Hi, everybody, good evening and thanks to those of you who are still sticking around for the evening session. So I think something that I find really interesting about medial patella luxation is certainly when I was at university, this was presented as one of the routine orthopaedic conditions, and something that should be relatively straightforward. And simple to treat, and if you see it turn up on your consulting list, maybe you think you've got a bit of an easy pass, and this will be quite an easy one to get through.
However, the more I learn about it, the more cases I treat, the more complex I realise this condition really is. The decision making regarding how to treat these cases can be far from simple. It's often based on experience or opinion rather than any hard evidence or facts.
And so my aim today is really to look at some of the underlying deformities associated with medial patellar relaxation and some of the treatment options available, but most importantly, to go through some cases and demonstrate the decision-making process that I use when I'm considering how to treat them. And where, where there is evidence-based medicine to back things up, I'll certainly present that as well. But a lot of what we're going to be talking about is based on experience, not just mine, but those of, my mentors in the field who've been doing this for certainly longer than I have.
So, hopefully that will help, and hopefully we can have a, a good discussion at the end. So speaking of mentors, before I start, I just want to recognise my mentor, Doctor Lui Desjardin. He is the originator of one of the novel techniques that we're going to talk about today.
So important to recognise that this didn't come up from me. He just, trained me how to do it. And some of the images in this presentation do appear courtesy of him as well.
So, despite pateternallaxation being one of the most common orthopaedic conditions in dogs that we encounter, our understanding of the anatomic abnormalities associated with it definitely remains incomplete. We know that Coxavara, Coxavalga, Dial femoral virus. A shallow trochleus sulcus.
Medal displacement of the tibial tuberosity and also medial bowing of the proximal tibia have all been implicated in the pathogenesis of the condition. Non-surgical treatment, we know, is largely ineffective in cases of medial paternal laxation, when they have associated clinical signs. Obviously, when we have a case that has no associated clinical signs, we generally do not recommend surgical intervention.
However, when they have clinical signs, there's very little that really seems to improve those, other than surgical treatment. And surgery consists of correcting all of the components which are contributing to malalignment of that qua quadriceps mechanism, and traditionally will include some or all of the procedures on this list here. And I'm sure most of you are very, very familiar with the top 4 of those.
So tibial tuberosity transposition, trochleoplasty, whether you choose to use a wedge or a block recession, or even abrasion in some places. Lateral imbrication, medial release of the soft tissue balancing procedures. Most people are very, confident with.
And when a case presents, and we think that those four procedures are going to be sufficient to relieve the patella laxation, then most of us are very confident. However, when we get on to cases where we think that's not going to be enough, and we start talking about other procedures such as distal femoral osteotomy, potentially the use of anti-rotational sutures in some people's hands, although it's not something that I personally use a lot of. Partial parastatittal pateectomy, maybe, other cases such as trochlear groove replacement or augmentation of the medial trochlear ridge.
All of these things have less evidence associated with them, and decision making regarding when to use them can be substantially more difficult. In the past, and when we read about relaxation in old textbooks or in older papers, the historical relaxation rate was reported to be as high as 48%. Now, I'm glad to report that that has definitely improved, when we recognise just how important realignment of the quadriceps was by, moving the tibial tuberosity transposition laterally.
But despite this, we still have a current relaxation rate in most studies reporting somewhere between 8 and 12%. So 1 in 10 dogs that goes through a patella luxation surgery, we can anticipate may well go on to have problems with relaxation in the future. And it has been postulated that this is because we are not appropriately addressing all of the factors that contribute to the quadriceps mechanism, malalignment.
And one of those obviously is that distal femoral virus that has been cropping up more and more in the literature recently. So a failure to address femoral virus as a factor contributing to quadricep's mechanism malalignment may be a cause of sub-optimal outcome or relaxation following surgery. And it has been suggested that corrective distal femoral osteotomy should be performed when femoral virus is excessive.
However, most canine femora do have some degree of virus, and the degree of that definitely varies both within and between breeds. So the degree to which femoral virus is excessive, and therefore the subsequent indications for distal femoral osteotomy are certainly not well defined. Previous publications have advocated that we should be considering distal femoral osteotomy when femoral virus angles exceed 10 or 12 degrees.
But when you look at where those recommendations have come from, they are based on subjective clinical experience rather than any objective measurements using any kind of validated method. It's a very controversial area. We don't even know really how we should be measuring femoral virus to have the most accurate idea of how much virus there is.
Should it be on radiographs? Should it be on CT? And exactly how should we be making those measurements.
Even that is controversial. So decision making on how to use the angle is even more so. And a recent study performed, at MSU with some other institutions involved as well, definitely called this angle into question.
Because we revealed no association between the femoral virus angle and the risk of postoperative complications following standard surgical techniques in dogs where the femoral virus angle extended up to 60 degrees. So, well above 10 to 12 degrees, and yet most of these dogs went on to have no complications whatsoever when they were addressed just with tibial tuberosity transposition and trooplasty. If we look at the literature and the evidence that we have regarding distal femoral osteotomy, it does consist mostly of small case theories, and they do document largely positive results.
Last year, in late 2017, there was a study that was released, which is by far the largest case series that has ever been published, looking at 66 cases which have been operated by distal thermal osteotomy. And that was by Brauer and others, some of the people out of Tufts University. And while the results of this paper are positive, we don't know from that paper how well those cases would have done if they had been operated via more traditional techniques.
There's no comparative studies available. And until the study that was performed at Michigan State, there had been very little focus on the impact of distal femoral virus on the complication rates and outcome following traditional corrective surgery. And the question I think we have to ask ourselves is, when is distal femoral osteotomy really necessary?
