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High Tibial Osteotomy (Synthes Tomofix plate)

    Overview

    Learn the High Tibial Osteotomy (Synthes Tomofix plate) surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the High Tibial Osteotomy (Synthes Tomofix plate) surgical procedure.
    This is a presentation of a medial opening wedge tibial osteotomy for isolated medial compartment osteoarthritis in a 52 year old man who works in heavy labour.
    In such a case it would be undesirable to consider arthroplasty as a surgical solution to his arthritis. Due to his young age and heavy work he is likely to fail a knee replacement at a young age requiring revision surgery, most likely in his sixties. The result of primary knee replacements are good however patients undergoing revision surgery can expect poor function with low PROMs scores. He may well still be at work at the age he requires an arthroplasty.
    Being in mind also that the knee has some healthy cartilage in the lateral compartment it would be shame not to “sweat the asset” of the knee and delay arthroplasty surgery for as long as possible. Osteotomy to offload the medial compartment has been shown to be an excellent procedure in these cases. By shifting the weight-bearing axis onto the lateral side of the knee excellent pain relief can be expected and can last for over 10 years. This can be achieved by essentially swinging the ankle laterally by opening a wedge in the medial tibia or closing a wedge in the lateral tibia. This is a description of the opening osteotomy.
    The presentation describes a biplanar osteotomy, so called as the opening is created in two planes. The opening osteotomy runs across the tibia from medial to lateral at a level proximal to the pes anserinus. The second osteotomy runs up behind the tibial tubercle. The advantage of this technique is that the anterior osteotomy controls sagittal and rotational displacement.

    Indications

    Indications:
    Isolated medial compartment osteoarthritis – this procedure is particularly suited to young adults with symptomatic osteoarthritis. These are the patients in whom it is wise to delay arthroplasty for as long as possible. A group particularly suited are young males who work in heavy labour, e.g. the building trade.
    Osteotomy is often used in combination with cartilage regeneration procedures such as autologous cartilage transplantation if the patient is in varus.
    Symptoms & Assessment:
    The patient complains of medial sided knee pain at rest and especially on weight-bearing. Anterior knee pain, including on stair climbing and lateral pain should be absent. The decision of surgical intervention should be reserved for those patients who have failed conservative measures such as analgesia, physiotherapy, off-loading braces and insoles to offload the medial compartment.
    Examination reveals a patient with medial sided tenderness. Ideally, for a good result from a high tibial osteotomy, any varus deformity should be largely correctable and any fixed flexion deformity should be less than 10%. It is possible to correct large deformities (>12 degrees) however careful planning is required and the surgeon may wish to consider a combined femoral and high tibial osteotomy.
    Investigations:
    Weight-bearing x-rays – including long-leg alignment views are vital to assess the appropriateness and the required correction angle. Techniques to plan the osteotomy are well described in publications from the AO group.
    MRI – can be of benefit to assess the other compartments of the knee (lateral and patello-femoral) and the integrity of the ligaments
    Arthroscopy – some surgeons prefer to confirm the status of the articular cartilage in the other compartments with an arthroscopy either staged or immediately prior to the osteotomy. Modern MRI is improving our ability to visualise articular cartilage and my preference is, if possible, to avoid any surgery in the knee joint with a view to the future as any eventual TKR is likely to have a better result in the “virgin” knee. I also question whether the findings of an arthroscopy, unless there is a big discrepancy between MRI findings and arthroscopy are going to change the plan in a young active male with highly symptomatic medial compartment OA.
    Aims:
    The aim of the procedure is to shift the weightbearing axis from the degenerate medial compartment to a more lateral position, thereby “sweating the asset” of the knee in terms of articular cartilage. I aim for the correction to intersect the lateral downslope of the lateral tibial eminence.
    Contraindications:
    Smoking
    Active infection
    Widespread osteoarthritis (lateral and patello-femoral compartment)
    Fixed flexion deformity >10% is a relative contra-indication bearing in mind that altering the sagittal slope of the osteotomy can improve a small fixed flexion deformity
    Very large fixed varus deformity
    Osteoporosis / osteopenia
    Alternative treatment options:
    Physiotherapy
    Analgesia to control symptoms
    Off-loading knee brace
    Shoe orthoses to realign the leg on weightbearing
    Arthroplasty

