;23(11):3296-305.
    Meta-analysis of 9463 knees (44 papers) showed comparable revision rates for fixed bearing UKR and mobile bearing UKR, 0.9 and 1.51 per 100 component years respectively.
    Adverse outcomes after total and unicompartmental knee replacement in 101,330 matched patients: a study of data from the National Joint Registry for England and Wales. Liddle AD, Judge A, Pandit H, Murray DW. Lancet. 2014 Oct 18;384(9952):1437-45.
    45-day mortality after 467,779 knee replacements for osteoarthritis from the National Joint Registry for England and Wales: an observational study. Hunt LP, Ben-Shlomo Y, Clark EM, Dieppe P, Judge A, MacGregor AJ, Tobias JH, Vernon K, Blom AW; National Joint Registry for England and Wales. Lancet. 2014 Oct 18;384(9952):1429-36.
    Outcomes of a Fixed-Bearing, Medial, Cemented Unicondylar Knee Arthroplasty Design: Survival Analysis and Functional Score of 460 Cases. Winnock de Grave P1, Barbier J1, Luyckx T1, Ryckaert A1, Gunst P1, Van den Daelen L1. J Arthroplasty. 2018 Apr 24. pii: S0883-5403(18)30392-9. doi: 10.1016/j.arth.2018.04.031.

    Reference

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