Thank you, Bruce. So this evening we're just going to talk about locking compression plates, looking at the principles of their, use applications and also some case examples as well. And I think over the last 25 years or so, osteosynthesis principles have evolved quite dramatically to promote a better balance between the preservation of the biological component of bone healing and also the optimisation of the mechanical properties of the repaired bone.
And the critical evaluation of traditional osteosynthesis techniques progressively led to this paradigm shift in orthopaedics, which became the foundation of a new concept known as biological osteosynthesis. And the purpose of biological osteosynthesis is to enhance bone healing and to decrease complication and failure rates as compared to our traditional techniques. From a biological standpoint, increased reliance on indirect, closed reduction and fixation techniques without seeking anatomical reduction, the minimal use of implants and certainly moving away from inter fragmentary fixation, as well as the limited use of bone grafts have all been proposed to minimise disturbance of the fracture site.
And from a mechanical perspective, new implants, among which is the locking compression plate, were designed to optimise construct stability while also reducing the footprint of that implant. So during this session, I plan to give a brief introduction regarding the evolution of locking plates and then look at the design of one specific example, the locking compression plate, in contrast to some of the others in the field. I'm then going to go on to discuss the biomechanics of the locking compression plate, the surgical technique for its utilisation, and then just look at some clinical applications and case examples, specifically covering when I think locking implants are justified, and also what the evidence base is behind that.
So first of all, to look at the evolution of locking plates. So in conventional compression plate constructs or non-locking bridging plate constructs, fixation stability is limited by the frictional force which is generated between the plate and the bone. And this force is created by axial screw forces and the coefficient of friction between the plates and the bone.
If the force exerted on the bone while the patient is ambulating exceeds that frictional limit, then we will have relative sheer displacement occurring between the plate and the bone, and that is going to cause a loss of reduction of your bone segments, loosening of the screws, or potentially both. For conventional plates, the bone screw interface is absolutely critical, and any damage or loss of strength here can lead to disastrous consequences. There are 2 major problems with our more conventional plates.
One is the necessity for accurate anatomical plate contouring, in order to avoid a loss of fracture reduction upon screw tightening. And one is the disruption of the periosteal blood supply that can be caused. If we want to optimise the frictional forces with our traditional implants, then the bone surface underneath the plate really needs to be free of soft tissue, and that includes the periosteum.
So from a biological perspective, extensive soft tissue and periosteal dissection in order to allow this compression of the plate against the cyst cortex is certainly ill advised, as this will compromise the local blood supply to the bone and therefore its healing potential. And subsequent delayed union will further jeopardise the long-term integrity of the bone implant interface, particularly at the level of the furthermost screws from our fracture site. Indeed, when axial loads overcome frictional forces, these screws will be subjected to the highest shear stresses.
And this stress concentration may lead to resorption of the poorly vascularized bone and subsequently to premature failure by a screw pullout. It'll start off with the screws furthest away from the fracture site, but as the load increases then on the remaining screws, further failure will ensue until we have a complete loss of construct stability. There are 2 major modes by which the screw bone interface can be lost.
One of those would be a vascular insult, so due to damage to the periosteum, and the other would be through mechanical failure. And either of these can lead to loss of the bone screw interface and then failure of the subsequent fracture repair. And the reliance of conventional plate constructs on the screw bone interface is particularly relevant when we consider the treatment of either paediatric or geriatric fractures, where bone strength may be insufficient to sustain the localised postoperative loads.
And this can certainly go on to result in implant loosening. And this you can see here is an example of a mechanical overload of the bone screw interface in a puppy. So despite the fact that the plate was placed appropriately, 6 cortices were engaged above and below the fracture, the bone screw interfaces failed due to the soft bone in this juvenile patient, and that's only 9 days postoperatively.
So locking plates do differ from our non-locking plates because the stability is not dependent on the frictional forces that are generated at the plate bone interface. And these implants consist of a plate and then a locking head screw. And the rigid coupling between the two is engineered to preclude all movement or angulations of the screw with respect to the plate.
And in this way, it mimics the behaviour of an external fixator, and certainly these implants are sometimes known as internal fixators. With locking implants such as the locking compression plate, local and regional loads are mainly carried by the strong and more reliable interface between the plate and the screw head. The emphasis is on plate screws interfaces rather than the bone screw interfaces.
If we lock the head appropriately of the screw into the plate hole, then this will confer axial and angular stability of the screw relative to the plate. And really the way that we think about this is that the plate screw interface can be entirely controlled by engineering and appropriate technique. So this is something that we can completely predict.
However, if we think about the screw bone interface, that's something that really is outwith the control of the surgeon. It's dictated by nature. So it's a little bit more comfortable with these locking implants, knowing that we're in control a little bit more and maybe can control what complications may or may not occur.
When we think about the history of locking implants, the very first locking plates, as we know them today, were the cesspool, which was produced in Poland, and the non-contact plate or the NCP which was made by Brinberg in Germany in 1998. From these very early designs, the LISS or the less invasive stabilisation system from Dupree synthes was produced. And also the PCI or the point contact fixator was also developed.
One of the major problems with these entirely locking systems was the fixed screw angle, which was largely dictated by the manufacturer. So screws can only be inserted at a given angle to the plate. There are some plates where a degree of angulation is possible, such as the PA system and the variable angle plate from synthes, but the downside of this is that you get a significantly weaker screw plate interface in those systems.
So when you can angle the screw, your interface is necessarily weaker. Other problems with these locking systems were that if we were a bit overenthusiastic with our contouring of the plates, we could damage the plate threads themselves. And also the ability to produce inter fragmentary compression with these systems was severely limited.
So when we think about the solution to that, that really is our locking compression plate that most people are familiar with today. And the advantages, of this are that it combines all of the advantages of our conventional limited contact dynamic compression plate, it's versatility, the ability to compress, the variable angle of the screws, with the increased stability of our locking systems. As we said, many angle stable systems are available, which primarily differ from each other in the design of the locking mechanism and the plate screw material.
For example, the new generation devices system, which is the dual hole locking plate, the synthes locking compression plate, the veterinary orthopaedic implants locking plate, and the securos locking plate of the PA system are all available. The main differences between the limited contact dynamic compression plate and the locking compression plate is in the design of the plate holes themselves. So the oval symmetrical plate holes of the limited contact dynamic compression plate are now replaced by combi holes, which feature two distinctive, slightly overlapping sections.
And the combi hole, as you can see here, is actually patented by debris synthes. The outermost section in relation to the centre of the plate is similar to that of the classic dynamic compression hole, and this is meant to accommodate standard bone screws. The innermost section is then designed as an open threaded cone, whose shape matches that of the conical and also the threaded head of the locking head screw.
And this allows increased versatility in treating various different fracture configurations by allowing the use of conventional or locking screws. When we look specifically at the design of the LCP system, in order to improve the contact area between the locking head screw and the threaded plate hole, and thus the strength of the locking mechanism, the thread features a double helix. The double helix in the screw head gives a very strong mechanical interface, while the single helix in the shaft of the screw provides a more biological interface with the bone.
