Total knee replacement- First stage revision with a hinged spacer and tibial tubercle osteotomy

This is the historic radiograph of a 75 year old lady who had previously undergone a two stage revision knee replacement for infection.
The image shows a well fixed stemmed revision knee replacement (DePuy TC3) with metaphyseal sleeves on both the femoral and tibial sides.

This is the lateral image of the same knee. There is no apparent osteolysis, nor loosening.

She was referred to the unit three years later with ongoing pain, swelling and stiffness.
Radiographs subsequently demonstrated osteolysis around the distal femur and proximal tibia. The sleeves and stems remained well fixed.

The distal femur showed signs of periostitis. The clinical features, raised inflammatory markers and radiographic features prompted the need for a radiological biopsy, which grew a coagulase negative Staphylococcus.
She was discussed in our infection MDT prior to surgical intervention.

A decision was made at the MDT to revise the knee in two stages. The first would involve the use of a hinged knee articulating spacer. A hinge was decided upon due to the bone loss and the the need for radical debridement including the collateral ligaments (any further surgery for infected PJI would be very unlikely to work).
The Stryker Stanmore Implants Worldwide system has an easy to use off the shelf hinge.
There are two sizes of knee – standard and small. The femoral trials can be seen at the top of the image (a). The tibia comes with either a short 140mm or long 180mm stem with both sizes. A fixed hinge, metal backed rotating hinge and polyethylene rotating hinge are available. They are shown in the middle of the image (b). 5mm is the minimum resection for the fixed hinge, 8mm for the polyethylene rotating hinge and 11mm for the metal backed rotating hinge.
Augments (c) are available from 5 to 20mm for both the tibia and femur.
The kit is straight forward and has a proven track record. In this case a short distal femoral replacement was used rather than the hinged knee shown in the image. It is fully compatible with the SMILES tibial components.
The fixed hinge is not commonly used – I use it here as an articulating spacer as it is (slightly) cheaper than the rotating hinge version. At the second stage a rotating hinge version will be used.

There are few instruments (5 trays in total), which is what makes this implant straight forward to use. The tray shown here has impactors and the tibial positioning plates (a). The pliers on the left of the image (b) are for inserting the circlip once the definitive axle is in.
The tibial trials are once again shown (c).

I don’t use the SIW cutting jigs. Most of the time they are not needed and any freshen up cuts can be done by hand. If the tibia needs re-cutting I use a standard jig from a primary knee set. Here the Genesis 2 tibial cutting jig is shown. There should be no slope for a hinged knee.

The old skin incision is used and extended proximally and distallyBy exposing virgin tissue the native tissue planes are easier to identify.

Full thickness skin flaps elevated on both sides of the incisionElevating flaps allows for better exposure and a more thorough synovectomy / debridement during the procedure. They need to be full thickness to preserve the remaining vascularity. Identifying a plane deep to the fat is key and peel back the flap from there.
The first of five microbiology samples is being taken in this image. The first is a fluid sample through the capsule into the knee.
Multiple other samples will be taken throughout the procedure with clean instruments each time; this is particularly important if cultures to date have been negative. A leucocyte esterase or alpha defensin (Synovasure) test can be used if there is diagnostic doubt but in reality this is rarely needed. A diagnosis and definitive surgical plan should be in place prior the procedure being undertaken.

Medial parapatellar approach to the kneeThe patella can usually be palpated, which will give you a clue as to the arthrotomy position. I use a medial parapatellar approach and am conscious I may need to do a quadriceps snip or tibial tubercle osteotomy if stiffness is an ongoing problem.
A generous medial release should be done; asking the assistant to externally rotate the leg helps in getting round to the posteromedial tibia.
I insert a Trethowan posteromedially on the proximal tibia and use the diathermy to peel back a sleeve of tissue subperiosteally. Keeping the sleeve of tissue in continuity helps with closure in this area; often the anteromedial tibia is bald at the end, which ideally should be avoided.

Thorough synovectomy and debridementIn infected cases it is crucial to excise as much infected tissue as possible. This begins with a synovectomy. Whilst my assistant pulls the quads medially with two tissue clamps I remove the infected tissue deep to it.
It is more difficult to do this on the lateral side and the extensor mechanism is potentially at risk. It is worthwhile taking some time on this step to aid exposure and allow subluxation or eversion of the patella. Do not go deeper than the articular surface when the patella is everted as the extensor mechanism is in danger.
If a decision has been made to use a hinged replacement (as in this case) then cutting the collaterals at this point further aids exposure and component explantation. I place a Hohmann retractor around the medial and then lateral aspect of the distal femur and remove the soft tissues (and collaterals) with the diathermy.

The debridement continues throughout the exposure part of the operation.
Here the extensor mechanism is being pulled laterally with tissue clamps and the capsule deep to it removed by sharp dissection. In stiff knees the movement should gradually improve enough to allow the patella to sublux laterally allowing access to the front of the knee.

