This step-by-step guide details the management of a cruciate deficient stifle using the TTA RAPID® Technique. It is recommended to view the videos and animations along with this guide.
Overview
IMPORTANT REMINDER: We strongly advise attending one of the TTA RAPID® workshops to acquire the necessary skills for performing TTA RAPID® surgery independently. This article is designed to offer guidance, but merely reading it is not adequate preparation.
Watch the following animation video to get an overview of the TTA RAPID® Technique.
Pre-Operative Assessment and Planning
Tibial Tuberosity Advancement (TTA)
Using good quality radiographs is necessary to calculate the degree of tibial tubercle advancement which will bring the tibial plateau to sit at 90 degrees to the straight patella ligament. Several methods of calculating the required advancement are available and each have their strengths and weaknesses.
TTA RAPID® Cages for advancement are available in 2.0, 3.0, 4.5, 6.0, 7.5, 9.0, 10.5, 12.0, 13.5, 15.0, 16.5, and 18.0 mm widths in a range of lengths. With the traditional method and the common tangent technique accurate positioning is key. The stifle should be in the reduced position and at a 135° flexion angle.
Calculating the Advancement
Calculating the tibial tuberosity advancement can be done in different ways: classic TTA template (Kyon); common tangent technique (Dennler); 2.07 x Tibial plateau length (Inauen); MMP Procedure (Ness). However, none of these techniques is perfect. A critical mind is advised when applying these measurements.
Using the TTA RAPID® Template
Using the TTA RAPID® template provided, a visual check is performed to confirm cage selection. The template is adjusted so that one of the lines extending proximally from the cage represents the chosen line of the osteotomy. The template is positioned so that the top of the cage sits approximately 3mm below the proximal extent of the tibia along this line and that the Maquet hole marker on the template just touches the cranial cortex. The calculated advancement and the thickness of the cranial cortex in the region of the simulated Maquet hole are recorded for later use. Note that each cage width requires a unique osteotomy length. The final length of implant is determined intra-operatively. The approach is through a medial skin incision.
Note the TTA Values
Note the following values as you will need them during surgery: XX / YY/ Z
What you will need
Essential Instruments
TTA RAPID® Saw Guide
The TTA RAPID® Saw Guide is an L-shaped device developed to facilitate accurate positioning of the osteotomy. It was designed to ensure that 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 next to these holes correspond with the size of the cage, preventing the osteotomy from being too distal. Additionally, the horizontal arm of the guide serves as a millimeter scale, preventing the osteotomy from being too caudal.
Product Code | Description |
|---|---|
132-4040-00 | TTA RAPID® Saw Guide, for cage sizes 6-15 mm |
132-4041-00 | TTA RAPID® Saw Guide, for cage sizes 3-4.5 mm |
132-4042-00 | TTA RAPID® Saw Guide, for tiny cage sizes 2-6 mm |
132-4030-10 | TTA RAPID® Saw Guide Pin, Ø 1.0 mm |
TTA RAPID® Spreader
The TTA RAPID® Lever Spreader is used to carefully and incrementally open the osteotomy to the required width. Available in three double-ended sizes, the spreaders measure 1mm wider than their stated size to permit insertion of a cage beneath them.
The TTA RAPID® Universal Spreader, on the other hand, with its tensioning and fixation screw, enables incremental opening of the osteotomy in a very controlled manner.
Product Code | Description |
|---|---|
132-4080-16 | TTA RAPID® Spreader, with tensioning and fixation screw, 16 cm |
132-4080-12 | TTA RAPID® Tiny Spreader, with tensioning and fixation screw, 12 cm |
132-4015-13 | TTA RAPID® Lever Spreader, 13.5 mm & 15 mm |
132-4010-13 | TTA RAPID® Lever Spreader, 6 mm & 12 mm |
132-4000-13 | TTA RAPID® Lever Spreader, 3mm & 9 mm |
TTA RAPID® Bending Iron
The TTA RAPID® Bending Iron is used for contouring the cage ears for accurate placement and is common to the original and modified techniques.
Product Code | Description |
|---|---|
132-4020-00 | TTA RAPID® Bending Iron, 120 mm |
TTA RAPID® Instrument Kit
The TTA RAPID® Instrument Kit contains the essential instruments that you would need to perform a TTA RAPID® surgery. It includes a sterilization tray, two TTA RAPID® Saw Guides + K-wires, TTA RAPID® Saw Guide Pin, two TTA RAPID® Lever Spreaders, a depth gauge, a drill guide, plate holding forceps, screw driver handle, screw driver shaft + holding sleeve, and a twist drill.
Joint Surgery
Performing a lateral arthrotomy?
If performing a lateral arthrotomy, leave open about the last centimeter of the joint capsule closest to the tibia. This allows enough slack to later perform the advancement.
TTA RAPID® Surgery Protocol
A step-by-step guide
The dog is positioned in dorsal recumbency, with the affected limb suspended from a stand. Care should be taken to avoid securing the dog's paws too tightly, as the affected limb will later be placed against the table during the TTA surgery. Ideally, the joint is thoroughly examined to assess the condition of the menisci and any remnants of the cranial cruciate ligament, with appropriate remedial measures taken if needed. The TTA RAPID® procedure is then initiated through a medial skin incision.
1. Sawing the crista tibiae
1.1
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.
1.2
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.
1.3
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.
1.4
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.)
Important: Do not press the horizontal arm against the bone as this will cause an oblique osteotomy!
1.5
Use the saw guide to create the osteotomy. Optionally, a blade can be used to open the fascia/periostium prior to the osteotomy.
2. Opening the osteotomy
2.1
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!
2.2
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 second spreader to increase the displacement as this will cause breaking of the cortex!
Repeat these steps until the required displacement is reached. The proximal end of the colour coded sheet metal guides can be inserted into the osteotomy and is useful to check the level of advancement of the tibial tuberosity.
2.3
The 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.
3. Fitting the cage
3.1
The ears of the cage need to be bent using the bending iron. TTA RAPID® 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.
3.2
Elevate the periostium from the bone in the region where the cage will be fixed.
3.3
Insert the TTA RAPID® cage into the osteotomy. Use bone forceps to make sure the ears of the cage are in close contact with the bone.
3.4
Once the TTA RAPID® 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.
3.5
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 RAPID® cage.
3.6
2.4mm screws are inserted into the TTA RAPID® 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 retighten all screws.
3.7
Application of Hydroxyapatite Paste inside and underneath the cage will accelerate healing of the osteotomy. Close the fascia where possible.
3.8
Close the wound using standard techniques.
CAUTION:
Patients undergoing TTA RAPID® surgery frequently experience a subjective sense of greater comfort during their initial post-operative recovery compared to those undergoing alternative osteotomy procedures. Nevertheless, it's crucial to acknowledge that TTA RAPID® involves a substantial and significant osteotomy. Therefore, both meticulous patient selection and comprehensive education for pet owners regarding post-operative management are imperative.
4. Post-Surgery Care
4.1
Casting / Bandaging is generally not required.
4.2
A light dressing can be applied for 3 to 5 days.
4.3
NSAIDS are provided for 3 to 4 weeks.
4.4
With the application of Hydroxyapatite Paste, clinical union can generally be anticipated within 6 weeks.
Questions?
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TTA RAPID® & RAPID Patella Luxation
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