Although there is this double helix in the screw head, the pitch of all of the screw threads is the same, which means that the rate of penetration into the bone is the same along the length of the screw. And this system leads to excellent locking of the screw head into the plate and optimal bone anchorage. In some of the other systems that are available, this is not the case.
So if the rates of penetration are not the same, then during insertion of the very first screw into the system, no problems are really noted, as there's no additional point of fixation. However, as subsequent screws are placed, when the threads of the head of the screw engage the plate, this will actually lift the plate from the bone slightly as the screw is travelling faster in the bone than it is in the plate. And unfortunately, this can lead to an increased risk of failure with those systems.
Locking screws have an increased core diameter relative to conventional non-locking screws, and this increased core diameter is important as it increases the area moment of inertia of the implant. This is necessary, as when locking plates are not anatomically contoured, the screws will be subjected to more cantilever bending than conventional screws, and they would therefore be at increased risk of screw breakage if they were the same core diameter. They have a shallower thread depth when they're compared to the conventional non-locking screws as well.
And this is because again, they don't suffer that same mode of failure. So the screw bone interface is less important than the screw plate interface. Locking screws will fail by either bending or breaking rather than by screw pullout.
Therefore, the larger core diameter is more important than that deeper thread, which for conventional screws is important as it maximises the surface area of contact between the screw and the bone, making screw pull out less likely. Locking compression plates have a profile that's very similar to that of the conventional limited contact dynamic compression plate. In particular, the under surface of the plate does feature undercuts between the plate holes.
And as a result, the area of moment of inertia of this implant, which characterises its ability to resist deformation, is fairly consistent both between and across plate holes. And this important characteristic does decrease the concentration of deleterious stresses near and at the level of the plate holes themselves. The more even the deformation of a plate under bending or torsional loads, the greater the mechanical advantages, including reduction of the risk of plastic deformation, as well as the risk of catastrophic failure, and therefore the increased fatigue life of that plate.
Locking plates also have certain biological advantages, so the periosteal blood supply beneath the plate is not compromised because compression between the plate and the bone does not occur. And preservation of the periosteal blood supply may improve healing and also decrease the risk of cortical bone necrosis and potentially infection, which we'll go on to discuss again when we talk about TPLOs later. Locking plates also do have this bevelled tip at the end, and that does facilitate their use in minimally invasive surgeries and percutaneous osteosynthesis, which obviously has even further biological advantages.
So there are alternate plates and hole designs. So the new generation devices, and the synthes systems, as we said, do allow the placement of both conventional and locking screws. If you look at the veterinary orthopaedic implants and then the PA systems, these feature a round plate hole design, which is really for locking screws only.
So the new generation devices, the synthes, and the veterinary orthopaedic implant systems feature a threaded screw head engaging and matching threaded screw hole. The PA system is different because this is made of titanium and it features a more a novel locking mechanism which relies on structural deformation of the vertical ridges at the periphery of the plate holes by the sharp cutting threads of the screw head when we're tightening the screw. So this does make the packs plate polyaxial, and it's the only one which is polyaxial, but this does work by increasing the structural damage to the plate in order to enable the screws to be angled.
And therefore this does make the screw plate interface less stable. And I think you can see that in these pictures here. So picture B here is where the screws have been tightened to 1 newton metre of torque, and in picture C they've been tightened to 2 Newton metres, and you can see there that definitely there is increased damage to those screw holes with the with the tightening at different angles and and strengths.
So moving on then to discuss the biomechanics of the locking compression plates. So in locking systems, the rigid interlock between the screw head and the plate will preclude all movement or angulation of the screw relative to the plate, rendering the system an angle stable system. And this is in contrast to the conventional systems where the screw head is allowed to wobble within the plate hole.
And the study that was conducted by Boudreaux and others in 2013 looked at the reliability of the locking mechanism of the various systems. And the veterinary orthopaedic implant screws consistently failed by metal fracture at the screw head shaft interface. This suggests that the design of the screw head driving mechanism results in a local stress riser.
So the screws do feature a relatively deep hexagonal coupling relative to the end of the thread. And this creates a thin metal ridge connecting the screw head and the screw shaft, which was postulated to lead to the systematic fracture of the screw at this point. The synthes screws tended to fail either by bending in about half of the cases or dislodging in the other half from the locking mechanism.
But the synthes coupling could sustain a significantly greater load before failure than any of the other systems. And this was postulated to be due to that double thread design which we discussed earlier, which increases that contact area between the screw head and the plate hole. Another reason for this improved performance of the Synthes screw could be the increased area moment of inertia.
So whereas all of the locking screws in this system had an external diameter of 3.5 millimetres, the core diameter did vary. So the core diameter of a synthes screw is 2.9 millimetres, and that's similar to the VOI screws.
It's relatively larger, however, than the new generation devices screws, which only had a core diameter of 2.6 millimetres, and the pack screws which only had a core diameter of 2.4 millimetres.
So really, I guess predictably with that, the PA screws and the new generation devices screws tended to fail by a combination of bending in 50% of cases or dislodging, but at much lower loads and the synthes screws were noted to fail. This actually, this curve actually comes from the pilot data from that study and actually it's, it's a little bit worse than what was presented in the, in the actual paper itself. But you can see here that with the synthes screws in the blue line here that the load to failure failure is almost double for the synthes system when we compare that to the veterinary orthopaedic implant system.
And also I think if you look at the magnified views of the threads, which you can see here, if you look at the veterinary orthopaedic implant threads, they do appear quite shallow, shallow, they're not very consistent, but look very less well engineered, whereas the syn these screws, you have that very, very deep thread, it's very consistent and appears highly engineered in these systems. When we think about the resistance to screw pull out and the importance of this toggling of screws, in this video you can appreciate the impact that toggling of the screw within the plate hole can have, and that is what allows these standard screws to fail by screw pullout. In contrast, in this video, the locking screws in the plate all move as one unit, and that means the screws cannot be sequentially loaded.
They therefore demonstrate an increased resistance to screw pullout, as this would require a large amount of bone damage to occur in order for these screws to actually loosen in this way. The clinical relevance of this is maybe a bit more obvious in, in this video. So if we look at this comminuted proximal tibial fracture when it's stabilised with a non-locking construct, cyclic loading, as would occur during weight bearing, results in screw pull out and loss of fixation.
And obviously at this articular surface, that would be devastating. If we then compare that to a fracture that's stabilised using a locking construct, the increased stability and resistance to pull out renders that construct significantly less likely to fail. The difference is also evident here in this, between locking and non-locking constructs.
It's demonstrated really nice. This is a video from the AO Foundation. And if we consider this apple to represent poor quality bone or maybe juvenile bone in a puppy, then with this non-locking construct that's being applied here, you can see when they put some For on this system that it is relatively easy for them to damage the interface between the apple or the pathologic or the juvenile bone and the screws.
