Fractures of the tibia are relatively common in the dog and cat, with tibial diaphyseal fractures the most commonly encountered injury of this bone. Greater than 50% of the fractures occur in animals less than one year of age, reflecting an increased prevalence of traumatic incidents in younger animals. The various patterns of tribal diaphyseal fractures can in many instances be associated with the age of the animal involved. Non-comminuted and greenstick, or incomplete, fractures are more commonly seen in juveniles; while comminuted fractures are seen primarily in adults. The disparity in frequency of comminuted fractures in adults versus juveniles may relate to the increased brittleness of adult bone and the decrease in capacity of such bone to absorb the energy inflicted. Regardless of age, the most frequent fracture type is the spiral, oblique fracture.
Numerous methods of external and/or internal fixation have been advocated for the treatment of tibial diaphyseal fractures. The method of fixation ultimately employed is dependent upon the age of the animal and the severity of the fracture. Simple fractures may be effectively treated with closed reduction and external fixation, an intramedullary pin, a combination of cerclage and an intramedullary pin, bone plate, or Kirshner-Ehmer splints. Complex fractures are better treated with bone plates or Kirshner-Ehmer splints.
As previously mentioned, simple and/or non-displaced fractures may be successfully treated by closed reduction and coaptation, especially in immature animals. The main advantage is that blood supply to the fracture site is not disrupted by an open surgical procedure. In cases in which it is difficult to maintain a satisfactory reduction, placing through and through pins above and below the fracture site and then incorporating the pins in a cast is an especially useful technique which is simple to perform and has the additional advantages of preservation of soft tissues and blood supply to the fracture site. Complications associated with closed reduction and coaptation, including inadequate immobilization and/or incomplete reduction of fracture fragments, as well as muscle atrophy and prolonged joint immobilization have led to increased utilization of open reduction and internal fixation techniques for more complex tibial diaphyseal fractures.
Intramedullary pinning of tibial shaft fractures is a successful method of treating spiral and oblique fractures. Intramedullary pins provide excellent axial stability but minimal rotational stability, and when used alone to treat fractures, it should be applied to rotationally stable fractures only. An intramedullary pin in conjunctions with multiple full cerclage and/or hemicerclage wire may be used to provide additional rotational stability. A tibial intramedullary pin is best introduced just medial and caudal to the tibial tuberosity on the medial side of the patella ligament with the stifle flexed. While retrograde introduction of a pin from the fracture site into the proximal tibia can also be performed, if the pin is improperly placed, significant interference with stifle joint function can occur. Intramedullary pins should be removed as soon as the healing process is complete, and immature animals must be watched closely for the timing of pin removal.
External skeletal fixation devices may be applied to the tibia in a number of different configurations, depending upon the age and the size of the animal and type of fracture present. The techniques involved in the proper applications of external skeletal fixators will be the subject of a future journal article. The device may be used with intramedullary pins and interfragmentary screw fixation. External fixators are particularly useful in open fractures since the device affords rigid immobilization without invading the traumatized area. It also allows aggressive, frequent treatment of associated soft tissue wounds while maintaining rigid fracture fixation. Complications associated with external fixators include pin tract infections and pin loosening or breakage.
The repair of tibial diaphyseal fractures with bone plates is advantageous in a number of clinical situations. Plate fixation of tibial fractures is generally reserved for those fractures not associated with severely contaminated or infected soft tissue wounds. Bone plates may be placed as compression, neutralization or buttress plates, depending on the fracture configuration. In simple transverse or short oblique fractures, bone plates applied as compression plates establish early axial and rotational stability and encourage early return to activity. In spiral, oblique and severely comminuted fractures, interfragmentary compression is best achieved with individual lag screws through the plate. Following fracture reconstruction, the bone plate is applied as a neutralization plate to increase the stability of the fracture site. If complete fracture reconstruction is not attained, the fracture defects should be filled with an autogenous cancellous bone graft; and the bone plate is applied as a buttress plate. In multiple fracture patients, plate fixation of tibial shaft fractures is often more appropriate than other forms of internal fixation, as plates and screws afford the most rigid fracture stabilization and encourage early ambulation.
In summary, closed reduction and external fixation is used quite successfully on immature animals. Increased severity of fractures in immature animals leads to the use of intramedullary pins, wires, and external fixators. Bone plate application is used almost exclusively on fractures on adults. The frequent use of bone plates in the mature animal is related to the greater number of highly comminuted and severe fractures observed in the adult.
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