Fracture Fixation: External Coaptation
World Small Animal Veterinary Association World Congress Proceedings, 2014
Bianca Hettlich, DACVS
Associate Professor, Small Animal Orthopedics, The Ohio State University, Columbus, OH, USA

Closed Fracture Reduction

When a fracture occurs there is often a change of the normal anatomy and alignment of bone. The surrounding muscles respond to this change by contracting (as a response to the injury/inflammation as well as to the potential change in bone length). Even under normal circumstances, muscles constantly contract and are well toned. When a fracture occurs, the affected muscles will contract more and add to overriding and shortening of the bone. Within several days, this muscle contraction becomes more permanent since scar tissue now forms in the injured area, making it more and more difficult to stretch the soft tissues again. Fracture reduction refers to the process of replacing bone fragments back in their original anatomic position. This can either be done in a closed fashion or with an open approach.

Closed reduction: certain fractures can be reduced without surgery by careful traction and manipulation of fragments from the outside of the body. You would choose closed reduction when you can treat the fracture with either external coaptation (splint or cast) or by adding an external fixator. Important rules apply to the use of external coaptation with fractures, which will be discussed later. If the fracture required internal fixation, it is generally easier to skip the effort and move to open reduction as the fracture will be exposed anyway.

Open reduction: this refers to surgical reduction with direct visualization of the fracture. Due to biological, mechanical and clinical factors, a lot of fractures are treated with open reduction and internal fixation. For unstable, more complicated, older and articular fractures, it is the method of choice. Excellent books for approaches are available (see references).

Apart from providing the best circumstances for proper bone healing, fracture reduction also aids reduction of pain and further soft-tissue trauma (such as laceration of muscles, vessels and nerves).

How to Perform Closed Fracture Reduction

 Stabilize the animal - treat for shock, secure airway, breathing, cardiovascular system

 Once stable enough, anesthetize patient - this will allow for best relaxation of muscles, minimize pain for the patient and improve your chances of successful fracture reduction

 Protect soft tissues since they are very important for fracture healing and function

 Muscles, blood vessels, nerves, lymphatics, etc.

 Avoid excessive manipulation

 Work slowly and steadily to overcome muscle contraction using traction, countertraction and manipulation

 Allow sufficient time for soft tissues to stretch and allow reduction

 Traction - you are pulling on the distal fragment/limb

 Countertraction - you use the patient's body weight and gravity to help relax muscles

 Manipulation - you use your hands (or percutaneous instruments) to reduce the fracture

 For distal limb fractures, you can hang the affected limb from a pole or a ceiling hook while the patient is in dorsal recumbency (to provide more countertraction/gravitational pull you would raise the limb attachment to literally pull the animal a little off the table)

 You can also use gauze, towels or other material to form a sling around the body and apply countertraction while the distal limb is placed under traction and the fracture manipulated

 Place appropriate external coaptation or external fixation once reduction is achieved

 If you use cast or splint, fracture must be below the elbow or stifle joint

 Can use external fixation with closed reduction, which can be placed minimally invasively and further protect soft tissues

 Always take post-reduction radiographs

Rules About Closed Fracture Reduction

If closed reduction and external coaptation or external fixation are the primary means to treat a fracture certain rules must be obeyed:

 The fracture must have at least 50% cortical contact (on the fracture surface, not along the side of the bone)

 Ensure rotational and angular (varus, valgus, procurvatum, recurvatum) alignment

External Coaptation for Fracture Management

With external coaptation (EC) (coapt = approximate), we use bandages with splints and casts to immobilize a limb. This can be done temporarily until permanent stabilization is performed (i.e., you splint a fracture until it can be plated), temporarily after surgery to add support, or as the primary means of fixation.

Benefits of proper EC would include:

 Minimal damage of soft tissues and blood supply at the fracture site

 Lack of implants, therefore no implant infection or loosening

 Cheaper, although must keep in mind total cost including all bandage changes, sedation, subsequent radiographs, visits, etc.

 'Easy' to do and does not need specialized equipment

 With the right cases, should have high chance of success

Despite these advantages, EC also has clear limitations and contraindications.

While EC can help to stabilize fractures, it does not provide rigid fixation. In fact, there can be up to 20 degree of motion at the fracture site! Splints and casts also do not counteract all forces that fractures are exposed to. Assuming that correctly applied, EC should neutralize bending forces well. However, compression, shear, and distraction are not neutralized. Rotation is often poorly counteracted since it can be difficult to totally immobilize the joint above and below. With the inability to neutralize so many forces, the best fracture configuration to treat with a splint or cast would be a simple transverse fracture with an interdigitating fracture surface in the distal limb.

Indications for External Coaptation (EC) for Fracture Management

 Fracture must be closed

 If wounds are present that require frequent bandage changes, the fracture will not be adequately stabilized

 Fracture must be reducible with at least 50% cortical contact

 Best fracture: simple, transverse

 Do not use for oblique (will shear) and comminuted fractures (will collapse)

 Must immobilize the joint above and below fracture

 Use when you can expect rapid fracture healing to avoid prolonged coaptation and fracture disease (secondary changes to bones, muscles and joints with prolonged immobilization)


Yes for EC

No for EC

Patient age and health

Young and healthy with great healing potential

Older or sick with diminished healing potential

Fracture configuration

Simple, transverse, greenstick, minimal displacement

Comminuted, oblique, very displaced, difficult to reduce

Soft tissue injury

Limited soft tissue injury to impair fracture healing

Open fractures, extensive internal soft tissue damage

Fracture location

Distal to elbow and stifle joint

Proximal to elbow and stifle (can't effectively immobilize)

Owner and patient compliance

Good owners and good patients

Poor (crazy dog, owner won't for bandage changes, etc.)

