Total knee replacement- PFC replacement (De Puy-Synthes)

These pre-op x-rays show osteoarthritis affecting all three compartments. The medial side is most effected.
Patallofemoral arthritis is very much evident & classically would present with pain worse coming downstairs or downhill rather than up.

.Set up the knee supports pre-operatively
I use 2 bolsters for the foot. The one nearest to the hip is the standard bolster and is used during surgery, the knee here as flexed around 100 degrees. The second, most distal is only used when closing. It detentions the tissues, making closure easier.
Please note, the foot and ankle in this patient are deformed following previous trauma.
Before prepping, confirm the clinical findings by performing an EUA, assessing any fixed flexion, varus or valgus deformities. Note any abnormal tibial or femoral angulation.

After skin prep and allowing it to dry, roll the stockinet fully up the leg and cut a longitudinal slit. Cover with ioban.
There are many ways to prepare the leg. I use this technique as I find that a limited amount of skin is exposed.
Although not part of usual practice, the surface anatomy of the tibial tubercle (TT), the patella ligament (PL) and the patella (Pat) have been marked.
The limb is elevated and then flexed at the knee prior to tourniquet inflation. Flexing the knee prior to inflation detentions the quadriceps mechanism.

The skin is incised in the midline from distal femur to the medial distal end of the tibial tuberosity, passing through the medial 1/3rd of the patella.This incision should be a straight line and should pass from the inferior aspect of the tibial tubercle to 3 to 4 fingers breadth above the patella.
The subcuticular fat is incised, exposing the border of vastus medialis superiorly
For orientation, I find the plane immediately above the vastus muscle and extend distally. If you remain in this plane you pass deep to the patella bursae. The patella ligament is thus exposed.

Incise medially along the patella ligament border, the patella and quadriceps tendon.Sharp dissection is used to locate the medial border of the patella tendon. This border is incised from the level of the distal tibial tuberosity to the inferior pole of the patella.
At the patella the incision continues medially, leaving a small cuff. When initially starting total knee replacements, lay the forceps against the medial patella border and incise medial to these.
Around the superior border of the patella I tend to leave a sharper superior turn. This remains obvious when closing, enabling correct opposition of tissues.
I incise the medial border of the rectus tendon, approximately 5 mm lateral the muscle of vastus medialis.

Remove a sliver of medial fat pad, which aids with the medial subperiosteal release (A).The medial subperiosteal release (or sweep) itself starts at the cut border of the medial capsule. The scalpel must remain on bone. The capsule should be stripped as one thick layer. The exposed tibial area will look like a ‘V’. The left limb of the V is the midline incision, the base is at the level of the base of the tubercle and the right limb of the V is extended medially. Do not release capsule medially at the level of the tubercle base.
The medial sweep is extended past the deep MCL. Significant and uncorrectable varus deformities will require greater, more posterior releases.
The superficial MCL is at risk during the sweep if it is too distally.

Release the tibial attachment of the lateral fat pad and If scarred, remove a sliver of the fat padI start distally and cut superiorly, away from the tendon. This frees the patella which can then be inverted.

Some recent studies have shown that outcome is improved if the fat pad is left in situ. I personally only remove a small portion if it is scarred / covered in a thickened fibrinous layer.
However a recent meta-analysis was inconclusive regarding strong correlations with pain, ligament shortening or function.
Preservation vs. resection of the infrapatellar fat pad during total knee arthroplasty Pt II…Nisar et al Knee 2019

The ACL is cut mid-substance and its imprint on the tibia is cleared.This exposes the lateral aspect of the medial plateau. I use this lateral border to help assess tibial rotation (see later).

Remove the PCL from its femoral origin in the notchNext using a diathermy, I remove the origin of the PCL, this is a PS (posterior sacrificing) PFC total knee replacement.
Care is required when approaching the posterior areas of the notch. The femoral artery is at risk.
The PCL origin is the lateral border of the medial femoral condyle. Using diathermy sweep this origin off the bone.
To assess whether the posterior notch is clear, a pair of forceps should slide into the posterior compartment of the knee with ease.

