Canis ISSN: 2398-2942

Fracture fixation: external skeletal fixator

Synonym(s): ESF, Splint, External fixation

Contributor(s): Joseph Harari


  • To stabilize a fracture using an external skeletal fixator (ESF) until healing is complete.
  • ESF is a device which secures the fracture fragments with percutaneous transfixation pins fixed outside the body to a rigid frame.
  • Frames can be made up of a variety of materials including stainless steel, titanium, carbon fiber and acrylic Fracture fixation: acrylic pin external fixation.


  • Linear:
    • Percutaneous fixation pins are attached to one or more connecting bars with clamps:
      • Acrylic/epoxy putty columns do not require clamps.
    • Constructs can be:
      • Uniplanar (type Ia) Fracture fixation: Type I ESF , biplanar (type Ib).
      • Bilateral frame (types IIa and IIb) Fracture fixation: Type IIA ESF 01 Fracture fixation: Type IIA ESF 02.
      • Bilateral biplanar (type III).
  • Circular:
    • Small diameter percutaneous wires fixed under tension to a connecting ring which in turn is connected to other rings with threaded rods.
  • Hybrid:
    • Combination of circular and linear fixation.
    • Hybrid of types I and II.


  • Primary or adjunctive stabilization of any fracture:
    • Most commonly used for fractures distal to the elbow and stifle.
    • Can also be used in certain femoral and humeral fractures (particularly in cats).
    • Acrylic and epoxy putty constructs are useful in some mandibular fractures.
    • Less commonly used for spinal and pelvic fractures Pelvis fracture repair 01 - external fixator Pelvis fracture repair 02 external fixator - post-operative.
    • Useful in infected/open fractures, so implants are not in contact with contaminated fracture site and where access to skin wounds is necessary:
      • ie Fractures where there is extensive tissue damage requiring continuing treatment, shearing injuries Carpus: shearing Injury.
    • Circular and hybrid frames are useful for juxtarticular fractures.
    • Transarticular fractures, eg carpal fractures.
    • Composite fracture repairs - in conjunction with internal fixation Fracture: internal fixation , eg IM pin Fracture fixation: pin , to avoid rotation during healing, eg transverse mid-shaft femur fracture.
    • Distraction techniques: combined with corrective osteotomies in treatment of limb deformity Epiphyseal fracture: distal radius +/- ulna (dynamic external fixator).


  • Minimally invasive:
    • Allows for closed and "open but do not touch" fracture reduction techniques thereby minimize damage to soft tissues/vessels (biological osteosynthesis Biological fracture fixation ).
  • Allows for open wound management Wound: management - overview while fracture is healing.
  • Usually well-tolerated by patient.
  • Adaptable:
    • The ESF construct is bespoke for each fracture.
    • Postoperative adjustment is possible - though this can be difficult.
      • Correct postoperative malalignment.
      • Gradual disassembly allows for controlled increases in loading of the healing fracture which may enhance osseous union.
      • ESF adjustment is obviously more difficult if an acrylic column has been used.
    • Lightweight (acrylic system) and carbon fiber systems are available.
  • Economical:
    • A limited number of pins, connecting bars and clamps can be used for multiple different fracture configurations.
    • Use of acrylic columns as connecting bars can further reduce costs.
    • Connecting bars and clamps can be cleaned and reused on multiple patients.


  • Straight connecting bars can restrict placing of pins and a compromise is inevitable - acrylic systems avoid this.
  • ESF placement is limited by the availability of safe corridors for percutaneous pin placement:
    • Greater soft tissue mass, eg the upper limb:
      • Reduces the size of the corridor for safe pin insertion.
      • Increases the risk of pin tract insertion.
      • Limits frame type used - type II, III and circular frames are not feasible in the upper limb.
  • Adjustments may need to be made to ensure rigidity is maintained (especially in the growing animal).
  • Acrylic systems - may preclude adjustment once acrylic is set.


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  • Good when correctly applied.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Corr S (2005) Practical guide to linear external skeletal fixation in small animals. In Practice 27 (2), 76-85 VetMedResource.
  • Lewis D D, Cross A R, Carmichael S et al (2001) Recent advances in external skeletal fixation. JSAP 42 (3), 103-112 PubMed.
  • Johnson A L, Egger E L, Eurell J A C et al (1998) Biomechanics and biology of fracture healing with external skeletal fixation. Comp Cont Educ Pract Vet 20 (4), 487-502 VetMedResource.
  • Harari J, Seguin B, Bebchuk T et al (1996) Closed repair of radial and tibial fractures using external skeletal fixation. Comp Cont Educ Pract Vet 18 (6), 651-65 AGRIS FAO.
  • Carmichael S (1991) The external fixator in small animal orthopedics. JSAP 32 (10), 486-493 VetMedResource.
  • Harari J (1990) External skeletal fixation. Vet Clin North Am Small Anim Pract 22, 1-161.

Other sources of information

  • Piermattei D L, Flo G L, DeCamp C E (2006)Handbook of Small Animal Orthopaedics and Fracture Repair: Fourth Edition.Saunders Elsevier, Missouri.
  • Johnson A L, Houlton J E F, Vannini R (2005)AO Principles of Fracture Management in the Dog and Cat.AO Publishing.