The polyethylene insert is the first thing to be removed Placing a retractor around the lateral aspect of the tibial tray moves the extensor mechanism out of the way allowing access to the polyethylene insert.
In most cases inserting an osteotome or Bristow under the polyethylene allows it to be disengaged from the tibial component and levered out. Some knowledge of the knee being revised however is needed. There may be a locking mechanism (a pin or screw), a high post (as in this case) or the implant may be monobloc. Each are dealt with in a different manner and as in all revision cases the plan may need to change during the operation.

In this case the knee replacement has a large central post which needs lifting out of the tibia. I use a Bristow once the anterior edge has lifted out. The tibial tray can be used as a fulcrum for the lever but some care is needed not to damage the bone deep to it. The patella tendon is also at risk if the retraction and flexion is performed too forcefully. If necessary I go back and release more soft tissue as shown in slides 10-12.
The patella needs to be clear laterally and ideally the knee should be able to flex to 90 degrees to allow the post to disengage. In some knees the polyethylene can be cut with a saw to aid extraction. This one has a metal post inside the poly and hence this is not an option.

The femoral component is exposed and removedOnce the polyethylene is out further scar tissue and capsule can be removed restoring a lateral gutter and again sequentially improving exposure and patella subluxation.
The prosthesis cement interface is identified by removing the covering soft tissues and using a sharp narrow osteotome (Lambotte) this interface is disrupted. I start on the lateral side as it is the easiest for me to reach. The assistant needs to apply counter pressure medially whilst the osteotome is repeatedly inserted under the femoral component.
I then work on the medial side, or ask my assistant to, as shown in the image. It is easiest on the anterior aspect first but as this becomes clear it is necessary to go as posterior as possible, following the condyles round the back. If the implant is not completely released the posterior condyle is at risk of coming off with explantation.
If the implant is still well fixed and as much of the bone cement interface as possible has been disrupted then a few blows on the anterior aspect of the replacement using a Bristow and hammer may help. Have your assistant ready to catch it if necessary.

The femoral component has been removed but the taper sleeve and stem have disengaged and remain. This is not uncommon. A Midas Rex with a thin bony burr is a good tool to circumferentially remove the bone from around the sleeve. A thin osteotome may also be needed.
Whilst the Midas Rex is being prepared I move on to removing the tibial component.

The tibia is further exposed by removing any soft tissue posterior to the tray. This allows the insertion of a Mikhail ‘double pronged’ retractor. The tips need to be on the bone itself to avoid a potential neurovascular injury. I use the diathermy to remove any soft tissue on the tibial surface to ensure the retractors are on the bone.

The tibial tray needs to be exposed as much as possible to help with explantation. Ideally this means identifying the implant cement interface circumferentially. The lateral side is more difficult as the extensor mechanism gets in the way.
Starting medially I insert a thin Lambotte osteotome between the implant and cement. The osteotome may hit the keel of the tibia centrally. I try and work in front of and behind the keel from medial to lateral. In most cases a straight shot with a thin osteotome under the tibial tray posteriorly from medial to lateral is enough to loosen and then extract a primary tibial component. A generous medial release is required to do this, as mentioned in slide 10.

If necessary remove more soft tissue to identify the bone implant interface further. Stick to the bone, particularly at the back of the knee.

The tibia radiographically is well fixed and this is true when extraction is attempted.
I cannot remove the tibia from the top end and risk doing more harm than good. This was recognised pre-operatively and a decision is made at this point to perform a tibial tubercle osteotomy (TTO).
The skin incision is extended distally by approximately 10cm.
A TTO is often required to remove a tibial sleeve or cone. It is worthwhile trying to extract it first but much time can be wasted at this point. I give myself a set amount of time (15-20 minutes) before deciding on an osteotomy.

The patella tendon, in particular the medial, lateral and inferior border, are further identified to minimise the risk of iatrogenic damage during the osteotomy.

The medial border of the tibia is exposed using a diathermy to plan the tibial tubercle osteotomy

The osteotomy extends distally by approximately 10cm and the wound should be able to accommodate this.
The soft tissues have already been cleared medially and this should be extended distally to below the tibial tubercle. It is crucial to keep the soft tissue attachments on the lateral side intact.
I mark out my osteotomy using multiple 2.5mm drill holes. My preference is to perforate the lateral side with the drill creating a weak points for the osteotomy to complete. This helps control the osteotomy but may not be possible with larger stemmed implants. I then complete the osteotomy medially and distally with an oscillating saw and thin saw blade.
A horizontal limb is made at approximately 7-10 cm below the tibial tubercle. If possible I try to keeping a bony bridge at the top end to prevent potential migration of the tubercle once it’s fixed. This can be created with a reciprocating saw if used. Again this is not always possible with more moderate bone loss and extracting stemmed implants.

