Tag Archives: TTA

Calling All Users in Southern Hemisphere!

Do you live in the Southern Hemisphere?

Are you performing TTA surgery for Cranial Cruciate Deficiency?

Are you interested in learning about the PAUL (Proximal Abducting Ulnar Osteotomy) for helping those tricky Elbow Dysplasia Patients?

If you answer yes to two out of three of the above questions then you will be interested in the following:

TTA Masterclass in Carrara, Australia Monday June 25th

This is a full day of lectures on the Tibial Tuberosity Advancement technique for those who are currently performing the technique and for those interested in finding out more about TTA. The technique devised by Slobodan Tepic and Pierre Montavon has been used by us at Torrington Orthopaedics in over 900 patients and worldwide by thousands of surgeons. In my view TTA is unsurpassed in terms of ease of use, low complication rate and restoration of Stifle Mechanics post surgery. Slobodan Tepic will be attending and running the Masterclass, a unique opportunity to learn from the originator of the technique. I (Andy Torrington) will also be there, discussing some of the refinements in technique and planning derived from my clinical experience. If you can make this I would definitely recommend registering using the link above or clicking here: Register

ALPS & PAUL Course in Carrara, Australia Tuesday June 26th

ALPS (Advanced Locking Plate System) has significant advantages in terms of biology and biomechanics when it comes to fracture management. The key principles and hands on experience will be part of this day course. The other subject for this day class is the PAUL (Proximal Abducting Ulnar Osteotomy) which is a new method to use for our patients with Elbow Dysplasia, either in the early phase of the disease or to ameliorate the chronic consequences of the disease. This is accomplished by modifying the load profile across the elbow, reducing the medial compartment pressures that are now known to be a significant cause of pathology and pain. The technique devised by Ingo Pfeil (Germany) has been used by over 30 surgeons worldwide (myself included). This is your chance to understand the rationale behind the technique and become familiar with the application of the technique in your patients.

Short Radius Syndrome

Don’t miss this opportunity. So far this course has been given in Europe and the USA only. This opens up the opportunity to use this technique to Orthopaedics Surgeons from the Southern Hemisphere without the “Long-Haul”.

Find out more by clicking here

If you have any queries of course you are welcome to post them here, but why not have a look on the Kyon website first as this will most likely answer your queries.

I know there are a good number of iPhone App users in the Southern Hemisphere in general and in Australia in particular. It would be great to meet you on one or both of these courses.

Tibial Tuberosity Advancement Planning Part 1: Radiographic Considerations

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First let me apologise for the lack of posts recently…things have been a bit hectic in the past couple of months. We now have over 1200 users accessing the site via the iPhone App which is fantastic. The key with these things though is user interaction, so if you have any comments or queries regarding this or other posts, don’t hesitate to feedback.

Introduction

This series is drawn from a presentation I prepared and presented at last weekend’s TTA training course at Zurich Vet School and at the Kyon Symposium 2012 again in Zurich. The point of this series is to explore the variables regarding post operative TTA radiographs and using our planning to control these, thereby getting a more consistent piece of surgery with more consistent outcome for our patients and clients. TTA (when performed with Kyon implants) is a procedure which forgives the surgeon for a reasonable amount of deviation from the ideal post operative appearance in most cases. It is for precisely this reason that we as surgeons need to be more diligent in terms of our planning. This sounds like a contradiction but if we consider that the ideal outcome will be derived from the ideal modification of the geometry of the tibia, when we miss the mark, we may not give our patients all of the potential benefits that have been shown to be associated with Tibial Tuberosity Advancement (TTA) such as normalisation of intra articular pressure profile and therefore the long term benefits that may be associated with this unique attribute (progression of DJD, Incidence of Late Meniscal Injury etc). So the surgeon “gets away with it” but our patients may not!

Goals of Planning

There are four main goals in our TTA planning:

Determining Optimal Plate Size.
Determining Optimal Plate Position.
Determining Osteotomy Position and Orientation.
Determining the required amount of advancement to give a 90 degree relationship between the Straight Patellar Tendon and the Tibial Tuberosity.

This post will deal with the key to establishing these measurements/assessments which is optimal positioning for radiography.

Basis for Precise Planning

It is not possible to achieve optimal planning from suboptimal radiographs. The key variables are:

Stifle Angle.
Rotation (Femur and/or Tibia).
The presence of femorotibial subluxation.

These must be controlled prior to engaging in planning for TTA.

