Intramedullary nailing

bahaa Ali Kornah-Al-Azhar Un. Cairo -EGYPT
Dr. Bahaa Ali Kornah
Prof.. Of Orthopedic
Al-Azhar University
Cairo - Egypt
‫وبركاته‬ ‫هللا‬ ‫ورحمة‬ ‫عليكم‬ ‫السالم‬

INTRAMEDULLARY NAILING
biomechanics:
Evolution and challenges
Dr. Bahaa Ali Kornah M.D.
Prof.. Of Orthopedic
Al-Azhar University-Cairo - Egypt

Objectives GOAL
 Introduction
 Evolution
 Classification
 Biomechanics
 Applications
 Special
Circumstances
 Recent Advances

GOAL OF OPERATIVE FRACTURE FIXATION
❖ Full restoration of function
❖ Faster return to his preinjury status
❖ Minimize the risk and incidence of
complications.
❖ Predictable alignment of fracture fragments

The purpose of implants
❖ to provide a temporary support
❖ to maintain alignment during the
fracture healing
❖ to allow for a functional rehabilitation

fractured bone needs
➢ - A certain degree of immobilization (mechanical
stability)
➢ -Optimally preserved blood supply
➢ -Biologic or hormonal stimuli in order to unite.
Biology and Biomechanics on Fracture
Healing

Stability
Request for fx treatment
Biology

Mechanical
stability,
Elastic fixation
provided by internal or
external splinting
of the bone
Absolute stability
rigid fixation that does
not allow any micro motion

HighRateof HealingHighRateof Healing
Spectrum of Healing
Absolute Stability =
10 Bone Healing
Biology of Bone Healing
THE SIMPLE VERSION...
Relative Stability =
20 Bone Healing
Fibrous Matrix > Cartilage >
Calcified Cartilage > Woven
Bone > Lamellar Bone
Haversian
Remodeling
Minimal
Callus
Callus

Fixation Stability
Reality
No callusCallus
Relative
– (Flexible)
– Eg IM nailing
- Bridge plating
Absolute
(Rigid)
– eg Lag screw/ plate
– Compression
plate

Introduction
 Fracture stabilized by one of two systems
 Compression
 Splinting
 Intramedullary fixation - internal splinting
 Splintage -micro motion between bone & implant
 Relative stability without interfragmentary compression.
 Entry point - distant from fracture site – hematoma
retained.
 Closed reduction and fixation (biological)

Intramedullary Nails
•
•
•
•
•
•
Relative stability
Intramedullary splint
Less likely to break with
repetitive loading than
plate
More likely to be load
sharing .
Secondary bone healing
Diaphyseal and some
metaphyseal fractures

• 1. bending stability.
• 2. axial stability.
• 3. translational stability.
• 4. rotational stability

Intramedullary Fixation
• Generally utilizes closed/indirect or minimally
open reduction techniques
• Greater preservation of soft tissues as
compared to ORIF
• IM reaming has been shown to stimulate
fracture healing
• Expanded indications i.e. Reamed IM nail is
acceptable in many open fractures

Intramedullary Fixation
•
•
•
Rotational and axial
stability provided by
interlocking bolts
Reduction can be
technically difficult in
segmental and
comminuted fractures
Difficult to Maintain
reduction of fractures
in close proximity to
metaphyseal flare

Evolution of IMN
1st generation
 Splints(1˚)
 Rotational
stability minimal
 Closed fit
 Longitudinal slot
along entire length
 Eg –K nail , V nail
2nd generation
• Locking screw -
improved
rotational stability
• Non- slotted.
• Eg- russel taylor nail,
delta nail
3rd generation
• Fit anatomically as
much as possible
• Aid insertion and
stability
• Titanium alloy
• Eg-trigen nail, universal
femoral nail nails with
multiple curves
, multiple fixation
systems
• Tibial nail with malleolar
fixation

Classification IMN
 Entry Portals :
❑ Centromedullary
❑ K nail ,1st
generation IMN
❑ Cephalomedullary
❑ Gamma nail
❑ Russell taylor nail
❑ PFN
❑ Condylocephalic nail
❑ Ender nail
Direction :
❑Antegrade
❑ Retrograde nailing

Centromedullary Nails
 First generation
 Contained within medullary canal
 Usually inserted from piriformis
fossa
 Proximal locking bolts - transverse or
oblique in pertrochanter
 Requires LT be attached to proximal
fragment for adequate # stabilization

