basic principles of Ex. Fix

1. External Fixation Overview and Principles
Dr. Ahmed AbdelGhani Alkhateeb
M.SC. (ORTHO.) , M.R.C.S. ( GLASGOW - U.K.) C.P.H.Q. , L.R.S. – P.D.

3. Objectives:
 Identify the indications and contraindications of
external fixation.
Describe the equipment, biomechanics, and
technique in regards to external fixation.
Review appropriate evaluation of the potential
complications and clinical significance of external
fixation.
Explain interprofessional team strategies for
improving care coordination and communication to
advance external fixation treatment and improve
outcomes.

4. Introduction:
• External fixation used to treat fractures
for more than 2000 years as a way to
immobilize the fracture while preserving
soft tissue integrity.
• The fixator design and biomechanics have
changed dramatically over the years, but
the principles remain the same.
• The primary goal of external fixation is to
maintain the length, alignment, and
rotation of the fracture.

5. Introduction:
• External fixation can serve as provisional
fixation or definitive fixation purposes.
• Both methods can be performed in
conjunction with partial internal fixation if
necessary.
• It is important for orthopedic surgeons at
a trauma center to be familiar with the
techniques and principles of external
fixation for various fractures of the upper
extremity, lower extremity, and pelvis.

6. Factors Affect Construct Stiffness and Stability:
 One method of changing the stability is to
alter the pin configuration.
 Placing pins closer to the fracture site, adding
more pins and increasing the spread of the
pins will all add to the stiffness of the
construct.
 However, one must also place the pins out of
the field of future surgical approaches during
definitive fixation.

7. Factors Affect Construct Stiffness and Stability:
 Any increases in pin diameter will
strengthen the construct to the fourth
power and reduce the stress at the bone-
pin interface.
 Increasing pin diameter has the greatest
influence on the stability of unilateral
frames.
 Larger pins increase the risk of a potential
stress riser and can ultimately lead to
fracture.
 For example; a 5 mm pin is 144% stiffer
than a 4 mm pin.

8. Factors Affect Construct Stiffness and Stability:
Another way to change the strength of the
construct is to increase the diameter of the rods
or secure it closer in proximity to the bone.
One can also add multiple bars to the same pins
to enhance stability.
Bars get secured to the pins by clamps.
The most common material for bars today is
carbon fiber, which is 15 % stiffer than stainless
steel bars.

9. Types of External Fixator:
External fixator types divide into several different
subcategories, including uniplanar, multiplanar,
unilateral, bilateral, and circular fixators.
By adding pins in different planes (i.e., placed
perpendicular to each other), one can create a
multiplanar construct.
 Uniplanar fixation devices are fast and easy to apply.
Bilateral frames are created when the pins are on
both sides of the bone and can also add additional
stability.

11. Types of External Fixator:
Circular fixators have gained popularity
with limb lengthening procedures but are
especially effective at allowing the
patient to weight bear and maintain
some joint motion during the treatment.
They are more difficult to apply and use
smaller gauge pins and more of them to
distribute the weight.

13. Types of External Fixator:
There are many different ways to change
and enhance the external fixation construct.
To complicate things further, there are also
hybrid frames which are a combination of
any of the previous constructs described.
The surgeon must create a level of stability
that is appropriate for optimal healing.
 It is essential also to have a good
understanding of basic fracture principals
because stiffer is not always better when it
comes to external fixation.

15. Clinical Significance:
External fixation plays a vital role in fracture care
today. Not only can it temporarily stabilize fractures,
but it can provide definitive fixation as well.
The use of external fixation in a damage control
setting can prevent the so-called “second hit”
phenomenon because of the quick application,
decreased blood loss, and minimally invasive
application.
Furthermore, by giving time for the soft tissues
swelling to subside in severe injuries, the risk of
infection and wound complication proportionally
decreases.

17. Biomechanics:
Maximizing pin size, pin number, pin
separation, pin proximity to the fracture, bone
to clamp/bar proximity, and the diameter of the
pins/connecting rod optimizes frame stability.
The ideal position for pin placement is a near-
far construct with a pin placed close to the
fracture site on both sides and a pin placed as
far away as possible on each side of the
fracture. Stiffness is also increased by double
stacking the connecting rods.