And I'm not sure we have the definitive answer to that question at this stage. In our experience, many dogs with femoral virus angles over 10 or 12 degrees do not experience relaxation or high rates of complications following routine medial paternal luxation stabilisation procedures without distal femoral osteotomy. And certainly, no direct association has been reported between femoral virus angles and the incidence of relaxation.
So that was really why we went ahead to perform this study, and looking at outcomes following corrective surgery for medial patellar luxation, but without distal femoral osteotomy. And I'm just briefly going to give you a rundown of that. I'm certainly not going to go into all of the, details of this study.
But we included dogs that had undergone surgical treatment of medial patellar luxation without distal femoral osteotomy, using tibial tuberosity transposition, trochleoplasty, and soft tissue balancing procedures only. We recorded the postoperative complications and then classified them as major or minor. And in addition to measuring the femoral virus angle for all of these dogs, we also measured the inclination angle, the anatomic lateral distal femoral angle, and the mechanical lateral distal femoral angle as well.
And we then did some statistics to evaluate for evidence of any association between femoral virus angle, incidents of complications, and also for any evidence between femoral virus angle and the outcome that these dogs went on to have. And the results showed no evidence of any association between femoral virus and any complication. No association between femora virus angle and the incidence of major complications.
And that dogs, dogs that had major complications did go on to have an increased odds of poorer outcome, but this was not associated with femoral virus angle. So we really just contributed to the controversy surrounding distal femoral osteotomy. So, having said all of that, when do I consider DFO to be indicated?
And it's certainly not in every case that has a femoral virus angle of over 10 or 12 degrees. There are many other factors that we need to consider. The femoral virus angle certainly is one of them, and whether that should be measured on radiographs or using 3D reconstructions of CT scans, that debate rages on today.
You can also use the published reference angles for the breed. They're not available for every breed, but they are available for some, including the Labrador, which we see commonly. So if they, if they are available, then we can consider those.
We can consider the angle on the opposite side, particularly for dogs that only have unilateral medial patellar luxation. If the angle is the same on both sides, and yet the dog only has medial patellar luxation on one side, then probably it's less likely that the femoral virus angle is contributing to the dog's medial patellar luxation. We also need to look at what other angular or torsional deformities the dog has.
We need to consider all of the co-existing abnormalities that can be associated with media patellar luxation. And we definitely need to consider whether this dog has evidence of cranial cruciate ligament disease as well, plus or minus meniscal damage, as that will certainly play a role in decision making. So, I'm going to go through a few cases here, and show you kind of decision making for those cases, and hopefully that will clarify a little bit of some of what I do.
So, this is Jenny. She was a 2 year old female neutered Labrador, and she presented for a left hind limb lameness. When she presented, she had a moderate weight-bearing lameness of that left hind limb, and she was certainly shifting weight off of it at stance.
She lateralized the left stifle while she was walking, and there was moderate muscle atrophy affecting the proximal left hind limb. She had a grade 4 medial patellar luxation with the patella sitting persistently on the trochlear ridge. And there was a moderate pain response on any attempt to reduce the patella, and also on application of retropatellar pressure as well.
But there was no instability in cranial draw or cranial tibial thrust on either side, and the rest of the orthopaedic examination and general physical examination were normal. So we started off by taking some TPLO radiographs of both stifles. And as you can see here on the left-hand side, we certainly have evidence of synoviar fusion.
There's a pacification encroachment of the infrapatellar fat pad, coral bulging of the subgastroemal fascial plane. And on the cord of cranial view, you can appreciate that the patella is certainly tracking on that medial side. If you compare that to the right.
On the right side, the stifle looks really largely normal. We then went on to take horizontal beam qua a cranial views of the femur. And before we go on to interpret these, I just want to talk a little bit about how carefully we have to position these.
So, craniocordal views of the femur must be appropriately positioned if we're going to be able to measure femoral virus angles. The femur has to be parallel to the long axis of the pelvis. The patella, ideally, should be centred, if it isn't luxated within the trochlear.
If the patella is located outside of the trochlear, then the radiograph should reveal parallel lines of the vertical walls of the intercondylar notch. So as you can see here, we have the parallel lines of the intercondylar notch, even though the patella is sitting outside. The abbela should ideally be bisected by their respective femoral cortices, and the tip of the lesser recantus should be visible up at the medial aspect of the femur here.
So particularly for Jenny, you can see here on the craniocordal view of the femur, that we definitely have a moderate femoral virus on the left in comparison to the right. The right side looks pretty straight, the left side definitively different. We can also see here she has some pericular osteophytosis in the left stifle.
She also has bilateral remodelling of the acetabula and the femoral necks, which appears to be worse on the right hand side. So for completeness, we did go ahead and take pelvic radiographs as well, to have a centred view over the hips, even though this was not considered to be Jenny's predominant problem. So we then went on to measure the femoral virus angles on both sides here.
And here you can appreciate, on the left-hand side, we have a femoral virus angle of 24.5 degrees. And this was compared to 6 degrees on the right-hand side.
We certainly have medial patellar luxation on the left. We do not have medial patellar luxation on the right. And as the femoral virus angle is increased beyond the recommended angle, so it's beyond our 10 or 12 degrees, it's also beyond the average for the breed, which for Labradors is considered to be 7 degrees.
And there is a substantial difference between the clinically affected and the non-clinically affected limb. It stands to reason that the femoral virus angle in this case is probably contributing substantially to the clinical presentation and therefore would be considered to justify correction. If we then go on to another case here, this is Blue.
Blue was a one year old female neutered Labrador. She presented again for assessment of left hind limb lameness. At one presentation, she had a moderate hind limb lameness there on that side.