1. Stifle Angle

There has been a bit of confusion here. The key is to remember that TTA is designed to provide femorotibial stability in stance phase. For this reason, all of the templating should be performed with the stifle in the normal standing angle on the mediolateral projection. This will vary from breed to breed and patient to patient. Previously people suggested that the stifle should be at 135 degrees extension, this should not be used for the reasons just stated. It can be difficult to assess the normal standing angle in cruciate deficient patients as, if the condition is unilateral, the contra lateral limb is likely being held in slight hyperextension to offload the affected limb, if it is bilateral, the patient’s pathological standing angle will be altered too. For this reason we should not simply rely on the person positioning the patient but go to the patient and palpate the Straight Patellar Tendon (SPT), if this feels to have low tone, then we are in an overextended position for that patient if it is very taut then we are likely in hyper flexion, we should use our experience in this assessment. If we see the following appearance on the radiograph then we are definitely hyper extended:

Note the wavy appearance of the Straight Patellar Tendon indicating Hyper Extension.

This abnormality is easily identifiable and the stifle should be re positioned to eliminate this appearance. Measuring advancement from hyper extended radiographs will underestimate the required amount of advancement and therefore influence post operative stability and all that may result from this.

2. Rotation.

Measuring from radiographs with rotated femur and/or tibia will seriously affect our measurement in terms of plate, advancement required and osteotomy position and orientation. We should reposition the patient until we have the ideal. Whilst there are adjustments we can make in our templating in radiographs with a rotated femur, it will always be more precise if our templating is from perfect mediolateral projection with femoral condyles superimposed. We will return to the issue of femoral rotation when we look at assessment of advancement. For now we will focus on Tibial rotation.

Given that the Cranial Cruciate Ligament (CCL) limits internal tibial rotation, pathology of the CCL will result in increased internal tibial rotation and therefore this is the most common problem encountered. We first need to be able to recognise when this has happened, and this is not as easy as determining femoral rotation. The key areas to look at are:

The caudal cortices of the Tibia.
The relationship between the Tibia and the Fibula.
The definition of the distal aspect of the Tibial Crest.

The images below show Perfect unrotated, internally rotated and external rotated isolated tibias:

The Tibia is perfectly positioned. The asymmetry of the caudal tibial cortices is minimal.

The Tibia is externally rotated and the medial cortex of the tibia is in a cranial position.

The Tibia has been internally rotated and the lateral cortex is now positioned cranially.

The degree of rotation above is not exaggerated beyond that which we may commonly encounter in our radiography pre surgery. The following image shows the change in relationship between the Tibia and Fibula associated with rotation of the tibia.

Left: Normal, Middle Internal Tibial Rotation, Right External Tibial Rotation

The Image below shows the impact on the definition of the Tibial Crest of the same types of rotation (this can also be seen above). The effect of this will vary between patients but in general if it is difficult to identify the distal aspect of the crest on the radiograph, go to the patient and palpate this area. If you can feel it distinctly in the patient, you should be able to see it on the radiograph!

3. Femorotibial Subluxation

If the tibia is cranially displaced (due to CCL pathology) on our planning radiograph, this will have a variable impact on our estimation of required advancement as the Tibial Tuberosity is already advanced. We need to identify landmarks that may indicate that this is present. These are:

The relationship between the Tibial Eminence and the intercondylar region of the femur.
The relationship between the caudal aspect of the tibial condyles and the femoral condyles.
The relationship between the Origin of the Long Digital Extensor Tendon and the Sulcus for this tendon on the tibia.

The image below shows these points. If we identify subluxation, we need to correct it before proceeding to templating otherwise we will undersize the cage and fail to achieve sufficient advancement. Note also that the tibia and femur are rotated on the radiograph below as identified by a lack of superimposition of the femoral condyles, indistinct fibula, indistinct distal aspect of the crest and increased distance between the tibial cortices.

If we avoid these three potential pitfalls, we will be more likely to achieve reliable measurements in our planning that will guide our surgical execution and determine our surgical outcome. We need to make precise measurements from well positioned radiographs in order to deliver the perfect opportunity for perfect outcome.

Next… Plate Size and Position.

TTA or Not?

