Total Knee Replacement- Vanguard cruciate retaining knee replacement(Zimmer-Biomet)

Examination under anaesthetic in this case revealed a varus deformity of 20 degrees which was only partially correctable to 10 degrees. The skin was intact with no previous scars. The lateral ligaments were intact and therefore a more constrained prosthesis was felt not to be necessary. The fixed varus deformity will most likely require an extensive medial release to achieve full correction.

There was a fixed flexion of 20 degrees. This could be caused by posterior femoral osteophytes which will have to be removed or a tight posterior capsule which will have to be released off the back of the femur. Resecting an added 2mm from the distal femur can help achieve full extension without compromising the level of the joint line.

AP xray revealed significant bone loss medially on the tibia and a distal femoral angle of five degrees. The Vanguard system allows for the use of tibial augments with a stem if required but still can use a standard femoral component.

Lateral view showed posterior osteophytes contributing to the fixed flexion. The posterior tibial slope was 7 degrees,

The knee is prepped using chlorhexadine 2%. An Iodophor-impregnated drape is used unless the patient has an iodine allergy. Ensure that antiseptic skin preparations are dried and pooling of alcohol based preparation is avoided. (Nice : Surgical site infections, prevention and treatment CG74)

The knee can be approached through a medial parapatellar, mid-vastus or a sub-vastas approach.
Either a traditional or minimally invasive technique can be utilized with the Vanguard Total Knee Instrumentation. It is important to note that minimally invasive methods can be utilized on nearly all patients undergoing total knee arthroplasty. However, it is important to have adequate patellar mobility, which can be assessed on physical examination prior to making the skin incision. If multiple scars from previous surgeries exist, skin incision placement will need to be evaluated, as well as elements of scarring, which may decrease soft tissue mobility.
Make the skin incision centered over the medial one- third of the patella extending from 1 cm above the superior pole of the patella to the tibial tubercle
Make a mini-medial parapatellar arthrotomy, beginning at the top medial corner of the patella and continuing down along the patellar tendon, ending at the patellar tendon insertion
With the knee in the extended position, perform the arthrotomy from 1–2 cm above the superior pole of the patella, extending to the level of the tibial tubercle. Perform fat pad excision to facilitate exposure and to improve patellar mobility.

Tibial resection.
Once the ACL has been excised the tibia is subluxed anteriorly. A homans retractor is used to protect the PCL and midline posterior structures. Bone spike retractors are used to protect the collateral ligaments.
An extra medullary tibial jig is used with a cutting block of 0 degree posterior slope. The margins of the tibial tuberosity and tibial eminence are used to set the rotation of the extra medullary tibial jig proximally. Distally the jig is lined up with the tibialis anterior tendon. The posterior slope is set parallel with the tibial crest. The standard tibial insert has 3 degrees built in. The posterior slope is adjusted depending on the native slope.
The tibia is cut being careful to avoid damage to the PCL or collateral ligaments.

Pemoral prep.
Osteophytes are removed from around the notch to aid accurate placement of the intramedullary alignment rod.

The drill entry point is located 1cm anterior to the PCL and slightly medial to the intercondylar notch Aim along the femur advancing gently to avoid cortical penetration.

Set the adjustable distal femoral resection guide to the desired valgus angle by pressing and turning the valgus angle dial. A valgus angle setting of 0 to 9 degrees is available.Usually aim for 5 degrees as this coincides with the Vanguard 360 system.
Select the depth of distal resection by turning the resection level dial. The distal resection depth can range from a simple 1 mm clean-up cut for revision scenarios up to 11 mm for severe flexion contraction. Don’t commit to extra distal femoral resection until after the trial and posterior osteophytes have been removed. This prevents over laxity in extension caused by raising the joint line.
Note: The standard distal resection is 9 mm, matching the distal thickness of the Vanguard Implant.

The distal femoral cutting block is pinned in place and the rod is removed. The distal femoral bone is resected making sure to protect the tibial plateau. Two resection slots of 0mm or +3mm are available for the distal resection. The 0mm slot will resect 9mm from the most prominent condyle. If additional distal resection is required, the +3mm slot will resect 12mm, 3mm more than the distal thickness of the femoral component.
If additional distal resection is required beyond the additional 3mm slot, shift the resection block proximal by utilizing the +2mm or +4mm 1/8″ pin holes.