Cephalomedullary
Nails
 second generation nails
 More efficient load transfer than DHS
 Shorter lever arm of IM device
decreases tensile strain on implant -
low risk of implant failure
 screws/blade inserted cephald into
femoral head and neck.
◼ Gamma nail
◼ Recon nail

C o n d y l o c e p h a l i c F i x a t i o n
 Morote nails
 Nancy nails
 Prevot nails
 Bundle nails
 Elastic stable intramedullary nailing (ESIN) -
 primary definitive pediatric fracture care .
 3 – point fixation or bundle nailing.
 Elastic and small - micro-motion for rapid fracture healing.
 Flexible -insertion through a cortical window.
 Examples
 Lottes nails
 Rush pins
 Ender nails :

Opposite  Apex of curvature – at level of fracture
site.
 Nail diameter -40% of narrowest
medullary canal diameter
 Entry point -opposite to one another
 Used without reaming.
 Commonest biomechanical error is lack
of internal support.

 Schneider nail [ solid, four fluted cross
section and self broaching ends.
 Harris condylocephalic nail [curved in two
planes, and designed for percutaneous,
retrograde fixation of extra capsular hip
fractures.
 Lottes tibial nail specially curved to fit tibia,
and has triflanged cross section.

Ender Nails
 Solid pins with oblique tip and an
eye in flange at or end
 Designed for percutaneous, closed
treatment of extra capsular hip
fractures

Rush Nails
❑Intended for fractures of diaphyseal or
metaphyseal fractures of long bones like
femur, tibia, febula, humerus, radius and
ulna.
❑Pointed tip facilitates easy insertion.
❑Curve at top prevents rotation and
stabilizes fracture.

Bundle Pinning
 C- or S – shaped, act like
spring.
 Principle introduced by hackethal.
 Many pins are inserted in to bone until
jammed within medullary cavity to provide
compression between nails and bone.
 Bending movements neutralized, but
telescoping and rotational torsion not
prevented

Applications IMN
❑ Diaphyseal fractures of long bones
❑ High proximal and low distal fractures of
long bones
❑ Floating hip, floating knee, floating
elbow.
❑ Aseptic and septic non-union
❑ Osteoporotic long bone fractures
❑ Pathological fractures
❑ Open fractures up to grade IIIA

Contraindications IMN
 Narrow and anomalous medullary canal
 Open growth plates
 Prior malunion - prevents nail placement
 History of intramedullary infection
 Associated ipsilateral femoral neck or acetabular
fracture (relative)

Mechanics (K Nail)
 Elastic deformation or “elastic
locking” of nail within
medullary canal
 Adequate friction of nail in both
fracture fragments
 To achieve elastic impingement-
 “V” profile or even better “clover-leaf”
design.

❑ Compressible in two directions
❑ Directions right angles to each
other
V Nail Clover Leaf Nail
❑ Compressible in only one
direction

Elastic Compressibility Of Clover – Leaf Nail

Solid Nail Elastic Nail
❑Not occupy full width of
medullary canal
❑Nail with elastic cross section
adjust to constrictions of
medullary canal.

Grosse – Kempf nail Russell – Taylor nail Brooker–Wills nail

Biomechanics of deforming forces

D
F = Force Bending moment = F x D
D
PlateIM Nail
Bending moment for plate
greater due to force being applied
over larger distance.
D = distance from force
to implant.

Comparision
• Nail cross section round
• Resisting loads equally in all
directions.
• Plate cross section
• rectangular resisting greater
loads in one plane versus
the other

Cortical contact
 - compressive loads
borne by bony cortex
 compressive loads
transferred to interlocking
screws (“four-point
bending of screws ”)
+
- -

Ideal Intramedullary Nail
 Strong and stable - maintain alignment and position
 Prevent rotation - interlocking transfixing screws
 Promote union - contact-compression forces at fracture
surfaces
 Accessible for easy removal

Ideal Intramedullary Nail set
✓the number of instruments should be kept to a minimum
simple to use.
✓minimise the number of implants necessary for a
complete size inventory.
✓For a given size of implant, the strength should be as
high as possible to guard implant failure.
✓it is desirable to maximise the flexibility of the implant
✓ to facilitate insertion without comninution;
✓ to transmit load to the bone to protect the implant while
minimising stress protection resorbtion.
✓ To stimulate the natural fracture healing mechanisms by
allowing adequate at the fracture interface.

