Patella Luxation in dogs & cats: How to do the surgery with RAPID LUXATION
Step 1: Placement of the patient
The dog which suffers from a patella luxation 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 surgery. Rapid Luxation is performed through a medial skin incision.
Step 2: Using the saw guide
The 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 result from the TTA Rapid technique, where the saw guides were originally developed for but will also be appropriate for the Rapid Luxation technique in order to 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.
Step 3: Making the osteotomy
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 guide is dropped over the pin using one of the numbered holes in the vertical arm. The number should be selected accordingly that the osteotomy will end below the Tibia Tuberosity.
3.) A peg is placed into one of the holes in the horizontal arm of the saw guide, selecting the cortical thickness in 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 saw 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 an oscillating saw to create the osteotomy. Optionally, a blade can be used to open the fascia/periostium prior to the osteotomy.
Step 4: Placing the implants
(following the medial Patella Luxation (PL) is described. With lateraler PL proceed the placing of the implants in lateral/medial opposite site)
1.) The Rapid Luxation Plate is placed on the tibia. The osteotomy should be in the middle of the Rapid Luxation Plate. The Rapid Luxation Plate is then screwed on the caudal side of the tibia (for MPL, (place screws on the cranial side for lateral patella luxation)).
2.) The Tibia Tappet is inserted on the cranial screw holes (top and centre screw hole for the 3-hole plates) of the Rapid Luxation Plate.
3.) Then the tappet can be rotated, it fixates itself in the screw holes of the Rapid Luxation Plate and transposes the tibia crest to the lateral side. The scale (in mm) on the top of the instruments shows exactly how far tibia crest is transposed
4.) During transposition using the tappet the stifle can be flexed and extended to check if there is perfect alignment of the patella and if the patella stays in place. If the alignment is not optimal, the transposition can be further increased.
5.) Finally the spacer will be placed between the plate and the bone. The tappet can then be removed. The cranial screws can be placed. Close the fascia where possible. Close the wound in a routine fashion.
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