Orthopaedic examination revealed mild pain upon extension or abduction of both hips. The range of motion of both hips was within normal limits. Upon manipulation of the left stifle, she certainly had mild joint pain, evident, effusion was palpable, and a grade 3 medial paternal luxation appreciated.
Again, there was no instability in cranial jaw or cranial tibial thrust, and the rest of her examinations were normal. So similarly to for Jenny, we started off with TPLO views of both sides. We can see here there's some effusion there on the left-hand side, and again we can appreciate medial tracking of the patella on that side.
If we then go on to look at the views of the femur, similarly, taken with those craniocordal views with a horizontal beam, it looks subjectively like there is a, you know, a, a similar degree of femoral virus there on both sides. One doesn't look substantially worse than the other. And again, because of the hip pain, we went ahead and took some hip radiographs and we can see we definitely have evidence of bilateral hip dysplasia and associated osteoarthritis as well.
So going back to the theme of uses here, we do certainly have what looks like a similar degree ephemeral virus angle on both sides. So 15 degrees on the clinically affected side and 14.5 on the clinically unaffected side.
So, in this case, although we're over that 10 or 12 degree cutoff that's been recommended in the literature, because we have a clinical condition on one side and not on the other, and our femoral virus angles are similar, we would consider that unlikely that the femoral virus angle is contributing significantly to the presentation, and therefore, we would be less likely to consider distal femoral osteotomy in this case. So Blue went on to be treated with a block recession sarcoplasty, tibial tuberosity transposition, and lateral imbrication. And these are her radiographs at 8 weeks postoperatively.
And at that stage, she was certainly progressing well with no evidence of paternal luxation, and she has continued to do well since with no evidence of relaxation. So, just a different case, you can see a different decision-making process, and certainly not as simple as 10 or 12 degrees, and over that, we have to do a distal ramo osteotomy. One more case to go through here.
This is Frankie. Frankie's an 18 month old male neutered Newfoundland. The owners had noticed a shifting bilateral hind limb lameness with Frankie, but when he presented, there was actually no evidence of lameness at all.
He did walk with a very upright pelvic limbstance, and orthopaedic examination did reveal bilateral medially luxating patelli at a grade 2. There was a moderate pain response on extension of both stifles, the left was slightly more painful than the right, but again, no instability in cranial jaw or cranial tibial thrust, and no significant stifle effusion palpable in this case. So we went ahead and took the TPLO views of the stifles, and really they're looking pretty unremarkable.
You might argue there's slightly more effusion there than you would ideally like on the right hand side, but really not a lot there that looks very significant. We then went ahead and took our views of the femur again, and really these look pretty interesting. So it's almost like an S bend in the configuration of this femur.
So it does look like there's maybe an increased femoral virus angle distally, but we also have what looks like a valgus of the femur more proximately. Again, we took radiographs of the hips, and in this case they were looking pretty unremarkable. So we did go ahead and take some measurements here and you can see that Frankie certainly does have a mild valgus deformity at the proximal extent, and then a 10.7 degree virus at the distant extent.
And Frankie actually hasn't undergone surgery at this stage. He actually has a pretty nasty skin infection, which we're struggling to control prior to surgery. However, we do not consider it likely that Frankie will require the femur to be straightened, as this S-shaped deformity that he has is made up of two different deformities which somewhat compensate for each other.
So we've got the valgus proximity and the virus distally. If correction were required, it's likely that we would need two osteotomies for this case, one at the centre of rotation and angulation of each deformity, and that would certainly make things pretty complex. I think something that you'll notice about all of these cases have presented are that they are all large breed dogs, and certainly that is because we are far more likely to consider distal femoral osteotomy in large breeds.
However, we do sometimes perform it in the smaller breeds as well, but it is important to realise recurrence following medialternalluxation surgery is more common in the larger breed dogs, and therefore, it's considered likely that femoral virus plays a more significant role in disease pathogenesis in these larger breeds. So if we're thinking about going ahead and performing distal ramo osteotomy, preoperative planning is absolutely critical for these cases, and it can be fairly complex as well, as you'll see in one of the cases I'm going to present a little bit later on. This series of pictures is from a programme that we use, which is called A View, but there are many other planning programmes that are available and more are becoming available all the time.
In this case, the dog that we can see here had a grade 2 medial patella laxation and a distal femoral virus angle of 17 degrees. And you can see here that we've measured the distance of the centre of rotation and angulation from the top of the proximal groove as being 23 millimetres. And our surgical plan in this case was initially that we were going to perform a lateral closing wedge ostectomy of 17 degrees, which would then go on to be stabilised using a laterally applied plate.
So a distal femoral lateral closing wedge ostectomy is the most commonly reported method for treatment of excessive distal femoral virus. And it is the technique which probably most of you are familiar with for this particular procedure. So this was the initial plan for this case, and our preoperative templating for this can be seen here.
And you see here, we have, again, we've marked our centre of angle, centre of rotation angulation as our 23 millimetres proximal. And this is, we're checking here that we're going to be able to place 3 bicortical screws distally to that osteotomy. It is critical that you get at least 3 screws in that distal segment if you're going to have sufficient stabilisation.
So the plan is we're going to perform our distal femoral osteotomy, and then if we need to afterwards, we'll continue and do a tibial tube or oste transposition and trochleoplasty as needed. I think what you can appreciate here is that the plate is very cranial at this distal extent. It's also very cranial at the proximal extent.
But this has been reported to cause problems in the distal extent here. And that's for several reasons. One is, you can see it's going to definitely impact on your ability to perform a trochleoplasty.