Pre Requisites
 Adequate preoperative planning
 Patient tolerance to a major surgical procedure
 Availability of nails of suitable length and diameter
 Suitable instruments, trained assistants, and optimal hospital
conditions
 Closed nailing techniques - whenever possible

INDICATIONS
Standard intramedullary nail
Non comminuted misdshaft
fractures (A). for non-comminuted
misdhaft

Interlocking fixation
Interlocking indications:
•Comminuted shaft fractures
(B).
•Subtrochanteric fractures (C).
•Distal third fractures (D).

Reconstructive fixation
Reconstructive indication:
•Combination fracture of the
shaft and neck (E).
•Intertrochanteric fractures (F).
•Combined intertrochanteric and
subtrochanteric fractures (G).
•Reconstruction following
tumour resection.

Pre Operative Planning
Biplaner Radiographic
Images
• Bone Morphology
• Canal Dimensions
• Fracture Personality
• Comminution
• Fracture Extensions
Length Of Nail
• Radiographs of contra
lateral femur (magnified)
• Traction radiographs
(comminuted #)
• Palpable greater
trochanter to lateral
epicondyle
• TMD (tibial tubercle–
medial malleolar
distance) for tibial nail
Diameter Of Nail
• Narrowest portion of
femoral canal at femoral
isthmus – lateral
radiograph
• 1.0 to 1.5 mm greater in
diameter than anticipated
nail diameter.

Nail Length
 Preoperative radiographs of fractured long bone
with proximal and distal joints
 AP radiograph of opposite normal limb at a tube
distance of 1meter
 Kuntscher measuring device :
 Ossimeter used to measure length and width
 Magnification is taken into account

Biomechanics
 Stability determined by
fracture site
1. Nail design
2. Number and orientation of locking screws
3. Distance of locking screw from
4. Reaming or non reaming
5. Quality of bone
 IM nails assumed to bear most of load initially,
gradually transfer it to bone as fracture heals.

Nail Design
 Factors contributing to biomechanical profile :
I. Material properties
II. Cross-sectional shape
III. Diameter
IV. Curves
V. Length and working length
VI. Ends of nail

Nail design
I- Material properties
 Titanium alloy and 316l
stainless steel.
 Modulus of elasticity
◼ Titanium alloy – same
as cortical bone
◼ SS – twice as cortical
bone
II- CROSS SECTIONAL
SHAPE
 Determines bending
and torsional strengths
 Polar moment of inertia
◼ Circular nail  diameter
◼ Square nail  edge
length
◼ High in nails with sharp
corners or fluted edges

A-schneider
B-diamond
C-sampson fluted
D-kuntscher
E-rush
F-ender
G-mondy
H-halloran
i-huckstep
J-AO/ASIF
K-grosse –kempf
L-russell-taylor
J,k,l-now commonly used
‘intramedullary nails’ cross-sectional designs

III. Nail diameter
Nail diameter affects bending rigidity
❑solid circular nail,
 Bending rigidity  third power of nail
diameter (D3)
 Torsional rigidity  fourth power of
diameter (D4)
Large diameter with same cross-
section are both stiffer and stronger than
smaller ones.

III. Nail diameter
• assessing medullary canal diameter in AP
and LV both site
• pre-operative radiograph by using the
templates provided.
• The canal must be reamed to at least 1 mm to
accept nail less than it

IV. Nail curves
 Long bones have curved medullary cavities
 Nails contoured to accommodate curves of bone
 Straight, curved or helical
 Average radius of curvature of femur - 120(±36) cm.
 Complete congruency minimizes normal forces and
hence little frictional component to nail’s fixation.
 Femoral nail designs have considerably less curve,
with radius ranging from 150 to 300 cm
 Im nails - straighter (larger radius) than femoral
canal

Nail curves
 Angle of herzog :
 11o bend in AP direction at junction of upper
1/3rd and lower 2/3rd of tibia nail
 Mismatch in radius of curvature –
 Distal anterior cortical perforation
 more reaming required during insertion

Hoop stress
 Circumferential expansion
stress during nail insertion
 Larger hoop stress can split bone
 Hoop stress reduction :
 Use flexible nails
 Over-ream entry hole by 0.5 to 1 cm
 Selection of ideal entry point

Posterior - loss of
proximal fixation
Ideal - posterior portion
of piriformis fossa
Anterior - generates
huge forces, can lead to
bursting of proximal

V. Nail length
A-Total nail length - Anatomical length tip of the greater
trochanter to the intercondylar notch.
length between proximal and
distal point of firm fixation
to bone
B-working length -
Working length
Affected by various factors
➢ Type of force (Bending ,Torsion )
➢ Type of fracture
➢ Interlocking and dynamization
➢ Reaming
➢ Weight bearing