Osteotomes are inserted from medial to lateral and the tibial tubercle slowly liftedThe lateral side will crack allowing the whole bony fragment (with extensor mechanism) to be retracted laterally. Multiple large osteotomes are used proximally and distally to gently lever open the osteotomy.
A TTO can also be used to access the knee when exposure is difficult due to extreme stiffness. The technique is the same although in most cases patience and appropriate sequential releases will get you access in the end.

The tibial sleeve and stem are exposedTwo osteotomes are used to lever the bony fragment to reduce the risk of fragmentation. It is vital to keep the lateral soft tissues intact.

Despite the osteotomy the tibia remains well fixed. Not everything loosens with infection, especially porous titanium sleeves!
Initially I use a thin osteotome to disrupt the exposed implant / bone interface and then switch to a Midas Rex with thin bony burr.

It is useful to keep as much bone as possible for later reconstruction. The proximal tibia may fragment with a heavy hand and an osteotome. The Midas Rex is a more delicate way of doing removing bone around the tibial component. Make sure the assistant keeps the burr cool with saline irrigation from time to time.

A Bristow or punch can be used to extract the tibial component, hitting it superiorly. If it still doesn’t budge I go back and try and remove more bone with the burr.

The tibial component has been removed preserving most of the proximal tibial bone stock.

Debridement of the tibial canalAccess to the canal is unimpeded. A curette or ‘backscratcher’ is initially used to remove any membrane in the canal, followed by the Charnley reamer which will open up the canal distally. I insert the backscratcher down the canal and keep the blade against the cortical bone whilst withdrawing it. I go around the tibia circumferentially to ensure all the soft tissues have been removed.
Flexible reamers over an olive tipped guidewire are occasionally required, particularly if there’s a distal pedestal of bone to remove. If there’s any doubt about canal perforation the image intensifier can be used.

Back to the femur.
The Midas Rex gets hot and irrigation should be used throughout. The surrounding tissues are also at risk from a high speed burr. Use the foot pedal only when the tip is in place around the bone sleeve interface.

The femoral sleeve remains well fixed so the bone is removed around it A femoral osteotomy or a window are options but in the presence of infection and the periosteal reaction in the distal femur I decide to remove a further 50mm of bone to extract the sleeve and perform a short distal femoral replacement.
The shortest distal femoral resection is 83mm with a standard fixed hinge implant.

The femoral artery is just behind the capsule and can often be palpated. I release the tourniquet before the definitive implantation to ensure i’ve not injured a significant vessel and to achieve haemostasis.

Debridement continues now that all the components are out. Dividing the knee into zones may help: anteriorly and the suprapatellar recess, medial gutter, lateral gutter and posteriorly.

The tibia is re-cut to remove any infected bone and to prepare it for the stemmed tibial componentI cut the proximal tibia freehand with an oscillating saw in this situation but any primary knee replacement jig will allow a freshen up cut. It needs to be at 0 degrees slope for the SMILES knee. In the revision scenario I aim to resect an extra 1mm of bone from the lowest point on the tibia.

The tibial canal is reamed and proximal tibia prepared for the fixed hingeA Charnley reamer is used to ensure there is enough room for a 180mm stem. I start with the small Charnley reamer before using the bigger one. I also make sure I keep one hand on the tibial shaft to ensure reaming is in the right direction and straight down the shaft. In difficult cases with bone loss or deformity the image intensifier or flexible reamers may be required.
If the larger Charnley reamer goes down, the definitive stem will too.

A standard long 180mm Stryker SIW fixed hinge tibial trial is insertedThe trial needs to bypass the osteotomy and hence the choice for a long stem.
With hinged implants there needs to be adequate room proximally for the larger tibial boss. This is especially true when there is a rotating hinge mechanism to accommodate. There are reamers on the set and a counterbore; these are easier to use when the proximal tibia is intact. I find a Midas Rex useful to fine tune the bone preparation when an osteotomy has been done, particularly if the tibial tubercle osteotomy needs thinning out for it to be closed appropriately. In this case there was adequate room proximally for the hinge and subsequent closure of the osteotomy.

Drill holes for cerclage wires to secure the osteotomyThere are many ways to close the tibial tubercle osteotomy. If the soft tissues and proximal tibial bone are adequate I use two 2mm Dall Miles cables. Wire or sutures are alternatives.

Drill holes are made in the proximal tibia with a 2.5mm drill and the cables fed through.

The cables are looped around the osteotomised tubercle and at this point I check that the osteotomy can be easily opposed. They can be loosely held for the time being with an artery clip.

The femoral canal is preparedThe femur is lifted up with a blunt Hohmann posteriorly and a Hey Groves clamp placed anteriorly.

