PRINCIPLE OF EXTERNAL FIXATION FOR OPEN FRACTURE.pdf

Principle for external fixation of open fracture

1. EXTERNAL FIXATOR
DR NOR FATINI

2. Learning Objectives
1.Indications for external fixation
2.Types of external fixators
3.Principle & Biomechanism of external fixation
4.How to do tibia external fixation
5.Aftercare
6.Complications of external fixator

3. EXTERNAL FIXATION
•A device placed outside skin which stabilizes bone fragments through wires or
pins connected to 1 or more longitudinal bars/ rings.
EXTERNAL FIXATOR
•A method fixation of fractured bone by means of pins passed through skin and
bone.

4. INDICATION
1.Fractures with severe soft tissue damage
2.Comminuted periatrticular fractures with soft tissue damage
3.Damage control surgery
4.Infected fractures
5.Nonunion fractures with bone transport
6.Wound management
7.Ligamentotaxis across joint
8.Arthrodesis
9.Deformity correction

5. FRAME DESIGN & CONFIGURATION
1.Pin fixator
A.Unilateral
•Uniplanar
•Biplanar
B.Bilateral
•Uniplanar
•Biplanar
2.Circular fixator

3.Hybrid

6. COMPONENTS OF STANDARD EXTERNAL FIXATORS
A.Pins (Schanz screws/Steinmann pins)
•Steinmann pins for bilateral frames
•Schanz screws, either self-drilling
or requiring pre-drilling
Schanz screw :
i.Size 4.0-6.0 mm for tibia &
femur
ii.Size 3.5mm for radius & ulna
iii.Size 2.5mm for metacarpal and
metatarsal

7. COMPONENTS OF STANDARD EXTERNAL FIXATORS
A.Pins (Schanz screws/Steinmann pins)
•Stainless steel tubes or carbon fibre rods
•Steinmann pins for bilateral frames
•Schanz screws, either self-drilling or requiring pre-
drilling
Schanz screw :
i.Size 4.0-6.0 mm for tibia & femur
ii.Size 3.5mm for radius & ulna
iii.Size 2.5mm for metacarpal and metatarsal
B.Clamps
•Pin to rod clamp: Clamps to fasten pins/wires to
tubes/rods
•Rod to rod clamp: Clamps to connect tubes/rods to
tubes/rods
C.Wires
•2.0 & 1.8 mm K-wires (± olives) for ring fixator
•Threaded K-wires for small external fixator
D.Rods
•Stainless steel vs Carbon Fiber
•Carbon 15% stiffer vs stainless steel

8. COMPONENTS OF STANDARD EXTERNAL FIXATORS

9. THE FRAME STABILITY

10. THE FRAME STABILITY
1.Schanz screws
a.Use a larger diameter schantz screw
b.Increase the distance between the 2
outermost schanz screws in each segment
(minimal distance at least 3.5cm)
c.Increase the number of schantz screws in each
fragment
d.Pins in different plane
e.Pin insertion angle
2.Rods
a.Reduced the distance btw the rods and bone (
skin to rod distance 2cm)
b.Double stacking – add a 2nd parallel rod on
the same plane
c.Rods in different plane
d.Increasing number or rods
e.Increasing rod diameter size
3.Configuration
a.Unilateral/V-shaped/bilateral or triangular
frame(multiplanar)

11. MODES OF FAILURE
1.Thermal necrosis may result in ring
sequestrum formation and cause early
loosening
2.Microcracking during insertion
3.High pin-bone interface stress
a.Side bar distance from bone
b.Pin diameter
c.Pin number
d.Drill hole size
oEqual size à micromotion à bone
resorption
oUndersized by 3 mm à exceeds yield
stress of bone
oUndersized 0.1 mm à bone is prestressed

12. SAFE ZONES FOR EXT FIX PLACEMENT
Humerus
•Proximal 1/3 - Anterolateral to lateral
•Midshaft - Anterolateral (avoiding radial
nerve posterolaterally)
•Distal 1/3 – Posterolateral to lateral

13. SAFE ZONES FOR EXT FIX PLACEMENT
Femur
•Anterolateral to posterolateral ( 30-40 degrees)

14. SAFE ZONES FOR EXT FIX PLACEMENT
Tibia
•Proximal - medial to anterolateral (120 degrees)
•Midshaft - antero to medial (90 degrees)
•Distal tibia - anteromedial to medial (60 degrees)

Metatarsal
•1st and 5th metatarsal

15. SAFE ZONES FOR EXT FIX PLACEMENT
Pelvis
a.Supraacetabular pin placement
•Proceeding from the ASIS crest, the site of entry is approximately 4–6
cm in a caudal direction, and 3–4 cm in a medial direction. In a supine
position, the alignment for drilling the screws is angled approximately
20° in a cranial direction and 30° inward.
b.Iliac crest pin placement
•The orientation of the os ilium can be determined by palpation with a
finger, screws are then inserted delicately between the two laminae of
the os ilium.

