Here you get all information about TTA (tibial tuberosity advancement) for dogs. Watch surgery videos and read in detail about the best surgery method to heal a dog knee – TTA RAPID implants.
Tibial Tuberosity Advancement (TTA) – How to do the surgery
Tibial Tuberosity Advancement is a popular technique to heal a cruciate ligament rupture of a dog. Here you find detailed information how to do a surgery with TTA RAPID. First of all you see a short 3D-video-animation of the surgery. And after that you can read in detail the surgery instruction. Firstly you begin with the pre-operative planning: how to do the x-ray and how to find the right TTA cage size. In the next step we introduce the TTA instruments you need to implant the cage into the dog knee. You see how to saw the tibia bone with the TTA RAPID saw guide. The point “Gerdy’s Tubercle” helps us with the orientation.
Later we carefully open the osteotomy with the spreader instrument. And finally you see how to implant the cage into the tibia.
IMPORTANT: For being able to do a TTA RAPID surgery on your own we deeply recommend to participate a workshop – for example with Dr. Yves Samoy, Ghent University, BELGIUM. Just having read this article is not sufficient.
So let’s get an overview of tibial tuberosity advancement by watching a TTA surgery:
Tibial Tuberosity Advancement (TTA) – Pre-Operative Planning
The dog is placed in a dorsal recumbency with the affected limb suspended from a stand. Make sure that the dog’s paws are not fixed too tightly, since the affected limb will be put against the table later in the TTA surgery. Preferably, the joint is investigated to assess the menisci and cranial cruciate ligament remnants. Remedial action is taken as necessary. TTA-Rapid is performed through a medial skin incision.
Calculating the tibial tuberosity advancement (TTA)
Calculating the tibial tuberosity advancement can be done in a different ways (classic TTA template (Kyon, by Slobodan Tepic); common tangent technique (Dennler); 2.07 x Tibial plateau length (Inauen); MMP Procedure (Ness); …). However, none of these techniques are perfect. A critical mind is advised when applying those measurements.
Use of the TTA RAPID template before the TTA surgery
1. Where possible, calibrate the radiograph of the dog knee on the screen to real size.
2. Place the TTA template over the radiograph and choose the appropriate TTA cage width.
3. Adjust the template position until the cage sits about 3mm below the proximal cortex on its caudal edge. Now measure the thickness of the cranial tibial cortex in the region of the black dot.
Tibial Tuberosity Advancement (TTA) Values
Note this values, you will need it during surgery: XX / YY/ Z
XX = Size of Implant from Template
YY = Implant deep (you find out, after the saw cut)
Z = thickness of the cranial tibial cortex in the region of the distal end of the osteotomy.
TTA Instruments
Now let us introduce the most important instruments you need to do a tibial tuberosity advancement with TTA RAPID. All instruments are contained in the TTA RAPID instruments set.
TTA Saw Guide
The TTA RAPID saw guide is an L-shaped device developed to facilitate the correct position of the osteotomy. It has been developed to ensure a sufficiently large cranial fragment is created for screw placement. The vertical arm of the guide has 2.5mm holes placed at strategic points, over a 1mm wide slot. The numbers beside the holes correspond with the size of the cage. This will prevent making a too distal osteotomy. The horizontal arm of the guide is a scale in millimeters. This will prevent making a too caudal osteotomy.
TTA Spreader
The TTA instrument set contains two spreaders with each two different working ends. These spreaders are used to carefully open the osteotomy. In addition to that the instruments set also contains bending irons, a depth gauge, drills, pins and a screw driver.
Tibial Tuberosity Advancement (TTA) – Surgery Video (live)
Before going in detail how to do the surgery itsself – let us watch a video about what is coming now.
TTA Surgery: Sawing the Osteotomy
Tibial Tuberosity Advancement – Tibial Tuberosity Advancement – Tibial Tuberosity Advancement – Tibial Tuberosity Advancement
1. A 2.5mm pin is placed through the joint capsule at the intersection of the femoral condyle and the tibial plateau. On the lateral side, the pin should start slightly in front of the level of “Gerdy’s Tubercle”. This pin is used as the proximal fixation of the saw guide.
