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16
Tibia Fractures

Kei Hayashi

Fractures of the tibia are relatively common in dogs and cats, accounting for 10–20% of all fractures [1–3]. Tibia fractures often result from trauma, and the majority of tibia fractures are diaphyseal fractures. Immediate immobilization of the crus is recommended and surgical treatment is often indicated. A variety of repair methods can be applied for tibial fractures, and the selection of repair technique depends on multiple factors, including the type and location of the fracture, the age of the animal, the presence of associated soft tissue defects and infection (particularly in open fractures), economic considerations, and the surgeon’s preference. The overall prognosis following fracture of the tibia and fibula is generally good when appropriate treatment is applied.

Locking plate (LP) systems can provide simple, reliable, and effective treatment of challenging tibial fractures, nonunions, and deformities. The application of locking plate implant systems may have several significant advantages over conventional repair options, particularly in the following four specific situations:

Diaphyseal fractures treated with a minimally invasive technique, often in a “bridging” plate function
Proximal or distal juxta‐articular fractures with a short segment of bone available for implant application
Revision of fracture repair complications including nonunions
Tibial deformity (pes varus and pes valgus) treated with corrective osetotomy/ostectomy based on the center of rotation of angulation (CORA) methods

16.1 Relevant Anatomy

The tibia has several unique anatomic features amenable to applications of locking plate systems. For example, the medial aspect of the tibia has a nominal soft tissue envelope, and therefore minimally invasive plate application can be performed easily, especially when a locking plate is used in bridging fashion. However, due to the tibia’s sigmoid shape, adequate contouring is often necessary to prevent postoperative limb deformity. Anatomical landmarks are relatively easy to palpate in the tibia, and identification of the joint space is crucial in LP application to prevent inadvertent insertion of screws into the joints, as the majority of LP systems employ fixed‐angle designs for screw placement. Wide variation in the length and shape of the tibia and fibula is seen among canine breeds. The anatomy of the tibia in cats is similar to that of dogs. The medullary cavity of the feline tibia appears to be more uniform in diameter than in dogs, but no other substantial differences have been noted.

The proximal half of the tibia is three‐sided proximally (medial, lateral, and caudal surfaces), whereas the distal half is essentially cylindrical and the entire medial part of the distal extremity of the tibia forms the medial malleolus. The proximal tibial metaphysis is relatively flat medially but is concave both laterally and caudally. All these surfaces blend into the tibial diaphysis, which is uniform in diameter but slightly S‐shaped. It curves from medial to lateral in the proximal one‐half and then from lateral to medial in the distal one‐half. The distal part of the tibia is flared slightly and forms the distal articular surface and the medial malleolus. The medial malleolus is the proximal attachment of the medial collateral ligament of the talocrural joint.

The cranial branch of the medial saphenous artery and vein and the saphenous nerve pass obliquely across the diaphysis of the tibia, and care must be taken not to injure this bundle during surgical approach to medial diaphysis of the tibia. Arteries (such as the tibial and popliteal arteries) and nerves (such as the peroneal and cutaneous nerves) run along the lateral and caudal aspects of the tibia and fibula; however, surgical lateral approaches are rarely required.

16.1.1 Practical Tips and Tricks

Locating joint spaces (stifle and tarsal joints) is crucial in LP application in order to prevent inadvertent screw insertion into a joint.
- Palpation of landmarks around stifle (e.g. tibial tuberosity, fibular head) and placement of 25G needles at the proximal extent of tibia will help locate stifle joint space.
- Palpation of medial malleolus will help locate talocrural joint space. It should be noted that the malleoli extend distal to the articular surface, and care must be taken not to place implants into talocrural joint space. In the majority of dogs, a safe corridor for screw insertion lies approximately halfway between the maximum peak of the malleolus and the start of the flare of the malleolus in the metaphysis.
The medial aspect of the tibia is well‐suited for LP application, as it has minimal soft tissue envelop and is relatively flat.
Wide variation in shape of the proximal tibia is seen among canine breeds. Examination radiographs of the contra‐lateral tibia will help identify this variation, if needed.
In general, LP systems do not require precise countering for fracture fixation. However, in the tibia, due to its S‐shaped anatomy, appropriate plate contouring is necessary to prevent postoperative valgus malalignment. Presurgical contouring of a plate using a ventrodorsal radiograph of the normal tibia as a template can help reduce operative time and facilitate minimally invasive plate osteosynthesis application.
The tibia’s S‐shape typically precludes placement of a large‐diameter intramedullary (IM) pin, and a large straight pin can cause valgus malalignment. If an IM pin is used (as a temporary reduction device, or as in a plate‐rod combination), a pin approximately 30–40% of the diameter of the medullary canal at the tibial isthmus is chosen.
The distal part of the tibia is flared slightly, which may provide some extra bone stock for screw placement, particularly when T‐plate or plate‐rod combination is chosen.

16.2 Minimally Invasive Plate Osteosynthesis of Diaphyseal Fractures

Diaphyseal fractures account for 70–80% of all tibial fractures. Oblique and spiral fractures are the most common fracture patterns recognized in small‐animal patients of all ages, whereas comminuted and open fractures are more common in mature animals. Minimally invasive plating techniques, particularly using a locking plate, have been introduced for repair of tibial fractures in an effort to improve bone healing [4–6]. This approach, also called minimally invasive plate osteosynthesis (MIPO), involves a small, medially located skin incision over the proximal and distal aspects of the tibia, remote from the fracture site (Figures 16.1–16.3) [4, 7]. A soft tissue tunnel is created between the periosteal surface of the tibia and the overlying muscular fascia connecting the two incisions (Figures 16.1 and 16.2). A plate is then slid along the surface of the tibia, and screws are applied through the proximal and distal incisions. An IM pin can be combined with MIPO application (Figure 16.3). The technique has clinical efficacy and greatly improves postoperative patient comfort, but there is no documented difference in healing times between MIPO and open plating techniques [6, 8].