So really just with one hand pulling here, you can see that the screws will all just toggle in the system and pull out without really damaging the apple substantially. In contrast, when we look at a locking construct being used in the same pathologic or juvenile bone, you can see here this is the locking system is being applied, and when they try and disrupt this interface, it's significantly harder. So with one hand, they absolutely cannot do it at all.
And eventually we go to a two-handed approach. I think if this was me, I probably have to have my foot on it, but definitely significantly more force being required to disrupt the repair, and failure only occurs after tearing out a wedge of that apple. So you see that even in very, very soft bone, that the, advantages that these locking systems can potentially have.
So one of the advantages that everyone always talks about with these internal fixators or locking constructs is the decreased need for anatomical plate contouring. And certainly it is a really big advantage and we'll discuss it a little bit more later, but it is important to not abuse that. And when we think about the.
Mechanics, there's a paper by Ahmed who showed that if we, there's no real difference in the construct strength for locking systems between the plate being placed directly on the bone, albeit with no compression, or with a 2 millimetre gap between the plate and the bone. So either is absolutely acceptable. However, if you extend that distance out to being more like 5 millimetres, then there is a significant decrease in construct stability.
So we can't completely ignore plate contouring, we still need to contour to a degree, but we can certainly get away with a degree of non- anatomic plate contouring, much better with these systems than we will with our conventional plates. When we use locking systems, we do really need to respect that screw insertion angle. If our screws are not placed coaxially, then the result is that we are going to cross thread those screws.
And when this happens, the screw plate interface is substantially reduced, and we can definitely expect lower failure failure loads in this situation, and also potentially differing modes of failure with decoupling of the screw head possibly becoming more prominent rather than screw bending or breakage. And certainly, recent studies have shown that malalignment by 10 degrees or even with 5 degrees can significantly reduce both the stiffness and the strength of the locking interface, which could in turn jeopardise the short-term stability of your construct. And this demonstrates the importance of the dedicated alignment guides and careful coaxial placement of the screws.
A meticulous use of the drill guides will result in optimal rigidity of that plate screw locking interface. And you can see here in this case example that cross threading has occurred in one of these screws that you can see that it certainly isn't at 90 degrees to the plate, which it should be, and the other giveaway is that the screw head is not sitting flush with the plate. So certainly these things can happen if we're not really careful with our insertion technique.
So the loss of constructability secondary to cross threading has been demonstrated in a paper by CARB, where you can see that there is a significant difference in the load that is required to produce displacement if you have those increasing degrees of angulation. So it is again really important to respect the, the appropriate insertion technique with these systems. So as we've mentioned previously, for the LCDCP to function, friction is definitely required between the plate and the bone, and the load will be transmitted through the plate bone interface as you can see in this video.
In contrast for the locking compression plates, all of the load is sustained by the implants with none of it being placed through the plate bone interface. Furthermore, because the locking compression plates and the locking head screws behave as a single rigid unit, the loads are more evenly distributed along the implant. And as a result, shear stresses at the level of the screw bone interfaces are relatively smaller than with our conventional plating systems.
Thanks to those rigid plate screw interfaces and the fixed angle characteristics, direct contact between the locking compression plates and the bone does become unnecessary. And due to that decreased need for anatomical contouring and the lack of transmission of load through the plate bone interface, epiperiosteal plate application can be performed, and the periosteal blood supply can be preserved. And preservation of the vasculature certainly may improve healing and decrease that risk of cortical bone necrosis.
As we did mention earlier, another advantage is that the plate does not need to be perfectly contoured, because the bone is not pulled towards the plate during screw tightening. And this can be really useful in the treatment of fractures if we're treating fractures minimally invasively, or if we're treating articular fractures where just a tiny discrepancy in plate contouring can result in male reduction of the fracture, and therefore the articular surface, which can have really serious consequences. Moving on then to the surgical technique and instrumentation for using these systems.
As we mentioned, it is really important to maintain that fixed angle between the plate and the screw without damaging the fine thread of either implant, and therefore drilling of the cortical pilot hole must be coaxial with the long axis of the plate hole. So proper alignment is achieved by the use of the plates specific dedicated drill guide, which is screwed into the combi hole. Due to the larger core diameter of the locking head screws, the pilot hole is slightly larger than that would be used for a size matched standard screw.
So the drill bit for a locking system would be a 2.8 millimetre drill bit as compared to a 2.5 millimetre drill bit for a 3.5 millimetre standard screw.
Following drilling of the pilot hole, the drill guide will then be removed and a properly sized self-tapping locking head screw inserted using a screwdriver, coupled with a torque limiting device. To reduce the risk of thread damage, as well as cold welding between the locking head screw and the locking compression plate, the applied torque is generally advised to be limited to 1.5 newton metres for a 3.5 millimetre screw.
There is quite a lot of specific instrumentation that's involved with the use of these systems, so there is an insertion handle, which screws into the lot of the combi holes again, which can be used to insert the plates and certainly is very useful, in applications minimally invasive, osteosynthesis, as you can see here. And there are also push pull devices which can help with positioning, giving you temporary stability and holding your plate against the bone, while you apply your more permanent fixations. So here's an example here of the surgical technique in a TPLO procedure.
So here we just, you see, we've applied our drill guide, and we're now drilling our pilot hole, remove the drill guide, and then we'll use our depth gauge to measure the length of the screw we're going to need, and clearly having a little bit of an issue with that. And then we're going to, use insert our screw routinely, using a torque limiting device, as you can see. So, thanks to the combi hole in the locking compression plate, this means that this construct can be used in multiple different modes.
The first one to talk about is they can, we can use these locking compression plates purely as conventional plates. So just using them with conventional screws and no locking screws at all. But that's really a fairly limited interest, because you can just use a standard plate for that.
We can also use them as true internal fixators and in these situations, we're only going to be using locking implants associated with them. And most of the time, these will be used as bridging elastic osteos synthesis techniques. In the system, you're going to place one screw on either side and then normally the other two more centrally, and often we'll only use 2 screws in each fragment with this technique.
It is important that we really plan our surgeries very carefully because after you have placed your locking screws, as you can see here, it really is not advisable to go ahead and then place conventional screws. The conventional screws will try and pull the bone towards the plate. That's how they work.
And obviously, with our locking system here, we've already fixed the relationship between the plates and the screws, and so you're going to potentially put add additional stress on your repair by doing this. So this is an example here of a fairly common ed mid diaphyseal tibial fracture that we've gone ahead and repaired. And in this situation, I think you can see several reasons why we might want to use a locking compression plate.
Clearly, this fracture is not going to be something that we want to really anatomically reduce. I'm not sure it would even be possible. Certainly we would cause quite a lot of disruption to the bone biology by doing so.
So we've elected to not, just align the joints above. Below and not reconstruct this fracture. If you look at the staples, clearly this, repair was also done in a minimally invasive fashion, so an additional advantage of this particular, implant here.