Any kind of recession trochleoplasty there, you're going to probably hit that distal screw. Now there is a way to avoid that, which I'll go through in a, in a few slides' time. But another problem here is that plates that are positioned this cranially with this technique have been reported to irritate the peripatella soft tissues and the patellar ligament and cause ongoing lameness, necessitating plate removal in the future.
So this was concerning us a little bit here. We were worried about our ability to perform a troleoplasty, and about the potential need for implant removal due to soft tissue irritation. So an alternative technique, which we have been using at Michigan State for the last several years, is a medial opening wedge, which can then be stabilised using an angle stable interlocking nail.
And the kit that we have here is the ILO system, so there are certainly other interlocking nail systems available, but none of which in the veterinary market have that angle stable interaction between the bolts and the nail. Medialal opening wedges like this are certainly not recommended if you're going to use plate fixation, as this will lead to a huge risk of implant failure. If the ostectomy reduction is not complete, we see cyclic bending on the force, forces on the laterally applied plate, followed by plate failure.
However, as the interlocking nail is an intramedullary device and it is placed in that neutral axis of the bone, it is consequently shielded against deleterious cyclic bending forces, meaning it's at far less risk of failure and can be used safely with an opening osteotomy. Another advantage is that when you put a straight implant into a curved bone, such as the femur, you do end up with this retro curvatum of the femur here. And this has been proposed that it is going to make the patella track more distally within the groove, which may improve tracking and reduce the risk of relaxation as well.
So, if you decide that you do want to perform a distal femoral osteotomy, which technique are you going to decide to use? As we mentioned a little bit earlier, the conventional technique is that distal femoral lateral closing wedge ostectomy, which you can see in the radiograph here. I'll go through this briefly, for those of you who have not performed it or who are not familiar with the technique.
The patient is positioned in dorsal recumbency. You will need full access to the entire limbs. You do need to drape pretty carefully to make sure you can, you provide this for yourself.
We start with a lateral surgical approach to the stifle joint and the distal femur. The distal femoral osteotomy site must be planned to ensure that you have that distal femoral segment large enough to accommodate at least 3 plate screws without any interference of the implants with the stifle joint. We then use a TPLO jig, which is applied to the cranial aspect of the femur, with the distal pin immediately proximal to the cartilage of the trochlear groove, and the proximal pin within the span of the planned bone plate.
It's really important that proximal pin is within the bone plate span. Otherwise, when you remove the pin, you leave a weak point just above your plate, and we can see femoral fractures through that weak point. We normally place the jins in the sagittal plane and place the jig on the medial side so that you can work on the lateral side of the femur without any interference from the jig.
The closing wedge angle of your osteo ostectomy is going to be based on your pre-operative planning. Most people will aim to correct to a zero degrees angle, so if you had a 17 degree virus, most people will remove, remove a 17 degree wedge. And we form a coplanar lateral closing way jostectomy and reduce the proximal and distal segments.
You can then use two K wires placed from discolateral to proximaledial, and distomedial to proximlateral to maintain the reduction of your ostectomy. And when you do that, it's important that you avoid the area of plate application. There's nothing more annoying than trying to put your plate on and realising one of your K wires is in the way.
And then we apply an appropriately sized plate, normally somewhere between 6 and 9 holes, and that's contoured and applied to the lateral aspect of the femur, again, ensuring that none of your implants interfere with stifle joint function. In the distal screws, we tend to angle those cordially, as you can see into the condyles there, so that you can avoid interference with your trochleoplasty or sarcoplasty. Or if, as we saw on our preoperative planning earlier, you think those screws are really going to interfere with your ability to perform a trochleoplasty, you can just place the screw most distal, most closest to your osteotomy here, and then place this one as a monocortical screw here.
Then perform your trochleoplasty. And then when you've finished your trochleoplasty and recessed your wedge, you can then switch this monocortical screw out for a bicortical and place this one, and they will actually pass through your recessed wedge and secure that in place. So that's a nice, trick if you think it's really going to interfere with your ability to perform a trochleoplasty.
The wedge that you've removed from your trochlear, you can crush up and you can remove, you can use the wedge from your bone as well, from the wedge that you've removed from the femur, crush those up to perform to form some graft, and you can place that at your ostectomy site. And then once you performed your ostectomy and stabilise that, reassess the patella, assess the stability and decide whether you need to go on to perform any ancillary procedures, particularly turosity transposition or soft tissue balancing, for example. So if we look at complications that can occur following this lateral closing wedge ostectomy, in a series of 41 dogs that was reported in 2013, the complication rate was reported to be quite high at 9%.
In some cases, where the osteotomy is not completely reduced immediately after surgery, we do see implant failure over the osteotomy site, as you can see in the first radiograph here on the left. In cases where your centre of angle of rotation and angulation is very low, sometimes you can't make your cuts at that point because you will not be able to achieve those three screws distally to your osteotomy. And in those situations, you're going to have to move that osteotomy more proximately.
When that happens, you end up with translation at the osteotomy site, so you mean you have to contour your plate more, as you can see here, and the, the piece of bone, the distal piece of bone will then be dragged towards the plate as you tighten your screws. And increased translation here can lead to an increased medial force and potentially increase the risk of recurrence of medial paternal relaxation. On the 3rd radiograph here, you can see that there is a complication we've already mentioned, that we have the plate, very, very cranial at the proximal and distal extents and say irritation of the quadriceps and peripatella soft tissues are potential complications necessitating plate removal in the future.
As well as that, they did also see complications, as you would expect with any osteotomy procedure, delayed healing and infection were also complications that were reported. So as we said, an alternative is to go ahead with this distal femoral medial opening wedge osteotomy. For this, your patient is positioned in lateral recumbency, with the patient on the edge of the table so you can easily introduce your nail.