Dislocate the tibia anteriorly using a Hohmann’s retractor.The Hohmann’s retractor is placed posterior to the cut PCL and slid down until it touches the posterior aspect of the tibia. Diving posteriorly with the Hohmann’s places the popliteal artery at risk.
As the PCL has been released, dislocation is usually easy. Forced external rotation of the tibia is not required.

With the diathermy held horizontally, a full length diathermy mark is made parallel and touching the lateral border of the medial tibial plateau which is brought forward to the most anterior aspect of the tibiaFrom this point another diathermy mark is made on the anterior aspect of the knee (A) . This will be the centre of the anterior aspect of the tibial tray. It usually, but not always corresponds to the medial 1/3, lateral 2/3 junction of the tibial tubercle (another rotational landmark). If they do not correspond I tend to use the diathermy mark rather than the tubercle landmark.

The medial and lateral menisci are resected.These sometimes sublux behind the posterior border of the tibia. They can be pulled forwards with either forceps or nibblers. I also clear fat pad from the anterior border of the femur. I tend to make an inverted T shaped incision and elevate the fat pad rather than resect it.

Align the tibial cutting jigThis is one of the most important steps when performing the total knee replacement. Parameters to consider include; cutting height of the jig, varus / valgus angulation, internal / external rotation and posterior slope and I will take each of these in turn, although in reality all of them are considered together.
Many manuals and op techs will state take 10mm from the lateral side or 2mm from the medial side. This is an over simplification. Firstly it only relates to varus deformity or cases where degenerative change predominantly effects the medial knee. For example, in a valgus knee with significant wear of cartilage, taking 10mm laterally will result in a very thick cut.
I would tend to take 6mm from the medial side, a 2mm resection is insufficient are there is likely no wear medially.
I therefore base the height of the resection visually using the Angel wing (A). It is slotted through the tibial resection guide and runs medially. It should be placed below the medial osteophytes.
To ensure that the tibia will sit with the correct rotation, the centre line on the cutting block (see next slide) should be parallel to the long axis of the lateral border of the medial plateau (previously marked with diathermy). In theory as the posterior slope is zero, this step should not matter with a PS type knee. However with a cruciate retaining knee, getting the rotation wrong will leave an oblique posterior slope.
Varus / and valgus alignment is obtained by sliding the jig at the ankle clamp. The rod should run down the centre of the tibia and distally be in the centre of the ankle. In practice unless the tibia is deformed the jig is set fully medial or one notch in from this.
A full image of the jig is seen on slide 11 of the Operation section of the Sleeved Total Knee presentation;
Sleeved Total Knee Replacement for Tibial Plateau Fracture (MBT DePuy)
Finally the posterior slope should be zero degrees (for the PS, cruciate retaining jigs are 3 degrees). This is again set at the ankle clamp. The angle wing should be orthogonal to the long axis of the fibula.

I prefer the ‘half block’ (A). I find that the full cutting block can sometimes stand proud, away from the tibia, especially if the patient is obese. If the tibial block sits away from the tibia the posterior slope may be effected.
Another error encountered when the tibial block is proud of the tibia is that the pins may work loose during resection, again potentially resulting in malalignment.

Insert a pin into the lateral neutral hole of the tibial cutting jig (A)The jig is now stable. I check the alignment parameters again and will confirm the resection level with the stylus. However there is a great deal of ‘play’ in the stylus and for me is only confirmatory.
Once all parameters are correct I insert the medial pin. (I insert the lateral pin first as usually in a varus knee the medial bone is hard and the pin can skirt off).

