TECHNIQUE

External Fixation in Rabbits (Disease Investigation & Management - Treatment and Care)

External fixation. Click here for full page view with caption

Summary Information
Type of technique Health & Management / Disease Investigation & Management / Techniques:
Synonyms and Keywords --
Description Editor's Note: 
  • Information on this page is to be used together with information given in the "Treatment" section of the page Fractures in Rabbits and with information given in the page Treatment and Care.
  • This page is intended to provide the reader with information of particular importance for the treatment of lagomorphs. It does not provide details of external fixation for fractures at different sites.
  • The reader should use the information in this text alongside their own experience in orthopaedic surgery and should consult relevant texts on small animal orthopaedic surgery as required.
Pre-operative preparation
  • Give pre-operative antibiotics 1-2 hours before surgery. (J213.5.w3)
  • Give pre-operative analgesia 1-2 hours before surgery. (J213.5.w3)
  • Anaesthetise the rabbit. See: Treatment and Care - Anaesthesia and Chemical Restraint - Lagomorph Anaesthesia
  • Place in an appropriate position.
Fixation
  • Reduce the fracture using closed or limited open reduction. (B601.17.w17)
    • Use closed reduction for a simple fracture. (B602.35.w35)
    • Use limited open reduction for an open or highly comminuted fracture. (B602.35.w35)
  • Choose pins of an appropriate size; each pin should be no more than 20% of bone diameter. (B601.17.w17)
  • Place each pin through a separate skin incision. (B601.17.w17, B602.35.w35)
  • Insert pins using low rotational speed (150 rpm). (B601.17.w17, B602.35.w35)
    • Do not use manual insertion as this causes wobble and resultant premature pin loosening. (B601.17.w17, B602.35.w35)
    • Do not use a high rotational speed as this leads to bone necrosis and thereby pin loosening. (B602.35.w35)
  • Angle the pins at 70 degrees to the long axis of the bone to reduce the risk of pin pullout. (B601.17.w17, B602.35.w35)
  • Place pins as near as possible to the centre of the bone to improve stability at the bone-pin interface. (B602.35.w35)
  • Place the first pins 1 cm from the fracture line. (B602.35.w35)
    • Setting the pins which are furthest from the fracture line first assists in ensuring proper alignment. (J213.5.w3)
  • Place three or four pins in each bone segment. (B601.17.w17)
    • Place three pins; four may produce excessive stiffness. (B602.35.w35)
    • Space pins as evenly as possible for maximum strength. (B602.35.w35)
  • Use acrylic (e.g. bone cement) as the connecting bar. (B601.17.w17)
    • Commercial external fixator bars and clamps are usually too heavy for rabbits. (B601.17.w17, B602.35.w35)
    • Drill the pins through plastic tubing before drilling into the bone; after pin placement, fill the tubing with acrylic resin or fast-setting bone cement. (J213.5.w3)
  • Place the connecting bar 1 cm away from the skin to allow for postoperative tissue swelling. (B601.17.w17, B602.35.w35)
    • Too far away reduces the strength and stiffness of the fixator. (B602.35.w35)
Post-operative care
  • See: Treatment and Care - Surgery - Post-operative care
  • Analgesia is necessary at the time of stabilisation and then continued post-operatively as necessary. (B606.10.w10)
    • Give pre-operative analgesia 1-2 hours before surgery. (J213.5.w3)
  • Antibiotics as necessary. (P112.1993.w1)
    • It is advisable to use antibiotics post-operatively. (B606.10.w10) for 3-5 days. (J213.5.w3)
    • Antibiotics are important post-operatively for open fractures to prevent osteomyelitis. (B606.10.w10)
  • Environment: clean and stress-free. (B606.10.w10)
    • Minimise the time in a hospital environment, which rabbits generally find stressful. (P112.1993.w1)
    • Provide a warm, quite environment. (P112.1993.w1)
  • Diet: nutritional support is important. (N12.38.w1)
    • Syringe feed with a herbivore recovery diet. (N12.38.w1)
    • Force feeding may be necessary if there is anorexia (make sure the rabbit is receiving appropriate analgesia, because pain is often manifested as anorexia). (B606.10.w10)
  • Fluids: oral or intravenous fluid therapy may be needed. (N12.38.w1)
  • Bedding: thick towels, torn-up paper or newspaper is recommended post-operatively. (J213.5.w3)
  • Wrap the fixator and limb with non-adhesive elastic bandage to reduce the risk of the fixator catching on the cage/housing. (J213.5.w3)
  • Evaluate the fixator every week. (B601.17.w17)
    • Clean the pin tracts with 0.05% chlorhexidine solution. (B601.17.w17)
    • Rewrap the bars with clean bandage material. (B601.17.w17)
  • Assess fracture healing by radiography at four to six weeks and then every two to three weeks. (B601.17.w17) 
    • See: Imaging in Lagomorph Diagnosis and Treatment 
    • Removal at four weeks is generally not advisable. (B602.35.w35)
    • Removal at six weeks may produce a stronger repair than if the fixator is left for 12 weeks. (B602.35.w35)
    • It is necessary to leave the fixator in place for a minimum of six weeks. (B606.10.w10)
(B601.17.w17, B602.35.w35, B606.10.w10, wrapping the fixator and limb with non-adhesive elastic bandage. (J213.5.w3))
Appropriate Use (?)
  • For fixation of limb fractures. (B601.17.w17, B602.35.w35)
    • Fractures of the humerus, radius, ulna, femur or tibia, not involving the extreme ends of the bones. (J213.5.w3)
  • For fixation of mandibular fractures. (J213.5.w3)
  • Versatile. (B601.17.w17)
    • Can be used for stabilisation of comminuted fractures with small bone segments distally and/or proximally. (B601.17.w17, P112.1993.w1)
    • Can be used with open fractures. (B537.1.w1, J8.42.w2, P112.1993.w1)
    • Can be used with metaphyseal fractures. (P112.1993.w1)
  • Involve minimal tissue damage. (B601.17.w17)
  • Provide rigid stability, protecting against rotation, bending and shear if properly applied. (B602.35.w35, P112.1993.w1)
  • Provide good anatomic alignment. (P112.1993.w1)
  • Do not interfere with joint function. (P112.1993.w1)
  • Easy to remove once the fracture has healed. (P112.1993.w1)
  • Relatively light weight. (P112.1993.w1)
  • Allow an early return to limb function. (P112.1993.w1)
  • Allows access to the injured area for dressing changes. (B537.1.w1)
Notes External skeletal fixators are described as follows:

Type I - half-pin 

  • Fixation pins penetrate only one skin surface, but penetrate both bone cortices.
  • Connecting bar and clamps are one one side of the limb only.

Type II - full pin 

  • Fixation pins pass through both skin surfaces and both bone cortices.
  • Connecting bars and clams are used on both sides of the limb, in a single plane.

Type III - biplanar

  • Combination of type I and type II splints placed at right angles to each other.
  • Connected to one another to form a rigid three-dimensional frame. 

(J8.42.w2, P112.1993.w1)

Complications/ Limitations / Risk
  • Do not use manual insertion of pins as this causes wobble and resultant premature pin loosening. (B601.17.w17, B602.35.w35)
  • Do not use a high rotational speed for insertion of pins as this leads to bone necrosis and thereby pin loosening. (B602.35.w35)
  • Commercial external fixator bars and clamps generally cannot be used as they are too heavy for rabbits. (B601.17.w17, B602.35.w35)
  • External fixators may get caught on the cage or other housing. (J213.5.w3)
    • This risk can be reduced by wrapping the fixator and limb with non-adhesive elastic bandage. (J213.5.w3)
Equipment / Chemicals required and Suppliers
  • Appropriate anaesthetic.

  • Pins of appropriate size: 

    • Use small diameter threaded or non-threaded pins. (B601.17.w17)
    • Positive profile threaded pins provide better purchase than nonthreaded pins. (B601.17.w17)
    • Threaded pins may be too large. (B602.35.w35)
    • Each pin should be no more than 20% of bone diameter. (B601.17.w17)
  • Low-speed drill.

  • Suitable material for connecting the pins (does not need to be sterile).

Expertise level / Ease of Use
  • This procedure should only be carried out by an individual with appropriate clinical training and practical experience.
  • The surgeon's familiarity with placing external fixators will affect ease of use. (P112.1993.w1)
Cost/ Availability
  • Cost of consumables - pins, and acrylic or other suitable material for connecting the pins.
    • Non-sterile polymethyl methacrylate e.g. Technovit (Jorgensen Laboratories, Loveland, Colorado, USA). (P112.1993.w1)
    • Epoxy resin. (P112.1993.w1)
    • Hexcelite. (P112.1993.w1)
    • Dental acrylics. (P112.1993.w1)
  • Cost of anaesthetic.

The costs of a surgical operation include those associated with: (J15.30.w1)

  • Pre-operative diagnostics (e.g. radiography, ultrasonography, blood tests)
  • Anaesthesia.
  • Perioperative medication (e.g. analgesics, antibiotics, fluids).
  • Surgical preparation (of the operating theatre and the patient, including staff time).
  • Consumables and equipment.
  • Time of the surgeon and assistant(s).
  • Post-operative hospitalisation.
Legal and Ethical Considerations In some countries there may be legislation restricting the use of this type of technique to licensed veterinarians. For example in the UK: "The Veterinary Surgeons Act 1966 (Section 19) provides, subject to a number of exceptions, that only registered members of the Royal College of Veterinary Surgeons may practice veterinary surgery." (See: LCofC1 - RCVS Guide to Professional Conduct 2000 - Treatment of Animals by Non-Veterinary Surgeons).
Author Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee John Chitty BVetMed CertZooMed MRCVS (V.w65)
References B537.1.w1, B601.17.w17, B602.35.w35, B606.10.w10, J15.30.w1, J213.5.w3, P112.1993.w1

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