And the approach involves your lateral arthrotomy at the distal extent. And then you can evaluate your cruciate ligaments and the depth of the trochlear. Then you can assess the degree of distal femoral virus intraoperatively and appreciate the line of the joint, which is going to be your osteotomy is going to be parallel to that line.
Then you can score the cortex. You can see the longitudinal line here is going to be used as a reference line to make sure that we don't induce any rotational deformity when we put this osteotomy back together. And the horizontal line is marking the line where the osteotomy is going to actually be performed.
The osteotomy is then performed at the level of the cora and parallel to the joint line. We can then use the trial nail from the set to ream the distal metaphysis for the nail. And we want to ream that parallel to the trochlea to make sure we get appropriate alignment.
And if you're going to perform a sulcoplasty, then you also want to ream this slightly cordially so that you'll be able to perform, perform the trochleoplasty without any interference from the nail. In terms of the proximal approach, this is via a subtrochanteric approach, and the nail is inserted as routinely described for traumatology cases. Cell capacity can then be performed as necessary, plus or minus atibutuosity or ancillary procedures as required to fully stabilise the patella.
So this is the case that you saw the preoperative planning for earlier. So this is our case with the 17 degree virus and grade 2 media patellar laxation. And you can see there the radiographs immediately postoperatively.
This is done via a proximal and distal approach. We don't open up the whole bone here, just open up high enough to get to the osteotomy and place our bolts at either end. And then you can see there that we've certainly reduced our femoral virus angle.
This was reduced down to an angle of 0. And then at 16 weeks you can see complete healing of osteotomy site. So just to work through a case here, this is Beau, this was a 6 year old male neutered Labradoodle.
And so far we've concentrated on the treatment of just distal femoral virus. But if we look through this case, we can see how our case is managed from start to finish, including any ancillary procedures that are necessary. So Beau had a severe weight-bearing lameness, affecting the right hind limb.
Orthopaedic examination, we had a fusion and medial buttress palpable over the right stifle, moderate laxity in cranial draw and cranial tibial thrust, and a grade 3 medial luxating patella was evident as well. The left stifle at this stage was within normal limits, and there were no other findings. So we started off with some radiographs of the stifles.
We did take both, but this is just the right stifle you can see here. And again, we can see effusion is evident in per-articular osteophytosis. So with this clinical signs, these are consistent with cranial cruciate ligament disease.
And it is important to remember when treating patellallaxation, concomitant cranial cruciate ligament disease and medial patellallaxation is very common. 13 to 23% of cases presenting with medial pate laxation will also have cranial cruciate ligament disease, and we do need to factor this into our treatment plan. There are many options available for treating both conditions simultaneously, including the tibial tuberosity transposition and advancement, the modified TPLO, the TPLO with tibial tuberosity transposition, and an extracapsular suture with a tibial tuberosity transposition as well.
There aren't many studies out there comparing these different techniques as to which 1 may be more favourable, but there is a recent study by Foron and others in 2017 that revealed the complication rate was reduced, and the outcome superior following tibial tuberosity transposition and advancement, when that was compared to the extracapsular suture and tibial tuberrosity transposition. Let's say comparisons to the other techniques have not been performed, so all we know is that the TTTA seems to be preferable to the TTT and extracapsular suture technique. So we did go on and take our craniocordal views of the femur with the horizontal beam, and you can see here, there certainly is a moderate femoral virus on the right hand side when compared to the left.
And when we measured this up, this was 18 degrees on the right and 11 degrees on the left hand side. Again, similar to our case, Jenny earlier, we've got a grade 3 luxation on the right and no luxation on the left. So the femoral virus is likely to be significant and we did decide to go ahead and correct that.
So this is the beginning of our preoperative planning for Bowe. You can see here we have marked the centre of rotation angulation, so the point of where the maximal deformity is coming from. And, we've marked our femoral virus angle of 18 degrees.
And these 3 blue dots here were the line where ideally, if our osteotomy was performed at the level of the cora, that's where our osteotomy would be. However, this definitely was not going to give us sufficient room to place either 2 bolts of a nail or 3 screws from a plate distally. And it was also going to compromise our ability to perform a trochleoplasty.
So we decided to move that cut more proximally, to the line here where our turquoise dots are. So this is where we've actually simulated our osteotomy line, so in this case it was a medial opening wedge, planning to stabilise this with the interlocking nail. And you can see here that it all looks great at this particular point.
And then we put our implants in place. And on the craniochordal view, this looks great. We can easily achieve two bolts distally.
We can see that we have a little bit of translation that's occurring because we did move the osteotomy more proximally from the cora. And with a plate that would result in a problem, as the bone segments would definitely translate as we saw earlier. And that would give us that increased medial force and potentially increased risk of recurrence of the patella laxation.
However, when we use an interlocking nail, the bone does not get pulled towards the plate, so we can avoid some of that translation. So that's a potential advantage of this procedure. So then we checked what our view would, what our plan looked like on the medial lateral view.
And you can see, we definitely have a problem here. The nail comes very, very proximal in that distal segment, and this would limit our ability to be able to perform a trochleoplasty. So we have to change our plan and we thought, well maybe if we just use a slightly shorter nail, then that will give us space to perform our troleoplasty.
However, that plan doesn't work either. Bolt number 3 is now far too close to the osteotomy line, that's going to risk instability. So we have limited options here.
We're going to have to move that osteotomy even further proximally in order to achieve appropriate implant stability. So, we've now moved our trochleoplasty, so that it's 25 millimetres proximal to the trochlear, as opposed to the planned 14. And this does leave us with, with sufficient space to perform a trochleoplasty distally without involving the nail.