    Setup

    The pre-operative planning for this operation is absolute vital. Long-leg alignment views are used to plan the required opening for the osteotomy. In this case the planning showed that an opening of 12 degrees is required.
    It is common practice to use a long straight radio-opaque guide such as the diathermy lead to check the weightbearing axis intraoperatively (well demonstrated in Prof Snow’s OrthOracle presentation: Proximal Tibial Osteotomy Using A Newclip Plate.) However I feel in my hands that this is open to error due to limb rotation and lack of weightbearing on the operating table. I prefer to make the calculations on the pre-operative films and execute the planned correction.
    Laminar airflow theatre
    Pre-operative antibiotics
    High thigh tourniquet
    Image intensifier
    Radiolucent operating table
    Side support
    Footplate and sandbag
    Saw and saw-blades (narrow)
    Medial tibial osteotomy plate

    Operation – 1

    The patient is set up as pictured. The flexed position is helpful for approach and fixation of the distal screws. The surgeon must however check before prepping the leg that adequate image intensifier images can be taken with the leg in full extension.
    For longer procedures (TKR, HTO, ACL reconstruction) I prefer to elevate the leg before inflating the tourniquet to minimise time.

    The knee is prepared with alcoholic betadine (provided there are no allergies) as presented in the image.

    The joint line is established and the tibial tubercle is identified. The incision is longitudinal starting in the midpoint of the medial tibial shaft and 2cm distal to the joint, extending distally for 6-8cm. The incision can be extended proximally or distally as required.

    The skin is incised down through the subcutaneous fat onto the tibial periosteum. Proximally the medial edge of the tibial tubercle is clear dissected to allow for the dissecting scissors to pass behind the patellar tendon just above its attachment. This defines the top edge of the tibial tubercle.

    Next the posterior edge of the tibia is identified, immediately above the pes anserinus. Even if not seen directly the pes can be easily rolled under a finger often as two horizontally orientated tendons lying against the antero-medial face of the tibia. In order to have a clear view of the periosteum the Hohmann retractor is required to elevate the superficial medial collateral ligament (MCL) and strip it posteriorly off the tibia, which is safely done by this blunt process. This is preferable to cutting through the MCL as the stripped ligament can heal back down post-operatively.
    Now the surgeon has a clear view to plan the two osteotomy lines that make up the biplane osteotomy:
    oblique osteotomy – runs from the top of the tibial tubercle (indicated by the scissors) at a 45 degree angle distally and posteriorly behind the tibial tubercle. It ends at the point of interception with the horizontal osteotomy
    opening osteotomy – the cortical opening runs parallel with the floor from the line of interception with the oblique osteotomy to the posterior edge of the anter-medial tibial shaft as indicated by the Hohmann, immediately proximal to the pes anserine tendons.
    These lines can be marked out with the diathermy.

    The oblique tibial tuberosity osteotomy is performed next using a oscillating saw, begin from the medial side. The osteotomy is completed using the saw (as opposed to using osteotomes) to improve control and avoid inadvertent fracture.

    Next the knee is brought into extension and a 2mm k-wire is drilled image intensification from to track the direction of the opening osteotomy from the planned line on the antero-medial shaft towards the tip of the head of the fibula. Remember that the final osteotomy will run parallel but 2mm distal to the k-wire. Occasionally two parallel k-wires can be inserted (see slide 7).
    The wires not only aid direction planning but also avoid propagation of any unintentional fracture into the joint. Instead the force will follow the line of the wires and exit through the lateral cortex. Furthermore a well-placed k-wire can help retract the anterior edge of the medial collateral ligament.

    This image shows the II image of the k-wire (proximally) and the first osteotome.

    Once the k-wire(s) are in the intended position the near cortex is opening with a saw. The first few millimetres can also be sawed parallel to the k-wire. The rest of the osteotomy however should be completed with osteotome to improve healing.

    This system has a series of osteotomes of varying width. Starting with the widest osteotome the osteotomy is created under image, approaching but not through the lateral cortex.

    In this image note how the first osteotome is close to the lateral cortex, pointing at the tip of the fibular head. The leg can be rotated under screening to ensure that it does not breach the lateral cortex.
    Whilst advancing the first osteotome I find it useful to insert slowly and remove working across the width of the osteotomy in an AP plane, especially ensre that the posterior cortex is osteotomised. Extreme caution must be taken at this vital stage not to inadvertently damage the neurovascular structures. A Hohmann at the level of the osteotomy should be placed directly onto the posterior cortex to protect the neurovascular bundle. I also prefer to not use a mallet but rather push through the posterior cortex by hand.
    The next widest osteotome is inserted slowly sliding beneath the first. If this is performed too quickly the stacking effect will crack the lateral cortex. Slow insertion allows for elastic deformation rather than fracture.