Cut the tibial plateau with a power sawTo protect the soft tissues use a Langenbeck (medially) a Hohmann’s (posteriorly) and a bone spike or Hohmann’s (laterally). The lateral retractor needs to be placed anterior to the axis of the tibia to sufficiently protect the fat pad and patella ligament.

The saw requires support to enable controlled resection.
I either rest the saw on my left hand or hold the blade release knob, this prevents ‘diving.’ Additionally, pressure is placed on the tibial jig with this hand to prevent it sliding forwards on the pins. A 3rd pin can be used to secure the jig.

The cut plateau is elevated with an osteotome and soft tissue attachments cut off it.The cut plateau should lift as a single piece. If there is resistance the saw cuts most likely have been insufficient.

Pull on the plateau and resect it clear of soft tissues, keeping close to bone. It is easier to start medially and work laterally. Stay close to bone, straying posteriorly puts the popliteal vessels and nerves in danger.

This cut plateau measures a 4 however this measurement has not taken into account the correct orientation of the tray nor whether any tibial osteophytes are removed. Always measure the size from the in-vivo tibia. Do not over rely on measuring the tibial size from the resected plateau

Drill the medullary canal in preparation for the intramedullary rod, starting in the centre of the anatomical axis of the femur.This usually corresponds to slightly (1/2 cm) above the notch and slightly (1/2 cm) medially. This can be judged by the AP and lateral radiographs.
The drill needs to advance up the centre of the femur without breaching it. I use the left hand as a guide. The thumb and index finger guide valgus and varus angulation but I also place the middle finger on the anterior femoral bone to gauge the amount of flexion and extension of the drill.

The femoral locating device, outrigger and distal femoral cutting block are attached to the IM rod.Lots to go at here in setting up the distal femoral cuts.
The distal locating device (A) is slid over the IM rod (B). This sets the valgus angle (0-9), it is also sided (L/R). The degrees are set and the angle locked. My standard cut is 5 degrees, slightly lower in fixed valgus deformity knees and greater in fixed valgus knees or patients with a short stature with ‘wide hips’ (i.e increased Q angle).
The outrigger (C) is placed in the distal locating device. The height is adjusted using button D. The distal cutting block (E) is placed on the outrigger. This is adjusted using the button (F).
The most distal cutting slot will resect at a level set and read on the outrigger scale. The other 2 slots will add an additional 4 and 8mm of resection.
There is an external alignment device which sits a marker over the centre of the femoral head. I have yet to see anyone use this.

Orientate the outrigger and cutting block to ensure correct rotation of the distal cut.This step is also very important. The outrigger’s centre of rotation is the IM rod which is in the mechanical axis of the femur. The outrigger should be aligned to the posterior condyles (Lateral, Lt & Medial, Md) so that greater medial posterior condyle is seen. This can be checked by placing the cutting block onto the resected tibial surface with an interposed spacer (the type seen in slide 28 later). This will ensure a rectangular space is created in flexion.
Whilst I accept this jig is only cutting the distal femoral cut, minor errors in flexion or extension will result in an oblique cut if the orientation is incorrect.
The angel wing is used to confirm cutting distance. The standard resection is 10mm. When significant cartilage or bone has been lost from the medial condyle, this should be reduced by 2mm. The angle wing should just ‘touch’ the notch.
Confirm that bone will be resected from the medial and lateral condyles. With valgus (and hence hypoplastic lateral femoral condyles) this is very important. If no bone is going to be resected it may be worth changing the alignment 1 degree or consider resecting 12-14mm from the lateral distal condyle and using a distal femoral augment in the femoral component.

Secure the distal femoral cutting block with pins in the neutral holesEnsure these pins get a good hold. In small patients there is a tendency for the medial pin to skirt of the medial side of the metaphysis.

Resect the distal femurA Hohmann is used to protect the medial and then lateral collateral ligament. Pushing back on the tibia elevates the femur, decreasing the risk of iatrogenic damage to the cut tibial surface.