And it does also give us plenty of room to place all of our bolts well away from the osteotomy line. So now we need to check, this looks good on a mediallateral view. Is it compatible with our craniocoral view?
And certainly, this still looks good, no, no signs of any complications here. Again, you can appreciate this minor translation of the segments relative to each other because of the movement of that osteotomy more proximally. So from this series of images, you can definitely see how important preoperative planning is for these cases.
If we create our osteotomy or our ostectomy before checking that the implants will fit, then you can really end up in a difficult scenario intraoperatively. So very important to plan these as accurately as you possibly can. So, in Bo's surgery, we did notice that the troch the cartilage within the trochlear groove was degenerate or missing, and therefore, a block recession or a wedge recession would not have been beneficial.
It would potentially also have compromised our nail if we'd gone too deep. So we elected to perform an abrasion trochleoplasty in this particular case. We did also perform a patelloplasty, in order to narrow the patella so that it would fit within the new groove.
The cranial cruciate ligament was completely ruptured and the remnants were removed. There was a bucket handle tear to the caudal pole of the medial meniscus, so we performed a hemi meniscectomy for this case as well. We performed a lateral capsular resection and invocation.
The medial opening wedge osteotomy as planned, stabilised with size 8 interlocking nail, and a tibial plateau levelling osteotomy, routinely using a 35 broad plate. And these are both postoperative radiographs here, so you can certainly appreciate this was by no means minimally invasive. I don't think I've ever seen a staple line quite this long.
But certainly, really happy with the results. We have the patella sitting in situ. We have, reduced our femoral virus angle to, I think it was 2 or 3 degrees.
And we have the TPLO performed routinely as well. And this was Beau just 6 weeks postoperatively, and you can see there that healing is progressing appropriately for this stage postoperatively. And Beau is now 6 months out from surgery and still progressing great with no relaxation and completely healed at this stage.
So I mentioned there patelloplasty or partial parasagittal patellectomy. And this is another novel procedure which has come into the literature since about 2013, 2014. And this is very commonly required in cats with medial patella luxation.
One feature of the feline stifle is the patella is wider in a mediaolateral direction relative to the femoral trochleus sulcus, and it's also flat in the craniocordal plane. And the wide and flat shape of the feline patella relative to the femoral trochlear sulcus may hinder stable tracking of the patella. And to address this, partial parasagittal pateectomy can be performed.
So during surgery, we assess whether the patella actually recesses into the recessed trochlear sulcus. And if the patella is wider than the trochlear sulcus, it will ride on the medial and lateral ridges. Just because we have recessed the trochlea with a block recession or a wedge recession does not mean the patella is engaging that new block.
And if the patella is riding on the ridges, this will reduce contact area between the patella and the femoral sulcus, and the patella will not be constrained by the trochlear. Normal tracking will therefore definitely not occur and patella luxation will probably persist. So the patella does need to be narrowed to match the medialateral width of the trochlear sulcus.
And the need for this has been confirmed in a recent abstract that was presented at ECBS in 2017, by Brioshi, and others. And they performed a CADver study using CTs of feline stifles, to investigate the effect of block recession trochioplasty with and without partial parasagittal patellectomy on the patellofemoral contact, the depth of patella recession. And the size of the trochlea and the patella.
And they did show that if a block recession was performed alone, the area of contact between the patella and the trochlea was significantly smaller. The depth of patella recession was unchanged, and the patella was wider than the trochlea. However, if they did a partial parasagittal patellectomy, then they saw the area of contact between the patella and femoral trochlear get significantly larger.
The patella did recess more deeply, and the patella was narrower than the trochlear sulcus. And basically they concluded that a block recession trooplasty alone does not improve patella recession and actually decreases patellofemoral contact area. And following block recession trochioplasty, the patella in cats will ride the trochlear ridges and lose contact with the sulcus.
And therefore, block recession trochioplasty should not be performed alone in cats and should always be combined with a partial parasatittal pateectomy. Now this is not only true in cats, we can see the same findings evident in dogs as well. And it is something we should assess intraoperatively and perform partial paraagitalpaectomy if required.
Also, dogs that have very chronic fluxation can sometimes build up significant amounts of fibrous tissue in the peripatella area, and this can have a similar effect to the patella just being too wide. So you may need to debride that fibrous tissue down as well in order to achieve patella stability. So in order to do this, the stifle is extended, and the patella is then retroflexed.
So you can see in this picture, the way we've done that, we've got a pair of forceps on either end of the patella here and the straight patellar ligaments, and we've just inverted the patella out to the side. You can then measure the width of the trochleus sulcus and the patella, and calculate the difference to determine how much of the patella width you need to remove. The partial parastatal patellectomy is then performed medially and or laterally using an oscillating saw.
So you can do this with Rogers if you don't have access to an oscillating sore as well. And care must be taken not to damage the overlying patellar ligament. Once you have your piece of bone removed, then minimal sharp dissection can be used to free it from the ligament, and that completes your ostectomy.
Following completion of that, you can return the patella to the trochlear sulcus and check your seating and tracking of the patella. And it is better to take a small section from both the medial and the lateral aspects of the patella rather than a large section from just one side. And the reason for that is that the depth of the patella is greatest in the middle of the patella.
So if you move a small section from both sides, you reduce the width of the patella without reducing the volume of the patella so much. If you remove too much volume from the patella, this may be more likely to lead to iatrogenic fracture. So this technique has been reported and published in 4 cats in combination with other standard techniques, and the medium-term outcomes were all very good.
However, theoretical risks do include damage to the straight patellar ligament, and weakening of the patella precipitating fracture if too much is removed. And the safe limit for how much can be removed really does remain unknown. This is quite a recent technique, so we haven't got much information on that.