2. The saw guide is dropped over the pin using one of the numbered holes in the vertical arm, corresponding with the size of the cage measured during pre-operative planning.
3. A peg is placed into one of the holes in the horizontal arm of the drill guide, selecting the number of millimeters measured during pre-operative planning.
4. Press the saw guide against the medial aspect of the tibia with protruding peg forced up against the cranial side of the tibia. Hold it in that position. Correct use of the drill guide will place the osteotomy just caudal to the cranial cortex of the tibia. (As a guide: In a large dog the cortex is approximately 5mm thick and in a small dog approximately 3mm.) DO NOT PRESS THE HORIZONTAL ARM AGAINST THE BONE, AS THIS WILL CAUSE AN OBLIQUE OSTEOTOMY!
5. Use the saw guide to create the osteotomy. Optionally, a blade can be used to open the fascia/periostium prior to the osteotomy.
TTA surgery: Opening the osteotomy
1. Depending on the required cage size, different osteotomy spreaders can be used to spread and hold open the osteotomy. Provided this is done carefully and slowly, allowing the bone time to adjust, the hinge is unlikely to fail. This being the most critical point of the surgery, the spreaders should be used with great caution!
2. Start with the 3mm spreader held sideways (thinnest part) located at the most proximal part of the osteotomy and gently turn it to spread open the osteotomy. Always turn the spacer downwards to minimise the forces on the fragment. A second spacer/spreader held sideways in the distal region of the osteotomy can be used to maintain the displacement.
CAUTION: DO NOT USE THIS 2ND SPREADER TO INCREASE THE DISPLACEMENT, AS THIS WILL CAUSE BREAKING OF THE CORTEX!!!
Repeat these steps until the required displacement isreached.
The proximal end of the colour coded sheet metal guides can be inserted into the osteotomy and is usefull to check the level of advancement of the tibial tuberosity.
3. he depth of the osteotomy is measured with a depth gauge at the proximal extent of the osteotomy. This measurement is rounded up to select the correct cage length.
TTA surgery: Fixating the TTA cage
Tibial Tuberosity Advancement – Tibial Tuberosity Advancement – Tibial Tuberosity Advancement – Tibial Tuberosity Advancement
1. The ears of the cage need to be bent using the bending stick. TTA implant ears on the caudal side (tibia) should point slightly upwards, while the ears on the cranial side (crista tibiae) should be tilted slightly downwards. Slight under-bending of the caudal ears and slight over-bending of the cranial ears will help compress the osteotomy against the cage.
2. Elevate the periostium from the bone in the region where the cage will be fixed.
3. Insert the TTA cage into the osteotomy. Use bone forceps to make sure the ears of the cage are in close contact with the bone.
4. Once the TTA cage is in place, check if the height of the cage is correct. This can be done by palpating the proximal tibia with the tip of a small mosquito clamp. You should feel about 3mm of bone above the top of the cage. More bone means a more distal placement of the cage and thus subsequently a more cranial displacement of the tibial tuberosity.
5. Large bone forceps can be used to give extra compression on the cage. This step is not essential if the distal cortex is still intact, but will result in a better bone contact with the TTA cage.
6. 2.4mm screws are inserted into the TTA cage. Start with the most cranial, most proximal screw.
The orientation of the screws should be medio-proximal to latero-distal (similar as the orientation of the fork in a standard TTA).
The second screw is the caudo-proximal screw. The orientation of this screw is cranio-medio-proximal to caudo-latero-distal (“Away from the joint, away from the osteotomy site”).
The rest of the screws are placed in the same fashion starting with the most proximal screws.
Once all screws are inserted, remove the bone forceps and re-tighten all screws.
7. Insertion of Hydroxy-Apatite paste inside and underneath the cage will accelerate healing of the osteotomy. Close the fascia where possible.
8. Close the wound in a routine fashion.