V. Nail length
 Shorter working length stronger fixation
 Transverse fracture has a shorter working length than
comminuted fracture
 Torsional stiffness 1/ to l
 Bending stiffness 1/ to l2
 Surgeon’s techniques to modify “ l ”
 Medullary reaming
 Interlocking

VI- Extreme ends
 K-nail
 Slot/eye in ends for extraction
 One end tapered to facilitate insertion .
❑ Holes for interlocking screws
 Some nails have slots near distal end
for placement of anti rotation screw
 Anterior slot-
Improved flexibility
 Posterior slot -
Increased
bending strength
 Non-slotted -
Increased torsional
stiffness and
strength in smaller
sizes

Interlocking of nail
 Recommended for most cases of IM nailing.
 Principle :
 Resistance to axial and torsional forces depends on screw – bone interface
 Length of bone maintained even in bone defect.
 Number of interlocks :
 Fracture location
 Amount of fracture comminution
 Fit of nail within canal.
 Placing screws in multiple planes - reduction of minor movement

Interlocking screw
 Location of distal locking screws affects
biomechanics of fracture
 Distal locking screws
 Closer to fracture site - less cortical
contact -increased stress on locking
screws
 Distal from fracture site -fracture
becomes more rotationally stable
 Interlocking screws positioned at least 2 cm
from fracture provides sufficient stability

Poller /blocking screws
 Corrects mal-alignment.
 Centers IM nail.
 Planned and inserted before
IM nail insertion.
 Saggital or coronal plane.

Poller screw
• When malalignment develops
during nail insertion,
placement of blocking (Poller
screws) screw, and nail
reinsertion improves
alignment.
• Most reliable in proximal and
distal shaft fractures of tibia.
• A posteriorly placed screw
prevents anterior angulation
and laterally placed screw
prevents valgus angulation.

Static locking
 Screws placed proximal and distal to fracture site
 Restrict translation and rotation at fracture site.
 Acts as a “bridging fixation”
 Indications :
 Communited
 Spiral
 Pathological fractures
 Fractures with bone loss
 Atropic non union

Dynamic locking
❑ Screws inserted only at one end (short fragment)
❑ Unlocked end stabilized by snug fit inside medullary cavity
(long fragment)
❑ Prerequisite: at least 50% cortical circumferential contact
❑ Indications
❑ Fractures with good bone contact
❑ Non unions
❑ With axial loading , working length in bending and torsion
is reduced - improving nail-bone contact

Dynamisation
❑ “Weaken stability”
❑ Never done in progressive normal healing
❑ Indications
❑ Established nonnunion
❑ Pseudoarthrosis
❑ Caution: premature dynamization adds to
shortening, instability and non-union.

Dynamisation
 Primary Dynamisation
 Dynamic locking of axially and rotationally stable
fractures at time of initial fracture fixation
 Secondary Dynamisation
 Removing interlocking screw from longer
fragment / moving proximal interlocking screw
from static to dynamic slot in nail
 Done in long bone delayed union and nonunion

Reamed Versus Unreamed
 Endosteal thermo-necrosis & endosteal cortical blood supply disruption
➢ Minimized by using sharp reamers with deep cutting flutes.
➢ Reaming - slow and smooth.
 Endosteal blood supply regenerates rapidly - high healing rates in reamed
nails.
 No difference in infection rates
 No overall difference in time to union

Reamed Versus Unreamed
❑ Reamed nail :
❑ High chance of embolization of bone marrow fat to lungs but this phenomenon is
limited & transient
❑ Fat extravasation greatest during insertion of nail in medullary cavity
❑ Not dependent upon increased intra medullary pressure
 Reamed nailing generally report no statistical difference in pulmonary
complications as compared to unreamed nailing

Open intramedullary nailing (OIN)
Primary indication :
 Failure to do closed nailing
 Nonunions
 Fractures requiring intramedullary
existing fixation in internal fixation
device.

 Advantages (OIN) :
 Less expensive equipment required than for closed nailing.
 No special fracture table / preliminary traction
 Absolute anatomical reduction
 Direct observation of bone - undisplaced / undetected
comminution
 Improved rotational alignment and stability.
 Prevents torquing and twisting in segmental fractures
 In nonunions, opening of medullary canals of sclerotic bone is
easier.

