Total knee replacement-Triathlon (Stryker) posterior stabilised knee

Analyse the leg for a pre-operative fixed flexion deformity of the knee. Where a pre-operative fixed flexion deformity exists increased distal femoral bone resection cuts may be required to allow the knee to straighten and posterior release might be needed. Note these factors should be identified before the patient comes to theatre and are readily observed in the clinic.

Test the competency of the collateral ligaments in the knee. One must make sure that the MCL is competent and has a definitive end point. In cases of extreme valgus play or an incompetent MCL a hinged total knee replacement is needed. In this case the varus deformity of the knee corrected to neutral and the MCL was competent.

Weightbearing pre-operative AP leg alignment film showing varus osteoathritis.

A prepped and draped limb. Here the limb has been covered with a proprietary Ioban skin incision drape. I favour this technique when the skin is healthy as it allows visualisation of the tibia throughout its entire length and omits the need for bulky drapes distally which can get in the way of the alignment rod instrumentation.

Reflect the soft tissues both medially and laterally (lateral in this photograph) to expose the quadriceps tendon proximally, the patella in the centre of the wound and the patella tendon distally. Use a single plane of dissection until you can see enough of the extensor mechanism. Excise any prepatella bursa if inflamed.

A mid-line incision has been made in the skin. This starts about a hand’s breadth proximally from the centre of the patella to just below the tibial tubercle distally. We now start to reflect the skin medially in the fascial plane.

Medial parapatellar approach: Identify the natural rolled edge of the patella tendon medially. This is an important landmark when making your medial para-patella approach. Incise along the border of the medial patella tendon from the patella superiorly to the tibial tubercle distally. Skirt the incision around the patella medially proximally until you reach the quadriceps tendon where a 5mm cuff of tendon should be left medially as you extend up the quadriceps tendon leaving the majority of the tendon lateral to the incision. Once the joint has been entered for the length of the approach, sublux the medial tissues to expose the medial femoral condyle shown. Reflect the medial tissues off the medial tibial plateau proximally, staying subperiosteal.
Stay on the tibial bone and reflect the tissues off the medial proximal tibia starting centrally from your medial para-patella incision working around the medial side of the tibial plateau. In the more fixed varus cases this release needs to be more extensive often passing the “equator” of the plateau.

Remove the ACL from the femoral notch. In this case I also am proceeding to mobilise the PCL fibres by releasing them off the femur as I am performing a posterior stabilised total knee replacement.

Remove the soft tissues only from the suprapatellar region above the articular surface of the femur, so that the anterior cortical surface is exposed. This is to expose the anterior aspect of the distal femoral bone. This is required later to size the femoral component, it is more efficient to do it now (iie get all the dissection performed in one go).

Confirm your resection by placing an angel wing into the slot and observing the resection line along both the medial and lateral margins of the tibial plateau. Note this image doesn’t show the angel wing flush on the cutting block.

Start with the intramedullary drill and locate the centre of the femoral canal. Use your free hand to grasp the distal femur to get a “feel” for the direction of the drill. Use the preoperative radiograph to approximate where you wish to start drilling. This should align with the anatomical axis of the femur. This is often 1cm anterior to the posterior cruciate ligament and slightly medial.

Seat the drill fully to include the drills wider proximal flare.

Insert the intramedullary rod ( green T-handle shown) once the femoral alignment guide has been attached into the femoral canal. 5, 6 and 7 degree valgus cut angle options are available on this cutting block. Choose your cut angle from your pre-operative planning on from the alignment AP leg Xrays.
Pin the alignment block to the condyles by hammering its medial and lateral pins. (annotated p – lateral pin). Place the universal resection guide onto the adjustment block and then insert its posts into the femoral block (annotated b). Set the desired resection level, for a standard primary TKR this is 8mm). A 10mm resection however should be considered in cases with a marked fixed flexion deformity.

Pin the distal resection guide into the distal anterior femur using two drilled pins. Placing the pin into the zero marked hole.

The second pin placement.

Remove the intramedullary rod, femoral alignment guide and adjustment block, leaving the pinned universal resection guide in place.

The universal resection guide after removal of the intramedullary rod, femoral alignment guide and adjustment block.

Confirm the distal femoral lateral and medial (pictured) condyle resections with an “angel wing” before cutting the bone. Place the angel wing into the cutting block slot and examine the amount of bone to be resected.

Confirm the distal femoral lateral (pictured) and medial condyle resections with an “angel wing” before cutting the bone.