So, certainly, commonly used for bridging osteopins, it's been used as a true internal fixator in this system. And this is the same dog 8 weeks postoperatively, you can see we have reached clinical union, certainly at this point. So the other way in which we can use these locking compression plates is as mixed constructs.
And again, as we mentioned, if we're going to do this, it is important that we place our conventional screws first, and then we can go ahead and place our locking head screws after that. And there are several times when you may want to use a bit of a combination system. This was one that we, used a, a combination system in, so this was an oblique fracture, but there were some fissures heading down towards the epiphysis distally.
And we wanted to use a plate rod construct, and a combination of the locking and non-locking screws. The reason why is because we felt it was going to be easier to use non-locking screws in a, in order to angle them appropriately into that distal segment. And we didn't want to be completely fixed by always having to be at a certain angle, certainly, in terms of wanting to avoid the foramen there.
And this is the same dog, 16 weeks postoperatively, and again, you can see healed very nicely. Again, this one's certainly not done in quite as minimally invasive fashion. We've still got an approach above and below the fracture, but really, they almost meet in the middle, so I'm not sure we can truly say that was a minimally invasive approach.
This is another example here. This was actually referred to us by a vet that's quite local to here who opened up the fracture and deemed it to be non-operable and recommended an amputation. When the dog came to us, we did use a double loop solage to reconstruct the subtrochanteric region there.
You will be able to see some additional metalwork. Some of the wires in there are on skewer pins, so I haven't been breaking drill bits in there. It is actually deliberate.
And in this situation, you can see there is actually a locking screw which we've actually managed to angle up into the femoral head and neck. And it does require some fairly careful plate contouring in order to be able to do this, but you can still use locking screws even in this region, if you're careful with, where you're aiming them and, and making sure your plate contouring is appropriate. So, moving on then to some clinical applications and some case examples, it's probably the most interesting thing is there's a lot of debate at the moment as to, you know, when is it really justified to use these locking implants and, and when shouldn't we?
And certainly that may be a little more relevant here in the US. Because our implants aren't subsidised at all. So for us, a cortical screw is $30 and the locking head screws are more like 100 to $110 per screw.
So for us it is something we really have to think about quite carefully and are we justified in passing that additional cost on to the owner. So, locking implants have certainly gained a lot of popularity, and they are very, very commonly used in veterinary medicine today. In people, locking plates definitely have a clear benefit in both juvenile and elderly patients, and also those with osteoporosis.
And many studies have reported the use of locking plates for appendicular fracture repair, but very few studies have actually directly compared the clinical use of locking and non-locking constructs. Locking systems have certainly been reported to be potentially advantageous in comminuted fractures, where the locking compression plate would be used as a bridging plate, as we saw earlier, and also in places where exact plate contouring is difficult, and in areas where other implants may prevent the use of bicortical screws. And although it's applicable in most fractures, the use of locking compression plates is particularly attractive in the treatment of paediatric fractures, pretty metahoceal fractures, and during minimally invasive percutaneous s osteosynthesis.
Paediatric paediatric fractures definitely do represent a biomechanical challenge, and that's inherent to the weak mechanical properties of that immature bone. Indeed, the low strength and low resistance to shear stresses of such bone jeopardises the integrity of that bone screw interface, which may in turn lead to construct failure via screw pullout. Furthermore, any damage, whether it's traumatic or potentially iatrogenic during surgery, to the periosteum will inevitably result in exuberant callous formation in these younger patients, and that can jeopardise functional recovery, particularly if we're close to a joint.
The use of conventional plates may also induce either stress concentration at the bone screw interfaces or plate plastic deformation, and in both cases, devascularization of the periosteum beneath the plate will result from compression against the bone. In contrast, if we use a locking compression plate, then we can preserve the periosteal blood supply. We can optimise that stress distribution between the screws, which in turn spares that inherently weak bone screw interface.
And thanks to the locking compression plate angular stability, the risk of failure of eye screw pullout will be considerably reduced, as, as we saw in our example with the Apple, it would require extensive bone destruction. The same design characteristics are also beneficial when we think about treatment of metaphycele fractures or metaphyscial osteotomies such as RTPLO. The greater resistance to bending that's conferred by the implant angular stability and by the relatively larger area moment of inertia of the locking head screws does contribute to shoring up the fixation, even in the presence of limited bone stock for screw anchorage.
In addition, because anatomical plate contouring isn't mandatory with these locking compression plates, plate application along these complex metaphycial shapes is substantially facilitated. And as a result, loss of reduction following plate application is considerably mini minimised. Also, because the use of monocortical screws is very effective with locking compression plates, the risk of inadvertent intra-articular screw placement can be substantially reduced.
And a further consideration is that the design of the locking compression plates is particularly adapted to minimally invasive plating techniques. So those bevelled plate extremities, the use of the insertion handles screwed into the threaded section of the combi hole, facilitate a traumatic placement and manipulation of the plate within that epiperiosteal space prior to fixation. And finally, as we saw in our humeral fracture, and as you can see in this one here too, the judicious placement of monocortical screws can facilitate the use of a plate in combination with an intramodullary pin.
And you can see here, certainly this was a, a humeral fracture that was repaired minimally invasively, and these are the postoperative radiographs, sorry, 4 weeks postoperatively. So, where are situations where locking screws can be particularly useful clinically then? And the higher resistance to screw pullout with locking implants is potentially particularly advantageous in our really thin bones, such as the pelvis, the mandible, and maybe the scapula.
Lateral bone plating is certainly the most common management strategy for ileal body fractures, and presumably this is because the approach is considered pretty simple, and we get really good visibility of our fracture through that approach. Other described methods certainly do exist. We've got dorsal plating, some people have even attempted ventral plating in dogs, interfragmentary pinning, placement of lag screws, intramodullary pinning, compound fixation with pins, screws, and orthopaedic wire, and PMMA.
And some people have even tried external skeletal fixation of these fractures. The most common complication associated with ileal fracture repair via lateral plate is implant failure, and this occurs in up to 62% of patients, so it's a huge number of these fractures that will suffer some screw loosening. And so the majority of these failures are attributed to either screw loosening or complete screw pullout, and in the worst cases this can lead to a loss of reduction and collapse of that pelvic canal.
And it has been suggested that one of the reasons for this high incidence of screw loosening is the poor quality bone which is found in the cranial part of the ileum. And the reference to poor bone quality appears to be made in relation to the frequency of screw loosening, the thinness of the allele wing, and also the poor feel of bone, which we encounter clinically when we're placing screws in the ileum. I'm sure we've all been there and kind of stripped screws when we've been invited that cranial allele wing kind of margin.
So I think we've probably all experienced that quite nasty feeling that the screws don't feel quite as secure as we would ideally like. It's often been hypothesised that locking plates may be superior to conventional implants when we're stabilising allele fractures, and this is again because of this perceived suboptimal screw purchase of these standard screws in the allele wing. And 1 K9X vivo study that was performed in 2014 actually failed to demonstrate any difference between the dynamic compression plate and a locking compression plate construct, in acute failure testing.