Patient breed

Anything but toy and miniature breeds

Toy and miniature dog breeds with radius/ulna fractures

Toy and miniature dog breeds present a particular challenge when they have 'the perfect' simple, transverse radius/ulna fracture, because despite fulfilling all of the 'yes' factors, they are almost always not good candidates for EC. This is due to diminished healing potential for radius/ulna fractures in these dog breeds (even in puppies), which will commonly leave them with a delayed or non-union after many months of splinting or casting. Internal plate fixation is the recommended fixation method for this particular injury in those dogs.

Important Rules to Be Obeyed When Using EC for Fracture Fixation

 Pick the right cases

 Patients must be concurrently confined

 Bandages should always start at the toes and continue proximally to avoid swelling of the foot due to poor venous return

 Abrasive material such as outer protective layers, cast or splint material should not touch the skin directly

 Stirrups can be used to prevent slippage of the bandage over the foot

 If pressure sores develop, do not apply more padding over the area but reduce the pressure by placing a doughnut over the sore

 Diligent monitoring of the bandage until it comes off

 You can't see what goes on underneath the bandage except when you change it

 Change regularly if everything is fine - at least every 5–7 days

 If in doubt or if patient acts painful, if there is strike through, odor, or slippage, or if the bandage becomes wet or dirty - change it immediately

 Limb and life can be lost due to bandage-associated complications

Distal Limb Bandages

The Robert Jones bandage can be used to temporarily immobilize limbs distal to the elbow or stifle joint. It relies on an extremely thick secondary layer such as cast padding or cotton which is then tightly compressed to cause uniform compression of the distal limb. Because of the large amount of padding, there is little risk of causing vascular compromise by tightening the outer protective layer. The finished bandage should sound like a ripe melon when being tapped.

The modified Robert Jones is the most commonly applied distal limb bandage in small animals. It uses much less secondary layer and is often referred to as a soft-padded bandage. Because less padding is used, the tertiary layer must not be overly tightened to prevent pressure necrosis. Splints and casts can easily be incorporated into the bandage. The tips of the toes or toe nails are often excluded from the bandage to allow for daily inspection. Care must be taken not to expose too much toe as this may cause swelling/constriction of blood flow.

Casts and Splints

Casts and splints are used to provide stability for joint injuries or fractures either for temporary support until surgery, as a means of definitive treatment or as an adjunct after surgical stabilization. They must only be used for injuries below the elbow or stifle joint as they cannot effectively immobilize injuries above those joints. They are incorporated into a modified Robert Jones bandage between the elastic gauze layer and outer protective layer.

Casts encircle the entire limb. Fiberglass casting tape is the preferred material as it produces a light weight, yet very rigid cast. A modified Robert Jones bandage is placed over the distal limb except for the outer protective layer. The bandage must not be too thick to avoid cast loosening and it must have an even surface free of wrinkles. While wearing gloves, the fiberglass casting tape is immersed in water to activate setting; excess water is shaken out. The tape is then unrolled over the soft-padded bandage from distal to proximal. Care must be taken to avoid folds, wrinkles or indentations in the cast as these can cause pressure necrosis underneath. The casting material must also not contact skin at the ends of the bandage. While overlapping the casting tape by 30–50%, 2 to 3 layers are applied to the limb. Once hardened, an outer protective layer can be applied to prevent excessive soiling of the cast. Casts are often bivalved with an oscillating cast saw to create two halves, which are then kept together by a layer of elastic gauze/cling and the outer protective layer. While bivalving a cast weakens its stability, it allows for fast cast removal in an emergency situation and is recommended.

Splints only cover one aspect of the limb. A variety of prefabricated splints made out of plastic or aluminum are available (lateral and spoon splints). Alternatively, fiberglass casting tape or thermoplastic material can be used to make custom splints. Using fiberglass tape allows great flexibility as it can be applied in any fashion desired. Most forelimb splints are applied to the caudal limb surface, while rear limb splints are applied laterally unless only the metatarsi and the foot are splinted, in which case a caudal splint is used.

The original indication for the Schroeder-Thomas (ST) splint was to immobilize distal femoral fractures that were otherwise not able to be bandaged. This splint suspends the pelvic limb in a rigid metal frame custom-made to match the outline of individual leg. This splint is not recommended anymore for femoral fractures as has a high incidence of muscle contracture with permanent loss of limb function when used for prolonged periods. For distal limb fractures, splints or casts offer valuable alternatives to the ST splint.

A Spica splint maintains either forelimb or pelvic limb in extension by application of a soft padded bandage and the addition of a strong lateral support splint that curves over the shoulder or pelvis. This splint is most commonly used in the forelimb after elbow luxation reduction. Prolonged immobilization must be avoided to prevent muscle contracture and joint damage.


Speaker Information
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Bianca Hettlich, DACVS
The Ohio State University
Columbus, OH, USA

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