Apply the cutting capture mechanism to the distal femoral cutting block. The capture mechanism slots into the block and is released by pressing the two black levers together.

Use a sagittal saw to resect the femoral condyles. Cut one condyle at a time protecting the collateral ligaments with a Hohmann as shown. A Kocher has been applied to one of the holding pins to stop the cutting block backing off the pins from the vibrations made by the saw.

The appearance after the distal femoral condyles have been resected.

Confirm the cut distal femoral surface is flat by placing a flat metal surface against the surface to appreciate its flatness. Leave the femoral pins in case you need to resect further from the distal femur after the extension gap has been analysed.

Remove any final remnants of the ACL/PCL or menisci at the back of the knee to expose the tibial surface fully. A Hohmann retractor has been placed on the posterior aspect of the tibia and on its lateral border to facilitate the tibia’s exposure. The lateral Hohmann is placed more anteriorly than you might think to aid retraction of the patella and its tendon laterally.

The proximal tibial resection can be performed with either an intra or extramedullary technique. In this case I display the use of an extramedullary referencing alignment.
Place the ankle clamp around the ankle and confirm that the jigs parts are unlocked. Ascertain the centre of the tibial plateau from the pre-operative AP xrays which will be between the tibial spines. Hammer the longer of the two spikes on the proximal aspect of the jig into the tibial plateau (annotated S). Now align the jig. For flexion/extension the long axis of the rod parallels the mid-coronal plane of the tibia. For varus/valgus alignment the rod is adjusted in a medial and lateral direction under the rod intersects the centre of the tibia. For the tibial slope, align the rod parallel to the tibia.
The cutting block is 0 degrees for posterior stabilised knee or 3 degrees for cruciate retaining replacement. Finally rotational alignment is confirmed when the rod is aligned with the centre of the ankle, typically in line with the second metatarsal. Once you are happy with all the alignment parameters hammer the second spike into the proximal tibia and lock the jig. Recheck your alignments to ensure no movement occurred during final seating of the proximal spikes.

Final seating of the two proximal spikes of the extramedullary jig.

Confirm the resection level by attaching the tibial stylus to the tibial resection guide, this can be 9mm referenced to the lowest point on the uneffected side, or 2mm to the lowest point on the effected side as shown in this case. ( A 9mm resection measured on lateral side is pictured).

A 2mm resection is pictured on medial side. Pin the tibial resection guide through its “0” holes with two pins.

The tibial resection guide with saw capture added to its proximal surface – after removal of external jig apparatus. Saw capture apparatus is not compulsory but I find it easier to control the saw blade and make a more accurate cut.

Use a sagittal saw in the tibial cutting blocks aperture. The medial side his being cut in this picture. Ensure you complete your cut especially on the lateral rim which is often missed.

Once the tibial cut has been made, remove the tibial cutting block and then the proximal tibial plateau is removed, start by using an osteotome to elevate it. Leave the tibial pins in until you have confirmed the extension gap.

Use a Kocher placed on the antero-medial aspect on the resected tibial plateau’s surface. Rotate the tibial plateau laterally and using sharp soft tissue dissection along its posterior rim remove the proximal tibial bone in one piece.

Take the gap measurer and place it into the gap between the cut surfaces of the tibia and femur. Confirm that the knee is balanced to both varus and valgus stressing and that it extends fully with no residual fixed flexion deformity persisting. Also check that the knee doesn’t hyperextend. Remove the femoral pins at this point if you are happy with the extension gap.

Return to the femoral preparation. Apply the femoral sizing block to the cut distal femoral surface and slide the feet of the femoral sizer under the posterior condyles. The block can be set for differing degrees of external rotation between 3 and 6 degrees for the left or right side. Typically 3 degrees is required for a standard TKR. A further check of rotation is performed by comparing the epicondylar axis line etched on the block to the patients epicondylar axis.

Apply the sizing stylus to the block in the correct side (right or left). The Stylus sits in the block and the size of the femoral component is measured off the lateral aspect of the anterior distal surface of the femur. The size is displayed in the aperture of the stylus.

Once you are happy with the rotation, pin the femoral sizing block with 2 pins.

The size has been selected from the stylus (slide 34) after it has been placed on the lateral femoral cortex. The femoral sizing block has slots on its sides that correspond to the size of the femoral component. Confirm the size by placing an angel wing into the cutting block, ensuring the femur’s anterior cortex won’t be notched when the anterior femoral cut is made. The angel wing should be anterior to the femoral surface.