The epicondylar access is marked as well as Whitesides line to set the rotation of the femoral component.

The A/P sizer is placed flat against the resected distal surface with the feet in contact with the posterior condyles of the femur. Use the 3 degree posterior feet option and size with the anterior femoral cortex. The telescoping stylus is placed slightly lateral to the midline on the anterior cortex. The adjustable rotational feet are right/left specific and may be rotated between 0 to 10 degrees of external rotation. In most cases the initial setting of 3 degrees is utilized. The femoral component size can now be read from the central scale.Then, using 1/8” drill bits, the two 4-in-1 cutting block location holes are drilled. Check that they are in line with the trans epicondylar axis.

Choose the slotted femoral contour guide which matches the selected size on the adjustable A/P sizing instrument, and place it into the 1/8″ holes drilled into the distal femur. Make sure the contour guide is sitting flush against the flat area of the distal femur.If additional stability is required, pins can be placed in the side holes provided. Once the block position is satisfactory, resect the anterior and posterior bone, and the anterior and posterior chamfers Use bone spike retractors to protect the collateral ligaments. Posterior osteophytes are then removed from the posterior femoral condyles using a curved osteotome. The femur can be elevated to aid the view by using the curved intramedullary rod.

A spacer block instrument is used to check the flexion and extension gaps. releases are carried out at this stage. Check for coronal stability in flexion and extension.
If medially tight in flexion consider releasing the anterior fibres of the deep MCL after removing any medial tibial osteophytes.
If medially tight in flexion remove posteromedial osteophytes and consider releasing the posteromedial corner with semimembranosus. On rare occasions in a very tight medial compartment release the PCL.
In a fixed valgus knee which is tight in extension release the ITB and the posterolateral capsule being sure to remove all posterofemoral osteophytes. If the knee is tight in flexion laterally release the anger fibres of ITB. In rare cases of severe deformity consider releasing the popliteus tendon but a more constrained prosthesis is required.

The flexion gap is checked using the spacer and alignment rod. Rotating the rod shows even opening of the medial and lateral compartments at 90 degrees of flexion. If the joint is tight medially osteophytes are removed from around the tibia and in this case the deep MCL was released to balance the flexion gap.

Similarly it is checked in extension line up with the ASIS proximally and the tibialis anterior tendon distally. The extension gap is checked and if tight the posterior osteophytes are removed for the femur and tibia. If the knee is still tight in extension after removing osteophytes from the back of the femur and tibia the posterior capsule may be released from the back of the femur.

The trials are inserted and balancing is checked again.

Full flexion and extension should be obtained.

The rotation of the tibial component is set by flexing the knee and checking the patella tracking. The rotation is marked and checked with the tibial tuberosity, usually midway between the medial edge and the centre of the tuberosity.

In flexion check that bifacet contact is obtained by the patella and the tibial component is not lifting. If patella tracking is not central consider materialising the femoral component or medialising the patella button. If the patella is subluxing laterally check the rotation of the femoral component.

The tibial preparation is completed. The tibia is fixed in place using the short pins, then carefully drive the trial punch into the guide until it mechanically stops. The size of the tibial component is checked so it reaches the cortex but avoid medial overhang.

Pulse lavage is used to prepare the bone ends and carefully dried.

The prosthesis is cemented using Palacos cement. A cement gun is used to provide good bone cement penetration.

Cement is also applied to the back of the prosthesis for cement on cement bonding. Make sure there is no moisture between the cement surfaces.

The tibial component is implanted first, in this case a mono block tibial component is used.

Cement is applied to the femur again using a cement gun and to the posterior femoral condyles of the femoral component. When inserting the femoral component there is a tendency for it to go into flexion so use the inserter. Excess cement is removed and the knee is compressed in extension.

Check for any missed excess cement especially on the articular surface. Flexion and extension is checked again. Look for around 1mm of opening, check patella tracking and full flexion.

Following a further washout the arthrotomy is repaired using PDS interrupted sutures.

Finally the wound is closed with clips to skin.

Postop X-rays show a well balanced and aligned prosthesis.

The lateral view demonstrates anatomic reconstruction of the posterior tibial slope, ( 3 degrees of posterior slope is built into the articular poly).