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The new VCOT (Veterinary Comparative Orthopaedics and Traumatology) journal arrived in my mailbox yesterday with interesting articles. However again my eye was drawn to an advert, this time from Veterinary Instrumentation advertising the Modified Maquet Technique. The image in the advert is drawn from an article in the 3/2011 version of VCOT. I have to dig through my back catalogue for the article itself but that can wait for another post. In the advert the following image is shown of the one month post operative radiograph:

1 month Post Op: Scanned from image in advert using iPhone

Now, I think even the untrained eye will look at this and wonder whether that cage is big enough. Remember the goal of TTA is to advance the Tibial Tuberosity to the point where the Straight Patellar Tendon is at 90 degrees to the common tangent. TTA is not just pushing the Tibial Tuberosity “out a bit” and getting it to stay there long enough to heal! There is no calibration device on the published image but I have been working on a TTA planning App (almost finished) which will draw all lines based on the selection of a few points. If the image is calibrated it will return sizes in mm and give optimal cage size and position. Even without this however it will draw the line representing required post op position of the Tibial Tuberosity. The image generated is shown below:

The cranial white line is the desired position for the Tibial Tuberosity Post Surgery.

Even with the cage in position, the Tibial Tuberosity is under advanced by just less than the cage size inserted. As the Tibial Tuberosity is under advanced, the benefits derived from TTA will not be realised (Stable stifle in stance phase, normalised intra articular contact pressure etc.).

It also appears from the first image that the cage has sunk into the caudal aspect of the osteotomy. This leaves an unaccountable variable when choosing cage size because one would have to calculate the required cage size and then add the unknown amount of sinking to the cage to achieve desired advancement. Almost certainly this embedding of the cage in the bone has arisen due to the lack of plate support.

What do you think? Is this a TTA?

Diagnosing CCL Rupture Part 2: Radiography

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Further Diagnostic Techniques 1

Radiography

The image shows the effects of increased joint fluid production on the soft tissues around the joint. These are non specific changes that do not definitively diagnose CCL pathology. We may also see evidence of Degenerative Joint Disease (DJD) and the extent of these changes will be influenced by chronicity and to some extent breed.

Radiograph showing reduction in Infrapatellar Fat pad and deviation of the caudal fascial plane secondary to increased Synovial fluid volume (effusion)

As with most orthopaedic radiography, positioning and correct exposure is essential to pick up these often subtle radiographic features. Over flexion of the stifle for example as in the image below will often reduce the appearance of the signs of effusion noted above. In the top case, the reduction in Infrapatellar shadow can be seen but the caudal fascial plane distortion is absent. Whilst the second radiograph obscures all meaningful information.

The 90 degrees of flexion seen here will often obscure the signs of effusion

This extreme flexion eliminates almost all meaningful information regarding synovial fluid volume.

Radiograph showing cranial tibial translation

This radiograph shows cranial tibial translation indicative of CCL rupture

Recommendation

The position of the stifle becomes even more critical in cases where TTA is planned. In general the current recommendation is that the stifle should be positioned in extension. This is not the often quoted 135 degrees but whatever represents the normal standing angle of the patient’s stifle. The third radiograph above whilst diagnostic of CCLR should not be used for templating for TTA as the tibia is already in a pathologically advanced position. This will reduce the accuracy of the required advancement for the procedure.

The craniocaudal view is less important in terms of diagnosing CCL pathology but is an essential view to rule out other pathologies that may result in effusion such as Femoral condylar osteochondrosis dissecans and neoplastic processes.

Conclusion

Essentially all effusion indicates is Active Joint Pathology. When this appearance is combined with appropriate history and patient age and breed, it may point in the direction of CCL pathology but is not Diagnostic.

Coming next… Synovial Aspiration and Palpation.

When is a TTA not a TTA part 2 a

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I apologise in advance if this post is more of a “rant” than a post. I received my copy of Veterinary Comparative Orthopaedics and Traumatology the other day and saw this advert on the back page:

VCOT 5/2011 Back Page

This post should not be construed as being anti-Securos, but it goes to the heart of what is and what is not a TTA. The procedure was devised and improved by Kyon in association with Pierre Montavon, no patent was established for the technique and thus there is a flood of “me-too” products on the market. Very few Veterinary Orthopaedic Manufacturers do not now have a “TTA” system. The problem I have with this is that it confuses any consideration of complication rate associated with the procedure. It introduces a new variable and in my view, never has the variability been higher than it is in the manufacture, quality control and appearance of “TTA” implants.