Apply the correctly sized 4 in 1 cutting block to the distal femur, using the two pin tracts drilled to hold the femoral sizing block. Check again that you won’t notch the anterior cortex of the femur with the angel wing.

Pin the 4 in 1 cutting block using its two oblique pin holes (the medial one is annotated p).

Once the 4 in 1 cutting block is stabilised cut the anterior femoral cortex.

Cut the anterior chamfer.

Cut the posterior condyles. Be careful not to go too deep especially in the central area as the neurovascular structures can be damaged in the popliteal fossa.

Cut the posterior chamfers.

Resect the medial posterior condyle, use a Hohmann retractor placed under the medial collateral ligament to protect it from the saw blade.

Remove the posterior condylar resected bone with a flat osteotome. To gain increased access to the posterior condylar area ask your assistant to simply push back on the proximal tibia.
Remove the posterior osteophytes. An easy way to get to the back of the knee is to have your assistant push hard on the proximal tibia posteriorly, this opens up the posterior aspect of the knee. With a sharp osteotome chisel the posterior osteophytes off both the medial and lateral femoral condyle.
Again be careful of not going into the popliteal fossa with the osteotome.

Remove the posterior osteophyte remants with a currette and bone nibbler/Kocher. Where the posterior structures are tight reflect them off the posterior aspect of the femur with an osteotome.

Check the flexion gap is balanced using the gap-balancer.
Confirm that the flexion gap is balanced both for varus and valgus strain with the knee bent at 90 degrees. If there is a mismatch between flexion and extension or imbalance in varus/valgus strain you will need to revisit your cuts to work out where the error is and recut as appropriate or perform soft tissues releases as needed.

Once you are happy that the knee is balanced proceed to the box cut for the posterior stabilised (PS) knee. Place the correctly sized PS cutting guide onto the distal femur. Align the PS box cutting guide for best coverage of the femur medio-laterally, so that the femoral component has its box centered over the intercondylar notch and the femoral component won’t overhang the medial or lateral sides of the distal femur.

Once happy with the position pin the PS cutting block.

Use a reciprocating saw to resect the medial and lateral edges of the box cut. Be very careful to not to go too deep into the notch. The depth of the cut is to the edge annotated “c”.

Impact the box chisel with a hammer until it is seated fully.

Remove any soft tissue remnants of the PCL with a Bovey and any loose bone with a curette.

Apply the appropriately sized femoral trial to the femur. Hammer this on confirming that it has seated equally on both sides. Fit the femoral component to the femur by using the box of the component to fit into the notch.

Confirm the size of the tibial tray using the resected tibial plateau’s undersurface to gauge this.
You should also note that the tibial component of the Triathlon knee system should be within 1 size of the femoral component.

Confirm the tibial tray size by comparing with the cut surface of the tibia. Next insert the tray into the knee with 9mm PS polyethylene.

Apply the Universal alignment handle to the tibial tray with the knee in extension. Next apply the alignment rod to the handle to confirm your overall alignment of the joint with the axis of the tibia. Confirm also the correct rotation of the tibial component.

Once you are happy with the rotational alignment of the tibial component mark the proximal tibia with the Bovey in line with the etched markings on the front of the tibial tray. This will allow for consistent tibial component placement when preparing its keel cut and also during cementation.

Measure the patella thickness and plan the depth of the patella cut you require -the depth of patella cut alters depending on the size of the patella, the table below shows the thickness of each patella size. Remove the same amount of bone as the thickness, do not “over stuff” the patella-femoral component by putting in too thick a patella button.

Asymmetric patella (mm)
Thickness (mm)
33
9
36
10
39
10
42
11
44
11

Hold the patella still with two Kochers one placed superiorly and one inferiorly to the patella. Use a sagittal saw to cut the patella. I favour a freehand technique but there is a measured caliper on the set where you can set the depth of resection.

Measure the remaining thickness of the patella – to confirm you have removed enough bone, and if not recut to the required thickness.

Apply the correctly sized patella template and clamp it to the patella. In this case I am using an asymmetric patella button. Symmetric buttons can be used. Ensure the button is placed in the optimal position for patellar tracking, this will typically be slightly medialised on the patella so that it sits in the trochlea of the femoral component, if lateralised the button will “ride” on the lateral aspect of the femoral component.

Drill the three cement fixation holes with the designated drill.

The patella surface after three cement fixation holes have been drilled. Remove all bone debris.

