Felis ISSN 2398-2950

Fracture fixation: external skeletal fixator

Synonym(s): ESF, Splint External fixation

Contributor(s): James Cook, Susan Rackard, J Yovich


  • 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.


  • 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), biplanar (type Ib).
      • Bilateral frame (types IIa and IIb).
      • 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 Elbow: luxation (postoperative) 01 - radiograph mediolateral  Elbow: luxation (postoperative) 02 - radiograph CrCd  Tibia: comminuted diaphyseal fracture 02 - radiograph .
    • Can also be used in certain femoral and humeral fractures (particularly in cats) Femur: fracture repair (postoperative) - radiograph CrCd  Fracture femur 02: repair comminuted proximal fracture - 6wks post-op 01  Fracture femur 02: repair comminuted proximal fracture - 6wks post-op 02  Fracture femur 02: repair intramedullary pin Kerschner Ehmer fixation tied in - photograph     Humerus: fracture repair - external fixation 05 .
    • Acrylic and epoxy putty constructs are useful in some mandibular fractures Mandible: bilateral caudal fracture and split hard palate repair .
  • Less commonly used for spinal and pelvic fractures Pelvis: fracture 03 repair - radiograph VD .
  • 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, eg 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 (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 treatment 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 colulmn 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.


  • Staright 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 problems.
      • 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 system - 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, Cross A R, Carmichael S et al (2001) Recent advances in external skeletal fixation. JSAP 42 (3), 103-112 PubMed.
  • Shahar R (2000) Relative stiffness and stress of type I and type II external fixators.: Acrylic versus Stainless Steel connecting Bars - A theoretical approach. Vet Surgery 29 (1), 59-69 PubMed.
  • Johnson A L, DeCamp C E (1999) External skeletal fixation. Linear fixators. Vet Clin North Am Small Anim Pract 29 (5), 1135-1152 PubMed.
  • Marcellin-Little D J (1999) Fracture treatment with circular external fixation. Vet Clin North Am Small Anim Pract 29 (5), 1153-1170 PubMed.
  • Guerin S R, Lewis D D, Lanz O I et al (1998) Comminuted supracondylar humeral fractures repaired with a modified type I external skeletal fixator construct. JSAP 39 (11), 525-532 PubMed.
  • McCartney W (1998) Use of the modified acrylic external fixator in 54 dogs and 28 cats. Vet Rec 143 (12), 330-334 PubMed.
  • Langley-Hobbs S J, Carmichael S, McCartney W (1996) Use of external skeletal fixators in the repair of femoral fractures in cats. JSAP 37 (3), 95-101 PubMed.
  • Bouvy B, Markel M D, Chelikani S et al (1993) Ex vivo biomechanics of Kirschner-Ehmer external skeletal fixation applied to canine tibiae. Veterinary Surgery 22 (3), 194-207 PubMed.

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. AP Publishing.