    The steps are repeated with gradually narrowing osteotomes placed inside the two widest osteotomes as shown. Again overenthusiastic hammering can crack the lateral cortex.
    Once the osteotome is complete the stacked osteotome are all removed.

    Next the adjustable wedge osteotome is inserted in the closed postion as in the image.
    The wedge can be opened to the desired pre-planned angle using a hex-head screwdriver.

    Again it is vital to open the wedge osteotome slowly to avoid cracking the lateral cortex.
    The tip here is to insert the wedge osteotome in the anterior half of the osteotomy so that the posterior cortex is clear to allow a laminar spreader to hold the osteotomy open once the wedge osteotome is removed.

    Before the wedge osteotome is removed the medial cortical gap can be measured in millimetres. This is to ensure that is does not close on removing the wedge osteotome. If is does close then the laminar spreader as shown can be slowly cranked open to reestablish the desired gap.
    At this stage the surgeon has a good view of the medial opening. Care must be taken to check that the opening is even at the front and the back. If the osteotomy is wider anteriorly the surgeon may inadvertently give the patient a fixed flexion deformity by increasing the tibial slope, and vice versa with too much posterior angulation. Altering sagittal slope can in fact be desirable. In the case of a chronically posterior cruciate deficient knee opening the wedge anteriorly (increasing sagittal posterior slope) moves the tibial resting position anteriorly. This has the effect of reducing the posterior sag.
    A further important check at this stage is to ensure that the arthritic medial compartment has not been closed by the opening osteotomy. This can have the opposite effect of increasing medial joint reaction force and increasing pain. If this is found then a gradual release of the superficial medial collateral ligament is required. This can be achieved with either sliding a Hohmann beneath the ligament and elevating it from front to back or more formally with a periosteal elevator.

    Any final adjustments can be made with the laminar spreaders. The osteotomy should be fairly responsive to minor adjustments. If not then it may be that the osteotomy is not complete. This is most commonly at the posterior cortex.
    Note that with the laminar spreader sitting with the curved handles pointing posteriorly the surgeon has an excellent view of the antero-medial tibial shaft.

    The plate can now be inserted and adjusted both under direct vision and under II.
    I find it most helpful to insert the drill guides into two of the three proximal holes in the T-shaped plate. This avoids over tenting the skin if 3 drill guides were inserted at the same time. 2 all for rotational control.
    The surgeon must ensure that:
    the height is correct, i.e. the proximity of the top of the plate to the medial tibial plateau. It must be low enough so that the screws do not penetrate the joint surface but high enough to allow the screw-hole in the next row to be within the proximal fragment.
    the shaft of the plate is sitting on the antero-medial tibial surface
    the screw-hole in the third row is over the distal fragment

    Wire-guides are then inserted into the drill-guides. 2mm k-wires are then inserted into the front two proximal drill holes under II to fix height and rotation.

    The third drill guide can now be inserted in the proximal row, drill measured and fixed with a locking screw. Now with the anterior wire and the posterior screw in situ the middle screw-hole’s wire can be removed, the hole can be drilled as in the image. The depth is measured and a locked screw is inserted.

    This is repeated with the anterior screw-hole. The fourth proximal fragment screw is inserted in the second row screw-hole.
    With proximal control established the plate is pretensioned. A cortical non-locking screw is inserted in the second hole on the shaft side of the plate i.e. BELOW the osteotomy. It is tightened until the plate sits flush on the shaft and left in place until the shaft locking screws are inserted.

    Once the locking screws are inserted in the shaft of the plate the gold cortical pre-tensioning screw can be removed and replaced with a locking screw.

    With all the locking screws in place (4 in the proximal fragment and 4 in the distal fragment) the laminar spreader is removed and the leg can be rotated under the II to ensure that the screws are not penetrating the joint surface and that the plate is sitting in the desired position.

    View of the proximal plate

    View of the distal plate.
    I prefer not to fill the osteotomy with bone graft or an artificial wedge. I would only consider autograft bone graft if I am performing a large osteotomy over 12-14mm.

    The wound is carefully irrigated using a large syringe. Avoid the use of pulse lavage to minimise irrigation of the osteotomy site and washing away the helpful blood clot.