The advert above states:

Faster and easier placement: How much easier and faster exactly? The TTA is a very forgiving procedure and I cannot see that there is any need for this procedure to be easier or any supporting evidence for this claim. The duration of surgery has an impact on Post Operative infection rate. But what is the claim here, that it halves the procedure, reduces it by 5 minutes, is faster for one specific surgeon or all surgeons?

No Fork: The benefit claimed here is that it offers greater versatility in contouring the plate. I have never felt constrained in my contouring by the fact that I am using a fork.

No Hammering: The benefit stated here is that you can separate the Tibial tuberosity and then apply the plate. This sounds fiddly and does not immediately suggest any great benefit over incomplete osteotomy and fork introduction. I would imagine that most surgeons using this system still perform a partial osteotomy, attach the plate and then complete the osteotomy.

More Flexibility: The benefit claimed here is that the plate can pivot around the top screw hole. The top hole is the key hole in the TTA and it is failure to plan for the position of this that causes most problems in aligning the plate. The ability to pivot the plate around an incorrectly positioned top hole does not immediately suggest benefit. The aim should be to plan carefully and execute precisely and no implant design will ever make this unnecessary. Strong Plan-Good Execution-Post Op check and learn. These are the keys to good TTA surgery.

Less Holes in Bone: Fewer stress risers is the claim here. The problem with screw placement as any Orthopaedic Surgeon knows is when the screw is tight and when it is not. The potential for fracture of the tibial tuberosity would be more highly associated with over tightening and misdirection of the screw than having a smaller number of holes in my opinion. A crack around the far side of the screw hole would be potentially more problematic than an increased number of holes. We have never seen (in over 700 cases) any issues associated with fork placement and subsequent failure.

No Forks: Less inventory. That is certainly true.

Less Complications: This is the big claim here and I suppose the main reason for my rant. This is apparently being “researched at the moment”. If it is still being researched, how can any conclusion be drawn? Complications associated with TTA are generally due to surgeon error (as long as the implants used are of sufficiently high quality), so the view that the XGen plate is associated with fewer complications seems spurious and I would like to see statistical data before this claim can realistically be made in an advert. I would also like to see a reference to peer reviewed article cited as a reference for this claim. Surely the statement “Less complications” when referring to a product or procedure should be followed by “…than XYZ”, the statement then is rather “empty” as it doesn’t reference the object against which it is being compared.

So when is a TTA a TTA? When it is a Kyon TTA! I think that any future papers on TTA should indicate the source of their implants in order that like to like comparisons of outcome and complications can be made.

When is a TTA not a TTA?

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This may seem like a strange question, surely TTA is Tibial Tuberosity Advancement. I suppose we need to ask how we know when anything is anything. We could argue that we know for example that a table is a table because it looks like a table. If we follow this argument then appearance to the senses is the defining characteristic of the object.
Function is also used to define an object. From a functional perspective, a table is an object that functions to hold objects in a stable position above the level of the ground. The inclusion of function with regards to correctly identifying an object is generally more powerful than observing its appearance. A garden trampoline looks like a table, but it certainly wouldn’t function as one. This would be an example of understanding that one object is not another despite sharing similar appearances as a result of lacking the characteristics that permit it to function as the true object.
In reality an object is a table when it functions as a table. Anything else is not a table. Function is derived from the various parts of the object acting to perform a specific action or behave in a specific way and therefore many things that function in a similar way will have similar parts arranged in a similar way. It is this last fact that often leads to the classification of objects by appearance and this often leads to reaching the wrong conclusion regarding the identification of an object.
How can we apply this to the question in the title: “When is a TTA not a TTA?”. Well I suppose if we go back to our analogy we would argue that it is when it looks like a TTA and functions like a TTA. On that basis, it is not a TTA if it simply looks like one!
My Definition of TTA: The definition of a TTA is an opening osteotomy of the tibia in the craniocaudal plane such that the tibial tuberosity comes to occupy a position cranial to the proximal tibia resulting in an angle between the Straight Patellar Tendon and the Tibial Plateau of 90 degrees. The advanced tibial tuberosity is held in this position by a plate anchored to the tibial tuberosity and the tibial diaphysis and a cage of variable size. The osteosynthesis should be of sufficient strength to withstand the distractive pull of the Quadriceps mechanism to permit the osteotomy gap to fill with bone.

A TTA...or is it?

