Posterior Cruciate-Retaining Total Knee Arthroplasty

CHAPTER 1

Good day, I'm Dr. Richard Scott attending surgeon at the New England Baptist Hospital. Today we're going to be replacing the knee of a patient with severe osteoarthritis and a bowed leg. The goal of the surgery is to realign the leg into a proper anatomic alignment by resurfacing the femur and the tibia and then choosing the proper thickness of plastic or polyethylene which is the articular surface to realign and stabilize the knee.

The patient is a 78-year-old female who has had several years of increasing medial pain in her left knee and a progressive varus deformity. She is status post right knee replacement done elsewhere and has had an excellent result. She lives part-time in England and part-time the United States and her first knee was done in England in fact, but she is spending more time now and has returned here and has elected to proceed with her knee replacement here with us.

The x-ray shows her varus deformity, complete loss of medial joint space, subchondral sclerosis, peripheral ossified formation, some lateral laxity is forming, and also a very unusual finding in varus knees of actual medial subluxation of the tibia beneath the femur. Classically, one sees lateral subluxation where the tibia is shifted laterally rather than medially. Her lateral film shows deficiency posteriorly in the tibia on the medial side, indicating that she has a deficient or absent ACL, and we will probably note that at the time of surgery. She also has a relatively shallow trochlear groove so again, so we will cut the distal femur in about three degrees of flexion in order to prevent the possibility of notching the anterior cortex as we prepare the femur.

CHAPTER 2

So I'm marking out the incision, so when we make our arthrotomy, I'm just confirming where the tubercle is. So we're correct level there. Make marks so that when we go to close things are lined up anatomically.

So now I'm going through the fat pad [of the] meniscus. The meniscus will pop off. And then we'll develop a little loose body here. Just peeling the capsule off the side of the tibia. Now I'm going to bring the knee into an extension so we can evert the patella. Whether you can follow me down here. And come all the way across and just sweep across the front of the knee and the patella and it everts automatically. So now I see if do I need a little more skin and capsule. Maybe a little more capsule here. Then we'll sew in the wound towel to keep the tissues from drying out.

This is the patellofemoral ligament which we're going to release to get better access to the lateral compartment. Now we go back to the medial side. Take out the anterior horn of the medial meniscus. First I'll take this part of the lateral meniscus out. So if she had an ACL we would take it out, but she doesn't have one. So we'll put this between the deep medial collateral ligament and the tibia. Peel the deep medial collateral ligament and the capsule off the anterior aspect of the tibia. And then this can come out. We're going to externally rotate the tibia and deliver it in front of the femur. And then make a stab wound outside the lateral meniscus. And now I'll take out what I can of the lateral meniscus. We'll encounter the lateral inferior genicular artery and vein in a moment.

Get the lateral inferior genicular vessels. I'm going to peel the tissue off the front of the tibia so we can see the anterior cortex of the tibia a little better. Can I have a Bovie please. All the veins here. Now I'm going to take out some of the tibia so I'll get a Z retractor, and this is what's going to accomplish most of our medial release, taking medial osteophytes and a little bit of tibia with it. So we going to take out about 3 or 4 millimeters rim of tibia and osteophyte and that will release the MCL in order to correct her varus deformity.

You take a curved osteotome and run it around before you resected this and then peel it off the MCL, usually the safest way to do it. Okay, great. Now that of course downsizes the tibia, so often you put a smaller size tibia than you do femur.

CHAPTER 3

So now I'm going to draw the Whiteside's Line down the center of the trochlea. Define where I feel the top of the notch should be - a little distorted in her anatomy. And then enter the canal just medial to that line in about a centimeter above the top of the notch. I use a gouge so that I can start a pilot hole and know exactly where my drill is going to go. Once in the canal, you enlarge it a little bit. And then I like to just gently push it and have it just find its way safely up the canal. I think it's going to be a 2-1/2, do you think? So you see, as I hit this slowly, the marrow is coming out, reassuring us that we are in fact in the center of the canal. So we've set it for 4 degrees of valgus and 9 millimeters of resection. So I'm going to cut this in 3 degrees of flexion. Initially, I'll cut it in neutral. And I'm going to move this down so I can take a little bit less to start. Thank you.