    Operation – 2

    The subcutaneous layer is closed with a braided undyed continuous suture.

    The skin is closed with clips.

    AP view of the osteotomy

    Lateral view of the osteotomy

    Post Operative

    Immediate post-operative care concentrates on:
    management of pain
    management of swelling
    observation of distal circulation, sensation and movement – compartment syndrome is a rare but reported complication
    Anti-thrombosis prophylaxis in the form of mechanical and chemical agents is commenced. Note that the patient will have an altered weight-bearing status for 6 weeks.
    Weightbearing status post-op is advisably:
    4 weeks at 25% partial weight bearing to commence once the patient has good quads control and intact plantar sensation, using a ROM brace for support (unlocked, full range)
    4 to 6 weeks post-op 50% partial week bearing to build up gradually
    Full weight bearing from week 6 – the patient can discard the ROM brace
    Physiotherapy can commence aiming for supervised full ROM. Post operative straight leg raising is allowed provided the fixation is good and bone quality is adequate.
    Skin clips can be removed at 14 days.
    Post-operative radiographs can be delayed to 6 weeks provided good intra-operative images were taken. Further x-rays are taken at 6 months and 1 year. If union is demonstrated at 1 year the surgeon can plan to remove the plate. It is my preference to remove the plate as these patients are likely to progress their arthritis and require arthroplasty albeit in many years to come. Therefore removing the plate at this stage means that the bone and soft tissue can recover in the intervening years.

    Recommended Reading

    Osteotomy surgery has been in practice for many years. The opening wedge tibial osteotomy really took hold in the 1990s as the implants improved. The advantage of the opening wedge over closing and domed osteotomy is the precision available to dial in the appropriate correction on the table. However the risk was that the implant needs to control excessive axial and torsional forces of the proximal tibia. The development of fixed angle titanium plate systems allowed excellent control even in openings in excess of 10 degrees. A comparative study by Agneskirchner JD et al (2006) Primary stability of four different implants for opening wedge high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc; 14(3):291-300 showed excellent biomechanical properties for the implant used in this case.
    The expected delay of total arthroplasty surgery following osteotomy around the knee is in excess of 10 years. Furthermore the conversion of a failed osteotomy to a total knee replacement (TKR) can yield patient satisfaction scores similar to a primary TKR of a previously unoperated knee. This can help the decision making process for a surgeon faced with a young patient with unicompartmental osetoarthritis that has failed conservative treatment. As demonstrated originally by Pearse A J, Hooper G, Rothwell A, Frampton C Osteotomy and unicompartmental knee replacement converted to total knee replacement – data from the New Zealand Joint Registry. J Arthroplasty. 2012 Dec;27(10):1827-31 and supported in subsequent publications the patient reported outcome scores of total knee replacement following a failed osteotomy are higher than scores recorded after a failed unicompartmental knee replacement. The evidence would therefore suggest that as a TKR delaying tactic the HTO is preferable to UKR in the long-term.
    Complications of the procedure described in the literature include:
    infection – range reported 0.8-10% but the vast majority are superficial infections
    DVT – range 2-5% clinically symptomatic DVT rate; the rate of PE is less widely reported but accepted to be rare
    non-union / delayed union – in their series of 323 patients Martin et al reported an aseptic non-union rate of 3% and delayed union of 12%. Martin R, Birmingham TB, Willits K, Litchfield R, Lebel ME, Giffin JR. Adverse event rates and classifications in medial opening wedge high tibial osteotomy. Am J Sports Med. 2014 May;42(5):1118-26.
    patellar baja – the opening wedge does risk altering the height of the patella however the stepped biplanar osteotomy gives the surgeon control over this. It is key to ensure that the distal tibia swings away from the knee rather than the proximal tibia being raised towards the knee, achieved by adequate MCL release. The literature would suggest that the alteration in patellar height is less in biplanar opening wege osteotomy than closing wedge osteotomy.
    fracture – undisplaced lateral hinge fracture risk is common around 20% and requires no specific alteration of management. However a displaced (>2mm) lateral hinge fracture reported by Martin et al can occur in 3%. Tibial plateau fracture was reported by the same group in 3% of cases.
    compartment syndrome is a rare but serious complication and most likely affects the anterior tibial compartment
    neurovascular injury – damage to the common peroneal nerve is less common in HTO versus closing wedge osteotomy due to the altered approach. Popliteal vessels are at risk during osteotomy.

    Reference

    • orthoracle.com

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