So because we don't know how much we can remove, we do just recommend removing the minimum necessary in order to achieve normal seating and tracking of the patella. And just take small sections and just keep checking, so you only take the the minimum required. Just very briefly going to touch on a couple of alternatives to abrasion trochleoplasty.
So, as you saw in Bowe's case, the cartilage was very degenerate, and, an osteochondral sarcoplasty, such as a block recession or a wedge recession, are not feasible when the osteophytes and cartilage erosion have severely damaged the trochlear groove. And in these situations, another option is probably needed. And one such option that has become recently more available is this trochlear groove replacement prosthesis, which is manufactured by Kaion.
And this is a two-component implant comprised of a base plate, which is screwed onto the femur, and then a trochlear prosthesis, which snaps onto that. And it's available in 10 different sizes. It is important, important to size appropriately as too large a prosthesis can lead to significant soft tissue impingement.
Obviously this has a very restricted width here, and you may need to perform a partial parasagittal patellectomy to ensure the patella fits within the new groove. There isn't really a lot of data available regarding follow-up for this procedure. There was a study in 2015 by Dokic and others which reported on the use of this prosthesis in 35 cases with, patellar luxation ranging from grade 2 to grade 4.
And 11 of the cases in that study had previously undergone surgical procedures which had failed to give satisfactory patella stability. They did have complications in 6 patients, 3 of which required surgical revision, but complete resolution of lameness was reported in 24 cases at the time of repeat evaluation at 12 weeks post-op, and in another 7 cases following longer term evaluation. And based on these results, it appears that the use of the trochlear groove replacement has the potential to decrease lameness associated with severe femoroatellar osteoarthritis, and also to improve patella stability.
And this may represent a valuable addition to the armoury of the small animal orthopod, when it comes to treating this sometimes challenging condition. But we definitely need further studies, comparing the use of this prosthesis to more conventional techniques, such as an abrasion cell capacity before we can state those advantages more definitively. Now when it comes to thinking about Beau's case, this probably would not have been appropriate, as the screws which secure the prosthesis would likely have interfered with the nail.
So probably not a solution for Beau, but a potential solution for other cases, with similar severe, degeneration of the cartilage within the trochlear grove. Another novel option available to assist in treating medial luxation cases is the ridgeop implant, which is manufactured by Orhamed. And this implant is used to augment the medial trochlear ridge and therefore eliminate any requirement for a traditional sarcoplasty procedure.
The ridge drop is a is a novel, high molecular weight polyethylene implant, which is secured in place using 3 2.7 millimetre standard cortical screws. It is available in different sizes, ranging from 1.5 to 3.5 centimetres, and the smallest one, the 1.5 centimetre implant, is available as both high and low profile options.
In contrast to the trochlear groove replacement, the ridge stop is probably not applicable for cases with severe femoro patella OA. It wouldn't give any advantage there over an abrasion, trochleoplasty. However, advantages of this system do include the fact that the procedure to place it is pretty simple, it's pretty quick.
The procedure is reversible, so you can return to more traditional techniques if this were to fail. Although moderate numbers of cases have been performed using this implant, to my knowledge, there's only really one abstract that's been published detailing follow up, for how these cases do. So we definitely need more information.
I believe a study is forthcoming from Doctor Scott Rutherford, who lent me some of these images, but certainly we do need more information on the long-term follow-up for these cases and how this implant holds up, years after surgery. The abstract that we have details the use of the implant in 17 cases with follow-up ranging from 1 to 18 months. And out of the 17 dogs, 14 had complete resolution of all clinical signs and 1 had incomplete resolution.
3 cases did have the implant removed subsequently, but details of why that was performed are not available in the short abstract that is available. These cases did then undergo traditional treatment for media patella luxation after the implant was removed and did go on to make a full recovery. So emphasising there, the, nice ability to revise surgery following placement of this implant if it doesn't work, which clearly with the trochlear groove replacement would not be possible.
If the trochlear groove replacement fails and has to be removed, and then really you're looking at very limited options, and they haven't been reported, but really you'd be limited to stifle arthrodesis or potentially stifle replacement. So, as for this case for bow, potentially this would have been appropriate because we could probably have angled the screws to avoid the nail. However, it would not have treated the femoro patella osteoarthritis any better than the abrasion troleoplasty that we did.
So probably not appropriate to use another implant, in that situation. But again, it's out there as an option for other cases. So in many cases, following distal femoral osteotomy and trochleoplasty, the patella is very stable.
However, in cases where luxation is still appreciated, you can still go on to perform a tibial tuberosity transposition as well. And in the largest case series of distal femoral osteotomy available to date, which is that one that was out, last year by Brauer and others, tibial tuberosity transposition was still required in 32 cases out of 66, so about 50% of cases still requiring tibial tuberosity transposition. In that study, cell capacity was required in 38 out of the 66 cases, lateral lubrication in 29, and medial release in 16.
So if we go back to think about Jenny, who was the first case we looked at in terms of decision making for distal femoral osteotomy, and she had that grade 4 medial patellar luxation and a 24 degree femoral virus angle, we did go ahead and perform a distal femoral osteotomy for her. She did still have instability of the patella after, and we did have to go ahead and perform a tibial tuberosity transposition for her as well. So I'm sure you're all pretty familiar with tibial tuberosity transposition as a surgical procedure, and I am not going to go into this in detail today.
I just want to mention one point about pin placement for these cases. If you look at these three cases, in my opinion, in one of them, the Tibuturosity transposition is performed inappropriately. Now, I did all of these, so I'm criticising myself.
But one of them is inappropriate. And just gonna give you a second to just look at those and see which one you think that is. Ignore all the additional things going on up here with this one.