So because she has a deficient trochlea, I'm going to revisit this with a 3-degree resection. Now we'll draw a Whiteside's line which is - I mean a line perpendicular to Whiteside's line. That's one way of determining rotation. Second way is to feel the transepicondylar axis. Here's the medial epicondyle - here's the lateral - very similar. The third is to empirically go few degrees, 3-degrees, off the posterior condyle. So I initially made a pre-cut so I can better assess the anatomy of the anterior part of the femur for sizing purposes. So where my finger is, is where I want to put my stylus right there. Harder to appreciate that when that trochlear bone is still there. So it comes to a 2-1/2. So that's 3 degrees off the posterior condyle. You can see that's identical to the Whiteside's so so far all 3 methods are the same.

Now I'm going to take off the medial osteophytes from the femur to complete my medial release. It's easiest to do these after you've already cut the distal femur and chosen [to be there?]. Now I think you can see how much room the MCL has, having removed the tibia, part of the tibia, and those osteophytes. So now we'll put the flexion gap on tension. This lamina spreader - you see how much it opens up because of our medial release. Now the lateral side on tension to 20 lb of pressure based on our tensiometer here. And then we bring our tibial alignment guide set for a 90 degree cut and see where that fits relative to these holes. And they're parallel, so we don't have to move this. Change the rotation.

So in this specific knee, all four methods are exactly the same, which is I think people who have their own way of doing it only one way most of the times are similar, but I think to me, the most important thing is having a symmetric flexion gap. And having done the medial release, it opens up the medial side so you don't have to externally rotate quite so much as well. Make our anterior cut. So get the Bovie. Do you have the Kocher, Jen? Thank you. Start it with a wide blade, and switch to the narrow.

So now I'm going to remove the posterior condyles, and I left the chamfer bone there on purpose so I can lever the bone out on them and not crush the bone. Is that better? Okay now we've completed with the chamfer. Now complete the posterior chamfers. There's a cyst here. So now we'll prepare the patella.

CHAPTER 4

There's usually a synovial fold on the quad tendon which should be removed as it's the nidus for the clunk syndrome. Now the tendon is clean. Take a little of the synovium off the field where the nose of the patella is right there. Measure the patella - most women are 22 to 24. She's on the smaller side may be even 21. 22. Now I'm gonna take the rongeur and make a blunt entry point for the saw cuz there's a sharp osteophyte that makes it difficult for me to get my saw started.

So if you have all the cartilage off here then you have a good cut. Now I'm going to measure the thickness here and then make it the cut level. So that's 14, so I can take a millimeter off of it and level the entire thing out. I look for where the nose of the patella is and how much room I have superiorly. This is a straight edge so you can check how level your cut is by just applying it to the edge of the patella. That's pretty good actually. Okay.

Let's see a 35 for trial. Yeah, that's better. I'll take the saw please. So I'm putting a 35, it's not quite fully capped here, so I'm just going to chamfer this bone - bevel it - so that no impingement if the patella were to tilt. And do the same thing here if we get a retractor. Thank you. Great.

CHAPTER 5

Make a little ledge for the the saw where this osteophyte is, and then we can support our tibial alignment guide just underneath that. So I'm putting this at approximately the zero mark on the deficient medial side. Should take at least 8 millimeters from the higher side, because the thinnest composite component is 8. I can protect the PCL by making that wedge cut centrally and then complete the resection on either side of it. I find taking this out in two pieces is often the safest way to do it. Now we'll prepare this to graft that hole.