18. Pin Care:
Up to 10% of external fixation pins
develop signs of infection.
Care must be taken to avoid pin site
infection or loosening.
Loose pins should be removed and
replaced, if necessary, to maintain fixator
stability.

20. Indications:
Clinicians use external fixation in orthopedic trauma,
pediatric orthopedics, and plastic surgery for an array of
different pathology. Below are a few of the indications for
external fixation devices:
 Unstable pelvic ring injuries.
 Comminuted periarticular fractures such as pilon, distal
femur, tibial plateau, elbow, and distal radius fractures.
 Fractures with large amounts of soft tissue swelling.
 Fractures in a patient that is hemodynamically unstable
or cannot undergo an open procedure.

22. Indications:
 Comminuted long bone fractures.
 Fractures with significant bone loss.
 Open fractures with soft tissue loss.
 Limb deformity and limb lengthening.
 Osteomyelitis with bone loss.

24. Indications:
 Immobilization of joint after soft tissue flap.
 Arthrodesis.
 Nonunion.
 Malunion.
 Infection.
 Traction to aid in intraoperative fracture
reduction.

25. Contraindications:
 External fixation is a relatively safe minimally
invasive procedure and can provide significant
benefit to the patient when used in the
correct setting.
 There are limited contraindications for its use
in orthopedics.
 Relative contraindications include an obese
patient where safely placing pins would be
difficult.

26. Contraindications:
A non-compliant patient is a relative
contraindication because he or she may not
follow up for the removal of the device.
Peri-prosthetic fractures can limit the bone
stock available to place the pins.
General contraindications include patient
refusal, unable to withstand the procedure
physiologically.

27. Complications:
The following list includes complications that can occur
with external fixation treatment:
 Pin site infection.
 Osteomyelitis.
 Frame or pin/wire failure or loosening.
 Malunion.
 Non-union.
 Neurovascular injury.
 Compartment syndrome.
 Refracture around pin.

35. References:
1.Behrens F, Johnson WD, Koch TW, Kovacevic N. Bending stiffness of unilateral and
bilateral fixator frames. Clin Orthop Relat Res. 1983 Sep;(178):103-10.
2.Kowalski M, Schemitsch EH, Harrington RM, Chapman JR, Swiontkowski MF.
Comparative biomechanical evaluation of different external fixation sidebars:
stainless-steel tubes versus carbon fiber rods. J Orthop Trauma. 1996;10(7):470-5.
3.Fragomen AT, Rozbruch SR. The mechanics of external fixation. HSS J. 2007
Feb;3(1):13-29.
4.Beltran MJ, Collinge CA, Patzkowski JC, Masini BD, Blease RE, Hsu JR., Skeletal
Trauma Research Consortium (STReC). The safe zone for external fixator pins in the
femur. J Orthop Trauma. 2012 Nov;26(11):643-7.
5.Nayagam S. Safe corridors in external fixation: the lower leg (tibia, fibula, hindfoot
and forefoot). Strategies Trauma Limb Reconstr. 2007 Dec;2(2-3):105-10.
6.Bible JE, Mir HR. External Fixation: Principles and Applications. J Am Acad Orthop
Surg. 2015 Nov;23(11):683-90. 7.Wojahn RD, Gardner MJ. Fixation of Anterior Pelvic
Ring Injuries. J Am Acad Orthop Surg. 2019 Sep 15;27(18):667-676. 8.Gausepohl T,
Koebke J, Pennig D, Hobrecker S, Mader K. The anatomical base of unilateral
external fixation in the upper limb. Injury. 2000;31 Suppl 1:11-20.
9.Ziran BH, Smith WR, Anglen JO, Tornetta P. External fixation: how to make it work.
J Bone Joint Surg Am. 2007 Jul;89(7):1620-32.
10.Mahan J, Seligson D, Henry SL, Hynes P, Dobbins J. Factors in pin tract infections.
Orthopedics. 1991 Mar;14(3):305-8.