Just concentrate on the 2 tuberosity. So, in my opinion, if you angle the pins distally, as you can see in this case, and you do not place a tension band wire, then you are very likely to suffer a vulsion of the tibial tuberosity. These pins going distally are not counteracting the pull of the patellar ligament to the same degree that a pin going proximally will.
Now if you're lucky in this situation, the tibial tuberrosity will simply pull off of the pins, leaving you with a tuberrosity with two pins in it. If you're unlucky, the wires will result in fracture of your tibial tuberrosity, which can make revision very, very difficult. Angling the pins more proximately, definitely counteracts the pull of the ligament much better if you are not going to place a tension band wire.
Now, in this little case, I did get away with this, there were no complications, but likely because there is a bony attachment left attached, distally, and the owners were very compliant. But if I had been less lucky, a vulsion may well have been a problem. And this is an example of this.
This is obviously a tibutu rosy, a vulsion fracture, rather than a tibutary rosy transposition, but the same principles apply. And you can see here that the pins have been angled distally relative to the tibuturosity, and are not going to be counteracting the full of the ligament very well. And this is what we ended up with 3 weeks postoperatively.
We have a fracture of the deburosity, it's severely displaced, and it was an absolute nightmare to revise. So I would counsel you to place your pins acting, directed proximally, or place attention band wire in order to avoid these kind of henished revision surgeries. So, last slide here, unfortunately, I, I can't give you a template for treatment, which you can use for every single patient.
Every patient must be evaluated as an individual. Meticulous positioning for radiography is essential so that you can perform detailed pre-operative planning. For cases that do have multiple deformities, a CT scan may be beneficial for a full evaluation, particularly for any torsional deformities.
You need to be ready to perform as many procedures as necessary in order to straighten the quadriceps mechanisms sufficiently and stabilise the patella. And even if a distal femoral osteotomy is performed, you may still need to perform a tibi oste transposition, sarcoplasty, and soft tissue stabilisation procedures. Don't rely on soft tissue procedures in isolation to stabilise the patella.
Really, the only time that would be appropriate is for a traumatic patella laxation, or one that's occurred after surgery and the breakdown of an arthrotomy. If you rely on the soft tissues, they will stretch over time, and relaxation will recur, unless the quad sex mechanism has been appropriately realigned. And finally, do remember, cranial cruciate ligament disease is common in these cases and may require surgical stabilisation as well.
OK. Thank you. That was absolutely great, Rachel, and apologies for that little cough, just getting out at the end.
Sorry, Karen, I I'm having one of those days. I thank you. I was just having a cough and then I realised I'd just unmuted myself, so apologies for that, Karen.
Right, I'm sure we will have some questions, so let's just have a look. I think we've sorted the notes out for people, so if you've got any problems with that, Richard, I think has sorted those out for us. Right, let me just See if anybody has got any questions.
If you've got any questions, do. Coming with those, at the moment we haven't got any, . I'm also happy to take questions if people want to just contact me directly on Twitter or anything that's absolutely fine too.
So Karen is, is . Very, good on, on Twitter. Obviously, you know, Facebook, if you want to put stuff in there, you can, you can see that.
Don't forget, Richard has said all the attendees are eligible for 15% off any new annual memberships by using VC 15 off on the website. Do give us your feedback on the website. It's been a, a, a labour of love this year, but I think it is a definite improvement on what we had.
Took a little bit longer than we would like, but do, give us your thoughts and feedback on that. Those of you will be going on in the next few days to pick up your recordings, which I suspect should be up by Tuesday, Wednesday at the latest. We'd hope to get them up earlier, but we'll, we'll see how we do with that.
So if we can get, why, why don't we get Sandra's, Actual presentation up. So Sandra, if you want to share your screen. And then if anybody's got any questions for Karen in the meantime, we can start .
To do that, Hillary said this was interesting, way above my level of orthopaedics, any suggestions for starting place for equipment? For for me laxation. Yeah.
Yeah. And you really don't need a huge amount of expensive equipment. Obviously, we have all the toys, which makes things very nice, but you definitely don't need a huge amount.
One of my favourite thing, a lot of people use the oscillating saw for their trooplasty and sulcoplasties. I'm, I'm actually a big fan of, yeah, I just use basically a hardback so that you can get from your local hardware store almost. So I tend to use a handsaw for my trochleoplasties.
I find, I'm less likely to cause any iatrogenic damage to the cartilage there. For the tibial tuberosity transposition, I find an oscillating so very useful. But during my residency, I was forced to use a just a handsaw for that too.
And also you can use osteotomes and mallets for those kinds of things as well. So it's really not very intensive in terms of the amount of equipment you need. It's more have a go on a few things and find what your preference is because I think there's a huge variation in what individual people choose to use relaxation.
You don't need a lot of intensive gear at all. That's great. Just Richard is putting up some links in the chat box so people want to look in there.
That's for the various, series that we're doing. So I know the mood series is coming up shortly. That's kind of following on from all the mindfulness stuff that we did.
We've also got Mike Kurtage returning with his, radiographic, reading of plates and so on. So just look out for those, if there's anything of interest, let us know. Otherwise, I think Rachel, thank you so much.
Oh my goodness, I've done it again. Karen. Sorry Karen.
I'm getting mixed up late in the day. Karen, thank you so much, that was really, really good, . Thankfully it's also getting a bit warmer where you are, so you will be even more freezing than we are.
So there's, we have these people who tell us they're in New Zealand or Trinidad and it's very hot, so. Having somebody who's colder than us, that does seem a bit unfair, but hopefully make you feel good about your temperatures, so that's fine. That's good.
Karen, thank you once again.