Check that the distal femoral cut is uniform with the flat surface of the distal cutting blockI always make ‘2 cuts’ with the saw. The initial cut removes the distal femur. I then withdraw the saw and repeat the cut. Often another 1 or 2 mm are resected.

Check the extension gaps with a spacer after the distal femoral cut.I use a spacer to check the extension gap. Ensure that the leg goes fully straight.
If not, posterior capsular releases or further resection of the femur will be required.

Check valgus / varus balance in extensionAgain the spacer is used for this. This knee was balanced and no releases were necessary.
I have covered the lateral releases in an earlier presentation;
Sleeved Total Knee Replacement for Tibial Plateau Fracture (MBT DePuy)
(slide 36 onwards)
Further medial releases can follow. These should be done sequentially and balance checked after each release.
The order of the releases are as follows;
Start with releasing the posteromedial capsule, then release the deep MCL.
Very occasionally I have performed a medial ostectomy, during this procedure, the tibial tray is downsized one size and lateralised. This leaves a few millimetres of tibia plateau medially, this is then resected decreasing tension on the MCL.

The two orientation lines I mark for aligning the femoral component are the transepicondylar and Whiteside’s line.
The epidcondyles are not uniformly shaped. The medial is a domed and the highest point should be marked (Md). The lateral is shaped like a reflected ‘C’. The depression within the ‘C’ should be marked. (Lt)
Whiteside’s line (WS) runs from the lowest point of the trochlear to the highest point of the femoral notch.

Use the femoral sizing guide to ascertain which size of femur is required and pin into position.This has already been covered in detail in the Sleeved TKA presentation however in summary;
The femoral sizing guide is placed flush against the distal femoral cut.
A stylus extends along the femur lifting the stylus arm. When the size is determined, lock this arm (A). Reference from the lateral femur as this is higher and there is therefore less chance of notching.
There are two types of guide with the PFC kit.
The anterior sizing guide will ensure the the anterior flange of the prosthesis lays flush with the anterior cortex of the femur, this resects 8mm of the posterior lateral condyle.
The posterior referencing guide references from the posterior condyles and likewise still ensures 8mm is taken from the posterior condyles.
Both work well when the size of the implant is an exact fit however patients may be ‘between sizes’
If a femur is between sizes different approaches to optimising the flexion gaps are required
For anterior references downsizing results in excess removal of bone posteiorly, resulting in an unstalbe flexion gap.
With posterior referencing downsizing results potentially in notching.
Therefore to correct for this in anterior referenced knees, move the drill guide slightly posteriorly and the reverse for a posterior reference guide.
Once the size is set (from A) the central portion of the guide is moved to the corresponding size and tightened (B).
A good review of alignment in total knee replacement can be found in the paper by Cherian et al.

Mechanical, anatomical and kinematic axis in TKA: Concepts and Practical Applications. Cherian et al. Curr Rev Musculoskelet Med. 2014 Jun; 7(2): 89–95

Finally pins are impacted into the drill hole pins, which when removed, create holes for insertion of the relevant sized cutting block.
The pins are asymmetric and position the chamfer cutting block in 3 degrees of external rotation.
This results in resection of 8mm from the posterior lateral condyle and 10-11mm from the medial. Again as the arc of radius of the medial condyle is greater more medial bone required resection to generate a ‘rectangular flexion gap.’
Details of this are documented in De Puy’s op-tech (please see link in the ‘implants’ section).

Check the femoral pin holes correspond to the orientation referencing linesFor a PFC knee the pin holes should be parallel to the transepicondylar axis (or the medial one slightly anterior) and orthogonal to Whiteside’s line.

Impact the femoral Chamfer cutting block and confirm that the anterior distal cut will not notch the femurEnsure this is sitting flush to the bone. If not check for fragments of distal femur that have not been resected cleanly. Errors here lead to valgus / varus or flexion / extension imbalance.