However, in this study, they did not carry out cyclic testing, and that may have affected those results. The biomechanical superiority of locking over non-locking constructs for the stabilisation of ileal fractures has also been confirmed in a recent ex vivo study using cadaveric feline pelvis, with an ileal gap fracture model. And in this study, they used dorsal plates with non-locking screws, lateral plates with non-locking screws, lateral plates with locking screws, and also orthogonal plating in some cases as well.
And what they found was that double plating certainly improved the stiffness and resistance to failure compared with all other fixations. So certainly the the double plating was better than everything. However, if we were just using a single plate, then the single locking plates did produce superior constructs compared with single non-knocking constructs.
Interestingly, they didn't find any difference between the dorsal and lateral non-knocking constructs. So although dorsal plating has been proposed as being, a way to avoid screw loosening in this biomechanical study that didn't really appear to be true, and that may be because we're actually plating. The pelvis on its compression surface surface, if we're actually using dorsal platings, it may not be biomechanically the most sound idea.
But certainly in this study, it's obviously only an Xvivo study. It does have flaws, but certainly the, superiority of locking implants in feline pelvis, was confirmed, in contrast to that previous study that did not demonstrate the same advantage in canine pelvis. So when we look at what clinical evidence do we have to support the use of locking plates in the ilium, one publication does show a very clear difference in clinical cases of fracture repair when comparing locking and non-locking plates for feline ileal fractures.
And this study compared conventional 2 millimetre dynamic compression plates and locking plates, and they used a combination of the Alps system. The rate of screw loosening was significantly higher in the group where conventional plates were used. They reported screw loosening in 50% of the cases that were repaired with a single laterally placed dynamic compression plate, compared with only 1 out of 13 cases that was repaired with a locking plate.
And they did do some double locking plate constructs as well, and in those cases, none of the cases suffered any screw loosing. However, it's a little bit difficult because although the difference in screw loosening was definitely apparent, when you look at what the clinical consequences were for these patients, all of the fractures healed and there was no significant difference in pelvic canal narrowing. So the actual, the clinical impact of this finding still remains unknown.
So I think it is definitely showing that biomechanically, these implants are superior, but clinically it didn't really make any difference to the cats. There was another study in 2017, which reported the use of locking tea plates for stabilisation of illegal fractures in 12 cats and five small dogs. And they used either 2.4 or 2.0 locking tea plates.
And in this study, they had 11 cases that had no change in the sacral index as the measure of pelvic canal diameter between surgery and follow-up radiography. And the remaining 6 cases really had very minimal change in their sacral index. So some of them got a little wider, some of them got a little more narrow, but I'm inclined to put that down to different measuring, .
Measuring, say, mistakes, because it really was very dif very, very minor differences. They didn't see any major or minor complications recorded for any case in that study, so it looks promising, but again, they weren't comparing locking versus non-locking, so it's a little difficult to know. There was also a small case series that was reported that documented lateral plating of canine and feline allele fractures, in 9 cases using locking TPLO plates.
And they certainly reported very satisfactory clinical outcomes with a very low complication rate, and they had no cases of screw loosening and actually no implant associated complications at all. So I think when we look at all of these studies together, the results certainly suggest that the risks of premature screw loosening and potentially then the risk of pelvic canal narrowing may be reduced through the use of locking plate constructs in cats and maybe small breed dogs as well. Additionally, the absence of screw loosening using one locking construct, in the study from 2017 by Scryma, indicates that the use of double locking plates, as has been reported previously, may not be critical to satisfactory outcomes in cats and small dogs.
So I guess summing that up, when do I actually consider using locking plates in the ilium? And really I would say in cats, I would preferentially, based on the evidence that we have, I would use locking plates all the time, as long as we don't have costs being a significant factor. So I would use them in cats.
For every, every allele fracture, if I could, certainly, I'm going to use them in cases where I think I have limited bone stock and actually that reported technique using the TPLO plates is, is a great one for those fractures that are occurring right back near the acetabulum, because the plate is basically contoured into the right, configuration for you as well. So certainly if I've got limited bones stock, and definitely in cases where I have poly trauma, if I have a cat that I've got an ileal fracture on one side and a femoral fracture or something on the other, I think certainly it, it's beneficial to have a more robust construct on the ileum to protect against premature failure. So certainly for me, and based on the evidence that we have, I think the use of locking plates in the ileum can certainly be justified.
If we think about dogs, as you can see here, this is a case where I have not used, a locking plate, despite there being an acetabular and allele fracture on the same side. I do think they appear to be at lower, lower risk for screw loosening. I don't think there's any problem with using a locking plate in the ileum in dogs.
Certainly it can still be used, but if you're concerned about finances, then I don't think I would worry unduly, about using a non-locking implant in the dogs, particularly the larger breed ones. So moving on then to acetabular fractures, and this is another place where locking implants have been considered to be theoretically quite an attractive option. And there's this is often an area where we, we think maybe this could be beneficial, there is limited bone stock available.
Certainly the contouring of acetabular plates can be a little bit difficult, and certainly there may be an advantage in, in being able to use. Cortical screws in some instances. However, in, in contrast to what might be expected, in a study that compared locking versus non-locking plates for acetabular fracture repair in an X vivo model, no differences were found between repair techniques for accuracy of anatomical reduction, for osteotomy gap after cyclic loading, or in the strength or stiffness of the constructs.
However, I think it's important to note this was an X vivo study, so the investigator's ability to contour the plates was definitely superior to that which we can normally achieve clinically, where full access to the fracture site can certainly be impeded by the soft tissues surrounding the hip joint. So the excellent contouring that they achieved in this study may have biassed these results with respect to maintenance of reduction after plate fixation. In the clinical patient, if we had less than perfect plate contouring, this would theoretically result in a difference between the two systems whereby a loss of primary reduction may have occurred with the standard, but not the locking plates.
Additionally, in this study, as an additional flaw that the locking plates were applied using monocortical screws only while the non-locking plates were applied using bicortical screws. And although monocortical screw use is proposed to provide sufficient stability and load transfer at the near surface with locking systems, bicortical lock fixation has been shown to be biomechanically superior to monocortical. And therefore, the fact that they applied these systems differently again, may have biassed the results of this study.
It's possible that if biocortical screws had been used with the locking system, we may have seen a biomechanical superiority, demonstrated. Unfortunately, despite these limitations, we haven't had a further clinical study or a follow-up biomechanical study performed with respect to this. So I think the, the jury remains out, on this, but certainly there were limitations with that study, and I think it's still potentially possible that locking systems may be beneficial for acetabulal fractures.
One place where there's really very little debate about the use of locking implants is with triple pelvic osteotomy. So, triple pelvic osteotomy is obviously performed in dogs with hip dysplasia in order to increase dorsal acetabular coverage and prevent subluxation of the femoral head. And triple pelvic osteotomy has a very high complication rate with respect to screw loosening, that occurs in somewhere between 29 and 63% of procedures when we use the conventional slocum canine pelvic osteotomy plate.
