Since the beginning of the millennium, locking plate technology has revolutionised TPLO surgery, more than any other surgical procedure.
Locking TPLO plates have made the procedure quicker and simpler with less dissection, less biological trauma, and osteotomy stability is much better. The risk of tibial tuberosity fracture and tibial plateau rock-back is much reduced.
TPLO locking plates use locking screws in the proximal tibial plateau segment and the plate is pre-contoured to match the shape of the proximal tibia. This means that the plate does not need to be contoured by the surgeon to the shape of the proximal tibia during surgery. This, saves time and avoids possible plate weakening caused by contouring.
The plate is designed so that the position and direction of the locking screws in the tibial plateau are angled distally away from the joint, and away from the osteotomy. This means that so long as the plate is placed correctly, intra-articular screw placement should be impossible. This is a major advantage as the potential for intra-articular screw placement is almost completely eliminated. To ensure this guarantee against intra-articular screw placement, the plate should not be contoured.
As locking plates do not rely on friction generated between the plate and the bone for stability, it is no longer necessary to elevate the soft tissues beneath the locking part of the plate (i.e. the medial buttress).
This is beneficial as removing the medial buttress involves unnecessary dissection, can be time consuming, causes bleeding, and could damage the medial collateral ligament damage with over-exuberant buttress removal.
As locking screws are angle stable, placement of locking screws in the tibial plateau segment means maximal stability of the tibial plateau. The chances of post-operative instability of the tibial plateau segment developing are minimised which is good as instability can lead to loss of osteotomy reduction, and increase in tibial plateau angle, known as “rock-back”, ot tibial tuberosity fracture.
Locking screws are very stable because of locking of the thread of the screw head into the thread of the plate hole i.e. metal to metal for these locking screws, the risk of stripping a screw in the soft cancellous bone of the tibial plateau is now impossible.
To use locking plates for TPLO surgery, a slightly expanded inventory of implants and equipment is needed. This includes:
Locking TPLO plate,
Locking drill guide,
Drill bit appropriate to the core diameter of the locking screws (e.g. 2.8mm for a 3.5mm locking screw),
Thus use of locking plates for TPLO surgery have numerous advantages but no real disadvantage. They are strongly recommended over non-locking plates.
Tips and tricks for locking TPLO plating.
The TPLO procedure is performed in the normal way, except that soft tissue / medial buttress elevation in the proximal tibial plateau segment is not necessary.
Once the tibial plateau is rotated and the osteotomy is stabilised, the TPLO locking plate is applied to the tibia and positioned appropriately.
Use a K-wire or needle to probe and check the position of that joint so ensure that the plate is correctly positioned over the bone of the tibial plateau, just distal to the stifle joint.
In particular, check that the most proximal locking screw is over tibial plateau bone, just distal to the stifle joint.
Screw placement order:-
In the distal tibial diaphysis segment, a single non-locking screws is placed
to secure the plate to the bone
1. Using the locking drill guide, all the proximal locking screws are placed in the tibial plateau segment.
2. In the distal tibial diaphyseal segment, a non-locking screw is placed in axial compression mode using the compression guide to compress the osteotomy.
3. The remaining distal screws are placed; these may be either locking or non-locking screws, and depending on the plate configuration but, locking is more stable.
4. Before placement of locking screws in the distal tibial diaphysis segment, all non-locking screws must be fully tightened.
New ViL Locking TPLO Plate Range
Design features / advantages:
Contoured to the shape of the post TPLO proximal tibia.
The most proximal screw is placed just below the stifle joint but the locking hole is angled distally by 3° for the 3.5mm plate, 2.0° for the 3.5mm broad plate, 1.5° for the 2.7mm plate and 2.3° for the 2.4mm & 2.0mm plate, avoiding intra-articular placement.
3-4 proximal locking screws provide maximal screw security in soft cancellous bone of the tibial plateau.
Medial buttress removal is not necessary because of the anatomic contour of the plate and locking screws proximally.
Distal segment allows placement of:
• 2 non-locking screws including 1 for axial compression and maximal osteotomy stability.
• then choice of 1 to 2 locking/ non-locking compression screws per plate hole.
Full range of plate sizes.
Fully compatible with Vi / AO style twin-start screw locking thread profile.