Use the angel wing to confirm that the anterior cut (A) will not notch the femur, check both medial and lateral sides (the lateral side is higher and more at risk of notching).
Following this the posterior cut is made (P)

Chamer cut the anterior and posterior femurI personally cut the medial anterior side first. It the cut is too posterior the chamfer jig can be anteriorised (confirm correct internal / external orientation first). Cutting incorrectly laterally first leaves a larger bony defect.

Cut the anterior (A) and posterior (P) chamfer cuts

Remove the femoral chamfer jig and ensure there are no raised or irregular areas of bone effecting the cut surfaces.
Use a nibbler or osteotome to remove any bony fragments that have not been removed with the saw.

Confirm the posterior chamfer cut has removed sufficient bone
I do this digitally. Do not use the IM rod to elevate the femur. This can snap in the canal.

Position the femoral jig for the box cutThe box cut should sit in the middle of the knee. Confirm before impacting pins. On the anterior femur I use the pins that are used to secure the tibial tray as these do not impinge against the saw when cutting the box.

Protect the tibia when cutting the box, using the angel wingEnsure that the saw is held parallel to the jig. Do not undercut the condyles.

The femoral trial is mounted on the introducerThe trial femur is secured onto the introducer by tightening the knob (A)

Impact the femoral trialI use the slaphammer mounted onto the introducer as I think this gives greater control. Keep your hand elevated to prevent inserting the trial in flexion.

As shown, I impact on the anterior lip of the notch to confirm there is no flexion of the trial.
If it doesn’t sit flush the underlying reason needs to be addressed.
The are multiple reasons for this but I find the following are most common.
Firstly there is some soft tissue interposition between the trial and the bone, remove this and retrial.
Alternatively, the femoral cuts are not complete and a small piece of bone has not been fully resected. (usually from one of the chamfer cuts). Remove this (usually with a nibbler).
Additionally the box cut may not have been deep enough. Use the rasp / file to smooth this down or replace the box cutting jig and re-cut.
Finally, the anterior femoral cut is in insufficient and the jig rocked into flexion during cutting. Attach the chamfer jig again and check. If this is OK check all remaining cuts.
If it doesn’t sit down after all these cuts it maybe that the alignment of the distal femoral cuts and the box is incorrect. Widen the box slightly with the rasp.

Insert the tibial tray and trial insert with the alignment handle.Take note when inserted whether it is tight medially or laterally. This may need to be addressed prior to inserting the definitive implant.
In flexion the only structures that are tight are the anterior fibres of the collateral ligaments and popliteus.

Cycle the knee through flexion and extension to seat the tibial trial component. The alignment handle can be used to ensure the tray and insert are aligned to the femoral component.
Check that there is no lift off in flexion. If so address the issues.
These are most commonly :
-tightness of PCL (not an issue in posterior cruciate sacrificing knee)
-Insufficient tibial slope (review and correct if necessary)
-Fat impingement of calf against thigh. (No acute adjustments required)
Mark with diathermy the orientation of the tibial component (again this is only a guide)

With the trials in-situ prepare the patella. Start by ensuring it can be dislocated and held horizontalA gentle release with the diathermy along the lateral border of the patella is usually sufficient to ensure it sits horizontally.

Measure the thickness of the patella with calipersRecord this number.

Resect patella bone depending on the size of the patella button required, the amount required being detailed on the patella jigs.As can be seen, resection levels are determined by the size of the patella button. This number is taken from the reading on the caliper. For example, the caliper initially measured 21mm. For a 35mm patella button (21-8.5) 12.5mm of residual target bone should be left, this is dialed into the patella cutting guide. A minimum of 12mm of patella should be maintained to ensue that fracture risk is minimised.