And when screw loosening occurs in these cases, this can result in loss of alignment of the bone segments, causing severe narrowing of the pelvic canal, pain, lameness, and screw trapping in the gluteal muscles, and it can obviously result in catastrophic failure, which requires additional surgery. And the biomechanical reasons for screw loosening do do include this, the fact that we've got this weaker juvenile bone. In these patients, we're normally operating at somewhere around 6 or 7 months of age, inadequate stability of the system.
And also, as you can see here, you get minimal contact of those osteotomy ends. So certainly, additional risk factors, include very cranial screw location, the use of pre-tapped cortical screws, and inadequate sacral purchase by the cranial screws. So several steps have been recommended to prevent screw loosening, and this has included placement of a ventral plate, use of ischial or ileoser collage wire, increased sacral screw purchase, an increased total screw number, and also potentially the use of a double pelvic osteotomy rather than a triple pelvic osteotomy.
But in 2006, a locking TPO plate was introduced to improve implant stability and in an attempt to reduce implant associated complications, specifically this very high rate of screw loosening. And the use of locking screws during triple pelvic osteotomy has been shown to substantially reduce the rate of screw loosening. Use of locking seven hole plates, with 3 to 5 locking screws resulted in a lower rate of major and minor implant associated complications than has been previously reported with non-locking implants.
And a study which investigated the use of locking and non-locking implants for a repair of rotational ileal osteotomies tested constructs for about 3000 cycles, and found a significant difference between constructs with respect to screw loosening. So a clinical case series has definitely shown advantages and biomechanical studies have shown advantages as well. So really not a lot of doubt here if you are performing triple pelvic osteotomy, then locking implants is certainly the way forward.
The maxillofacial complex in the dog is probably the most, is, is the most prominent part of the skull, and that does render it vulnerable to pretty severe injuries. And this is another area where the merits of locking implants are often discussed, mostly due to the paucity of bone stock that we have available. However, mini plates have been used for maxillofacial osteosynthesis in people since the 1970s, and they are ideally suited for comminuted or simple maxillofacial fracture repair because of their size and also how easy they are to contour.
While advanced maxillofacial reconstruction is not performed as commonly in animals, Budrio used mini plates for maxillofacial fractures and achieved excellent function and cosmesis in a couple of studies back in 1996 and in 2004. And another study by Artsy and others in 2015 reported very positive outcomes following internal fixation of Maxillofacial fractures using titanium mini plates in seven dogs, with a really long follow-up of up to 94 months. And in this case series, only one implant was ever removed and that was actually secondary to the development of nasal aspergillosis in that patient, so not really a surgical complication per se.
Following implant removal in that dog, there were no adverse consequences. And in that paper, they report that they use non-locking implants in maxillofacial fractures preferentially, due to the ease of contouring of these of these implants, and also the ability to angle screws, which they felt was very important. So, in dogs today, there is no evidence to support the use of these knocking implants, in the maxillofacial fractures.
However, there is one recent publication right in 2017, where they biomechanically evaluated intact mandibles and simulated mandible fractures, stabilised with either a non-locking or a locking unilock 2 millimetre construct. While both repairs were definitely weaker than intact bone, the locking implant in this in this system did have a higher stiffness in comparison to the non-locking group. So I don't think we have a definitive answer here as to whether they they should or should not be used in magillofacial fractures, but certainly it may be worth consideration, the use of locking implants based on your individual case characteristics.
In both human and veterinary surgery, the use of a wide variety of different fixation devices has been described to maintain peri-articular fracture and osteotomy reduction. Achieving screw engagement with 6 cortices per fragment may not be possible with straight plates, due to the small size of juxtra-articular fragments and the successful use of conventional T-shaped plates has been reported for stabilisation of small fragments involving the distal radius and for supracortalloid fractures as well. However, in very small fragments, achieving the required number of cortices even with these tea plates can be very difficult.
And as the biomechanics of blocking plates differs, the number of screws required for stability is potentially reduced, and this can offer a potential advantage because less screws may be required in a small peri-articular bone fragment. Recently, the use of locking plates in the stabilisation of peri-articular fractures has gained popularity in the treatment of these fractures in humans. The number of screws required in each fragment is still not completely clearly defined.
However, it has been suggested that adequate stability can be achieved with a minimum of 2 locking screws per fragment, which may prove advantageous when we're stabilising small bone segments. Another potential advantage of the locking plates here, as we alluded to earlier, is the ability to achieve stability without perfect plate contouring, which can be challenging and time consuming with these complex contours of the metaphyseal bone. In comparison with the conventional bone plating, when the bone is pulled towards the plate during screw tightening, this does not occur when we're using locking plates, and this will reduce the risk of induction of malalignment.
And in this case here, this was a 6 month old Labrador. He was hit by a car and we initially went in and placed the medial plate, which is that locking compression plate, the synthes version there. We placed that with some locking and some non-locking screws, as we discussed earlier.
So we wanted to be able to angle those non-locking screws, which is why we used a combination. We then placed the transcondylar screw from laterally, really then just treated this like a lateral condylar fracture. And we did use the string of pearls plate, the other, another locking plate there, as contouring on the lateral side, with these plates can be a little more difficult, and the string of pearls plate can often offer some advantages, in terms of contouring in more dimensions of freedom.
And these are the radiographs that 6 weeks postoperatively, you can see healing very well, at this stage, reached really clinical union at that point. So what is the evidence that we have to support the use of locking plates for peri-articular fractures in our veterinary species? Tan and Johnson in 2016 reported a series of perioticular fractures or osteotomies that were all stabilised using a notch.
Tea plate. And they had 9 dogs and 2 cats with articular or peri-articular fractures involving a variety of different places, distal femur, proximal tibia, proximal ulnar. There was a few ilei in there and distal radius as well.
And they stabilise those with either a 2.0 or a 2.4 notched head locking tealate.
And all of their fractures did go on to progress to clinical union with only 2 postoperative complications reported, which were related to skin necrosis and also stress protection, in those cases as well. And this is a case example here. This was a little Chihuahua who presented to me, I have to say, I, I didn't believe the owner when she first came in.
She told me it was an agility Chihuahua. I was, I was, Are you serious? I have seen several videos of this dog since, and he really is quite good at agility.
It's, it's quite good to watch. But she was really adamant that this dog needed to get back to doing, agility to a high level, and I was, gave her a relatively guarded prognosis for that. I thought we might have to remove the plate later.
After this fracture repair, but you can see here, we did use this notched tea plate, in this dog, this is actually a 1.5 millimetre version, so a little different to the Tan and Johnson study. But, certainly, it worked very well in this case.
