Tibial Plateau Leveling Osteotomy for Cranial Cruciate Ligament Rupture

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Tibial Plateau Leveling Osteotomy for Cranial Cruciate Ligament Rupture

Mary Sarah Bergh

20.1 Introduction

Cranial cruciate ligament (CCL) disease is a common cause of pelvic limb lameness in dogs worldwide and surgery is often recommended to allow a faster and more complete return to function [1]. While numerous surgical procedures have been described to treat stifle pain and instability that occur secondary to CCL deficiency, the tibial plateau leveling osteotomy (TPLO) has been one of the most commonly performed orthopedic procedures worldwide and is the only surgical procedure that has been shown to allow a return to normal clinical function [25]. Initially developed and reported by Slocum and Slocum in 1993, the TPLO eliminates cranial tibial subluxation through a rotational cylindrical osteotomy in the proximal tibia that decreases the tibial plateau angle (TPA), thereby eliminating cranial tibial thrust. The osteotomy is stabilized with a bone plate [6]. Initially, only the Slocum TPLO plate was used for the TPLO due to patent restrictions, but once the patent expired, numerous bone plates were applied to and designed specifically to be used to stabilize the TPLO. Of these, both locking and nonlocking constructs have become widely available for dogs and cats of all sizes.

20.2 Locking TPLO Plate Design

While the shape, specific design features, and the locking mechanism differ between manufacturers, locking TPLO plates share the commonality of allowing the screw to lock into both the bone plate and the bone. (Figure 20.1) As such, direct contact to the bone is not necessary for construct stability. Some locking TPLO plate designs are precontoured to match the shape of the proximomedial tibia. This feature not only minimizes the offset of the plate from the bone and subsequent working length of the screws but can also decrease surgical time.

Image described by caption.

Figure 20.1 Examples of commercially available locking tibial plateau leveling osteotomy (TPLO) plate designs. (a) String of pearls TPLO plate (Orthomed, Huddersfield, West Yorkshire); (b) Unity cruciate plate (New Generation Devices, Glen Rock, NJ); (c) Synthes locking TPLO plate (DePuy Synthes Vet, West Chester, PA); (d) TPLO CurveTM plate (Biomedtrix, Whippany, NJ). The proximal portions of plates c and d are precontoured to fit the shape of the proximomedial tibia.

Fixed‐angle locking screw holes dictate the direction that the screw can be placed. The angle of these screws is often directed to avoid the joint surface and converge in the region of maximal bone stock. The Synthes bone plate (DePuy Synthes Vet, West Chester, PA), for example, directs the proximal screw 3° distally and 5° caudally, the cranial screw 3° caudally, and the caudal screw is directed 3° cranially. This convergent placement of locking screws provides superior anchorage to bone, as compared to locking screws placed in parallel orientation and nonlocking screws, because more bone must be displaced for screw stripping to occur [7].

Several TPLO plate designs allow a combination of both locking and standard screw fixation. This hybrid fixation allows for axial compression if the nonlocking screw is placed in load fashion in a DCP hole. Such interfragmentary compression results in direct bone healing across the osteotomy (Figure 20.2). The Biomedtrix TPLO CurveTM plate (Biomedtrix, Whippany, NJ) achieves compression across the osteotomy site in a novel fashion: an angled compression hole rotates the plate to compress the osteotomy cranially, and an axial compression slot compresses the osteotomy distally (Figure 20.3). Other plate designs, such as the string of pearls TPLO plate (Orthomed, Huddersfield, West Yorkshire), allow pure locking fixation that would provide bridging fixation unless interfragmentary compression is applied with other means.

Image described by caption.

Figure 20.2 Immediate postoperative (a and b) and eight‐week follow‐up radiographs (c and d) from a tibial plateau leveling osteotomy (TPLO) performed on a 36 kg female spayed Labrador retriever using a Synthes 3.5 mm locking TPLO plate with hybrid locking fixation. Locking screws were used in the proximal portion of the plate and conventional cortical screws were used to achieve axial compression in the distal portion of the plate. Uncomplicated direct bone healing occurred across the osteotomy site.

Image described by caption.

Figure 20.3 Intraoperative photograph (a) and immediate postoperative radiographs (b and c) of a TPLO stabilized with TPLO CurveTM plate. This plate has two compression holes to allow compression across both the cranial and distal aspects of the osteotomy and is coated with a silver‐based plasma antimicrobial coating.

The Synthes TPLO plate design allows both locking screw and conventional screw fixation in all holes of the proximal portion of the plate and either one or two holes in the distal portion of the plate. When both screw types are used, the standard screws should be secured prior to the placement of the locking screws. While the author routinely uses locking screws in the proximal portion of the plate and standard screws in the distal portion, locking screws may be used in the distal portion for very large dogs, for dogs that have subjectively poor bone quality, or if stripping of the cis‐cortex of one of the standard screws occurs during insertion (Figure 20.4). A standard screw may be used in the proximal portion of the plate if the locking screw strips the drill hole or if redirection of the screw is desired to avoid crossing the osteotomy or articular surface.

Image described by caption.

Figure 20.4

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Jun 13, 2021 | Posted by in SUGERY, ORTHOPEDICS & ANESTHESIA | Comments Off on Tibial Plateau Leveling Osteotomy for Cranial Cruciate Ligament Rupture

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