External Skeletal Fixation
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External skeletal fixation of long bones consists of inserting two or more pins each in the proximal and distal bone fracture fragments. The pins are connected by clamps to an external connecting bar. They are useful to treat to a wide variety of fractures. They are particularly useful for infected fractures, comminuted fractures, certain osteotomies, and cases with delayed wound healing or when supplementation with other internal fixation methods is required. Several types of external skeletal fixators exist. Classification is based upon the number of planes that the pins pass through in space and how many skin surfaces are penetrated.

Type Ia: Unilateral- Uniplanar
Type Ib: Unilateral-Biplanar
Type II: Bilateral-Uniplanar
Type II Modified: Bilateral-Uniplanar
Type III: Bilateral-Biplanar
    Before application of final connecting bar.


Steinmann Pins

Fixation pins come in several different varieties and lengths. Increasing the number of pins in a fracture fragment increases the overall rigidity of the device. The maximum number of pins in each fragment should not exceed four.

Smooth transfixation pins - Good for use in young patients with simple, stable fractures, and animals exotic with very small bones. They are inexpensive, but can prematurely loosen.
Threaded - negative profile transfixation pins (Ellis pins) - The diameter of thread portion is smaller than the smooth portion. They have better holding power in bone than smooth pins.
Threaded - positive profile transfixation pins - The diameter of thread portion is greater than smooth portion. They have excellent holding power. Currently, these are the most widely used for external skeletal fixation.



Clamps function to secure the fixation pins to the connecting bars. Different types are available depending on whether you perform an IMEX, Securos, or the traditional method of fixation using Kirschner-Ehmer (KE) clamps. When securing the IMEX SK clamps first tighten the bolt attaching the clamp to the connecting bar. This allows for adjustments to be made to the fixation pins until proper alignment is reached. Once alignment is achieved, the bolt for the fixation pin can be tightened. For the other two methods only a single bolt is tightened to secure the clamps in one step.

IMEX SK single clamp
IMEX SK double clamp
IMEX bolts
Securos clamp
Kirschner-Ehmer clamp


Connecting Bars

Connecting bars support an external skeletal fixator by connecting proximal and distal fracture fragments. Carbon fiber rods are the most commonly used connecting bars for the IMEX SK fixation method. With Securos and KE clamps, stainless steel Steinmann pins are used. Stainless steel connecting bars can also be used for the IMEX SK system.

Carbon fiber rods
Steinmann pin


Additional External Skeletal Fixation Instrumentation

Drill sleeves: 2.0, 2.5, 2.7, 3.5mm
Drill bits: 2.0, 2.5, 2.7, 3.5mm
3.1mm drill bit (most commonly used for IMEX fixation)
3.2mm drill bit (most commonly used for Securos fixation)
Allen wrenches
Jacob's chuck
Jacob's chuck key
Jacob's chuck with key
Pin cutter
Small pin cutter


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 Copyright © 2006 - University of Pennsylvania School of Veterinary Medicine, All rights reserved.
 Faculty: Dr. Robert Gilley
 Student: Randi Gold V'09