Apply the correctly sized trial patella button, ensure its flush with the cut surface of the patella. Remove the Kochers.
Now trial the knees range of movement and check the patella tracking.
Ensure the patella sits stably in the trochela notch through the range, that the knee fully extends, has a good range of flexion, and is balanced in valgus and varus throughout the range. At this point also confirm you are happy with the tibial base plates rotation as aligned with the patient tibial tubercle. Malrotation of the baseplate could lead to patella maltracking.

Finish preparing the tibia.
Place a blunt Hohmann retractor posteriorly to the tibia. Place a swab in the femoral notch to protect the prepared femur as you retract on the Hohmann and dislocate the tibia anteriorly.

Place a sharp Hohmann laterally and a ring handled spike medially to fully expose the cut surface of the tibia. Apply the correctly sized tibial trial baseplate to the tibia. Align it with the two marks made previously with the Bovey (slide 56). Place two pins into the tibial trial baseplate.

A final check of alignment is made by placing the alignment rod through the tibial tray handle. Confirm you are happy with this final position of the tibial component.

It is now time to prepare the tibial keel punch. In this case I have used the saggital saw to start the keel’s entry point on the medial side, as the patient had hard medial subchondral bone from his varus osteoarthritis.

Impact the keel punch, until it is fully seated flat on the tibial baseplate.

Remove the keel punch by lifting up the keel punch handle and pulling it forward, the picture above shows the handle half way forward. Fully move the handle to forward to elevate the keel punch out of the bone.

The final appearance of tibia after keel preparation.

Lavage the tibia with a pulsatile system and then dry the proximal tibial bone once cleaned. I use a chlorhexidine fluid wash.

The appearance of the tibia after cleaning.

Cement is applied on the proximal tibial plateau and a small ring doughnut of cement is applied on the undersurface of the tibial component. The tibial component is held with a lever operated tibial baseplate impactor/extractor handle.

Impact the tibial component, aligning it with the two previously made Bovey marks (slide 56). Impact with the baseplate handle impactor and confirm seating once this removed by impacting again with the tibial impactor (as shown above).

Remove any loose cement from around the edges of the tibial baseplate. Pulsatile lavage the femoral bone in preparation for cementation and then dry the bone.

Apply a “horseshoe” of cement over the anterior and distal resections on your femur including the anterior chamfer. Apply cement to the posterior aspect of the entire femoral component. Take care not to use much cement in the posterior condylar area as this will extrude behind the femur and you will not be able to get it out.

Impact the femoral component gently whilst mounted on the femoral impactor (pictured).

Switch to the freehand impactor to finally seat the femoral component.

Remove the excess cement from the box and medial and lateral gutters of the femoral component. Ensure that the femoral component is seated correctly and evenly. Next insert the trial liner, shown in orange. Once the trial liner is seated extend the knee and cement the patella as you wait for the cement to cure.

Extend the leg and hold in extension whilst you lavage the patella.

Apply cement to the back of the patella. Identify the three lug holes on the back of the patella by “poking” a McDonald’s instrument through the cement.

Apply the patella button to the patella by aligning its three pegs into the three predrilled holes. If you are struggling at this point to align the patella correctly use a gentle rotational movement to seat the patella. I find this helps to locate the holes.

Whilst the cement is curing. Instill local anaesthetic into the soft tissues. I use 0.1% bupivicaine with adrenaline (volume dependent on the patient’s weight).

Once the cement has cured remove any excess cement with a sharp osteotome.

Slide the polyethylene insert into the tibial tray, angling posteriorly.
Ensure no loose tissue/cement/bone is in the tibial tray as this will prevent polyethylene seating.

Finally seat the polyethylene insert using the reduction tool. Confirm the polyethylene is correctly seated by observing that it is reduced on both the medial and lateral sides and that the locking wire (in the liner) locks under the barbs on the anterior inner surface of the tibial baseplate. Release the tourniquet at this time once the knee is reduced. Lavage the joint removing any loose bone/cement. Achieve haemostasis using the diathermy.

Reduce the patella over the front of the knee. Repair the medial parapatellar incision. In this picture loop PDS monofilament suture is used. Repair is best done in flexion.

The fat layer has been closed with 0 Vicryl, now I start in the midde with 2/0 quill in two layers, starting subdermal and then subcutaneously.

The skin is closed with 2/0 quill in two layers one subdermal and one subcutaneously.
Apply glue to finish closure.

The dressing is applied once the glue has dried.

Post-operative AP radiograph.