You can see we've got adequate healing there, that's at 8 weeks postoperatively, and we are now 18 months past this point, and this dog has returned to successfully winning in, Chihuahua agility. So, a, a good outcome for that particular case. In terms of, more evidence for peri-articular fractures, there is also a case series of 13 cases of YT humeral condylar fractures, which were stabilised using bilateral string of pearls, locking plates, and they were replaced by a combined medial and lateral approaches.
And they report functional outcome as being excellent in 10 dogs, good in 2 and poor in one, and that was a study by NES in 2009. And certainly this compares pretty favourably with some of the other previously reported techniques. But again, we don't have a study that provides a direct comparison.
So again, I think this looks like it's promising for peri-articular fractures, certainly when you've got a paucity of bone stock, but we don't have that definitively to say that it's better. The 1.2 millimetre mini locking te plate system has also been postulated to be useful for radius and ulnar fracture repairs in toy breed dogs.
In one study, all of the fractures that they had achieved union and a successful return to normal function without any catastrophic complications, and that was all achieved within an adequate time period, which they defined as 8 weeks. And this was even though 4 of these cases were actually revisions after a prior surgery which had failed. If we think about repeated surgery, that does tend to lead to further disruption of blood supply, more trauma to the soft tissue structures, and potentially would be expected to result in higher rates of non-union and maybe decreased rates of return to normal function.
But the results of this study from 200. 16 by KA and others did validate the effectiveness of this mini locking plate system for treatment of these radiocellular fractures with these positive results. But again, we don't have any study that definitively compares locking to non-locking.
So promising results, but we can't say for sure, that they demonstrate superiority. One of the areas where, the use of locking plates certainly has, really exploded is in, in the use of, locking plates with TPLO procedures. And locking TPLO plates are now widely available from numerous different manufacturers.
Some of them are pre-contoured, and at least theoretically they provide several advantages in comparison to conventional non-locking TPLO plates. However, certainly in some countries, locking plates are typically more expensive, and so a clinically relevant question is whether there are any true benefits of using locking TPLO plates that can warrant this extra cost associated with their use. The most obvious potential advantage of using locking TPLO plates is the extra mechanical stability that they may provide.
In turn, TPLO plates might decrease the change in tibial plateau following surgery, so reduce the risk of rockback, and potentially the incidence of catastrophic mechanical failure. And although these advantages might be true, there is not a huge amount of data to definitively support that this is the case, considering how common this procedure really is. Biomechanically, we do have some evidence that one X vivo cadaveric mechanical study demonstrated that the mean loads to failure were higher with locking plates than with non-locking plates.
Similarly, another Xvivo study demonstrated that the same locking plate provided greater stiffness when loaded axially in comparison to the slocum plate. And yet another study demonstrated that the use of locking plates with locking screws induced less translation of the proximal tibial fragment than the use of locking plates with non-locking screws. However, that very same study failed to demonstrate any difference in construct stiffness or cycles to failure, when loaded axially depending on whether locking or non-locking screws were used.
So some promising data there, but again, maybe not giving us all the information that we need. If we then look at the clinical evidence that we have supporting locking plate use for TPLO, reviewing the data, in contrast to the X vivo data, one study actually concluded that the use of locking plates and screws resulted in greater medialateral translation of the proximal tibial fragment. The authors in that study recommended that it must be, we must, make sure that we have accurate alignment of the proximal tibial fragment prior to application of the locking plate and screws in order to avoid that.
Another retrospective study showed that the amount of change in tibial plateau angle during the convalescent period was slightly less with the use of locking screws. And this group also concluded that bone healing was faster with the use of locking screws. However, if we look at what the difference in the change in tibial plateau angle was, it was only 1.29 degrees versus 2.59 degrees between the two groups.
So, potentially that's fairly inconsequential in terms of the difference. Furthermore, there were no significant differences in complications between locking and non-locking groups in that particular study. More recently, another group showed that there was no significant difference in the change in tangle during the convalescent period if locking plates were used or not used.
The difference between groups in that study was that the immediate postoperative tibial plate angle was lower with the use of locking TPLO plates, that there was no significant difference between groups in osteotomy healing or in the perceived stability of the two different constructs. More recently, again, a retrospective study did show that there was a lower incidence of infection in dogs weighing greater than 50 kilogrammes if locking plates and screws had been used. While the exact cause for this is a little unclear, it could include greater construct stability, or this may be related to the preservation of greater periosteal blood flow that we discussed earlier.
But this study was retrospective in nature, so it's a little difficult to say for sure what the reasons for that, reduced infection rate were. So, based on all of that, then, when do I consider the use of locking plates for TPLO? I think in summary, there are numerous potential benefits to the use of locking plates.
However, there isn't really conclusive evidence demonstrating that complications are reduced or the outcomes are superior with the use of locking plates and screws. We do really need some further studies, so that we can, assess the value of using that locking plate technology. But All that said, there does not appear to be any real notable negative effect of, of using these locking TPLO plates.
The only disadvantage for using them would be, that of cost. And so, really, I used locking TPLO plates in all of my TPLOs. And I would say, particularly important in cases like this.
So this was, an 11 month old Rottweiler who, had undergone a untreated. Tibial tube rosier vulsion. If I go back a little bit, we can see that there.
So this was a, a chronic tibial turosier vulsion, which occurred. And, we waited for it to heal because at this stage, we couldn't really do a huge amount about it. The proximal tibial physis has clearly been affected as well, and we have a dramatically increased tibial plateau angle in this case.
So here, we're going to need to use a combination cranial closing wedge and tibial plateau level. Osteotomy in order to correct that excessive tibial plateau angle. And certainly complications are more commonly encountered in these cases.
And in these cases, even if you don't normally use locking implants for your TPLOs, I would definitely recommend the use of them here. So you can see the dramatic tangle that we started with. This is our post-op result.
And not only have I used one locking plate in this system, I've actually gone ahead and used an additional locking plate, again, the SOP. Contoured up and around that, that, locking plate for the original TPLO. And certainly this case went on to do very well, healed at 8 weeks, and, luckily for us on the other side, just could have a standard TPLO.
But, certainly in these systems, when you've got very small bone fragments, when you've got an increased risk of failure, so even if you don't normally use locking TPLO plates, I would counsel that they would be justified, in these slightly more complicated cases. So, when we look at, locking implants in cats, this is another area where sometimes people propose locking implants may have a particular benefit. There is really no firm evidence to support this to date, however, the evidence that we have is limited to retrospective studies without a control group, some case theories, and some expert opinion as well.
So nothing definitive. We haven't had any prospective randomised trials, there's no large controlled cohort studies that have been published. However, cats are pretty unique patients in many respects.
Their musculoskeletal system is capable of pretty impressive performance, and the range of motion of feline joints is greater compared to the canine. This flexibility is very important for them for their daily tasks and must be maintained wherever possible. Most cats that do present to hospitals are free roaming, and confining these patients postoperatively to a very small area can be pretty challenging for owners.
While some cats can tolerate the restriction very well, a great number of them tend to go on the rampage. And this will not only stress the stability of any fracture repair, but it's also going to stress the owner's compliance, I would suggest. Unfortunately, cats also show a fairly high rate of non-union, especially in the tibia and the proximal ulnar.