Release the fat pad immediately adjacent to the patella, clamp the patella resection jig and resect the bone required.This can be fiddly procedure. The arms of the clamp need to be on the deep surface of the extensor mechanism (A) and the anterior surface of the patella needs to be pushed firmly against the 2 ‘prongs’ of the knurled fork (yes they call it a knurled fork). Maintain this pressure to ensure that the patella does not lift as the clamp is tightened. The switch is set to ‘lock’ during tightening (switch shown in next slide)

The depth of resection can be confirmed visually before resection. The most medial extent of patella cartilage should be flush to the arms of the cutting jig. (A)
Once cut the calipers should be use to ensure that the same patella depth is found across the whole patella. (i.e there has been no oblique cut). If there has been either recut or use a rasp. There is a rasp with the kit which is used to rasp the box cut if required
Locking switch (B)

As noted in the introduction, this patient had extensive patellofemoral OA. The bone was sclerotic and eburnated. Over-drill any eburnated bone. Over drilling was the only method to ensure that bone cement would penetrate sufficiently. However to avoid as much of the sclerotic bone as possible the patella button had been downsized (I used a 35mm button instead of a 38mm one) and medialised.

Apply the patella button jig and confirm button alignment. With the spikes of the patella template jig inserted into the cut patella surface, reduce the patella. The jig should be orthogonal to the long axis of the limb. This confirms orientation of the patella button.

Drill the peg holes for the patella buttonIt was noted immediately after this shot that the wrong drill was about to be used. There are two very similar looking drills in the PFC set. One is a ‘lug drill’ used to create holes for the cruciate retaining PFC, this is a long drill. The drill for the patella button is much shorter. Both look similar!

Place the patella button trial in the drilled lug holes and remeasure the patella depth.This should be the same (plus or minus a millimeter). If it is thinner than the original, the extensor mechanism will be compromised and the patient may develop a lag. If the new depth is greater, so called ‘overstuffing,’ the patient may develop chronic anterior knee pain.

Sublux the tibia anteriorly to apply tibial tray jigThis also takes time and concentration. There are many ways to assess orientation of the tibial tray.
I tend to size the lateral size first, ensuring that the tray is on bone, I then slide the medial side anteriorly until the central anterior marker is on my original diathermy mark. This can also be the junction of the medial 1/3 – 2/3 rd junction of the tibial tubercle. I also stand behind the knee and look down at the tray. The front of it should be inline with the tibial spine (which can be palpated).
Many other surgeons will not do this but instead rely on the lines made during the cycling of the knee and the alignment established in slide 45. This is acceptable.
The tray is secured with two (short) fixation pins.

Prepare the tibial keel with the tibial drill and then keep the punch ready.The tibia is first prepared with the drill which goes through the drill bushing which is attached to the punch guide (A) (drill not shown here).
The keel punch is then impacted. It will stop when it abuts the keep punch guide.

The knee implants are checked, removed from packaging and stored.
Take care not to scratch them

Whilst bacterial load within a laminar flow tent is very low, I still keep the implants protected whilst preparing the bone etc prior to implantation.

Push bone cement into the cement pockets on the undersurface of the tibial trayAs soon as mixing is complete (and before the cement is workable) I remove a small amount and fill the cement pockets on the tibial tray. There has been recent discussion concerning potential loosening of tibial trays. Unpublished data suggests that early application of cement to the tray increases its chemical bonding and excludes air from the cement pockets.

The tray is kept aside as the tibia is prepared
Richard Baker in his TKA presentation;
Total knee replacement-Triathlon (Stryker) posterior stabilised knee.
has beautifully shown that the tibia needs to be washed until it is white with no blood seen at all. It needs to be dried by manually slapping down onto a dry swab placed on the cut tibial surface.