If necessary the cut can be adjusted to ensure it is perpendicular to the shaft.
This allows the collar to sit flush with the bone (more important in a second stage or definitive procedure as there is usually a hydroxyapatite collar that should have good osseous contact).

The trial femoral component is insertedCharnley T handle reamers can be used to open up the femoral canal. If it is tight or if there is a deformity or obstruction II or flexible reamers can be used. The stems come in 10-15mm sizes when using the modular system. With the integrated short DFR the stem is 13mm, which tapers to 8mm.
The length of the DFR is modular. It can be lengthened by 15mm increments.

The knee is trialled with a long fixed hinge tibial trialThe components are joined together with a trial axle. This is inserted by hand from medial to lateral.
As mentioned earlier the advantage of the Stryker SIW system is the simplicity. A standard femur must go with a standard tibia and vice versa.

Augments are available for the tibia (5,10,15 and 20mm sizes) but as this is a first stage spacer the joint line can be adjusted using green augment (cement) if needed.
The knee is trialled for range of movement and patella tracking. The osteotomised bone can be temporarily held in place with a Kocher. With an endoprosthesis it is also important to check leg length as this can be inadvertently altered. I check the soft tissue tension and range of movement and then double check the proposed implant length with the length of bone resected.

Further debridement and washCopious lavage with aqueous chlorhexidine.

The (definitive) implants.
From right to left: a short standard sized left integrated distal femoral replacement, long fixed hinge tibial component with polyethylene bumper, circlip and axle.

Antibiotic loaded cement is spread liberally around the components.As the components are being used as a spacer they will only be loosely cemented in. I wrap cement around the proximal portion of the implant and loosely insert it. It”s easier to insert the tibial component first.
Depending on the infecting organism antibiotics can be added to the cement. In this case 1g of vancomycin is added to each mix of cement.

The tibia is inserted with the first double mix of antibiotic loaded cementEnough cement is used to prevent movement but whatever goes in now still needs to come out at the second stage! I try not to insert cement too far down the canal as this can hinder the 2nd stage. If local delivery is needed in the shaft Stimulan beads (see slide 52 ) can be inserted and pushed down.
The implant needs to be positioned in front of the posterior loop of cables and pushed gently into the tibial canal. An impactor is provided on the set but usually not needed in a first stage with only partial cementation.

The cables are then tightened, initially by handExcess cement is removed, particularly around the osteotomy site. If left there is an increased non-union risk.

Once the osteotomy is reduced and clear of cement the cables can be further tightened.
On the Dall Miles kit is a tensioner. Turning the handle clockwise tightens the wires. The bone is often soft and care needs to be taken not to damage or fragment the tibial tubercle by overtightening. I use both feedback from the tensioner and visual inspection of the osteotomy to judge the appropriate tension.
By having the cables behind the tibial stem secure fixation is achieved and no restrictions are required post-operatively.

Similarly a second double mix of antibiotic impregnated cement is used to loosely secure the femoral component
I try and insert both components in quick succession. This means that either of them can be adjusted if necessary before the cement cures. It also allows the hinged knee to be assembled and the leg kept in extension whilst curing occurs.

The femoral component is loosely cemented inThe femur needs to lifted up by the assistant and the knee flexed to get the component in. This also allows any cement posteriorly to be removed.
If a rotating hinge is used it is crucial not to drop cement down the tibial assembly. This is difficult to remove and means the rotating hinge will not fit properly.

The components are secured together via an axleThis bit can be fiddly. It is necessary to line up the femoral and tibial components perfectly before the axle will go in. I use a Kocher initially to achieve this and then my assistant holds the knee whilst the Kocher is removed and the axle inserted.
In this image the tourniquet has recently been released.

The circlip is inserted after the axle (a) and secures it in place.
Both the axle and circlip can be inserted either medial to lateral or lateral to medial. The medial side is usually easier and my standard practice.
The circlip needs to be pinched with an artery clip and then inserted. It has to sit in a groove in the femoral component and should rotate freely once in. If it doesn’t then a gentle tap of the axle ensuring it is fully seated may be required.

The axle is secured with the circlip (b)

The cerclage wires are cut now that everything is in place. I keep the cut ends short as they can be irritating to the soft tissues. Further wash with saline is then performed.

Stimulan beads are inserted as a further local delivery method for antibioticsCalcium sulphate (Stimulan) beads can be pre-mixed with antibiotics and left in the wound. They are better in deeper wounds and where there is a good soft tissue envelope. They are absorbable but not uncommonly cause the wound to ooze, particularly if they are placed superficially.

Vicryl sutures to close the arthrotomyI tend to close the knee in flexion to ensure appropriate tension on the extensor mechanism

The metal wires are adequately covered but can be palpable in thinner patients

Skin closure with clips and a Redivac drain

Post-operative AP image

The tibial tubercle osteotomy has approximated nicely in this post-op lateral image.