Complete the removal of the posterior tibial spine avulse it away from the PCL. Now we'll complete removal of the medial meniscus. I'll get a bone hook and a rake. I'm taking out the remnant of the medial meniscus now. Yeah, you can move the light now. Onto? Away from where it was yeah. That's the rest of the medial meniscus. Now we move that forward - great. Now we're going to level out this cut make sure it's nice and smooth. I'm surprised Jackie. I thought it was going to be a 2, but you're correct.

CHAPTER 6

So we'll put our trial femur on with the rigid inserter and then move it medially laterally so it's flush the trochlear cortex. Now we'll remove overhanging osteophytes which are obvious here. Right into the cyst. Can you see it? Going to take off the intercondylar phytes so we can see the PCL a little better. The PCL will be right behind me. And here you can see PCL fibers right here.

Okay now we're going to take off any uncapped femur using the prosthesis as a guide. It's a pretty good fit. 10. I'll take a unisaw blade - use it as a burr to fine tune the cut here - little more on the meniscus. Okay, great. So we'll trial with a 10 to start and see if we need more or less. So when testing the flexion gap, we see how hard is it to pull this out. So that tension looks pretty good for a flexion. I can also feel the PCL and feel the edge of it here which is on tension. If it's too tight as we go into high flexion, the tibial component will lift off like so, but I think that's not bad at all. So we're fine inflection. So we need a knee that comes to full extension and then we will rotate the tibia until it's congruent with that.

For the rotation I want the femoral and tibial rotation to be congruent in extension. Now we'll test the patellar tracking and see there's no lift off now with the patella located. So we have a knee that comes to full extension, stable - medially and laterally - and the patella tracks well. So you really can see. May I have a Schnidt please? This is the osteoarthritic cyst here that we're going to pack full of cancellous bone. So. You see the Bovie mark for the rotation alignment of the tibia based on its relationship with the femur.

CHAPTER 7

Okay. Okay. Can I see a Smith P (rongeur)? So this is osteophyte still leftover. So now that I know where the tibial component is going I can remove that. You can bring everything on the table except for the insert. So I'm mainly going to push it. Harder bone medially than laterally so I'm going to relieve that. Otherwise, the hard bone will push the component laterally. And we're going to take an instrument that will make several little holes. This has 7 cleats on it so I can penetrate the sclerotic bone for cement penetration. Before we mix, we're going to fill up the cyst with bone graft.Yes, we'll irrigate first.

CHAPTER 8

So it's important to get the cyst wall cleaned out. 35 patella, 2-1/2 left, 2-1/2 CR. Yeah, top three, good? Pressurize the cement in the femur and then we're going to put some on the posterior condyles for intrusion there. So this is the zone 4 of the knee society zone. And the one most likely to have radiolucencies in the long term. And if you get wear debris synovitis, the most likely portal of entry. The further the femur is impacted the tighter is the flexion gap so I put the trial insert in now. It's easier to get it in. Can I see a Schnidt please? And we’ll take off some of the extra fat pad, freshen it up. Still want to leave some behind for blood supply to the patella and the patellar tendon. Okay. Let me take that out. I want to see how hard it is. Can I have a pituitary?

Julie can you bring in a curved insert please? Yeah, 10 curved. Little bit right there. So now we're going to get to the little bit of extruded cement here. We'll leave that. May I see the Bent Hohmann? Add that over here and make sure that, anyone behind. Now we're going to look underneath to make sure I didn't snow plow cement to the back. Open up the 10 curve size 2-1/2. 2-1/2, 10mm curve. Thank you.

CHAPTER 9

So we're going to look at the stability: inflection, varus and valgus stress, no opening; 60 degrees, same; 30, same; full extension.

CHAPTER 10

We'll irrigate it out. So if one had to do a release, tightest fibers are usually this anterolateral band right here. So you start here and go from lateral to medial and from anterior to posterior. We will close the proximal capsule first. Now I'm going to close the fat pad. A separate layer. Okay thanks.