16. HOW TO DO EXT FIX TIBIA
1)Patient preparation - This procedure is normally performed in
a supine position.
2)Pin placement - make use of the safe zones and be familiar
with the anatomy of the lower leg.
3)Reduction - Apply manual longitudinal traction to leg and
maintain reduction.
4)Pin insertion - Drilling in thick tibial crest may be associated
with excessive heat generation and risk the drill bit may slip
medially or laterally damaging the soft tissues.
As the anteromedial tibial wall provides adequate thickness
for the placement of pins, this trajectory is preferable.

17. HOW TO DO EXT FIX TIBIA
1) Pat ient preparat ion
2) Pin placement
3) Reduct i on
4) Pin insert ion
5)Frame construction - Insert a pin into each main fragment in
one plane. Connect the pins with one rod to which 4 clamps
have been added. At this point, some correction to the
reduction is still possible. Tighten the clamps.
6)On both sides of the fracture, add an additional pin close to the
fracture zone using the rod-to-pin clamps as guides. Tighten the
clamps. Adjust number of pins and rods to increase frame
stability.
7)Prevent plantar flexion contracture - In patients with severe
soft-tissue involvement, it may be helpful to add a pin in the
foot (one of the tarsal or metatarsal bones) to maintain the
ankle at a 90° angle.

18. AFTERCARE
qPin-site care
ØProper pin insertion technique is more important than any pin-care protocol
ØPin sites should be kept clean. Any crusts or exudates should be removed. The pins may be cleaned with saline/
disinfectant solution/alcohol.
ØNo ointments or antibiotic solutions are recommended for routine pin-site care.
ØDressings are not usually necessary once wound drainage has ceased.
ØPin-insertion sites need not be protected for showering or bathing with clean water.
qPin loosening or pin tract infection
ØRemove all involved pins, debride, curette and irrigate the pin sites in OT and place new pins in a healthy location.
ØTake specimens for a microbiological study to guide appropriate antibiotic treatment if necessary.
ØBefore changing to a definitive internal fixation an infected pin tract needs to heal. Otherwise infection will result.

19. AFTERCARE
qMobilization
ØUnless there are other injuries, mobilization may be performed on day 1.
ØStatic quadriceps exercises with passive ROM of the knee should be encouraged. Early active ROM of knee and ankle
is encouraged.
ØTo achieve a full ROM within the first 4-6 weeks. Maximum stability is achieved at the time of surgery.
qWeight bearing
ØIf external fixation is considered as the definitive device, weight bearing should be encouraged early.
ØAs soon as callus formation is visible and once there are no clinical signs of instability, the patient can start to bear
full weight.
ØAfter removal of the external fixator, it may be prudent to protect the leg temporarily in a splint or brace.

20. AFTERCARE
qFollow up
ØSee patient 7-10 days after surgery for a wound check. X-rays are taken to check the reduction.
ØThe patient should be seen every 4-6 weeks in follow-up with examination and x- rays until union is secure, and
range of motion and strength have returned.
qWhen to remove ?
ØIf definitive external fix – till union occur
ØIf planning for definitive internal fixation – period of 2 weeks to allow pin track to heal with antibiotic coverage
ØInfection after removal of ext fix can be reduce by :
I.Fixator removed in sterile condition
II.Removal of skin edges and curate soft tissue, wound not surgically closed but covered with dressing
III.Pin site kept isolated till definative fixation completed through separate incision not involving pin tract

21. RISK AND COMPLICATION
a.Pin tract infection (which can lead to abscess formation, osteomyelitis, and the need for pin
replacement)
b.Aseptic loosening
c.Loss of reduction
d.Impingement
e.Neurovascular injury
f.Incisional hernia

22. ADVANTAGES
üLess damage to blood supply of bone.
üMinimal interference with soft-tissue cover
üUseful for stabilizing open fractures
üRigidity of fixation adjustable without surgery
üGood option in situations with risk of infection.
üRequires less experience and surgical skill than
standard ORIF.
DISADVANTAGES
ØPin and wires penetrating the soft tissues
ØRestricted joint motion
ØPin track complication in long lasting external
fixation
ØCumbersome frame and not always tolerable
ØLimited stiffness in certain locations (e.g., femur
fracture in adults)
EXTERNAL FIXATION

23. References
•The elements of fracture fixation Thakur 4th edition
•AO Surgery Reference

24. THANK YOU!