And certainly if you have open fractures, comminution, patients that are older, higher body weights or concurrent injuries, this will increase the risk for a failure of bone fusion and potentially the necessity for a revision surgery. So for all these reasons, locking implants have potentially, been postulated to have some advantages. A study by Vallarico and others in 2016 reported the use of the locking compression plate, in both the 20 and 24 in 64 feline long bone fractures and 11 canine fractures.
Unfortunately, looking through that data, even when you look really carefully, it's not really possible to evaluate which complications were sustained in cats versus dogs, but in this series, there were 7 implant-related complications, including 3 cases of plate bending, a 1 plate breakage, 2 IM pin migrations, and 1 implant pullout. The average number of cortices that they engaged was 4.5 per.
Frag in their comminuted fractures. And they did not show any association between the number of cortices engaged, and the complications that were encountered. So even those that only had 2 screws per fragment, did not have a higher risk of complications in that study.
So this indicates that the use of 2 screws per fragment in comminuted fractures does appear to be appropriate for cats, as has been described in people. And this is an example here of a, of a cat that, has an intact ulnar but has fractured the radius, and we do see this relatively commonly in cats actually. And because of the displacement of the radi.
Head there and we did actually go ahead and recommend a, internal repair. And you can see here we have used a locking plate, and we have used a locking plate that has only allowed us two screws in that flexible segment. So certainly, this might be a cause for concern, with, with a non-locking implant, but with a locking implant, you might be more confident.
Guerrero and others in 2014 again described the use of the Alps system for fracture repair and arthrodesis in cats and dogs. Again, a little difficult to pull out which complications were cats and which were dogs here, but, they only saw complications requiring revision surgery in three cases. One was a fracture through the.
Hole. One was where monocortical screws pulled out of the bone. And in this system, they had only 3 monocortical locking screws placed approximately in all 3 pulled out.
So certainly, really the complications in this series can be put down to surge and error and an early learning curve with using the system. When we have another study, this is by Nigeria and others out of Japan in 2015, and they reported to the Alps system again, for fracture repair in 32 cats, and only encountered a 3.2% postoperative complication rate.
So if we look at all of these studies together, the complication rates are reported range somewhere between 3 and 9%. And certainly that's pretty promising when we compare to our historical literature for feline fractures. However, again, we can't say definitively that it's locking plates that represent that advantage.
Maybe it's just an improvement in what we do generally. Improvements in asepsis, it could be any number of things when we compare back to historical literature. But certainly used of locking plates here and these cats seeming to be promising.
We do have biomechanical benefits that we've previously talked about and that have been demonstrated in the feline ileum and the feline mandible. But really that's the, the, the stretch of the evidence that we have to support locking plates in cats. So, when do I consider the use of locking plates in cats?
Really, for me, it's dependent on anatomical location and fractured type as well. So certainly, if I'm encountering an ileum fracture, I will most likely use a locking implant. The surgical approach is also taking into consideration, as locking implants are especially useful for use with minimally invasive osteosynthesis, and also useful when we're placing implants in a bridging fashion, where we have particular concern regarding preserving that blood supply to the fracture site, and also when small juxtaarticular fragments are present and when anatomic plate contouring could be anticipated to be fairly challenging.
. Certainly, patient factors do need to be taken into account as well. If we have a juvenile patient with poor bone quality or a, a very geriatric patient with poor bone quality, I'm going to be more likely to consider the use of a locking implant. And this was one of those cases here, so this.
This was a case, Norman, he was a 19 year old cat, and he presented with that very concerning history, no history of trauma, 19 year old cat, and a distal tibial fracture here with some fissures progressing, distally down close to the joint. And although radiographically, we couldn't see any evidence that this was a pathologic fracture, the history did concern us somewhat. And even if it wasn't pathologic, we had some concern regarding bone quality in an older cat.
So we did elect to, completely reconstruct this fracture with sol and then use a locking plate in neutralisation mode over the top. And it turned out that probably this wasn't anything particularly pathological, because, Norman went on to progress very well, but unfortunately, due to his age, and the fact that he was progressing so well, he only refused any further postoperative radiographic follow-up. But we did see him back and examine him, 13 months post-op, and he's currently has no signs of complications, so the repair is, either the fracture is healed or the plate is still doing its job for us, one or the other.
Certainly, same cases bridging synthesis, small juxar articular fragments, I will be inclined to use these locking plates. And the only time when I'm really again worried about not making that decision is where finances are a significant concern. So there are a few other proposed clinical indications, just briefly to mention, locking implants have been postulated to be advantageous for stabilisation of scapular fractures.
Again, due to that paucity of bone stock that we have similar to in the ilium, there is no evidence to support this at this time. So really, choosing to use a locking construct here is, is personal preference. Biomechanical studies showed no advantage of a locking construct over a non-locking construct here.
And clinical studies have not been performed. One study did postulate that the addition of a locking plate, and this was an SOB in this system, did create, to create a double plate construct, may be useful in shoulder arthrodesis. And certainly that study concluded that further evaluation was, was necessary, but there's been no further study that I know of, to date.
With monocortical screw purchases being adequate for stable fixation in good quality cortical bone, the locking compression plates may also be particularly suited for vertebral body fractures, stabilisation, or other vertebral instabilities, such as with, Wobbler's syndrome, where bicortical purchases can be associated with life-threatening risks. So certainly, in those situations, they may be worth considering. So in conclusion, I think certainly with locking systems, there are numerous advantages to them, both biological and mechanical, but unfortunately we still have limited clinical evidence, to support their use.
We do have definitive evidence in the feline ilium, we have evidence for triple pelvic osteotomy, and we have some reasonable evidence there for, for tibial plateau levelling osteotomy as well. In my experience, they are particularly useful for use with paediatric fractures, metaphycele fractures, and associated with minimally invasive techniques, and that would be where I would most commonly, advocate for their, for their use. Just finishing off, I'd just like to acknowledge, Doctor Loria Jardin.
He's, he is my mentor here at Michigan State. Some of the images that I've used here do appear courtesy of him, so just to recognise that before we finish, and at that stage, I can take any questions people may have. Karen, thank you very much.
That was absolutely fascinating and food for thought beyond mention. I do like the the pictures and the, the success stories. I'm sure there have been a few where the, the, the healing has been delayed and that, but, amazing to see the work that you guys are actually doing with us.
Thank you. Folks, I'm sorry that we've run over so badly. I'm sure as none of you have left, you've enjoyed it as much as I have.
Karen, I'd just really like to once again thank you for all your time and everything else. And for those of you that are going to be at BSAVA, find Karen, she's gonna be there, go and listen to her lectures and say hi to her. So it's from my side, Karen, once again, thank you, Rich in the background and for everybody who attended.
Thank you so much for being with us tonight and I look forward to seeing you on the next members webinar. Good night, everybody.