Ensure good interdigitation of cement into bone prior to tibial component insertion by pressurising the cement into the tibiaMore recent studies have shown that using a cement gun increases the interdigitation of cement into the bone. My attempts at this have been less successful than others (although in preparation of this presentation I note that in one article the cement gun nozzle was cut at 23 degrees) so I will revisit this.
I ensure good interdigitation by forcing the cement hard down into the bone using the spatula. After this initial layer of cement is laid down it is dried with a swab before any further is added.
A good review regarding cementing is that of Refsum et al.
Cementing technique for primary arthroplasty: a scoping review. Refsum et al Acta Orthopaedica 2019

Insert the tibial component ensuring that the orientation correct.It is important that no soft tissue is interposed between implant and cement. I use a Hohmann’s retractor (A) with it’s greater surface to retract the fat pad and immediately before final impaction I will ensure the cement surface is dry and free from blood or lipids.

Impact the tibial tray with the nylon tray impactorKeep the impactor central to ensure an even pressure across the tibial tray. Excess cement is then removed with a MacDonald’s.

Ensure the femur is free from blood and has been dried.
I place all cement onto the femur prior to impaction and none on the bone. To my knowledge most knees fail secondary to debonding on the tibial side. Certainly as part of revision workload femoral loosening in isolation is rare.
However I am going to retry femoral cementing with a nozzle cut at exactly 23 degrees!
Impact the femoral component.

Impact the definitive femoral component with the femoral impactorAgain ensure the implant does not fall into flexion.

Remove excess cement with a MacDonalds.

Apply cement to the patella and insert the patella button prior to pressurising with the patella clamp.The patella clamp has two sides, the side with the silicone ‘o’ ring is placed against the patella button, the other size has spikes for the patella bone, do not get these the wrong way around.
When squeezing ensure the locking knob is set to ‘lock’
If the patella has been cut correctly the ‘o’ ring will remain over the dome of the patella button as the implant is tightened. Remove excess cement.

The knee is kept in extension and lavaged. I note others use slight flexion with axial loading. I do not think there are major clinical differences so long as the knee is kept very still, avoiding sheering forces through the cement during curing.

After cement curing dislocate the tibia anteriorly for insert impaction.Use gauze in the trochlear to prevent implant scratching.

Remove any excess cement again
The forces generating in knee extension are greater than those generated by manual impaction and it is inevitable that some more cement will have extruded. Ensure this is cleared, especially behind both the media and lateral tibia areas.

With the tibia subluxed insert the definitive polyethylene insertThe posterior lip of the liner sits under the locking mechanism at the back of the tibial tray, the anterior surface of the liner rests on the anterior lip of the tray

Impact the tibial poly liner to ensure appropriate seating and locking of the poly insert.A gentle tap is all that is requred to reduce and lock the polyethylene home. If a gentle tap is not working then check that there is not soft tissue interposition or that the femoral condyles are not impinging, if so further flex the knee and apply slightly more pressure with the posterior Hohmann.

Finally reduce the patella and confirm trackingOnce the patella is reduced again confirm ligament balance, ROM and tracking.

The simplest method to ensure that the arthrotomy is anatomically reduced is to start at the superior angled cut which was made during the initial approach to the knee. Place an interrupted suture at this ‘corner.’ Then flex the knee (to the most distal bolster, slide 2)

Close the arthrotomy with interrupted suturesFrom the superior to inferior pole of the patella the arthrotomy is closed with interrupted sutures. The superior and inferior arms are closed with continuous sutures.

I will use both a deep and superficial fat layer if required. Often, even in (the rare) slim patient two layers are required in the fat layer in the suprapatella area.

Remove the Ioban and reprep the exposed skin
I use subcuticular monocryl for the skin wound.

Unless allergic, I always use glue and an Aquacell dressing.

Confirm implant position with post operative radiographs
The post-operative films are reviewed. The key points to review are the orientation of the implant withing the tibia (the distance from the outer tibial tray to the centre of the tibial post should be equal on a TRUE AP film. I also note that getting a true AP film in the post operative period can be difficult as the patients are often in pain and getting the knee fully extended at day 2 may be challenging.
Also look for extruded cement.
On the lateral films, the femoral box should be orthogonal to the long axis of the femur.