So that is all about appearance then, there is a gap, there is a plate, there are screws and there is a cage. The key part of that (overly long) sentence above though is “resulting in an angle between the Straight Patellar Tendon and the Tibial Plateau of 90 degrees”. That sentence is key because it is that aspect of the appearance that gives TTA its function. If we have a set of post op radiographs following TTA and that element is missing then:

That is not a TTA

No combination of plate, screw, fork, cage is a TTA unless it stabilises the cruciate deficient stifle. The goal of TTA; neutralisation of the cranial displacement of the tibia in a Cruciate Deficient stifle has been shown to be achievable by Kim and Pozzi. Their work is “Proof of Concept”. The goal is however only achieved when the angle of the common tangent of the femorotibial joint is perpendicular to the Straight Patellar Tendon. Surely if this is the goal, and we do not achieve it; we have failed.

Question: How many surgeons measure the relationship between the Common Tangent and the Straight Patellar Tendon Post Operatively? Be honest now. Instead, the tendency is to focus on the implant position, the osteotomy and so forth. This is the same as someone selling a Trampoline as a table! Failure to understand how something actually functions leads to the production of things that look similar but do not possess the appropriate mechanical characteristics.

Call to Arms: If you are a TTA surgeon, measure how close to the goal you got.

Did we even get close to the target? Did we hit the Bull’s eye? If you don’t check the target after you shoot, you won’t know! If you don’t check your post op radiographs for proximity to the goal, you won’t know either.

So if we write in our clinical notes: Performed TTA, but don’t follow that statement with ” and achieved a post op angle of 90 degrees” then the first statement was wrong.

This is the first in a series of articles on TTA. If you are the kind of reader that likes a conclusion, then here it is:

Cranial Cruciate Rupture and TTA (part 1)

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The Cranial Cruciate Ligament (CCL) maintains the stability of the Tibia relative to the Femur when the foot is in contact with the ground. It stops the Tibia from sliding forward when weight is put on the limb. When the CCL is weak or completely ruptured, it is unable to maintain this stable relationship. As a result the knee gives way under the patient when they transfer weight onto the affected limb. This is an unusual experience and causes pain by stretching the joint capsule. The patient responds by reducing load through the leg and this results in the appearance of the lameness. In man this is usually caused by an injury, whilst in most dogs this happens because the ligament weakens prematurely. This process can begin as early as seven months of age. Unfortunately in many breeds such as Labradors, Rottweilers, Retrievers, Boxers and Springer Spaniels; this will occur in both stifles simultaneously. This can result in severe poverty of action in the hindquarters, making it difficult for them to stand up and they may need help to get up from rest. This can also be seen in Hip Dysplasia which has a similar breed predisposition and is often present in dogs with CCLR. This can result is some confusion from time to time regarding the diagnosis. Cranial Cruciate Ligament Rupture requires surgical management for a successful outcome.

Tibial Tuberosity Advancement

There are many techniques to stabilise the Cranial Cruciate Deficient stifle. Tibial Tuberosity Advancement (TTA) is our favoured method management for the reasons discussed below. TTA was devised by Slobodan Tepic (Kyon) and Pierre Montavon (University of Zurich) and is used worldwide to restore stability instantaneously to the Cruciate Deficient Stifle.

Torrington Orthopaedics and Tibial Tuberosity Advancement

Why TTA?

TTA is a procedure that has a repeatedly excellent outcome in our hands. Patients are using the limb within a few days of surgery and require very little Rehab input to achieve excellent outcomes. The implant quality and design from Kyon is second to none and this makes us comfortable to use this technique in the entire spectrum of sizes of and lifestyles of our patients. Recent work by Kim and Pozzi has shown that TTA is the only technique that normalises the stresses in the stifle post surgery. TPLO has many of the benefits in terms of early limb use and so forth, but research from the same group shows that TPLO increases the stresses in the medial (inner) compartment of the stifle. We do not want to provide a stable stifle that will result in increased wear of the medial compartment over time.

Many practices do TTA why should we choose Torrington Orthopaedics

We have performed over 650 TTAs.
All of our surgeons have been trained directly by Kyon at one of their approved courses and two of the surgeons here (Andy Torrington and Turlough O’Neill) are instructors for the Kyon course.
Torrington Orthopaedics is the only UK venue for Kyon TTA training courses.
Our close association with the originating company means that we are at the forefront of developing and enhancing the technique.
We only use Kyon implants and not the cheaper and often poorly manufactured “Me too” products on the market.
Our implant failure rate was zero in this set of 650 patients.
Our complication rate was less than 1%.