Clinical Sciences, Faculty of Veterinary Medicine, University of Montreal, St-Hyacinthe, QC, Canada
Orthopaedic cerclage wires are made of medical quality stainless steel. Monofilaments are used because they are more rigid and easier to twist. They come in several diameters that are expressed in gauges (GA). The most commonly used are 18 GA in dogs and 20–22 GA in small dogs and cats.
There are 2 types of cerclages:
- Cerclages that we need to be cut from a reel and that are twisted with an instrument.
- Periosteal elevator
- Large needle holder (Berry) or wire twister
- Loop-cerclages that are tied with a special tightening instrument.
- Periosteal elevator
- Wire tightener
- Neutralisation of forces acting on fractures
- Alone, but most frequently in combination
- Cerclages and pins, cerclages + plate/screws
- Can also be used to immobilise/stabilize bone fragments after reduction. Then a permanent mode of fixation will supplement to adequately neutralize all forces acting upon the fracture.
- Generally used in fracture repair
- Long oblique
- Comminuted when diaphyseal reconstruction is possible and when a primary mode of fixation will be used.
- External fixator
- Interlocking nail
Principles of Application
- Use when the fracture line is at least twice the diameter of bone.
- Use if the fracture can be perfectly reduced.
- Use an appropriate size cerclage.
- Use to provide a rigid and stable fixation; the cerclages must not be mobile.
- Impairs vascularisation
- Impairs bone healing
- Leads to non-union
- Apply circumferentially directly on bone, avoiding the inclusion of soft tissues and vascular supply.
- Apply perpendicular to bone.
- Use at least 2 cerclage wires.
- Space them at least 1cm apart; to avoid interference with bone healing.
- Apply them at least 0.5 cm from the extremities of the fracture line
- Use cerclage wires with other means of fracture fixation.
Hemicerclage wires can be used to:
- Prevent rotation in short oblique or transverse fractures
- Immobilize bone fragments
- Stabilize fissures
Their use implies that hemicerclages perforate/traverse at least one cortex on each side.
When traction or tension is the dominant force, the use of a mode of fixation implying a tension band is of utmost importance. We can observe a force to neutralize when a muscle group, or a tendon/ligament attaches on a bone:
- Greater trochanter, olecranon, tibial tuberosity, calcaneum, malleolus, etc.
The most efficient method to resist a traction force is by using a tension band. They are used when avulsion fractures are observed or when using targeted osteotomies in surgical approaches. We need to combine:
- 2 Kirschner wires placed perpendicularly to the fracture/osteotomy line and a figure of 8 orthopedic wire that passed through bone distally and around the 2 K-wires proximally.
This allows a perfect reduction of the fracture/osteotomy and, most importantly, the conversion of a tensile force into a compressive force!
The use of IM pins in small animal surgery started in the ‘40s. It seems to be associated with the development of anesthesia, aseptic technique, antibiotics and expertise. Despite the limitations of their use, IM rods remain the most widely used and widespread method of fixation in veterinary orthopedics worldwide.
- The most rigid implant in angulation
- Easy to put in place
- Little traumatic
- Less inventory
- Material for insertion
- Easier to remove when needed
- Do not neutralize all forces
- Dissemination of infection during open fractures, by seeding contaminants proximally and distally within the medullary cavity
Smooth stainless-steel pins are available in many sizes with a variety of tips:
- Trocar (3 sharp sides)
- Chisel (2 sharp sides)
- Threaded either at the end or at the center
(Also called K-wire)
These are very small pins <1/16” (0.5 to 1.5 mm)
- More elastic than Steinmann pins
- In small dogs and cats
- They are also used with some external fixators.
- 0.028”; 0.035”; 0.045”; 0.054”; 0.062”
- 0.7 mm; 0.9 mm; 1.1 mm; 1.4 mm; 1,6 mm
Principles of Application
- Used mostly for fractures.
- Can be introduced retrograde (through the fracture site) or normograde (through one end of the bone).
- Must fill 60 to 75% of the medullary cavity (the smallest diameter of the cavity) during fractures of the diaphysis of long bones.
- Have a minimum of 3 points of contact with the bone (insertion point, fracture cortex and metaphysis opposite to the insertion site) because their ability to reduce movement depends on the contact surface with the endosteum.
- Two or more pins can be used, as this increases the resistance to rotational forces by increasing the contact points.
- Technique called «stack pinning».
- Distal fractures or Salter-Harris fractures
- Multiple crossed rods can be used
- Resists bending forces
- But offers very little resistance to forces
- tension (axial), therefore:
- During unstable fracture
- In combination with orthopedic cerclage and/or hemicerclage wires
- External fixation device
- Independent of IM rod
- Attached to the IM rod
- Comminuted fracture whose reduction cannot be adequately maintained
- Does not require special post-operative care
- The end of the pins coming out of the bone can cause irritation and the formation of a seroma
- The pin can be removed when indicated, when the union is completed (6–12 weeks)
Other Types of Pins
- Intramedullary rod (nail) with the addition of screws inserted through the bone and stem partly proximal and distal to the stem
- Provides additional resistance against torsional and compressive forces
- Neutralizes forces that IM pins cannot
- In general, we insert 2 screws/bolts proximally and 2 screws/bolts distally
Crossed Dynamic Pins
- Either Rush pins
- (More flexible than Steinmann’s stem and offering an oblique tip for sliding in the medullary cavity and a hook at the other end)
- Either small Steinmann pins or K-wire
- Indicated for bone end fractures
- ex. : metaphysis, growth plate
- Must have 3 points of contact with the bone to ensure that the fracture is stable
- Fracture stability due to the elasticity of the pins