DISADVANTAGES (OIN) :
❑Skin scars
❑Fracture hematoma evacuated.
❑ Bone shavings created by reaming medullary canal often are lost.
❑Infection rate increased.
❑ Rate of union decreased.
❑ If a locking nail is used, locking is difficult without image
intensification

Nailing in open fractures
 If initial debridement adequate and timely , definitive stabilization with
reamed intramedullary nailing
 with severe soft tissue injuries that require a second debridement,
temporary external fixation reasonable
 increased risk of infection after use of external fixation pins longer than 2
weeks followed by reamed intramedullary nailing.
 Rapid initial management approach allows delayed conversion to a
medullary implant at 5 to 10 days.

Nailing in openfractures
❖ Fractures with delay in initial debridement of more than
8 hours - staged nailing.
❖ Acceptable complication rate (11 % infection rate in
type iii open fractures)
❖ No relationship between infection rate, non union with
timing of nailing or associated soft tissue injury

Aseptic non unions
 Without bone defects-primary im nailing or exchange
Nailing if well aligned
 With bone defects -IM nailing with bone grafting
 corticocancellous graft material - harvested with
ria(little donor morbidity)

Exchange nailing
➢ Biological effects :
 Reaming of medullary canal – promotes union
➢ Mechanical effects :
 Larger-diameter intramedullary nail – improved
stability
❖ Exchage nail – at least 1mm
larger than previous nail
❖ Canal reaming until osseous tissue
observed in reaming flutes
Removal of current
intramedullary nail
Reaming of medullary
canal
Placement of an larger
intramedullary nail

Septic non union
 Main aim - eradicating infection
 Osseous stability important in management of infected nonunion
 Stabilization with antibiotic impregnated cement coated nail after
serial debridement.
 Cement nail elute high concentration of antibiotic in local sites for
up to 36 weeks.

Antibiotic impregnated cement nail

40gms of bone cement is
taken and mixed with 2 to 4
gms of powder when dough is
semi solid.
It is wrapped around K nail
of size 6 to 7 mm and rolled
between two palms.The rod
is then passed through the
holes of the nail major
usually 8 to 9mm diameter
to maintain uniformity of
diameter.

In polytrauma , early femoral stabilization decreases incidence of
severe fat embolism and pulmonary complications (ARDS).
Nailing with reaming will not increase pulmonary complications
Early intramedullary nailing may be deleterious and is associated
with elevation of certain proinflammatory markers - (il)-6.
Early external fixation of long bone fractures followed by delayed
intramedullary nailing – high risk patients.
Nailing in damage control orthopaedics (DCO)
/ early total care (ETC)

❑ 50% (↓)in mortality patients who underwent femoral shaft
fracture stabilization beyond 12 hours
This timing was hypothesized to allow for adequate
resuscitation
 Exact and optimal timing of femoral shaft fracture nailing
remains unclear in polytrauma(esp. Chest injuries)
Nailing in damage control orthopaedics
(DCO)/early total care (ETC)

Removal
 Timing controversial
 Indications :
 Patient request(after union)
 Pain, swelling secondary to backing out of implant.
 Infected nailing
 Full weight bearing immediately after removal
 Femoral nail removed after 24-36 months ,
 Tibial nail 18-24 months

Failure IMN
❑ When fracture healing is delayed or nonunion occurs.
 IM nails usually fail in predictable patterns.
 Unlocked nails
◼ fail at fracture site or through a screw hole or slot.
 Locked nails
◼ screw breakage or fracturing of nail at locking hole
sites(proximal hole of distal interlocks )

Recent advances
 Biodegradable polymers
 Nickel-titanium shape-modifiable alloys
 can improve stability as they change shape after
insertion and recover curvature as they warm.
 IM nails coated with bmp

Conclusion
➢ IMN -Implant of choice in diaphyseal
fractures
➢ Multiple factors determine final construct
stiffness, should be understood and
considered when choosing IM nail
➢ Ideal intramedullary nail is yet to be invented

1
• .CAMPBELL OPERATIVE ORTHOPAEDICS 11TH EDITION
2.The science and practice of Intramedullary Nailing – Bruce D. Brown
3.ROCKWOOD AND GREENS
4.INTERLOCKING NAILING-DD.TANNA
5.The elements of fracture fixation – Anand J Thakur
6.Prospective study of distal end radius fracture by an
intramedullary nailing JBJS aug3 2011
Bibliography

Bahaa Ali Kornah
bkornah@gmail.com
‫د‬/‫قرنة‬ ‫بهاء‬bahaa Ali Kornah-Al-Azhar Un. Cairo -EGYPT

Intramedullary nailing

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Intramedullary nailing